TWI Industrial Member Report Summary 452/1992
By B J Ginn
High alloy austenite stainless steels (eg 20-25Cr, 20-25Ni, 6Mo, 0.2N) offer excellent corrosion resistance, but may suffer preferential corrosion of weld metal produced autogenously or with matching fillers. Normal practice is to use overalloyed, Ni-base consumables, but the necessity for adequate filler addition complicates welding, for example pipe root runs. The present work is part of a continuing programe to define the conditions under which non-matching fillers are needed, and to optimise the performance of autogenous or matching composition weld metals.
Autogenous bead on plate TIG welds were made in 5mm UNS31254 steel covering arc energy from 0.27-2.5kJ/mm, and using Ar or Ar+3%N2 shielding gases. Potentiodynamic and ferric chloride pitting tests were carried out, with metallographic examination.