Welding
Welding is the most common way of permanently joining metal parts. Heat is applied to the pieces to be joined, the metal melts and fuses together to form a permanent bond. The resultant weld joint is as strong as if the two parts were one. Because of its strength, welding is used to construct and repair ships, automobiles, spacecraft and to join steel beams and reinforcing rods in buildings, bridges and highways. There are three basic methods used to create the heat necessary to weld metals. The most frequently used process is called arc welding and uses electricity to create heat as electrical current arcs between the tip of an electrode and the metal parts to be joined. In resistance (or spot) welding, heat is created by resistance to the flow of electrical current through the metal parts. In gas welding, the flame from the combustion of gases is used to melt the metal. It is the welder's responsibility to control the amount of heat and the size of the melted area and to add the proper amount of filler material so that the parts form a strong bond or joint. Welders must know how to use gas and electric welding equipment safely, and how to plan their work from drawings or specifications.
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