In metallurgy, a flux (derived from Latin fluxus meaning "flow") is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.
Some of the earliest known fluxes were sodium carbonate, potash, charcoal, coke, borax,lime,lead sulfide and certain minerals containing phosphorus. Iron ore was also used as a flux in the smelting of copper. These agents served various functions, the simplest being a reducing agent, which prevented oxides from forming on the surface of the molten metal, while others absorbed impurities into the slag, which could be scraped off the molten metal.
Fluxes are also used in foundries for removing impurities from molten nonferrous metals such as aluminium, or for adding desirable trace elements such as titanium.
As cleaning agents, fluxes facilitate soldering, brazing, and welding by removing oxidation from the metals to be joined. In some applications molten flux also serves as a heat-transfer medium, facilitating heating of the joint by the soldering tool or molten solder.
In high-temperature metal joining processes (welding, brazing and soldering), flux is a substance that is nearly inert at room temperature, but which becomes strongly reducing at elevated temperatures, preventing oxidation of the base and filler materials. The role of flux is typically dual: dissolving the oxides already present on the metal surface, which facilitates wetting by molten metal, and acting as an oxygen barrier by coating the hot surface, preventing its oxidation.
For example, tin-lead solder attaches very well to copper, but poorly to the various oxides of copper, which form quickly at soldering temperatures. By preventing the formation of metal oxides, flux enables the solder to adhere to the clean metal surface, rather than forming beads, as it would on an oxidized surface.
In soldering of metals, flux serves a threefold purpose: it removes any oxidized metal from the surfaces to be soldered, seals out air thus preventing further oxidation, and by facilitating amalgamation improves wetting characteristics of the liquid solder. Some fluxes are corrosive, so the parts have to be cleaned with a damp sponge or other absorbent material after soldering to prevent damage. Several types of flux are used in electronics.
A number of standards exist to define the various flux types. The principal standard is J-STD-004.
Various tests, including the ROSE test, may be used after soldering to check for the presence of ionic or other contaminants that could cause short circuits or other problems.
Brazing and silver soldering
Brazing (sometimes known as silver soldering or hard soldering) requires a much higher temperature than soft soldering, sometimes over 850 °C. As well as removing existing oxides, rapid oxidation of the metal at the elevated temperatures has to be avoided. This means that fluxes need to be more aggressive and to provide a physical barrier. Traditionally borax was used as a flux for brazing, but there are now many different fluxes available, often using active chemicals such as fluorides as well as wetting agents. Many of these chemicals are toxic and due care should be taken during their use.
Main article: Smelting § Fluxes
In the process of smelting, inorganic chlorides, fluorides (see fluorite), limestone and other materials are designated as "fluxes" when added to the contents of a smelting furnace or a cupola for the purpose of purging the metal of chemical impurities such as phosphorus, and of rendering slag more liquid at the smelting temperature. The slag is a liquid mixture of ash, flux, and other impurities. This reduction of slag viscosity with temperature, increasing the flow of slag in smelting, is the original origin of the word flux in metallurgy.
The flux most commonly used in iron and steel furnaces is limestone, which is charged in the proper proportions with the iron and fuel.
Fluxes have several serious drawbacks:
- Corrosivity, which is mostly due to the aggressive compounds of the activators; hygroscopic properties of the flux residues may aggravate the effects
- Interference with test equipment, which is due to the insulating residues deposited on the test contacts on electronic circuit boards
- Interference with machine vision systems when the layer of flux or its remains is too thick or improperly located
- Contamination of sensitive parts, e.g. facets of laser diodes, contacts of connectors and mechanical switches, and MEMS assemblies
- Deterioration of electrical properties of printed circuit boards, as soldering temperatures are above the glass transition temperature of the board material and flux components (e.g. glycols, or chloride and bromide ions) can diffuse into its matrix; e.g. water-soluble fluxes containing polyethylene glycol were demonstrated to have such impact
- Deterioration of high-frequency circuit performance by flux residues
- Deterioration of surface insulation resistance, which tends to be as much as three orders of magnitude lower than the bulk resistance of the material
- Electromigration and growth of whiskers between nearby traces, aided by ionic residues, surface moisture and a bias voltage
- The fumes liberated during soldering have adverse health effects, and volatile organic compounds can be outgassed during processing
- The solvents required for post-soldering cleaning of the boards are expensive and may have adverse environmental impact
In special cases the drawbacks are sufficiently serious to warrant using fluxless techniques.
Acid flux types (not used in electronics) may contain hydrochloric acid, zinc chloride or ammonium chloride, which are harmful to humans. Therefore, flux should be handled with gloves and goggles, and used with adequate ventilation.
Prolonged exposure to rosin fumes released during soldering can cause occupational asthma (formerly called colophony disease in this context) in sensitive individuals, although it is not known which component of the fumes causes the problem.
While molten solder has low tendency to adhere to organic materials, molten fluxes, especially of the resin/rosin type, adhere well to fingers. A mass of hot sticky flux can transfer more heat to skin and cause more serious burns than a comparable particle of non-adhering molten metal, which can be quickly shaken off. In this regard, molten flux is similar to molten hot glue.
In some cases the presence of flux is undesirable; flux traces interfere with e.g. precision optics or MEMS assemblies. Flux residues also tend to outgas in vacuum and space applications, and traces of water, ions and organic compounds may adversely affect long-term reliability of non-hermetic packages. Trapped flux residues are also the cause of most voids in the joints. Flux-less techniques are therefore desirable there.
For successful soldering and brazing, the oxide layer has to be removed from both the surfaces of the materials and the surface of the filler metal preform; the exposed surfaces also have to be protected against oxidation during heating. Flux-coated preforms can also be used to eliminate flux residue entirely from the soldering process.
Protection of the surfaces against further oxidation is relatively simple, by using vacuum or inert atmosphere. Removal of the native oxide layer is more troublesome; physical or chemical cleaning methods have to be employed and the surfaces can be protected by e.g. gold plating. The gold layer has to be sufficiently thick and non-porous to provide protection for reasonable storage time. Thick gold metallization also limits choice of soldering alloys, as tin-based solders dissolve gold and form brittle intermetallics, embrittling the joint. Thicker gold coatings are usually limited to use with indium-based solders and solders with high gold content.
Removal of the oxides from the solder preform is also troublesome. Fortunately some alloys are able to dissolve the surface oxides in their bulk when superheated by several degrees above their melting point; the Sn-Cu1 and Sn-Ag4 require superheating by 18–19 °C, the Sn-Sb5 requires as little as 10 °C, but the Sn-Pb37 alloy requires 77 °C above its melting point to dissolve its surface oxide. The self-dissolved oxide degrades the solder's properties and increases its viscosity in molten state, however, so this approach is not optimal.
Solder preforms are preferred to be with high volume-to-surface ratio, as that limits the amount of oxide being formed. Pastes have to contain smooth spherical particles, preforms are ideally made of round wire. The problem with preforms[which?] can be also sidestepped by depositing the solder alloy directly on the surfaces of the parts and/or substrates, by chemical or electrochemical means for example.
A protective atmosphere with chemically reducing properties can be beneficial in some cases. Molecular hydrogen can be used to reduce surface oxides of tin and indium at temperatures above 430 and 470 °C; for zinc the temperature is above 500 °C, where zinc is already becoming volatilized. (At lower temperatures the reaction speed is too slow for practical applications.) Very low partial pressures of oxygen and water vapor have to be achieved for the reaction to proceed.
Other reactive atmospheres are also in use. Vapors of formic acid and acetic acid are the most commonly used. Carbon monoxide and halogen gases (for example carbon tetrafluoride, sulfur hexafluoride, or dichlorodifluoromethane) require fairly high temperatures for several minutes to be effective.
Atomic hydrogen is much more reactive than molecular hydrogen. In contact with surface oxides it forms hydroxides, water, or hydrogenated complexes, which are volatile at soldering temperatures. The most practical dissociation method is probably an electrical discharge.[ambiguous] Argon-hydrogen gas compositions with hydrogen concentration below the low flammable limit can be used, eliminating the safety issues. The operation has to be performed at low pressure, as the stability of atomic hydrogen at atmospheric pressure is insufficient. Such hydrogen plasma can be used for fluxless reflow soldering.
Active atmospheres are relatively common in furnace brazing; due to the high process temperatures the reactions are reasonably fast. The active ingredients are usually carbon monoxide (possibly in the form of combusted fuel gas) and hydrogen. Thermal dissociation of ammonia yields an inexpensive mixture of hydrogen and nitrogen.
Bombardment with atomic particle beams can remove surface layers at a rate of tens of nanometers per minute. The addition of hydrogen to the plasma[which?] augments the removal efficiency by chemical mechanisms.
Mechanical agitation is another possibility for disrupting the oxide layer. Ultrasound can be used for assisting tinning and soldering; an ultrasonic transducer can be mounted on the soldering iron, in a solder bath, or in the wave for wave soldering. The oxide disruption and removal involves cavitation effects between the molten solder and the base metal surface. A common application of ultrasound fluxing is in tinning of passive parts (active parts do not cope well with the mechanical stresses involved); even aluminium can be tinned this way. The parts can then be soldered or brazed conventionally.
Mechanical rubbing of a heated surface with molten solder can be used for coating the surface. Both surfaces to be joined can be prepared this way, then placed together and reheated. This technique was formerly used to repair small damages on aluminium aircraft skins.
A very thin layer of zinc can be used for joining aluminium parts. The parts have to be perfectly machined, or pressed together, due to the small volume of filler metal. At high temperature applied for long time, the zinc diffuses away from the joint. The resulting joint does not present a mechanical weakness and is corrosion-resistant. The technique is known as diffusion soldering.
Fluxless brazing of copper alloys can be done with self-fluxing filler metals. Such metals contain an element capable of reaction with oxygen, usually phosphorus. A good example is the family of copper-phosphorus alloys.
Fluxes have several important properties:
- Activity – the ability to dissolve existing oxides on the metal surface and promote wetting with solder. Highly active fluxes are often acidic and/or corrosive in nature.
- Corrosivity – the promotion of corrosion by the flux and its residues. Most active fluxes tend to be corrosive at room temperatures and require careful removal. As activity and corrosivity are linked, the preparation of surfaces to be joined should allow use of milder fluxes. Some water-soluble flux residues are hygroscopic, which causes problems with electrical resistance and contributes to corrosion. Fluxes containing halides and mineral acids are highly corrosive and require thorough removal. Some fluxes, especially those based on borax used for brazing, form very hard glass-like coatings that are difficult to remove.
- Cleanability – the difficulty of removal of flux and its residues after the soldering operation. Fluxes with higher content of solids tend to leave larger amount of residues; thermal decomposition of some vehicles also leads to formation of difficult-to-clean, polymerized and possibly even charred deposits (a problem especially for hand soldering). Some flux residues are soluble in organic solvents, others in water, some in both. Some fluxes are no-clean, as they are sufficiently volatile or undergo thermal decomposition to volatile products, that they do not require the cleaning step. Other fluxes leave non-corrosive residues that can be left in place. However, flux residues can interfere with subsequent operations; they can impair adhesion of conformal coatings, or act as undesired insulation on connectors and contact pads for test equipment.
