Choosing the right polarity is part of the process of setting up a TIG welding machine for best effect,and is made fairly simple by the straightforward controls found on most of these welding implements today. Like all arc welding,TIG welding is accomplished by making a complete circuit through the welding gun, the workpiece, and back to the welding machine itself again.This is achieved by attaching a welding clamp to the metal as close as possible to the actual welding site.
The welding clamp is wired to the main body of the welding machine and allows the electric circuit to completed through the metal and the various attachments of the welding implement itself. The welding clamp, also referred to as a “work clamp” and with similar names, is either a literal, physical clamp (typically an alligator clamp) which is snapped onto the edge of the metal, or, more often, a magnetic clamp that is affixed close to the joint.
Make sure that all of the elements of the TIG welder including the welding clamp are in place so that the circuit is properly completed. Then, it is up to you to choose the correct polarity for the type of metal you are welding. Polarity will determine the direction in which the circuit is made, and different polarities are needed for different types of welding substrate.
Polarities for TIG
The usual TIG polarity is DCEN (direct current electrode negative), which means that the electricity is being projected out of the welding gun and into the base metal. From there, it flows into the welding clamp and back to the main body of the welding machine. This concentrates heat on the metal, ensuring a good welding pool, strong penetration if needed, and a long electrode lifespan.
All types of steel are usually welded with DCEN when you are using a TIG welding machine, while specialized welding may be carried out with DCEP. In DCEP welding direct current electrode positive the electricity flows out of the welding machine and into the workpiece through the welding clamp, then back into the welding machine through the welding gun.
It is a somewhat disorienting thought that your TIG welder is sucking the electricity out of the base metal, rather than projecting it into it, when you are using DCEP, but this actually the case. DCEP welding burns out the electrode very quickly, since the heat generated by the air’s electrical resistance is concentrated on the tungsten rather than the base metal. DCEP welding is usually done at low amperage on very thin metal to reduce heat, and uses a thick electrode that is more resistant to heating.
Alternating current, or AC, is used for welding aluminum with a TIG welder. As previously mentioned, this prevents aluminum oxide from building up and contaminating the weld. Some special metal welding, such as magnesium alloys, is also carried out using AC.