Page 26 - Welding Robots Technology, System Issues, and Applications

Welding Robots
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designed to make longitudinal seams in pipe. The process was patented by
Robinoff in 1930 and was later sold to Linde Air Products Company, where it was
renamed Unionmelt® welding. Submerged arc welding was actively used during
the 1938 defense buildup in shipyards and in ordnance factories. It is one of the
most productive welding processes and remains popular today.

Gas tungsten arc welding (GTAW) had its beginnings in an idea by C.L. Coffin to
weld in a non-oxidizing gas atmosphere, which he patented in 1890. The concept
was further refined in the late 1920s by H.M. Hobart, who used helium for
shielding, and P.K. Devers, who used argon. This process was ideal for welding
magnesium and also for welding stainless steel and aluminum. It was perfected in
1941, patented by Meredith, and named Heliarc® welding. It was later licensed to
Linde Air Products, where the water-cooled torch was developed. The gas tungsten
arc welding process has become one of the most important gas arc welding
processes.

The gas shielded metal arc welding (GMAW) process was successfully developed
at the Battelle Memorial Institute in 1948 under the sponsorship of the Air
Reduction Company. This development utilized the gas shielded arc, similar to the
gas tungsten arc, but replaced the tungsten electrode with a continuously fed
electrode wire. One of the basic changes that made the process more usable was
the small-diameter electrode wires and the constant-voltage poser source (a
principle patented earlier by H.E. Kennedy). The initial introduction of GMAW
was for welding nonferrous metals. The high deposition rate led users to try the
process on steel, but since the cost of inert gas was relatively high at the time, the
cost savings were not immediately evident.

In 1953, Lyubavskii and Novoshilov announced the use of welding with
consumable electrodes in an atmosphere of CO 2 gas. The CO 2 welding process
immediately gained favor since it utilized equipment developed for inert gas metal
arc welding, but could now be used to perform more economical welds with steels.
Since the CO 2 arc is a hot arc requiring fairly high currents for larger electrodes,
the process only became widely used with the introduction of smaller-diameter
electrode wires and more efficient power supplies. Those power supplies used the
short-circuit arc variation, also known as Micro-wire®, short-arc, or dip transfer
welding, all of which appeared late in 1958 and early in 1959. This variation
allowed welding on thin materials and every position, and soon became the most
popular of the gas metal arc welding process variations.

Another variation was the use of inert gas with small amounts of oxygen that
provided the spray-type arc transfer. It became popular in the early 1960s.

A more recent variation is the use of pulsed current. The current is switched from a
high to a low value at a rate of once or twice the line frequency (50 Hz in Europe).

Soon after the introduction of CO 2 welding, a variation utilizing a special electrode
wire was developed. This wire, described as an inside-outside electrode, was