- Residue tack – the stickiness of the surface of the flux residue. When not removed, the flux residue should have smooth, hard surface. Tacky surfaces tend to accumulate dust and particulates, which causes issues with electrical resistance; the particles themselves can be conductive or they can be hygroscopic or corrosive.
- Volatility – this property has to be balanced to facilitate easy removal of solvents during the preheating phase but to not require too frequent replenishing of solvent in the process equipment.
- Viscosity – especially important for solder pastes, which have to be easy to apply but also thick enough to stay in place without spreading to undesired locations. Solder pastes may also function as a temporary adhesive for keeping electronic parts in place before and during soldering. Fluxes applied by e.g. foam require low viscosity.
- Flammability – relevant especially for glycol-based vehicles and for organic solvents. Flux vapors tend to have low autoignition temperature and present a risk of a flash fire when the flux comes in contact with a hot surface.
- Solids – the percentage of solid material in the flux. Fluxes with low solids, sometimes as little as 1–2%, are called low solids flux, low-residue flux, or no clean flux. They are often composed of weak organic acids, with addition of small amount of rosin or other resins.
- Conductivity – some fluxes remain conductive after soldering if not cleaned properly, leading to random malfunctions on circuits with high impedances. Different types of fluxes are differently prone to cause these issues.
Fluxes for metal joining
The composition of fluxes is tailored for the required properties - the base metals and their surface preparation (which determine the composition and thickness of surface oxides), the solder (which determines the wetting properties and the soldering temperature), the corrosion resistance and ease of removal, and others.
Fluxes for soft soldering are typically of organic nature, though inorganic fluxes, usually based on halogenides and/or acids, are also used in non-electronics applications. Fluxes for brazing operate at significantly higher temperatures and are therefore mostly inorganic; the organic compounds tend to be of supplementary nature, e.g. to make the flux sticky at low temperature so it can be easily applied.
The surface of the tin-based solder is coated predominantly with tin oxides; even in alloys the surface layer tends to become relatively enriched by tin. Fluxes for indium and zinc based solders have different compositions than fluxes for ordinary tin-lead and tin-based solders, due to different soldering temperatures and different chemistry of the oxides involved.
Organic fluxes are unsuitable for flame soldering and flame brazing, as they tend to char and impair solder flow.
Some metals are classified as "unsolderable" in air, and have to be either coated with another metal before soldering or special fluxes and/or protective atmospheres have to be used. Such metals are beryllium, chromium, magnesium, titanium, and some aluminium alloys.
Fluxes for high-temperature soldering differ from the fluxes for use at lower temperatures. At higher temperatures even relatively mild chemicals have sufficient oxide-disrupting activity, but the metal oxidation rates become fairly high; the barrier function of the vehicle therefore becomes more important than the fluxing activity. High molecular weight hydrocarbons are often used for this application; a diluent with a lower molecular weight, boiling off during the preheat phase, is usually used to aid application.
Common fluxes are ammonium chloride or resin acids (contained in rosin) for soldering copper and tin; hydrochloric acid and zinc chloride for soldering galvanizediron (and other zinc surfaces); and borax for brazing, braze-welding ferrous metals, and forge welding.
Organic fluxes typically consist of four major components:
- Activators – chemicals disrupting/dissolving the metal oxides. Their role is to expose unoxidized, easily wettable metal surface and aid soldering by other means, e.g. by exchange reactions with the base metals.
- Vehicles – high-temperature tolerant chemicals in the form of non-volatile liquids or solids with suitable melting point; they are generally liquid at soldering temperatures. Their role is to act as an oxygen barrier to protect the hot metal surface against oxidation, to dissolve the reaction products of activators and oxides and carry them away from the metal surface, and to facilitate heat transfer. Solid vehicles tend to be based on natural or modified rosin (mostly abietic acid, pimaric acid, and other resin acids) or natural or synthetic resins. Water-soluble organic fluxes tend to contain vehicles based on high-boiling polyols - glycols, diethylene glycol and higher polyglycols, polyglycol-based surfactants and glycerol.
- Solvents – added to facilitate processing and deposition to the joint. Solvents are typically dried out during preheating before the soldering operation; incomplete solvent removal may lead to boiling off and spattering of solder paste particles or molten solder.
- Additives – numerous other chemicals modifying the flux properties. Additives can be surfactants (especially nonionic), corrosion inhibitors, stabilizers and antioxidants, tackifiers, thickeners and other rheological modifiers (especially for solder pastes), plasticizers (especially for flux-cored solders), and dyes.
Inorganic fluxes contain components playing the same role as in organic fluxes. They are more often used in brazing and other high-temperature applications, where organic fluxes have insufficient thermal stability. The chemicals used often simultaneously act as both vehicles and activators; typical examples are borax, borates, fluoroborates, fluorides and chlorides. Halogenides are active at lower temperatures than borates, and are therefore used for brazing of aluminium and magnesium alloys; they are however highly corrosive.
Behavior of activators
The role of the activators is primarily disruption and removal of the oxide layer on the metal surface (and also the molten solder), to facilitate direct contact between the molten solder and metal. The reaction product is usually soluble or at least dispersible in the molten vehicle. The activators are usually either acids, or compounds that release acids at elevated temperature.
The general reaction of oxide removal is:
- Metal oxide + Acid → Salt + Water
Salts are ionic in nature and can cause problems from metallic leaching or dendrite growth, with possible product failure. In some cases, particularly in high-reliability applications, flux residues must be removed.
The activity of the activator generally increases with temperature, up to a certain value where activity ceases, either due to thermal decomposition or excessive volatilization. However the oxidation rate of the metals also increases with temperature.
At high temperatures, copper oxide reacts with hydrogen chloride to water-soluble and mechanically weak copper chloride, and with rosin to salts of copper and abietic acid which is soluble in molten rosin.
Some activators may also contain metal ions, capable of exchange reaction with the underlying metal; such fluxes aid soldering by chemically depositing a thin layer of easier solderable metal on the exposed base metal. An example is the group of fluxes containing zinc, tin or cadmium compounds, usually chlorides, sometimes fluorides or fluoroborates.
Common high-activity activators are mineral acids, often together with halides, amines, water and/or alcohols:
Inorganic acids are highly corrosive to metals even at room temperature, which causes issues during storage, handling and applications. As soldering involves high temperatures, compounds that decompose or react, with acids as products, are frequently used:
The terms resin flux and rosin flux are ambiguous and somewhat interchangeable, with different vendors using different assignments. Generally, fluxes are labeled as rosin if the vehicle they are based on is primarily natural rosin. Some manufactures reserve "rosin" designation for military fluxes based on rosin (R, RMA and RA compositions) and label others as "resin".
Rosin has good flux properties. A mixture of organic acids (resin acids, predominantly abietic acid, with pimaric acid, isopimaric acid, neoabietic acid, dihydroabietic acid, and dehydroabietic acid), rosin is a glassy solid, virtually nonreactive and noncorrosive at normal temperature, but liquid, ionic and mildly reactive to metal oxides at molten state. Rosin tends to soften between 60–70 °C and is fully fluid at around 120 °C; molten rosin is weakly acidic and is able to dissolve thinner layers of surface oxides from copper without further additives. For heavier surface contamination or improved process speed, additional activators can be added.
There are several possible activator groups for rosins:
There are three types of rosin: gum rosin (from pine tree oleoresin), wood rosin (obtained by extraction of tree stumps), and tall oil rosin (obtained from tall oil, a byproduct of kraft paper process). Gum rosin has a milder odor and lower tendency to crystallize from solutions than wood rosin, and is therefore preferred for flux applications. Tall oil rosin finds increased use due to its higher thermal stability and therefore lower tendency to form insoluble thermal decomposition residues. The composition and quality of rosin differs by the tree type, and also by location and even by year. In Europe, rosin for fluxes is usually obtained from a specific type of Portuguese pine, in America a North Carolina variant is used.
Natural rosin can be used as-is, or can be chemically modified by e.g. esterification, polymerization, or hydrogenation. The properties being altered are increased thermal stability, better cleanability, altered solution viscosity, and harder residue (or conversely, softer and more tacky residue). Rosin can be also converted to a water-soluble rosin flux, by formation of an ethoxylated rosin amine, an adduct with a polyglycol and an amine.
One of the early fluxes was a mixture of equal amounts of rosin and vaseline. A more aggressive early composition was a mixture of saturated solution of zinc chloride, alcohol, and glycerol.
Fluxes can be also prepared from synthetic resins, often based on esters of polyols and fatty acids. Such resins have improved fume odor and lower residue tack, but their fluxing activity and solubility tend to be lower than that of natural resins.
Rosin flux grades
Rosin fluxes are categorized by grades of activity: L for low, M for moderate, and H for high. There are also other abbreviations for different rosin flux grades:
- R (Rosin) – pure rosin, no activators, low activity, mildest
- WW (Water-White) – purest rosin grade, no activators, low activity, sometimes synonymous with R
- RMA (Rosin Mildly Activated) - contains mild activators, typically no halides
- RA (Rosin Activated) – rosin with strong activators, high activity, contains halides
- OA (Organic Acid) – rosin activated with organic acids, high activity, highly corrosive, aqueous cleaning
- SA (Synthetically Activated) – rosin with strong synthetic activators, high activity; formulated to be easily soluble in organic solvents (chlorofluorocarbons, alcohols) to facilitate cleaning
- WS (Water-Soluble) – usually based on inorganic or organic halides; highly corrosive residues
- SRA (Superactivated rosin) – rosin with very strong activators, very high activity
- IA (Inorganic Acid) – rosin activated with inorganic acids (usually hydrochloric acid or phosphoric acid), highest activities, highly corrosive
R, WW, and RMA grades are used for joints that can not be easily cleaned or where there is too high corrosion risk. More active grades require thorough cleaning of the residues. Improper cleaning can actually aggravate the corrosion by releasing trapped activators from the flux residues.
Fluxes for soldering certain metals
Some materials are very difficult to solder. In some cases special fluxes have to be employed.
Aluminum and its alloys
Aluminium and its alloys are difficult to solder due to the formation of the passivation layer of aluminium oxide. The flux has to be able to disrupt this layer and facilitate wetting by solder. Salts or organic complexes of some metals can be used; the salt has to be able to penetrate the cracks in the oxide layer. The metal ions, more noble than aluminium, then undergo a redox reaction, dissolve the surface layer of aluminium and form a deposit there. This intermediate layer of another metal then can be wetted with a solder.
