Welding – is a thermal joining process used to make joints between materials, usually metals or thermoplastics. A heat source is used to melt the base (or parent) materials together and on cooling they fuse together. Some welding techniques use pressure in conjunction with heat, or by itself, to produce the weld.
In many welding processes a filler material of the same or a compatible chemistry is introduced between the base materials forming a weld pool which becomes the joint. Depending on the weld configuration (butt, full penetration, fillet, etc.) the resulting welded joint can be stronger than the base material.
Another general feature of welding is that it requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized.
Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal.
Brazing – is a thermal joining process in which base or parent materials, metal alloys, cermets or ceramics, can be joined by introducing a molten filler metal between their surfaces. In many instances capillary attraction is the force which causes the molten braze filler material to be drawn between the parent materials.
By definition brazing takes place below the melting point of the parent materials but above 450°C. Because the parent materials are not melted during the brazing process the heat affected zone resulting can be less than for other thermal joining processes.
Brazing is a versatile process that can be used to join dissimilar materials such as copper and its alloys, precious metals, ferrous metals, nickel alloys, aluminium, tungsten carbide, PCD and a range of ceramics.
Brazing relies of the parent materials to be sufficiently free from oxides to alloy the molten brazing alloy to form a bond with the parent materials. This is achieved by using a chemical flux, a protective or chemically reducing gas or a vacuum.
Soldering – is a thermal joining process which is similar to brazing in many ways. By definition soldering takes place below the melting point of the parent materials and below 450°C. Because the soldering alloys (soft solders or solders) melt at comparatively low temperatures soldering can be used to join materials that cannot be exposed to high temperatures or where a large heat affected zone is undesirable.
Solders tend to be comparatively soft and not strong materials and in turn soldered joints are not as strong as welded or brazed joints. Like brazing, soldering often makes use of a flux or a protective atmosphere to achieve an oxide free surface upon which the solder can form a bond with the parent materials.
Soldering is a widely used process in the electronics industry and in a wide range of industrial applications.
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