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Industries & Professions /
Welders and Welding Technicians
Welders use various kinds of equipment and processes to create the heat and pressure needed to melt the edges of metal pieces in a controlled fashion so that the pieces may be joined permanently. The processes can be grouped into three categories. 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, plasma 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; oxy-gas 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 method), 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.
Welding technicians fill positions as supervisors, inspectors, experimental technicians, sales technicians, assistants to welding engineers, and welding analysts and estimators. Some technicians work in research facilities, where they help engineers test and evaluate newly developed welding equipment, metals, and alloys. When new equipment is being developed or old equipment improved, they conduct experiments on it, evaluate the data, and then make recommendations to engineers. Other welding technicians, who work in the field, inspect welded joints and conduct tests to ensure that welds meet company standards, national code requirements, and customer job specifications. These technicians record the results, prepare and submit reports to welding engineers, and conduct welding personnel certification tests according to national code requirements.
Some beginning welding technicians are employed as welding operators. They perform manual, automatic, or semiautomatic welding jobs. They set up work, read blueprints and welding-control symbols, and follow specifications set up for a welded product.
As welding inspectors, welding technicians judge the quality of incoming materials, such as electrodes, and of welding work being done. They accept or reject pieces of work according to required standards set forth in codes and specifications. A welding inspector must be able to read blueprints, interpret requirements, and have a knowledge of testing equipment and methods.
Closely related to this work is that of the welding qualification technician. This person keeps records of certified welders and supervises tests for the qualification of welding operators.
Other welding technicians work as welding process-control technicians. These technicians set up the procedures for welders to follow in various production jobs. They specify welding techniques, types of filler wire to be used, ranges for welding electrodes, and time estimates. Welding technicians also provide instructions concerning welding symbols on blueprints, use of jigs and fixtures, and inspection of products.
Equipment maintenance and sales technicians work out of welding supply houses. They set up equipment sold by their company, train welding operators to use it, and troubleshoot for customers.