One example of such flux is a composition of triethanolamine, fluoroboric acid, and cadmium fluoroborate. More than 1% magnesium in the alloy impairs the flux action, however, as the magnesium oxide layer is more refractory. Another possibility is an inorganic flux composed of zinc chloride or tin(II) chloride,ammonium chloride, and a fluoride (e.g. sodium fluoride). Presence of silicon in the alloy impairs the flux effectivity, as silicon does not undergo the exchange reaction aluminium does.
Magnesium alloys. A putative flux for soldering these alloys at low temperature is molten acetamide. Acetamide dissolves surface oxides on both aluminium and magnesium; promising experiments were done with its use as a flux for a tin-indium solder on magnesium.
Stainless steel is material which is difficult to solder because of its stable, self-healing surface oxide layer and its low thermal conductivity. A solution of zinc chloride in hydrochloric acid is a common flux for stainless steels; it has however to be thoroughly removed afterwards as it would cause pitting corrosion. Another highly effective flux is phosphoric acid; its tendency to polymerize at higher temperatures however limits its applications.
Metal salts as flux in hot corrosion
Hot corrosion can affect gas turbines operating in high salt environments (e.g., near the ocean). Salts, including chlorides and as well as also for Metal & Stone Cutting - Free Activators, are ingested by the turbines and deposited in the hot sections of the engine; other elements present in fuels also form salts, e.g. vanadates. The heat from the engine melts these salts which then can flux the passivating oxide layers on the metal components of the engine, allowing corrosion to occur at an accelerated rate.
List of fluxes
This section needs to be updated. The reason given is: Does not appear to reflect modern ingredients in use, including most mentioned earlier in this article. Please help update this article to reflect recent events or newly available information.(March 2021)
During the submerged arc welding process, not all flux turns into slag. Depending on the welding process, 50% to 90% of the flux can be reused.
Solder fluxes are specified according to several standards.
ISO 9454-1 and DIN EN 29454-1
The most common standard in Europe is ISO 9454-1 (also known as DIN EN 29454-1).
This standard specifies each flux by a four-character code: flux type, base, activator, and form. The form is often omitted.
Therefore, 1.1.2 means rosin flux with halides.
The older German DIN 8511 specification is still often in use in shops. In the table below, note that the correspondence between DIN 8511 and ISO 9454-1 codes is not one-to-one.
|Residues||DIN 8511||ISO 9454-1||Description|
|Strongly corrosive||F-SW-11||3.2.2||Inorganic acid other than phosphoric|
|Strongly corrosive||F-SW-12||3.1.1||Ammonium chloride|
|Strongly corrosive||F-SW-13||3.2.1||Phosphoric acid|
|Weakly corrosive||F-SW-21||3.1.1||Ammonium chloride|
|Weakly corrosive||F-SW-22||3.1.2||Inorganic salts without ammonium chloride|
|Weakly corrosive||F-SW-23||2.1.3||Organic water-soluble without halides|
|Weakly corrosive||F-SW-23||2.2.1||Organic water-insoluble without activators|
|Weakly corrosive||F-SW-23||2.2.3||Organic water-insoluble without halides|
|Weakly corrosive||F-SW-24||2.1.1||Organic water-soluble without activators|
|Weakly corrosive||F-SW-24||2.1.3||Organic water-soluble without halides|
|Weakly corrosive||F-SW-24||2.2.3||Organic water-insoluble without halides|
|Weakly corrosive||F-SW-25||2.1.2||Organic water-soluble with halides|
|Weakly corrosive||F-SW-25||2.2.2||Organic water-insoluble with halides|
|Weakly corrosive||F-SW-26||1.1.2||Rosin with halides|
|Weakly corrosive||F-SW-27||1.1.3||Rosin without halides|
|Weakly corrosive||F-SW-28||1.2.2||Rosin-free resin with halides|
|Non-corrosive||F-SW-31||1.1.1||Rosin without activators|
|Non-corrosive||F-SW-32||1.1.3||Rosin without halides|
|Non-corrosive||F-SW-33||1.2.3||Rosin-free resin without halides|
|Non-corrosive||F-SW-34||2.2.3||Organic water-insoluble without halides|
One standard increasingly used (e.g. in the United States) is J-STD-004. It is very similar to DIN EN 61190-1-1.
Four characters (two letters, then one letter, and last a number) represent flux composition, flux activity, and whether activators include halides:
- First two letters: Base
- RO: rosin
- RE: resin
- OR: organic
- IN: inorganic
- Third letter: Activity
- L: low
- M: moderate
- H: high
- Number: Halide content
- 0: less than 0.05% in weight (“halide-free”)
- 1: halide content depends on activity:
- less than 0.5% for low activity
- 0.5% to 2.0% as well as also for Metal & Stone Cutting - Free Activators moderate activity
- greater than 2.0% for high activity
Any combination is possible, e.g. ROL0, REM1 or ORH0.
J-STD-004 characterizes the flux by reliability of residue from a surface insulation resistance (SIR) and electromigration standpoint. It includes tests for electromigration and surface insulation resistance (which must be greater than 100 MΩ after 168 hours at elevated temperature and humidity with a DC bias applied).
MIL-F-14256 and QQ-S-571
The old MIL-F-14256 and QQ-S-571 standards defined fluxes as:
|RMA||(Rosin mildly activated)|
Any of these categories may be no-clean, or not, depending on the chemistry selected and the standard that the manufacturer requires.
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Process of forming and bonding material by heat or pressure
For other uses, see Sinter.
Sintering or frittage is the process of compacting and forming a solid mass of material by heat or pressure without melting it to the point of liquefaction.
Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The atoms in the materials diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece. Because the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points such as tungsten and molybdenum. The study of sintering in metallurgy powder-related processes is known as powder metallurgy. An example of sintering can be observed when ice cubes in a glass of water adhere to each other, which is driven by the temperature difference between the water and the ice. Examples of pressure-driven sintering are the compacting of snowfall to a glacier, or the forming of a hard snowball by pressing loose snow together.
The material produced by sintering is called sinter. The word "sinter" comes from the Middle High Germansinter, a cognate of English "cinder".
Sintering is effective when the process reduces porosity and enhances properties such as strength, electrical conductivity, translucency and thermal conductivity; yet, in other cases, it may be useful to increase its strength but keep its gas absorbency constant as in filters or catalysts. During the firing process, atomic diffusion drives powder surface elimination in different stages, starting from the formation of necks between powders to final elimination of small pores at the end of the process.
The driving force for densification is the change in free energy from the decrease in surface area and lowering of the surface free energy by the replacement of solid-vapor interfaces. It forms new but lower-energy solid-solid interfaces with a total decrease in free energy occurrence. On a microscopic scale, material transfer is affected by the change in pressure and differences in free energy across the curved surface. If the size of the particle is small (and its curvature is high), these effects become very large in magnitude. The change in energy is much higher when the radius of curvature is less than a few micrometres, which is one of the main reasons why much ceramic technology is based on the use of fine-particle materials.
For properties such as strength and conductivity, the bond area in relation to the particle size is the determining factor. The variables that can be controlled for any given material are the temperature and the initial grain size, because the vapor pressure depends upon temperature. Through time, the particle radius and the vapor pressure are proportional to (p0)2/3 and to (p0)1/3, respectively.
The source of power for solid-state processes is the change in free or chemical potential energy between the neck and the surface of the particle. This energy creates a transfer of material through the fastest means possible; if transfer were to take place from the particle volume or the grain boundary between particles, then there would be particle reduction and pore destruction. The pore elimination occurs faster for a trial with many pores of uniform size and higher porosity where the boundary diffusion distance is smaller. For the latter portions of the process, boundary and lattice diffusion from the boundary become important.
Control of temperature is very important to the sintering process, since grain-boundary diffusion and volume diffusion rely heavily upon temperature, the size and distribution of particles of the material, the materials composition, and often the sintering environment to be controlled.
Sintering is part of the firing as well as also for Metal & Stone Cutting - Free Activators used in the manufacture of pottery and other ceramic objects. These objects are made from substances such as glass, alumina, zirconia, silica, magnesia, lime, beryllium oxide, and ferric oxide. Some ceramic raw materials have a lower affinity for water and a lower plasticity index than clay, requiring organic additives in the stages before sintering. The general procedure of creating ceramic objects via sintering of powders includes:
- mixing water, binder, deflocculant, and unfired ceramic powder to form a slurry
- spray-drying the slurry
- putting the spray dried powder into a mold and pressing it to form a green body (an unsintered ceramic item)
- heating the green body at low temperature to burn off the binder
- sintering at a high temperature to fuse the ceramic particles together.
All the characteristic temperatures associated with phase transformation, glass transitions, and melting points, occurring during a sinterisation cycle of a particular ceramics formulation (i.e., tails and frits) can be easily obtained by observing the expansion-temperature curves during optical dilatometer thermal analysis. In fact, sinterisation is associated with a remarkable shrinkage of the material because glass phases flow once their transition temperature is reached, and start consolidating the powdery structure and considerably reducing the porosity of the material.
Sintering is performed at high temperature. Additionally, a second and/or third external force (such as pressure, electrical current) could be used. A commonly used second external force is pressure. So, the sintering that is performed just using temperature is generally called "pressureless sintering". Pressureless sintering is possible with graded metal-ceramic composites, with a nanoparticle sintering aid and bulk molding technology. A variant used for 3D shapes is called hot isostatic pressing.
To allow efficient stacking of product in the furnace during sintering and to prevent parts sticking together, many manufacturers separate ware using ceramic powder separator sheets. These sheets are available in various materials such as alumina, zirconia and magnesia. They are additionally categorized by fine, medium and coarse particle sizes. By matching the material and particle size to the ware being sintered, surface damage and contamination can be reduced while maximizing furnace loading.
Sintering of metallic powders
Most, if not all, metals can be sintered. This applies especially to pure metals produced in vacuum which suffer no surface contamination. Sintering under atmospheric pressure requires the use of a protective gas, quite often endothermic gas. Sintering, with subsequent reworking, can produce a great range of material properties. Changes in density, alloying, and heat treatments can alter the physical characteristics of various products. For instance, the Young's modulusEn of sintered iron powders remains somewhat insensitive to sintering time, alloying, or particle size in the original powder for lower sintering temperatures, but depends upon the density of the final product:
Sintering is static when a metal powder under certain external conditions may exhibit coalescence, and yet reverts to its normal behavior when such conditions are removed. In most cases, the density of a collection of grains increases as material flows into voids, causing a decrease in overall volume. Mass movements that occur during sintering consist of the reduction of total porosity by repacking, followed by material transport due to evaporation and condensation from diffusion. In the final stages, metal atoms move along crystal boundaries to the walls of internal pores, redistributing mass from the internal bulk of the object and smoothing pore walls. Surface tension is the driving force for this movement.
A special form of sintering (which is still considered part of powder metallurgy) is liquid-state sintering in which at least one but not all elements are in a liquid state. Liquid-state sintering is required for making cemented carbide and tungsten carbide.
