Heat treatment:

Heat treatment of huge carbon steel parts is completed to take benefits of crystalline defects and their effects and therefore acquire certain desirable conditions or properties.

In During manufacture, through varying the rate of cooling (quenching) of the metal, grain size and grain patterns are controlled. Grain features are controlled to generate various stages of hardness and tensile strength. Commonly, the faster a metal is cooled, the smaller the grain sizes will be. That will make the metal harder. As hardness and tensile strength rise in heat-treated steel, ductility and toughness decrease.

The cooling rate used in quenching depends on the technique of cooling and the size of the metal. The uniform cooling is significant to avoid distortion.  Classically, steel parts are quenched in water or oil.

Since, of the crystal pattern of categories 304 stainless steel within the reactor tank (tritium production facility) then heat treatment is unsuitable for increasing the hardness and strength.

Welding could induce internal stresses which will remain inside the material after the welding is completed. Within stainless steels, like as type 304, the crystal lattice is face-centered cubic (austenite). In During high temperature welding, a few surrounding metal might be elevated to among 500º F and 1000º F.  Within this temperature region and the austenite is transformed into a body- centered cubic lattice structure (bainite).  While the metal has cooled, regions surrounding the weld hold a few original austenite and a few newly formed bainite. The problem arises since the "packing factor" (PF = volume of atoms/volume of unit cell) is not the similar for FCC crystals as for BCC crystals.