FUSION ZONE AND HEAT-AFFECTED ZONE CRACKING SUSCEPTIBILITY OF STABILIZED AUSTENITIC STAINLESS-STEELS

Fusion zone (FZ) and heat affected zone (HAZ) cracking behaviour of th ree stabilised stainless steels were studied using the Varestraint hot cracking test. Materials ranged in solidification mode from fully aus tenitic D9 to primary austenitic 347 and primary ferritic 321. The mat erials exhibited high cracking susceptibility in the FZ and base metal HAZ. In the weld metal HAZ, type 347 was highly susceptible, while al loy D9 and type 321 were resistant to cracking. The FZ cracking behavi our could be related to the stabilisation ratio (Nb, Ti)/C rather than the P + S content and Cr-eq/Ni-eq ratio, as in unstabilised stainless steels. In fact, analysis of cracking data using the Cr-eq/Ni-eq v. P + S content diagram did not reveal any systematic trend in cracking s usceptibility. In the base metal HAZ, the high cracking in type 347 as well as in type 321 was found to be caused by the high impurity level s in conjunction with the pressure of niobium and titanium. Cracking o ccurred much less in alloys D9.