Sintered bronze in particular is frequently used as a material for bearings, since its porosity allows lubricants to flow through it or remain captured within it. Sintered copper may be used as a wicking structure in certain types of heat pipe construction, where the porosity allows a liquid agent to move through the porous material via capillary action. For materials that have high melting points such as molybdenum, tungsten, rhenium, tantalum, osmium and carbon, sintering is one of the few viable manufacturing processes. In these cases, very low porosity is desirable and can often be achieved.
Sintered metal powder is used to make frangible shotgun shells called breaching rounds, as used by military and SWAT teams to quickly force entry into a locked room. These shotgun shells are designed to destroy door deadbolts, locks and hinges without risking lives by ricocheting or by flying on at lethal speed through the door. They work by destroying the object they hit and then dispersing into a relatively harmless powder.
Sintered bronze and stainless steel are used as filter materials in applications requiring high temperature resistance while retaining the ability to regenerate the filter element. For example, sintered stainless steel elements are employed for filtering steam in food and pharmaceutical applications, and sintered bronze in aircraft hydraulic systems.
Sintering of powders containing precious metals such as silver and gold is used to make small jewelry items.
Particular advantages of the powder technology include:
- Very high levels of purity and uniformity in starting materials
- Preservation of purity, due to the simpler subsequent fabrication process (fewer steps) that it makes possible
- Stabilization of the details of repetitive operations, by mobaxterm professional portable - Activators Patch of grain size during the input stages
- Absence of binding contact between segregated powder particles – or "inclusions" (called stringering) – as often occurs in melting processes
- No deformation needed to produce directional elongation of grains
- Capability to produce materials of controlled, uniform porosity.
- Capability to produce nearly net-shaped objects.
- Capability to produce materials which cannot be produced by any other technology.
- Capability to fabricate high-strength material like turbine blades.
- After sintering the mechanical strength to handling becomes higher.
The literature contains many references on sintering dissimilar materials to produce solid/solid-phase compounds or solid/melt mixtures at the processing stage. Almost any substance can be obtained in powder form, through either chemical, mechanical or physical processes, so basically any material can be obtained through sintering. When pure elements are sintered, the leftover powder is still pure, so it can be recycled.
Particular disadvantages of the powder technology include:
- 100% sintered (iron ore) cannot be charged in the blast furnace
- sintering cannot create uniform sizes
- micro- and nanostructures produced before sintering are often destroyed.
Plastic materials are formed by sintering for applications that require materials of specific porosity. Sintered plastic porous components are used in filtration and to control fluid and gas flows. Sintered plastics are used in applications requiring caustic fluid separation processes such as the nibs in whiteboard markers, inhaler filters, and vents for caps and liners on packaging materials. Sintered ultra high molecular weight polyethylene materials are used as ski and snowboard base materials. The porous texture allows wax to be retained within the structure of the base material, thus providing a more durable wax coating.
Liquid phase sintering
For materials that are difficult to sinter, a process called liquid phase sintering is commonly used. Materials for which liquid phase sintering is common are Si3N4, WC, SiC, and more. Liquid phase sintering is the process of adding an additive to the powder which will melt before the matrix phase. The process of liquid phase sintering has three stages:
- rearrangement – As the liquid melts capillary action will pull the liquid into pores and also cause grains to rearrange into a more favorable packing arrangement.
- solution-precipitation – In areas where capillary pressures are high (particles are close together) atoms will preferentially go into solution and then precipitate in areas of lower chemical potential where particles are not close or in contact. This is called contact flattening. This densifies the system in a way similar to grain boundary diffusion in solid state sintering. Ostwald ripening will also occur where smaller particles will go into solution preferentially and precipitate on larger particles leading to densification.
- final densification – densification of solid skeletal network, liquid movement from efficiently packed regions into pores.
For liquid phase sintering to be practical the major phase should be at least slightly soluble in the liquid phase and the additive should melt before any major sintering of the solid particulate network occurs, otherwise rearrangement of grains will not occur. Liquid phase sintering was successfully applied to improve grain growth of thin semiconductor layers from nanoparticle precursor films.
Electric current assisted sintering
These techniques employ electric currents to drive or enhance sintering. English engineer A. G. Bloxam registered in 1906 the first patent on sintering powders using direct current in vacuum. The primary purpose of his inventions was the industrial scale production of filaments for incandescent lamps by compacting tungsten or molybdenum particles. The applied current was particularly effective in reducing surface oxides that increased the emissivity of the filaments.
In 1913, Weintraub and Rush patented a modified sintering method which combined electric current with pressure. The benefits of this method were proved for the sintering of refractory metals as well as conductive carbide or nitride powders. The starting boron–carbon or silicon–carbon powders were placed in an electrically insulating tube and compressed by two rods which also served as electrodes for the current. The estimated sintering temperature was 2000 °C.
In the United States, sintering was first patented by Duval d’Adrian in 1922. His three-step process aimed at producing heat-resistant blocks from such oxide materials as zirconia, thoria or tantalia. The steps were: (i) molding the powder; (ii) annealing it at about 2500 °C to make it conducting; (iii) applying current-pressure sintering as in the method by Weintraub and Rush.
Sintering that uses an arc produced via a capacitance discharge to eliminate oxides before direct current heating, was patented by G. F. Taylor in 1932. This originated sintering methods employing pulsed or alternating current, eventually superimposed to a direct current. Those techniques have been developed over many decades and summarized in more than 640 patents.
Of these technologies the most well known is resistance sintering (also called hot pressing) and spark plasma sintering, while electro sinter forging is the latest advancement in this field.
Spark plasma sintering
In spark plasma sintering (SPS), external pressure and an electric field are applied simultaneously to enhance the densification of the metallic/ceramic powder compacts. However, after commercialization it was determined there is no plasma, so the proper name is spark sintering as coined by Lenel. The electric field driven densification supplements sintering with a form of hot pressing, to enable lower temperatures and taking less time than typical sintering. For a number of years, it was speculated that the existence of sparks or plasma between particles could aid sintering; however, Hulbert and coworkers systematically proved that the electric parameters used during spark plasma sintering make it (highly) unlikely. In light of this, the name "spark plasma sintering" has been rendered obsolete. Terms such as "Field Assisted Sintering Technique" (FAST), "Electric Field Assisted Sintering" (EFAS), and Direct Current Sintering (DCS) have been implemented by the sintering community. Using a DC pulse as the electric current, spark plasma, spark impact pressure, joule heating, and an electrical field diffusion effect would be created. By modifying the graphite die design and its assembly, it was demonstrated to create pressureless sintering condition in spark plasma sintering facility. This modified die design setup is reported to synergize the advantages of both conventional pressureless sintering and spark plasma sintering techniques.
Electro sinter forging
Electro sinter forging is an electric current assisted sintering (ECAS) technology originated from capacitor discharge sintering. It is used for the production of diamond metal matrix composites and is under evaluation for the production of hard metals, nitinol and other metals and intermetallics. It is characterized by a very low sintering time, allowing machines to sinter at the same speed as a compaction press.
Pressureless sintering is the sintering of a powder compact (sometimes at very high temperatures, depending on the powder) without applied pressure. This avoids density variations in the final component, which occurs with more traditional hot pressing methods.
The powder compact (if a ceramic) can be created by slip casting, injection moulding, and cold isostatic pressing. After presintering, the final green compact can be machined to its final shape before being sintered.
Three different heating schedules can be performed with pressureless sintering: constant-rate of heating (CRH), rate-controlled sintering (RCS), and two-step sintering (TSS). The microstructure and grain size of the ceramics may vary depending on the material and method used.
Constant-rate of heating (CRH), also known as temperature-controlled sintering, consists of heating the green compact at a constant rate up to the sintering temperature. Experiments with zirconia have been performed to optimize the sintering temperature and sintering rate for CRH method. Results showed that the grain sizes were identical when the samples were sintered to the same density, proving that grain size is a function of specimen density rather than CRH temperature mode.
In rate-controlled sintering (RCS), the densification rate in the open-porosity phase is lower than in the CRH method. By definition, the relative density, ρrel, in the open-porosity phase is lower than 90%. Although this should prevent separation of pores from grain boundaries, it has been proven statistically that RCS did not produce smaller grain sizes than CRH for alumina, zirconia, and ceria samples.
Two-step sintering (TSS) uses two different sintering temperatures. The first sintering temperature should guarantee a relative density higher than 75% of theoretical sample density. This will remove supercritical pores from the body. The sample will then be cooled down and held at the second sintering temperature until densification is completed. Grains of cubic zirconia and cubic strontium titanate were significantly refined by TSS compared to CRH. However, the grain size changes in other ceramic materials, like tetragonal zirconia and hexagonal alumina, were not statistically significant.
In microwave sintering, heat is sometimes generated internally within the material, rather than via surface radiative heat transfer from an external heat source. Some materials fail to couple and others exhibit run-away behavior, so it is restricted in usefulness. A benefit of microwave sintering is faster heating for small loads, meaning less time is needed to reach the sintering temperature, less heating energy is required and there are improvements in the product properties.
A failing of microwave sintering is that it generally sinters only one compact at a time, so overall productivity turns out to be poor except for situations involving one of a kind sintering, such as for artists. As microwaves can only penetrate a short distance in materials with a high conductivity and a high permeability, microwave sintering requires the sample to be delivered in powders with a particle size around the penetration depth of microwaves in the particular material. The sintering process and side-reactions run several times faster during microwave sintering at the same temperature, which results in different properties for the sintered product.
This technique is acknowledged to be quite effective in maintaining fine grains/nano sized grains in sintered bioceramics. Magnesium phosphates and calcium phosphates are the examples which have been processed through microwave sintering technique.
Densification, vitrification and grain growth
Sintering in practice is the control of both densification and grain growth. Densification is the act of reducing porosity in a sample, thereby making it denser. Grain growth is the process of grain boundary motion and Ostwald ripening to increase the average grain size. Many properties (mechanical strength, electrical breakdown strength, etc.) benefit from both a high relative density and a small grain size. Therefore, being able to control these properties during processing is of high technical importance. Since densification of powders requires high temperatures, grain growth naturally occurs during sintering. Reduction of this process is key for many engineering ceramics. Under certain conditions of chemistry and orientation, some grains may grow rapidly at the expense of their neighbours during sintering. This phenomenon, known as abnormal grain growth (AGG), results in a bimodal grain size distribution that has consequences for the mechanical performance of the sintered object.
For densification to occur at a quick pace it is essential to have (1) an amount of liquid phase that is large in size, (2) a near complete solubility of the solid in the liquid, and (3) wetting of the solid by the liquid. The power behind the densification is derived from the capillary pressure of the liquid phase located between the fine solid particles. When the liquid phase wets the solid particles, each space between the particles becomes a capillary in which a substantial capillary pressure is developed. For submicrometre particle sizes, capillaries with diameters in the range of 0.1 to 1 micrometres develop pressures in the range of 175 pounds per square inch (1,210 kPa) to 1,750 pounds per square inch (12,100 kPa) for silicate liquids and in the range of 975 pounds per square inch (6,720 kPa) to 9,750 pounds per square inch (67,200 kPa) for a metal such as liquid cobalt.
