Bright Annealing
Annealing process conducted under an inert or reducing atmosphere to prevent surface oxidation, scaling, and discoloration.
When annealing under protective gas, the point is that the hot surface doesn't come into contact with oxygen. Otherwise scale forms, which you then have to remove laboriously. The protective gas, usually nitrogen or argon, displaces the air and keeps the surface clean while the structure relaxes and welding stresses are reduced. But watch out with the protective gas: hydrogen in it can cause hydrogen embrittlement and cracks in the wrong steel, and gases containing carbon dioxide can decarburize or carburize the edge zone. That ruins the hardness and makes the weld prone to cracking. So normally use pure nitrogen or argon and purge the furnace well before heating up.