A Review on Pulsed TIG Welding

In the fabrication of equipment’s, machinery etc. made from stainless steels such as pipe, automotive exhaust gas system, chemical industrial equipment, etc., arc welding using shielding gas is often used. Higher quality welds with fewer defects like porosity, and cracking and material properties closer to the parent metal are most required in the present manufacturing processes. TIG pulse welding is one of the generally applied welding methods. Pulsed TIG welding achieves a good control of heat input. Heat affected zone (HAZ) decreases the strength of the weld and hence Pulsed TIG welding process is carried out to reduce the HAZ. The current from DC power source is supplied in pulses having a predetermined duration for the peak and low values. When the current is maintained at high on-position, welding takes place with the required penetration. Distortion is the major problem in welding of thin sections. This distortion is controlled in pulsed TIG process. The metallurgical advantages of pulsed TIG welding are grain refinement on fusion zone, the reduced width of HAZ, less distortion, control of segregation, reduced hot sensitivity and residual stresses. It was observed that pulsed TIG welding produces finer grain structure of weld metal than conventional TIG welding (without arc pulsation). In fact, excess heat reduces the material's ability to resist corrosion. In the pulsed-current mode, the welding current rapidly alternates between two levels. The higher current state is known as the pulse current, while the lower current level is called as background current. During the period of the pulse current, the weld area is heated and fusion occurs. Upon dropping to the background current, the weld area is allowed to cool and solidifies. Pulsed current TIG welding has a number of advantages including lower heat input and consequently reduces distortion and warpage in thin workpieces. In addition, it allows for greater control of the weld pool and can increase weld penetration, welding speed, and quality. Some researchers have done work to understand the effect of various welding parameter such as welding speed, welding current, gas flow and heat input etc. that are influences on responsive output parameters such as tensile strength, a hardness of welding by using optimization philosophy. Minitab 18 software is used to find optimum parameter.