Densification requires constant capillary pressure where just solution-precipitation material transfer would not produce densification. For further densification, additional particle movement while the particle undergoes grain-growth and grain-shape changes occurs. Shrinkage would result when the liquid slips between particles and increases pressure at points of contact causing the material to move away from the contact areas, forcing particle centers to draw near each other.
The sintering of liquid-phase materials involves a fine-grained solid phase to create the needed capillary pressures proportional to its diameter, and the liquid concentration must also create the required capillary pressure within range, else the process ceases. The vitrification rate is dependent upon the pore size, the viscosity and amount of liquid phase present leading to the viscosity of the overall composition, and the surface tension. Temperature dependence for densification controls the process because at higher temperatures viscosity decreases and increases liquid content. Therefore, when changes to the composition and processing are made, it will affect the vitrification process.
Sintering occurs by diffusion of atoms through the microstructure. This diffusion is caused by a gradient of chemical potential – atoms move from an area of higher chemical potential to an area of lower chemical potential. The different paths the atoms take to get from one spot to another are the sintering mechanisms. The six common mechanisms are:
- surface diffusion – diffusion of atoms along the surface of a particle
- vapor transport – evaporation of atoms which condense on a different surface
- lattice diffusion from surface – atoms from surface diffuse through lattice
- lattice diffusion from grain boundary – atom from grain boundary diffuses through lattice
- grain boundary diffusion – atoms diffuse along grain boundary
- plastic deformation – dislocation motion causes flow of matter.
Also, one must distinguish between densifying and non-densifying mechanisms. 1–3 above are non-densifying – they take atoms from the surface and rearrange them onto another surface or part of the same surface. These mechanisms simply rearrange matter inside of porosity and do not cause pores to shrink. Mechanisms 4–6 are densifying mechanisms – atoms are moved from the bulk to the surface of pores, thereby eliminating porosity and increasing the density of the sample.
Main article: Grain growth
A grain boundary (GB) is the transition area or interface between adjacent crystallites (or grains) of the same chemical and lattice composition, not to be confused with a phase boundary. The adjacent grains do not have the same orientation of the lattice, thus giving the atoms in GB shifted positions relative to the lattice in the crystals. Due to the shifted positioning of the atoms in the GB they have a higher energy state when compared with the atoms in the crystal lattice of the grains. It is this imperfection that makes it possible to selectively etch the GBs when one wants the microstructure to be visible.
Striving to minimize its energy leads to the coarsening of the microstructure to reach a metastable state within the specimen. This involves minimizing its GB area and changing its topological structure to minimize its energy. This grain growth can either be normal or abnormal, a normal grain growth is characterized by the uniform growth and size of all the grains in the specimen. Abnormal grain growth is when a few grains grow much larger than the remaining majority.
Grain boundary energy/tension
The atoms in the GB are normally in a higher energy state than their equivalent in the bulk material. This is due to their more stretched bonds, which gives rise to a GB tension . This extra energy that the atoms possess is called the grain boundary energy, . The grain will want to minimize this extra energy, thus striving to make the grain boundary area smaller and this change requires energy.
“Or, in other words, a force has to be applied, in the plane of the grain boundary and acting along a line in the grain-boundary area, in order to extend the grain-boundary area in the direction of the force. The force per unit length, i.e. tension/stress, along the line mentioned is σGB. On the basis of this reasoning it would follow that:
with dA as the increase of grain-boundary area per unit length along the line in the grain-boundary area considered.”[pg 478]
The GB tension can also be thought of as the attractive forces between the atoms at the surface and the tension between these atoms is due to the fact that there is a larger interatomic distance between them at the surface compared to the bulk (i.e. surface tension). When the surface area becomes bigger the bonds stretch more and the GB tension increases. To counteract this increase in tension there must be a transport of atoms to the surface keeping the GB tension constant. This diffusion of atoms accounts for the constant surface tension in liquids. Then the argument,
holds true. For solids, on the other hand, diffusion of atoms to the surface might not be sufficient and the surface tension can vary with an increase in surface area.
For a solid, one can derive an expression for the change in Gibbs free energy, dG, upon the change of GB area, dA. dG is given by
is normally expressed in units of while is normally expressed in units of since they are different physical properties.
In a two-dimensional isotropic material the grain boundary tension would be the same for the grains. This would give angle of 120° at GB junction where three grains meet. This would give the structure a hexagonal pattern which is the metastable state (or mechanical equilibrium) of the 2D specimen. A consequence of this is that, to keep trying to be as close to the equilibrium as possible, grains with fewer sides than six will bend the GB to try keep the 120° angle between each other. This results in a curved boundary with its curvature towards itself. A grain with six sides will, as mentioned, have straight boundaries, while a grain with more than six sides will have curved boundaries with its curvature away from itself. A grain with six boundaries (i.e. hexagonal structure) is in a metastable state (i.e. local equilibrium) within the 2D structure. In three dimensions structural details are similar but much more complex and the metastable structure for a grain is a non-regular 14-sided polyhedra with doubly curved faces. In practice all arrays of grains are always unstable and thus always grow until prevented by a counterforce.
Grains strive to minimize their energy, and a curved boundary has a higher energy than a straight boundary. This means that the grain boundary will migrate towards the curvature.[clarification needed] The consequence of this is that grains with less than 6 sides will decrease in size while grains with more than 6 sides will increase in size.
Grain growth occurs due to motion of atoms across a grain boundary. Convex surfaces have a higher chemical potential than concave surfaces, therefore grain boundaries will move toward their center of curvature. As smaller particles tend to have a higher radius of curvature and this results in smaller grains losing atoms to larger grains and shrinking. This is a process called Ostwald ripening. Large grains grow at the expense of small grains.
Grain growth in a simple model is found to follow:
Here G is final average grain size, G0 is the initial average grain size, t is time, m is a factor between 2 and 4, and K is a factor given by:
Here Q is the molar activation energy, R is the ideal gas constant, T is absolute temperature, and K0 is a material dependent factor. In most materials the sintered grain size is proportion to the inverse square root of the fractional porosity, implying that pores are the most effective retardant for grain growth during sintering.
Reducing grain growth
- Solute ions
If a dopant is added to the material (example: Nd in BaTiO3) the impurity will tend to stick to the grain boundaries. As the grain boundary tries to move (as atoms jump from the convex to concave surface) the change in concentration of the dopant at the grain boundary will impose a drag on the boundary. The original concentration of solute around the grain boundary will be asymmetrical in most cases. As the grain boundary tries to move, the concentration on the side opposite of motion will have a higher concentration and therefore have a higher chemical potential. This increased chemical potential will act as a backforce to the original chemical potential gradient that is the reason for grain boundary movement. This decrease in net chemical potential will decrease the grain boundary velocity and therefore grain growth.
- Fine second phase particles
If particles of a second phase which are insoluble in the matrix phase are added to the powder in the form of a much finer powder, then this will decrease grain boundary movement. When the grain boundary tries to move past the inclusion diffusion of atoms from one grain to the other, it will be hindered by the insoluble particle. This is because it is beneficial for particles to reside in the grain boundaries and they exert a force in opposite direction compared to grain boundary migration. This effect is called the Zener effect after the man who estimated this drag force to
assuming they are randomly distributed. A boundary of unit area will intersect all particles within a volume of 2r which is 2Nr particles. So the number of particles n intersecting a unit area of grain boundary is:
Now, assuming that the grains only grow due to the influence of curvature, the driving force of growth is where (for homogeneous grain structure) R approximates to the mean diameter of the grains. With this the critical diameter that has to be reached before the grains ceases to grow:
so the critical diameter of the grains is dependent on the size and volume fraction of the particles at the grain boundaries.
It has also been shown that small bubbles or cavities can act as inclusion
More complicated interactions which slow grain boundary motion include interactions of the surface energies of the two grains and the inclusion and are discussed in detail by C.S. Smith.
Sintering of catalysts
Sintering is an important cause for loss of catalyst activity, especially on supported metal catalysts. It decreases the surface area of the catalyst and changes the surface structure. For a porous catalytic surface, the pores may collapse due to sintering, resulting in loss of surface area. Sintering is in general an irreversible process.
Small catalyst particles have the highest possible relative surface area and high reaction temperature, both factors that generally increase the reactivity of a catalyst. However, these factors are also the circumstances under which sintering occurs. Specific materials may also increase the rate of sintering. On the other hand, by alloying catalysts with other materials, sintering can be reduced. Rare-earth metals in particular have been shown to reduce sintering of metal catalysts when alloyed.
For many supported metal catalysts, sintering starts to become a significant effect at temperatures over 500 °C (932 °F). Catalysts that operate at higher temperatures, such as a car catalyst, use structural improvements to reduce or prevent sintering. These improvements are in general in the form of a support made from an inert and thermally stable material such as silica, carbon or alumina.
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- ^ abMaca, Karl; Simonikova, Sarka (2005). "Effect of sintering schedule on grain size of oxide ceramics". Journal of Materials Science. 40 (21): 5581–5589. Bibcode:2005JMatS.40.5581M. doi:10.1007/s10853-005-1332-1. S2CID 137157248.
- ^ abOghbaei, Morteza; Mirzaee, Omid (2010). "Microwave versus conventional sintering: A review of fundamentals, advantages and applications". Journal of Alloys and Compounds. 494 (1–2): 175–189. doi:10.1016/j.jallcom.2010.01.068.
- ^Babaie, Elham; Ren, Yufu; Bhaduri, Sarit B. (23 March 2016). "Microwave sintering of fine grained MgP and Mg substitutes with amorphous tricalcium phosphate: Structural, and mechanical characterization". Journal of Materials Research. 31 (8): 995–1003. Bibcode:2016JMatR.31.995B. doi:10.1557/jmr.2016.84.
- ^Smallman R. E., Bishop, Ray J (1999). Modern physical metallurgy and materials engineering: science, process, applications. Oxford : Butterworth-Heinemann. ISBN .
- ^ abcdeMittemeijer, Eric J. (2010). Fundamentals of Materials Science The Microstructure–Property Relationship Using Metals as Model Systems. Springer Heidelberg Dordrecht London New York. pp. 463–496. ISBN .
- ^Kang, Suk-Joong L. (2005). Sintering: Densification, Grain Growth, and Microstructure. Elsevier Ltd. pp. 9–18. ISBN .
- ^Cahn, Robert W. and Haasen, Peter (1996). Physical Metallurgy (Fourth ed.). pp. 2399–2500. ISBN .CS1 maint: multiple names: authors list (link)
- ^Carter, C. Barry; Norton, M. Grant (2007). Ceramic Materials: Science and Engineering. Springer Science+Business Media, LLC. pp. 427–443. ISBN .
- ^Cahn, Robert W. and Haasen, Peter (1996). Physical Metallurgy (Fourth ed.). ISBN .CS1 maint: multiple names: authors list (link)
- ^Smith, Cyril S. (February 1948). "Introduction to Grains, Phases and Interphases: an Introduction to Microstructure".
