Welding
20Cb-3 (Carp-20) stainless have been satisfactorily welded by the shielded fusion and resistance welding processes. Do not try to Oxyacetylene weld, carbon pickup in the weld may occur. Since austenitic welds do not harden on air cooling, the welds should have good toughness. It is importance to keep the heat input and joint restraint to a minimum to avoid hot cracking. When a filler metal is required, use AWS E/ER320LR welding consumables. These "low-residual" consumables greatly improve the resistance to weld hot cracking, which can be a problem, especially with higher heat inputs and thicker sections. The alloy has been used in the as-welded condition; however, for elevated temperature service, a postweld stabilizing heat treatment should be considered.
I would also suggest that after each pass a dye penetrant test be performed.