10.1 History of GMAW
Stephanie Oostman
Development of GMAW
While electric arc welding started in the 1800s, gas metal arc welding (GMAW) didn’t make it onto the welding scene until the 1920s when General Electric designed it under similar constructs of gas tungsten arc welding (see Chapter 11). It was an early version based on the concept of using a consumable, continuously fed electrode operating on a constant voltage (CV) circuit. It wasn’t until the Battelle Memorial Institute picked up the development of the process in 1948 that we began to see the wire-feeding process that we are more familiar with today. GMAW has continuously had advancements and improvements since its inception.
GMAW was used for exclusively joining nonferrous metals until 1953, when the use of carbon dioxide (CO2) was introduced as an atmospheric shielding gas. This change in gas mixtures allowed for both ferrous and non-ferrous welding applications. However, the only transfer mode—which we will explore in detail later in this chapter—developed at the time was spray transfer, which used a large-diameter electrode wire. The addition of CO2 to the shielding gas in steel applications meant higher heat, which in turn discouraged some welders from using it and limited the versatility the process now holds in the present day.
Then in 1958 to 1959, short circuit transfer mode was developed, which allowed for a smaller diameter electrode wire to be utilized. It took a more advanced power supply but required lower heat levels, making it popular with the growing sheet metal industries at the time. Its smaller wire is also how this process came to be called micro-wire and the behavior of short circuit transfer mode earned the term dip transfer.
More advancements were made in the 1960s and 1970s to the original spray transfer process, introducing what is called spray transfer pulse, which assisted in lowering overall heavy heat input into the work pieces, among other benefits.
GMAW and other welding processes are continuously updated as equipment manufacturers and technology advance. This is by no means a fully encompassing history of GMAW, and the welding technology will adapt further in our lifetimes.
Basics of the Process
GMAW is what is referred to as a semiautomatic process. because although the welder controls the gun and the travel speed, travel angle, work angle, and electrical stickout (the length the electrode wire protrudes from the end of the nozzle), they preset the wire-feed speed (WFS), current, voltage, and gas flow rate (typically in cubic feet per hour) on the welding machine before starting. GMAW could be set up as a fully automatic welding process if used in conjunction with a computer numerical control or robotic type system.
The GMAW process uses a solid wire electrode that is continuously heated and fed from the welding machine and into the weld pool. The wire runs through the gun conduit cable, sometimes referred to as a whip, which contains a liner sheath ins