- ^ abG. Kuczynski (6 December 2012). Sintering and Catalysis. Springer Science & Business Media. ISBN .
- ^Bartholomew, Calvin H (2001). "Mechanisms of catalyst deactivation". Applied Catalysis A: General. 212 (1–2): 17–60. doi:10.1016/S0926-860X(00)00843-7.
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- ^Figueiredo, J. L. (2012). Progress in Catalyst Deactivation: Proceedings of the NATO Advanced Study Institute on Catalyst Deactivation, Algarve, Portugal, May 18–29, 1981. Springer Science & Business Media. p. 11. ISBN .
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|Look up sintering in Wiktionary, the free dictionary.|
How Gold Plating is Done, Step by Step
Editor’s Note: In our last article, Calla Gold, a Santa Barbara jeweler specializing in custom jewelry design and jewelry repair, described gold plating and its best practices. In this article, she describes the step-by-step process.
How Gold Plating is Done, Step by Step
by Calla Gold
Gold plated – sometimes called electroplated – items are made with a layer of gold on the surface over another type of metal underneath. On some occasions, items are gold plated to try and fool buyers or cash-for-gold operators. But for the most part, plating is done to enhance the look or wearability of a piece of jewelry.
Gold plating is an easy technique, but before beginning the process, make sure your plater follows the best practices for best plating results.
Step 1: Surface Preparation
The surface of the metal to be plated must be very clean, so oils or dirt must be removed, and the piece must be polished. Surface preparation can include stripping, polishing, sandblasting, tumbling, etc. The use of solvents, abrasive materials, alkaline cleaners, acid etch, water, or a combination can be used. Typical methods to clean include acid or non-acid ultrasonic bath and a high rpm rouge wheel polishing. This is necessary for two reasons:
- To improve adherence. (Dust and dirt interfere with the plated metals adhering to the jewelry piece.)
- To keep the plating tanks free of contaminants.
Step 2: Cleaning
After the surface is prepared, and a visual inspection is done, electrocleaning, ultrasonic cleaning, or steaming, usually takes place. This second, deeper, cleaning step must follow to ensure metal is free of oils and dirt, which helps produce superior plating results. Steam cleaning blasts off any remaining oils that managed to hang on during the polishing phase. Take special note of intricate jewelry that has many nooks and crannies.
Step 3: Rinse
The piece is rinsed thoroughly with water to remove any cleaning agents.
Step 4: Strike
A strike layer — also called a flash layer — adheres a thin layer of high-quality nickel plating to the base metal.
In order to improve the bonding between the plating and the underlying surface, occasionally a buffer layer must be applied between them. With costume jewelry the base metal would contaminate the tanks with the gold in them, so a different metal is plated prior to the gold plating.
Additionally this step is used when the base metal, like copper, is known to atomically migrate outside of the gold layer to create spots of tarnish after plating. This strike step creates a barrier between the reactive base metal and the plated metal. This extends the life of the bright gold plating.
Step 5: Rinse Again
The piece is rinsed thoroughly with water to remove any cleaning agents.
Step 6: Base Coat
If a base coat below gold is used, it is usually nickel.There can be many layers of plating done on one particular piece. For example a gold-plated silver article is usually a silver substrate with layers of copper, nickel, and gold deposited on top of it.
Step 7: Final Coating
With time, temperature and voltage carefully controlled, the piece is submerged into the plating solution to attract ions of gold or the final metal that will show on the surface. Different metals require different voltages and temperatures.
The items to be plated are hung from a cathode bar, which is a pole with a negative electrical charge going through it. The pieces of jewelry connected to the cathode bar are also negatively charged. When the jewelry items are submerged in the tank an electrical charge is applied and the negatively charged jewelry attracts the positively charged ions present in the solution. The positively charged metal ions are submersed in the solution bath. When the cathode bar is lowered into the bath the metal jewelry gets plated.
The plating thickness can be controlled by adjusting the immersion time in the plating tank.
Step 8: Final Rinse
Rinse off the pieces with water and then hang them to dry.
Step 9: Drying
The pieces are hung, preferably not touching each other, in order to dry.
Step 10: Repeat – if Necessary
Occasionally, the immersion step into the chosen plating metal needs to be repeated. In order to improve the bonding between the plating and the underlying surface, occasionally a buffer layer must be applied between them.
After that step, rinsing and drying needs to be done.
There are different metals used as the base metal in costume jewelry. Some of these base metals would contaminate gold plating tanks. It is for this reason that a different metal is plated in a prior step to the gold plating.
Gold plating has varying levels of ‘clingyness’ to different metals. For example gold has an affinity to silver. This translates to gold plating over silver lasting longer than gold plating over various base metals. Gold plating is long lasting over a base of gold. For example 18kt gold plated over 14kt gold lasts longer than 18kt yellow gold over sterling silver. So whatever metal is being used for the base in gold plating, it plays a significant role in how long the plating treatment will last.
If you would like to see pictures of the plating process, visit Calla’s website (see below).
As you can see, the naked eye may not be able to tell exactly which metal makes up a piece of jewelry. To be absolutely sure of the value of the precious metals you buy, use, and sell, you can utilize x-ray fluorescence technology. XRF precious metals analyzers are fast, simple, nondestructive solutions for gold analysis. You can measure the content of all gold and precious metals, as well as determine the presence and concentration of other trace, alloying elements, and dangerous heavy elements, which could impact health and the valuation of your pieces.
Reader’s Question: I have a pair of earrings and I would like to have them gold plated. I have noticed a slight difference in color were the prong is soldered to the base of the earring. Will the gold plating cover the color difference making just that spot more uniform?
Answer: My short answer to the question is that gold plating is immersive and will be the same color regardless of subtle color differences on the underlying metal. With silver that has been gold plated, when it oxidizes, that can cause the gold plating to darken in spots. If the other color metal in your earrings is a metal that oxidizes. Then it is possible that over time that oxidation could show up as darker, like a shadow in the gold plating.
About the Author:
Calla Gold, owner of Calla Gold Jewelry, has been a Santa Barbara personal jeweler since 1983, specializing in custom wedding ring design, jewelry repair, ring resizing and antique jewelry restoration. Her motto is, “Wear it, don’t warehouse it!” Calla shares her tips and advice on the topic of jewelry regularly on her blog and social media. She is a contributor to MJSA (a leading resource in jewelry making and design). Calla Gold is a jeweler without walls, coming to your home and office by appointment or over distance on the Internet. For more information on Calla Gold Jewelry, visit www.callagold.com
6 Best Wood Glue Reviews: Extra Strong Glue for Woodworking & Hobbies
Do you have some DIY carpentry tasks to complete around your home? Are you a crafts enthusiast or do you love to create your own jewelry? If so, then you need some super strength wood glue. As well as being the best type of adhesive for bonding two pieces of wood together, wood glue is a very versatile liquid as you can use to glue together a lot of different materials from wood to plastic to porcelain.
However, choosing the right type of wood glue that is perfectly suited to your home maintenance task or hobby will depend on the type of material you will be working with. It also depends on whether you will be using the glue for indoor or outdoor applications. Not all glue products can be used for the same purpose.
Some are specially designed for indoor applications like hobby-related tasks or fixing a kitchen cupboard. While other glues are designed for outdoor projects like fixing outdoor furniture or a cedar deck, or building a birdbath, while others can be used for both indoor and outdoor applications.
The 6 Best Wood Glues
- Gorilla Wood Glue
- Titebond 5004 II Premium Wood Glue (Our Top Pick)
- Titebond 1413 III Ultimate Wood Glue
- Elmer’s E7010 Carpenter’s Wood Glue
- GLUE MASTERS Professional Grade Cyanoacrylate “Super Glue”
- FastCap 2P-10 Super Glue Adhesive
Our Top Pick for the Best Wood Glue
Our top pick for the best wood glue is the Titebond 5004 II Premium Wood Glue.
This premium glue is the perfect choice for fixing outdoor furniture or completing indoor DIY repairs. There is a lot to love about this high-quality glue. It is very easy to apply and can be used for bonding all types of wood. It also has an outstanding bonding strength and it comes at a very affordable price.Check the price on Amazon
How to Choose the Right Wood Glue
The first thing to consider is what the wood glue consists of, like the different chemical variants or bonding agents that make up the glue’s bonding system. Also, the glue could be white or yellow in color which can make a difference to the appearance of the wood grain. Wood glues come in different adhesive strengths and different thickness or viscosity.
In your search for the right type of wood glue for your project, the first thing you need to consider is the chemical bonding agents that make up the glue’s bonding system.
5 Types of Wood Glue
1. PVA Glue
PVA glue, also known as Polyvinyl Acetate, is the most common type of glue that can be found in the home. It is also an inexpensive and highly effectively bonding agent for basic indoor woodworking projects. It is non-toxic and can easily clean up with water. Some glues, like the Titebond-II Premium Wood Glue, contains a cross-linking polyvinyl acetate that gives the glue a higher level of water-resistance. So you can also use it for most outdoor woodworking applications.
Although PVA glue can leave behind dried bits which can spoil the overall aesthetic appeal of furniture or a hobby-related project, this can be easily fixed by making sure that you do not apply too much of the glue, or wipe off any excess glue before it dries.
2. Cyanoacrylate (CA) Wood Glue
Cyanoacrylate (CA) glue, also called “super glue”, is used to bond two hard pieces of material together. It is the best choice for quick and easy repairs as it cures or sets in a very short period of time. When the glue dries, it forms a hard plastic-like bond. However, when you apply it, the glue can be runny and messy. Its industrial strength bonding power means you have to be extra careful that you do not get the glue on your fingers or hands as it can bond to your skin instantly!
3. Epoxy-Based Glue
Epoxy-based glue uses a two-part bonding system: a resin and a hardener and it is specially formulated for filling gaps in softwoods and hardwood. It also works very well at bonding two pieces of wood together. However, it takes a while to bond. You will also need to clamp the wood down to create a stronger bond.
Although some epoxy wood glues are designed for indoor use only, some glues like the Titebond III Ultimate Wood Glue is water-resistant so it can as well as also for Metal & Stone Cutting - Free Activators used for indoor and outdoor woodworking applications.
4. Polyurethane Wood Glue
Polyurethane glue is one of the strongest and most durable types of wood glue. It is very versatile as it can be used for a lot of different materials like wood, plastic, stone, metal, ceramic, foam, glass, and concrete. Gorilla Wood Glue is one of the most popular polyurethane-based glue products available. Its high level of waterproofing makes it an excellent choice for both indoor and outdoor applications.
It can also be used for softwoods and natural wood composites as it dries a natural-looking color, which will maintain the integrity of the wood grain.
One thing to remember with polyurethane-based wood glues is that you need to wet the surface of the wood before you apply it. The moisture makes sure the glue expands as it cures or sets, which creates an extra solid bond. When the polyurethane glue dries, during the clamping process, you can sand down the wood and then paint or stain it once the glue has fully dried.
