Welding Processes:

 Welding Technology  component that tended to saturate the transformer. Primary this was overcome by applying a similar d.c. voltage, although of opposite polarity, to the circuit so that the d.c. component was balanced out. It was done with storage batteries, but subsequently this was found that large capacitors in series with the arc had the similar effect.

The purity of the shielding gas was developed from 98 to over 99.95 % as the procedure developed, particularly as a result of the requirement for high purity gases for the welding of aluminium alloys and reactive metals. Argon, the only inert gas available outside the USA, attained popularity even in that country, being the chief gas utilized for manual welding, although the higher arc voltage and, hence, greater penetration of the helium-shielded arc was found of value in automatic welding. Helium tungsten-arc and argon tungsten-arc techniques both were rapidly applied to the welding of a range of non- ferrous metals, which had proved hard to weld, by other methods.

Along aluminium, as with magnesium, the new procedure gave greater scope to the engineer due to the absence of flux. Earlier fillet welds and other types of joints in which flux may be trapped had to be ignored because of the danger of corrosion after welding. The more concentrated heat input of the tungsten-arc welding process over gas welding enabled welding speeds to be enhanced and improved the metallurgical quality of welds. Although there were various advantages to the procedure it was also found to have restriction. The separate addition of filler metal needed the use of both the welder's hands and, therefore, access to hard joints tended to be restricted and positional welding was difficult and slow.

Gas Tungsten Arc Welding (GTAW) is an arc welding procedure that uses an arc between a tungsten electrode (non-consumable) and the weld pool. The procedure is used with shielding gas and without the application of pressure. The process might be used with or without the addition of filler metal. Figure 5 shows the gas tungsten arc welding procedure.

GTAW which has become indispensable as a tool for various industries due to the high-quality welds generated and low equipment costs. The reason of this chapter is to discuss the basic of the GTAW process, the equipment and consumables utilized, the process procedures and variables, applications, and security considerations.

The possibility of utilizing helium to shield a welding arc and molten weld pool was first investigated in the year 1920s. However, nothing was done with this method till the beginning of World War II while a great need developed in the aircraft industry to replace riveting for joining reactive materials such like magnesium and aluminium. By using a tungsten electrode and direct current arc power with the electrode negative, a stable, efficient heat source was generated with which outstanding welds could be made.