Forge welding
From Wikipedia, the free encyclopedia
Forge welding, or pattern welding is a welding process of heating two or more pieces metal and then hammering them together. Its use is ancient, doubtlessly being the first method devised for the joining of metals. It was first applied to wrought iron and steel, but is now used to join a host of similar and dissimilar metals. However, with the invention of electrical and gas welding methods during the Industrial Revolution, forge welding has been largely replaced.
Forge welding between similar materials is caused by solid-state diffusion. This results in a weld that only consists of the materials without any fillers or bridging materials.
Forge welding between dissimilar materials is caused by the formation of a lower melting temperature eutectic between the materials. For this reason many dissimilar metals welded together with superior properties of the weld.
Often a flux is used to keep the welding surfaces from oxidizing and producing a poor quality weld. The flux also mixes with the oxides that do form and lowers the melting temperature and the viscosity of the oxides. This enables the oxides to flow out of the joint when the two pieces are beaten together. A simple flux can be made from borax, sometimes with the addition of iron filings.
The welding temperature is above the forging temperature, and not so very far away from the melting point of the metal. It is typically 50–90% of the melting temperature. Steel welds at a lower temperature than iron. The metal may take on a glossy, or wet, appearance at the welding temperature. Care must be taken to avoid burning the metal, which is overheating to the point that it gives off sparks from rapid oxidation.
One of the most famous applications of forge welding is in the production of Japanese katana blades. During the process a billet of steel is repeatedly drawn out, folded back and welded upon itself. The katana, kris, and other Damascus steel products are fine examples of pattern welded objects.
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| Welding | |
| Arc welding: Shielded metal (MMA) | Gas metal (MIG) | Flux-cored | Submerged | Gas tungsten (TIG) | Plasma | |
| Other processes: Oxyfuel | Resistance | Spot | Forge | Ultrasonic | Electron beam | Laser beam | |
| Equipment: Power supply | Electrode | Filler metal | Shielding gas | Robot | Helmet | |
| Related: Heat-affected zone | Weldability | Residual stress | Arc eye | Underwater welding | |
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See also: Brazing | Soldering | Metalworking | Fabrication | Casting | Machining | Metallurgy | Jewelry |
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