Shielded Metal Arc Welding (SMAW)
The Shielded metal arc welding process uses an electric arc between a consumable flux-covered metal electrode (stick) and the base metal (metal being welded). Heat from the electric arc melts both the end of the electrode and the base metal to be joined. This process is often used for maintenance work and small production welding. Heavy pipe welding is done almost exclusively with shielded metal arc welding.
Welders must wear an approved helmet with proper lenses for shielded metal arc welding, gloves, and protective clothing. The welding workstation must be well ventilated.
Gas Tungsten Arc Welding (GTAW)
Gas tungsten arc welding uses the heat of an electric arc between a nonconsumable tungsten electrode and the base metal. A separate welding filler rod is fed into the molten base metal, if needed. A shielding gas also flows around the arc to keep away air and other harmful materials. Gas tungsten arc welding is particularly desirable for welding stainless steel, aluminum, titanium, and many other nonferrous metals. GTAW can be done in any position with excellent results. The nonstandard term TIG (tungsten inert gas) welding is also used to identify this process.
Gas tungsten arc welding generates intense heat and light, with no metal spatter. The welder must wear an approved welding helmet, gloves, and welder’s clothing.
Gas Metal Arc Welding (GMAW)
In gas metal arc welding, an electric arc between a continuously fed metal electrode and the base metal produces heat. The heat melts the base metal and the electrode, creating the weld. The arc is shielded by a gas that is supplied through the torch. This process is popular in production and repair shops. It is often referred to by the nonstandard term MIG (metal inert gas) welding.
When welding GMAW, the welder must wear an approved helmet, gloves, and welder’s clothing. The welding area must have good ventilation.
Oxyacetylene Welding (OAW)
The oxyacetylene welding process combines oxygen and acetylene gases to provide a high-temperature flame for welding. The flame provides enough heat to melt most metals. Other Oxyfuel joining processes include oxyfuel gas welding, torch soldering, and torch brazing. Commonly used fuel gases include acetylene, hydrogen, natural gas, butane, propane, and LP gas mixes. Acetylene and oxygen are most often used because when burned together, oxyacetylene produces a hotter flame that any other fuel gas/oxygen combination.
Welding goggles should be worn for eye protection. Gloves, nonflammable clothing, and all other required safety clothing should be worn to protect against burns. Good fire safety and prevention techniques should be employed. Proper ventilation must be provided.