The Job of a Welder – How Metal is Fused or Cut for Industrial Purposes
The arc welding process derives heat from an electric arc between two electrodes or between an electrode and the workpiece. The gas welding process produces heat by burning a mixture of oxygen and some other combustible gas, such as acetylene or hydrogen. The resistance welding process obtains heat from pressure and resistance by the workpiece to an electric current. Two of these processes, the arc and gas methods, can also be used to cut, gouge, or finish metal.
Depending on which of these processes and equipment they use, welders may be designated arc welders, gas welders, or acetylene welders; combination welders (meaning they use a combination of gas and arc welding); or welding machine operators (meaning they operate machines that use an arc welding process, electron-beam welding process, laser-beam welding process, or friction welding process). Other workers in the welding field include resistance machine welders; oxygen cutters, who use gas torches to cut or trim metals; and arc cutters, who use an electric arc to cut or trim metals.
Skilled welders usually begin by planning and laying out their work based on drawings, blueprints, or other specifications. Using their working knowledge of the properties of the metal, they determine the proper sequence of operations needed for the job. They may work with steel, stainless steel, cast iron, bronze, aluminum, nickel, and other metals and alloys. Metal pieces to be welded may be in a variety of positions, such as flat, vertical, horizontal, or overhead.
In the manual arc welding process (the most commonly used), welders grasp a holder containing a suitable electrode and adjust the electric current supplied to the electrode. Then they strike an arc (an electric discharge across a gap) by touching the electrode to the metal. Next, they guide the electrode along the metal seam to be welded, allowing sufficient time for the heat of the arc to melt the metal. The molten metal from the electrode is deposited in the joint and, together with the molten metal edges of the base metal, solidifies to form a solid connection.
Welders determine the correct kind of electrode to use based on the job specifications and their knowledge of the materials. In gas welding, welders melt the metal edges with an intensely hot flame from the combustion of fuel gases in welding torches. First, they obtain the proper types of torch tips and welding rods, which are rods of a filler metal that goes into the weld seam. They adjust the regulators on the tanks of fuel gases, such as oxygen and acetylene, and they light the torch. To obtain the proper size and quality of flame, welders adjust the gas valves on the torch and hold the flame against the metal until it is hot enough. Then they apply the welding rod to the molten metal to supply the extra filler needed to complete the weld.
Maintenance welders, another category of welding workers, may use any of the various welding techniques. They travel to construction sites, utility installations, and other locations to make on-site repairs to metalwork.
Some workers in the welding field do repetitive production tasks using automatic welding equipment. In general, automatic welding is not used where there are critical safety and strength requirements. The surfaces that these welders work on are usually in only one position.
Resistance machine welders often work in the mass production of parts, doing the same welding operations repeatedly. To operate the welding machine, they first make adjustments to control the electric current and pressure and then feed in and align the workpieces. After completing the welding operation, welders remove the work from the machine. Welders must constantly monitor the process in order to make sure that the machine is producing the proper weld.
To cut metal, oxygen cutters may use hand-guided torches or machine-mounted torches. They direct the flame of burning oxygen and fuel gas onto the area to be cut until it melts. Then, an additional stream of gas is released from the torch, which cuts the metal along previously marked lines. Arc cutters follow a similar procedure in their work, except that they use an electric arc as the source of heat. As in oxygen cutting, an additional stream of gas may be released when cutting the metal.