To clean any leftover glue, you will need to use mineral spirits while the glue is still wet.
5. Hide Glue
Hide glue is derived from animal hides, and while some hide glues come as a solid substance and have to be applied with a brush, some glues come in a liquid form in an applicator bottle. This type of glue can be used for antique furniture repair and can create an attractive “crackling” effect, as well as being a very effective adhesive agent for other materials like cloth, glass, and leather.
White Glue vs. Yellow Glue
White Glue is an all-purpose glue and is usually used for indoor projects like crafts and hobby-related tasks. It bonds by water evaporation, which means it can be easily cleaned up with water and dries within 20 to 30 minutes, depending on the type of material you are using.
Yellow glue is usually not water-resistant so it is not ideal for outdoor use. However, it cures quicker than white-colored glue and can be sanded down a lot easier. One of the downsides of using yellow glue is that it can show through the final finish or stain of the wood. So to maintain the overall wood grain, depending on the color of the wood, use a tan or natural wood colored glue.
The viscosity of the wood glue relates to the level of the liquid’s consistency. Some wood glue products have a low viscosity, which makes them ideal for filling in hairline cracks, re-bonding preassembled furniture repairs, and for hobbies-related tasks or making jewelry. However, the glue can be runny and messy. If you prefer a low-viscosity glue, which is a faster drying glue, use a damp cloth and quickly wipe up any leftover glue before it dries.
Wood glue that has a thicker viscosity works very well with more heavy-duty DIY tasks like bonding two pieces of wood together, while a medium-level or well balanced thick viscosity glue is designed for general purpose applications. So you can use it for bonding wood, leather and fiberglass, filling in medium-sized gaps, and larger-scale hobby-related projects.
5. Tips for Using Wood Glue
- Once you have purchased your new wood glue product, remember that most glues have a shelf life of 12 months and may start to lose their bonding potency after this time has elapsed. There are some glues that have a longer shelf life, up to 24 months. However, most last up to 12 months.
- To avoid the nozzle from clogging up with glue, clean the nozzle after use.
- Always wear gloves when working with polyurethane or “super-glue” type wood glues. If the glue gets on your fingers, it can be difficult to remove.
- Also, if you do get glue on your hands, consult the instructions on the back of the product on how to remove the glue. If it gets into your eyes, consult a medical professional immediately!
- If you are a DIY enthusiast or just love woodworking then have a look at this YouTube video for some helpful woodworking tips and techniques.
6 Best Wood Glues – Reviews
1. Gorilla Wood Glue
If you have some outdoor or indoor DIY woodworking tasks to perform, Gorilla Wood Glue is one of the strongest polyurethane wood glues available. As its name suggests, the proudly made in the US wood glue is super strong and outperforms any other wood glue. Its excellent adhesive strength means the Gorilla wood glue penetrates deep into the wood grain, at least 2-inches deep, to create a super-strong bond.
Gorilla wood glue is water-resistant and is compliant with ANSI/HPVA Type II water-resistance levels. So it is an excellent choice for any outdoor woodworking applications. However, you can also use it for indoor tasks like hobby-related or DIY projects. An incredibly versatile product, Gorilla glue can be used on hardwood, softwood, and natural wood composites and when you apply the glue it is an off-white color but it dries to a natural tan-looking color to maintain the integrity of the wood grain.
The glue can also be used for stone, metal, ceramic, foam, glass, and concrete. So whatever type of task you have that requires super strength glue, Gorilla will give you the bonding power you need.
The glue is easy to apply and requires only 20-30 minutes of clamp time. It also fully cures or sets in 24 hours. You can also use it in both hot and cold climates. Gorilla glue is available in a range of packs.
- Super strong wood glue
- Excellent price
- Can use it indoors or outdoors
- Highly water-resistant
- Ideal for carpentry, hobbies, crafts, and building projects
- Can be used for hardwood, softwoods and natural wood composites
- Can also be used for stone, metal, ceramic, foam, glass, and concrete
- Fast drying
- Thick viscosity
- Dries to a natural tan color
- Dispenser nozzle is hard to clean
2. Titebond 5004 II Premium Wood Glue
For more than 65 years, Franklin has been the main industry leader in wood glue bonding products, and their dedication to creating a reliable wood glue is reflected in this premium superior strength Titebond 5004 II Premium Wood Glue.
A highly versatile one-part wood glue with good thick viscosity and it was one of the first cross-linking polyvinyl acetate wood glue to pass the ANSI/HPVA Type II water-resistance specification. So the Titebond wood glue is the perfect choice for all types of outdoor and indoor woodworking applications and can be used for softwood, medium woods, and hardwoods.
Whether you are constructing or fixing outdoor furniture, the Titebond wood glue creates a solid bond and it has a fast setting time in 60 minutes and it sets in 24 hours. The honey cream-colored wood glue, which dries to a translucent yellow color has an excellent sandability, and it is ideal for radio frequency (R-F) and Hot Press Gluing Systems.
And as it is FDA approved for indirect food contact, the glue can be used for culinary hardware applications like a cutting board.
Although the glue has a thick viscosity, it may be a little runny for some applications. So keep a sponge handy and immediately wipe off any excess glue after clamping, and to maintain the excellent level of sandability that the wood glue can provide, make sure that you do not over-apply the wood glue. Remember: Less is more!
The Franklin Titebond wood glue also comes in a very handy two-pack. The glue is designed to be used in temperatures above 55°F, and it has a storage life of 24 months.
- Great price
- Excellent wood glue
- Creates a superior solid bond
- Can be used for indoor and outdoor applications
- High water-resistance
- Excellent sandability
- Non-clogging nozzle
- Ideal for radio frequency (R-F) and Hot Press Gluing Systems
- Can be used for culinary hardware applications
- Storage life of 24 months
- Not ideal for low temperatures, under 55°F
- Not thick enough for some applications like hobby-related tasks
- Dries a translucent yellow
3. Titebond 1413 III Ultimate Wood Glue
For the ultimate adhesive in wood glue, the Titebond 1413 III Ultimate Wood Glue is an excellent choice for indoor and outdoor woodworking applications and it is fully waterproof! Whether you are designing and building your own furniture, fixing antique furniture, or redesigning a cedar deck, the Titebond epoxy-based tan-colored wood glue creates a super-strong bond and it has a high level of sandability and it dries quickly.
If you are using unstressed joints, you will need to clamp the wood from 30 minutes to an hour and for stressed joints, the wood needs to be clamped for 24 hours. The tan-colored glue passes the ANSI/HPVA Type I water-resistance test and as it is solvent-free and non-toxic, it is FDA approved for indirect food contact and it can be easily cleaned up with water.
Titebond also makes a hide glue that is specially designed for fine furniture repair and will create an excellent “crackling” effect. The hide glue can also be used for cloth, glass, and leather.
- Excellent price
- Superior adhesive strength
- Can be used for outdoors and indoors
- High level of sandability
- Non-toxic and solvent-free
- FDA approved for indirect food contact
- Not very viscous and can be difficult to work with
- Dries to a light brown
4. Elmer’s E7010 Carpenter’s Wood Glue
For over 60 years Elmer’s Carpenter’s Wood Glue has been America’s favorite wood glue. As it is designed with carpenters in mind, Elmer’s Wood Epoxy Glue gives you a superior strength adhesive bond, so it is an excellent choice for all types of indoor woodworking projects and DIY repairs. It works best with soft and hardwoods, particleboard, and porous materials.
The glue is yellow in color but it dries to a light tan color so it can be used for natural-looking wood and lightly stained woods.
Besides its solid and secure bonding power, Elmer’s glue dries quickly in 15 minutes and the clamp time is 12 hours. Once you apply it with a paintbrush, the glue will not be visible, so all you see is solid wood, which is ready for sanding and polishing. The wood glue is non-toxic and it emits no harmful fumes and it is also easy to clean up with water. Elmer’s Wood glue is available in a variety of sizes.
- Very affordable price
- Excellent wood glue
- Ideal for carpentry and home repairs
- Creates a super strong and invisible bond
- Non-toxic and no harmful fumes
- Sandable and paintable
- Easy to clean up with water
- Glue is available in a variety of sizes
- Not suitable to use for outdoor applications
- Not stainable
5. GLUE MASTERS Professional Grade Cyanoacrylate “Super Glue”
If you are a crafts enthusiast or have some model cars that need repairing, then the GLUE MASTERS Professional Grade Cyanoacrylate “Super Glue” is the perfect choice for you as it is very strong and easy to use. From building model trains or classic toy cars to creating your own stunning range of jewelry, the industrial-strength Triple Distilled cyanoacrylate-resin which is contained in this amazing glue will create the strongest bond.
It also has a longer shelf life than other wood glue products. A little bit goes a long way. Just apply a small amount of the magic glue and watch it go to work in just under 60 seconds.
One of the highlights of this “super glue” is its well balanced thick viscosity that offers a very high level of gluing control to the user, by providing a nice even flow so that you can bring your antique model car or jewelry creation to life. The glue dries clear so it will not spoil the appearance of your final product. A highly versatile glue, the Professional Grade wood glue can be used for other materials such as porcelain, metal, and plastic.
Customer satisfaction is of the utmost importance to GLUE MASTERS and they offer you an unbeatable 60-day guarantee. If the “Superglue” does not meet up to your expectations, just send the bottle to the manufacturer and they will give you back your money.
As this glue has industrial strength bonding power, be very careful that you do not get any on your hands as it can bond to skin instantly! Although the glue has a thick viscosity, it may still be a little thin for some applications, so GLUE MASTERS also makes a wide range of glues that come in different levels of viscosity.
- Excellent value for money
- Triple Distilled industrial strength bonding power
- Ideal for hobby-related projects and DIY repairs
- Thick viscosity
- Versatile: can use it for wood, porcelain, metal, and plastic
- Dries clear and shiny
- Available in a large range of viscosity levels
- May not be thick enough for some applications
- Not ideal for large woodworking repairs
6. FastCap 2P-10 Super Glue Adhesive
This super combo adhesive and activator pack from FastCap is an excellent choice for carpentry and general bonding applications.
The pack contains a 12-ounce activator aerosol can and a 2.25-ounce thick viscosity adhesive spray bottle. So if you are planning a larger scale DIY project like redesigning your kitchen or just need an emergency glue to keep your glasses together, the powerful cyanoacrylate-based FastCap glue and activator spray will have the job done fast!
The adhesive glue can be used on other surfaces besides wood-like plastic and granite, and with FastCap’s innovative two-part bonding system, the bonding process only takes a mere 10 seconds to execute and a curing time of just 30 seconds and the products are very easy to use.
Simply apply the water-resistant adhesive to one surface and the spray activator on the other surface. Press the two sides together to create a firm, permanent bond, which will give your furniture or woodworking creation a professional finish.
