TIG welding equipment consists of mainly gas valve with flow regulator, welding torch, power cable, power source for welding, tungsten electrode, gas nozzle, collet to hold the nozzle, welding power source, high frequency unit, DC suppressor unit, inert gas cylinder, cooling water supply, filler wire and gas solenoid valves.
The welding torch may be air or water cooled if welding current is above 150 Amps.
The electrode material can be of tungsten or an alloy of tungsten which is generally thoriated tungsten or zirconiated tungsten which possess the capacity of holding higher current, high resistance to contamination and produce a stable arc when compared with pure tungsten electrodes. The tungsten alloy is used when copper is welded in nitrogen atmosphere nitrogen gets reacted with tungsten quickly but for aluminum welding with argon gas shield, pure tungsten electrode is found more suitable.
The other inert gases used in welding are helium, argon-helium mixtures, hydrogen and argon-hydrogen mixtures. Helium gas increase heat input when added thereby increasing weld speed and penetration. By adding hydrogen, the welds are cleaner and heat is increased too but at the same time may encourage porosity and cracking too. Metals like aluminum, copper, nickel and their alloys, mild steel and stainless should be welded using argon.
AC welding machines or DC with reverse polarity is used to weld aluminum, magnesium and their alloys because reverse polarity on these two metals removes oxide deposition film. DC welding machines are in practice to weld copper and its alloys, nickel and stainless steel. To keep the arc ignited and steady, a high frequency unit is engaged. Also, to avoid arc blow, erratic arc and overheating of welding transformer, a DC suppressor unit is integrated in the electric circuit. The DC suppressor balances the current wave and reduces the effect of current which comes into function due to the fact that arc voltage is higher when electrode is positive than when it is negative.
Filler rod is used normally when welding thicker metal and should be of same chemical composition that of the metal work piece. The rods come in either in the form of straight fixed lengths or coils.
To regulate the flow of gas and water, solenoid valves are installed in the system which start the water and gas before the arc ignites and stop the same after the welding is over, tungsten electrode has cooled and weld molten pool gets solidified.
