Final answer:
The variant of TIG welding used for steels is Pulsed TIG welding, which controls heat input and reduces distortion in welded materials.
Step-by-step explanation:
The variant of TIG welding that is used for steels is D) Pulsed TIG welding. Welding is a process of joining metal materials using heat and solder. TIG welding, which stands for Tungsten Inert Gas welding, is a process that uses a non-consumable tungsten electrode to produce the weld.
When welding steel and other metals that may react with the atmosphere, it is often desirable to use a variant called Pulsed TIG welding. This method involves pulsing the welding current to maintain a stable arc, control heat input, and reduce distortion in the welded materials.