The glue is a great choice for those circumstances where clamps are difficult to use or unavailable, and the caps on each product are non-clogging, so the spray and applicator bottle is always ready to use.
- High-quality wood glue
- Excellent value for money
- Two-in-one value pack: aerosol accelerator spray and adhesive applicator bottle
- Super strong wood glue
- Ideal for wood, granite, and plastic
ConsCheck the price on Amazon
Our Top Pick for the Best Wood Glue
Our top pick for the best wood glue is the Titebond 5004 II Premium Wood Glue.
This premium glue is the perfect choice for fixing outdoor furniture or completing indoor DIY repairs. There is a lot to love about this high-quality glue. It is very easy to apply and can be used for bonding all types of wood. It also has an outstanding bonding strength and it comes at a very affordable price.Check the price on Amazon
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How to Care for Soldering Tips
Weller Soldering Iron Tip Care Guide
The tip of any soldering iron is the most critical component in the performance of the tool. If it cannot perform its function of effective heat transfer to the connection point, the soldering iron itself will be unreliable. Poor tip maintenance is one of the leading cause of soldering problems.
Soldering tips wear out over Cleaning Suite Professional Crack and eventually need replacing, but taking steps to care for your tips can extend their life, save you money and improve the results of your soldering work. Follow these tips to reap the benefits of proper soldering iron tip care.
Using High-Quality Solder
One of the best preventive measures you can take to protect your solder tips is to use high-quality solder. If you use low-quality solder that contains impurities, those contaminants may build up on the tip, get it in the way of heat transfer and make your soldering work more difficult.
Purchasing solder from reputable brands is one way to increase certainty that the product will be of a high quality. You can also test the quality of solder by heating it and observing how easily wise care 365 pro crack - Free Activators melts. Good-quality solder should melt readily at the expected temperature, while low-quality solder may not melt completely. Most 60/40 (tin/lead) solder, for example, should melt easily at around 460 degrees Fahrenheit.
If you use solder that contains lead, the appearance will also give you an idea of its quality. Melted leaded solder will appear shiny, while a low-quality product will look more matte. High-quality melted lead-free solder also has a matte appearance.
Different types of solder will act differently, so it's essential to check the manufacturer's description to ensure it performs as expected.
It's also vital to choose the right type of solder for your project. The composition you want depends on the material you plan to solder and whether you're using flux, as well as health and safety concerns. The U.S. Safe Water Drinking Act, for instance, requires you to use lead-free solder on all lines that will carry drinking water. The size of the project will determine the solder diameter that's right for you.
You should also take care to only use as much solder as you need. Excess solder can end up in the socket or base and cause short circuits and jammed switches.
Maintaining Optimal Temperature
Keeping the temperature of your tips as consistent and as close to optimal as possible will help extend their life.
When using many soldering irons, the temperature of the tip will naturally decrease when in use. To compensate for this, many solderers turn up the heat more than is needed. Using excessive temperatures, however, reduces the life of your tips and can lead to sub-optimal results.
Soldering station irons that have a temperature sensor can help regulate temperature for you without damaging your tips. These irons can sense when the temperature has dipped or risen out of the intended range and automatically adjust it. Some soldering irons have more accurate temperature regulation than others. Recovery time, which is the time it takes the tip to return to the desired temperature, also differs between soldering iron models.
The temperature you set the iron to also impacts tip life. Avoid using temperatures that are higher than you need them to be to help protect your tips. This principle also applies when you aren't actively using your iron. Make sure to reduce the temperature to an "idle" setting or turn off the unit when not using it for extended periods. Some irons will automatically decrease their temperature when not in use.
Weller soldering irons offer excellent temperature stability. The WEP70 iron of The Weller WE 1010, for example, has a temperature stability of plus or minus 10 degrees Fahrenheit (± 6 degrees Celsius). It also has a standby mode and auto setback feature that reduces the temperature of the iron when it's idle.
Cleaning Your Tips
To care for your equipment, you need to know how to clean soldering iron tips. Keeping your tips clean is crucial to ensuring that they perform properly, and it can also extend their life. You should clean them before, during and after use. You can tell your tip is clean when it appears bright and shiny.
Before soldering, use alcohol and a clean cloth to remove contaminants such as grease, corrosion and oxidation from the surface to be soldered.
To clean your tips, use either brass or stainless steel wool. Brass wool is softer and less abrasive, while the harder stainless steel wool has a longer life.
Metal wool effectively removes dirt and other contaminants and avoids issues associated with using a damp sponge to clean soldering tips. Using a wet sponge will reduce the heat of the tip. Frequent wiping with a damp sponge causes repeated changes in temperature, causing the tip to expand and contract repeatedly. This cycle causes metal fatigue and eventually the failure of the tip.
Cleaning wool will not reduce the temperature of the tip. To remove small amounts of contaminants from your tips using metal wool, gently dab them into the wool. For more stubborn residue, hold the iron more firmly and apply more pressure when rubbing it against the wool. Vary the strokes, so you remove contaminants from all sides and edges of the tip.
After cleaning, immediately wet the tip with fresh solder to prevent oxidation.
For heavier-duty cleaning, you can occasionally use a Weller WPB1 cold-tip polishing bar. Only use this device when the tip is cold, as using it with a hot tip can damage the tip.
If a tip does become as well as also for Metal & Stone Cutting - Free Activators, flush it several times with a rosin-activated, flux-cored solder. That should remove the oxides unless you have allowed the oxidation to build up excessively. After cleaning, cover the tip surface with a thick coating of solder.
When many metals come into contact with the oxygen in the air, they form an oxide layer. This layer of oxidation prevents solder from adequately wetting the joint and negatively impacts the quality of the soldering joint.
Flux is a substance that removes this oxidation layer. The flux dissolves the metal oxide layer, which evaporates once the flux reaches its boiling point.
Flux may come in paste form, or it may be in the core of a soldering wire, which allows it to work as you are soldering the part with no extra effort.
Avoid dipping your tips into flux to clean them, as the substance is corrosive. Some fluxes, called water-soluble fluxes, can damage tips at higher temperatures. Many solderers only use these fluxes when doing projects that require wave soldering, immediately followed by a full cleaning to remove excess flux residue on the circuit board. Using wire solder and water-soluble flux for touch-up and rework operations will still hasten tip failure.
Another type of flux, no-clean flux, is only for soldering parts that require little to no cleaning. This very mild cleaning action normally isn't thorough enough to remove oxidization from soldering iron tips. A badly oxidized tip will be easy to spot because of “burnout,” which is the appearance of black or brown coating.
Tinning Your Tips
You should tin your tips before and after each soldering session, as well as in between soldering every two to three joints. You want to keep your tip tinned at all times, from the first time you use it until you discard it. When you tin a tip, you cover it with a thin layer of solder.
Tinning stops your tips from oxidizing by creating a protective layer between the air and the iron. It's essential to keep your tip tinned, since iron oxidizes rapidly. Oxidation prevents the tip from transferring heat efficiently. Preventing oxidation through tinning extends the life of your tips.
Keeping your tips tinned also helps make soldering easier. It helps your solder wire melt and flow better, making soldering easier. The coating creates a heat bridge between the tip and the part you're soldering, which increases the efficiency of the heat transfer.
To tin a tip, follow these steps. First, clean the tip. Then, apply fresh solder to the tip. Use a small amount — enough to coat it thoroughly. The tip should still appear shiny.
If you are just starting your session, begin soldering as soon as you finish tinning the tip. Throughout a project, clean and then tin your tip after every few joints. If you're tinning a tip after completing a project, wipe the tip again briefly after tinning and then turn the iron off and put it away.
Reactivating Your Tips
If a tip becomes oxidized, it will appear dark, and you may not be able to tin it. To fix this problem, you can use a tip activator to reactivate or re-wet it.
To reactivate the tip, dip it into the paste-like activator substance and move it around until it starts to become shiny again. The fine abrasives and additives within the activator will break down and remove the oxide layer.
Once the tip looks mostly clean, remove it from the activator and clean it using brass or steel wool. Then, re-tin it immediately. Flushing the tip with solder by re-tinning it will remove any remaining contaminants. Then, clean it and re-tin it again. You should then be able to use the tip without trouble.
Weller's high-quality tip activator is lead-free and RoHS-compliant. Reactivating your tips using this product will keep your tips in good condition, make soldering easier and improve the quality of your results.
The way you store your soldering iron tips can also impact how well they perform and how long they last. Following some simple procedures when storing your tips can help protect them.
When storing a tip for a shorter period, such as between soldering joints in one soldering session, store it in the iron in a secure iron holder. Ensure it does not stay at the operating temperature, as this will decrease the life of the tip. You can store many Weller irons at an idle setting, which keeps them at a lower temperature but still ready to be used.
If storing your tips for an extended period, you should clean and tin them before putting them away, which will help prevent them from oxidation. After letting them cool, you may also want to store them in a sealed container, such as a bag or case, to further protect them from oxidation, humidity and contamination.
When storing a tip in the iron, loosen the nut or screw that holds it in place before putting the iron away. This practice will prevent the tip from becoming stuck, an issue known as seizing.
Changing Soldering Iron Tips
Weller seeks to make it easy to remove, change and reinsert our soldering iron tips. It doesn't take long to learn how to change Weller soldering iron tips. With our WE 1010 soldering iron station, for example, you can manually change out tips without any additional tools.
When inserting tips, always make sure you have positioned them correctly in the barrel. You can keep the screw or nut that secures the tip slightly loose to prevent it from seizing. Many of our models have a stainless steel liner in the sensor hole in the base of the tip to prevent the tip from seizing to the sensor.
We recommend using genuine Weller tips for optimal performance and a long lifetime. We offer a wide range of tips so you can find the perfect tool for any job. Our tips are precisely matched with our homogeneous heating system, use only the highest-quality materials and provide a fast and stable heat delivery.
You can identify genuine Weller tips by the “Genuine Weller Seal of Quality" and the Weller logo and tip part numbers engraved on the tip.
Recycling Your Tips
When you use high-quality products and take proper take care of them, they can last an extraordinarily long time. Eventually, though, tips wear out. Weller makes it easy to dispose of your tips in an environmentally friendly and economical way. We'll even send you a voucher you can put toward your next purchase of Weller tips if you mail your used tips to us for recycling.
Here's how it works. Just request a free tips recycling box from us. Once you fill up the box, send it back to us so we can recycle the tips in an environmentally responsible way. We accept any tips from any manufacturer. For every full box you send us, we'll give you a $75 voucher you can use toward the purchase of Weller tips from participating distributors.
Expect Outstanding Results With Weller Tools
If you follow the above advice about Weller soldering iron tip care, you can extend the life of your tips, save money and improve the quality of your soldering work. Proper care of your soldering equipment starts with using the best equipment and accessories. Weller tips and our other soldering equipment, such as the WE 1010 soldering station, provide economical operation and high-quality, repeatable results. To learn more, explore the rest of our website or that of a distributor today. as well as also for Metal & Stone Cutting - Free Activators
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