LYCOS RETRIEVER 
Welding: Metals
built 650 days ago
After welding, a number of distinct regions can be identified in the weld area. The weld itself is called the fusion zone—more specifically, it is where the filler metal was laid during the welding process. The properties of the fusion zone depend primarily on the filler metal used, and its compatibility with the base materials. It is surrounded by the heat-affected zone, the area that had its microstructure and properties altered by the weld. These properties depend on the base material's behavior when subjected to heat. The metal in this area is often weaker than both the base material and the fusion zone, and is ... where residual stresses are found.[28]
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Like common stand-alone generators, welding generators are powered by small gasoline engines and have regular 115V and 230V electrical outlets. Used by contractors, farmers/ranchers, maintenance personnel, homeowners and metalworking artists for welding, they ... provide 4,500 to 10,000 watts of power for running tools, lights and appliances. Prices are comparable to, or less than, regular generators of similar quality and power.
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Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed the workpiece, making it possible to make long continuous welds. In the past, this process was used in the manufacture of beverage cans, but now its uses are more limited. Other resistance welding methods include flash welding, projection welding, and upset welding.[23]
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Metal fume fever is caused by breathing in metal oxide particles produced by welding galvanized metal. The particles react with the lining of the lungs, making the worker start to feel sick a few hours after exposure.
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You will become familiar with the physical and chemical properties of commonly used metals in the welding trade. You will study the effect of the heating and cooling cycle involved in welding operations (with particular attention given to the heat affected zone). You will ... review the use of heat to correct distortion and to change the physical properties of metals, and the classification system for identifying metal.
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Governments and councils employs welders to perform maintenance welding that is done on utilities, bridges, etc. Yet another group involves wholesale and retail establishments. These would include auto and agricultural equipment dealerships, metal service centers, and scrap yards.
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