Tungsten inert gas welding
From DDL Wiki
Revision as of 22:54, 9 September 2007
Process
In TIG welding, two similar metals are placed adjacent to one another. The TIG operator then attaches a grounding strap to one or both of the pieces of metal. Using a foot pedal which regulates current, the operator applies high-amperage electrical current to the joint line along which the two parts are to be welded. The current is applied using a TIG torch, which usually consists of an insulating handle which houses a hollow tungsten electrode which is sharpened to a fine point (for steel welding) or a rounded point (for aluminum). Additionally, the torch contains a gas feed line which leads to the hollow electrode. Inert gas at pressure is fed through this line, to the electrode, and then over the hot metal; this prevents oxidation and contamination of the metal at the joint. The intense heat generated by the metal’s natural resistance to current melts the two pieces along the joint line in close proximity to the electrode. As the operator moves the torch down the joint, he will intermittently apply additional metal by introducing a thin rod of similar metal into the arc between the torch’s electrode and the joint. Addition of this filler rod serves several purposes: first, it ensures consistent material thickness at the weld joint. Also, adding filler metal at the joint ensures retention of mechanical properties at the joint, whether for bearing load or sealing gasses and liquids in containers or pipes. Finally, adding filler allows the TIG operator to ensure proper weld penetration on thicker joints by first beveling both pieces at the joint and then building up filler in this joint. After the operator has finished welding the joint, the TIG torch is left over the hot metal for a small amount of time without applying any current. This ensures that the remaining mass of molten metal cools completely while cloaked by the inert gas.
