A Study of the Stress Relief Cracking Susceptibility of A533b Class 1 and A508 Class 3 Steels

摘要

The stress relief cracking (SRC) susceptibility of particular casts of A533B Class 1 and A508 Class 3 stells was assessed by a constant displacement stress relaxation tests. The cracking susceptibility in the presence of a stress raiser, was determined. The SRC behavior of simulated coarse grained heat affected zone (HAZ) microstructures was determined for both steels and the effect of subsequent grain refinement of the HAZ was evaluated on the A533B cast. In the coarse grained HAZ samples of the A508 and A533B steels discontinuities in the load relaxation curves occurred which indicates the onset of cracking and complementary potential drop measurements monitored crack growth. Auger electron spectrocopy shows that low ductility intergranular fracture is associated with segregation of the trace impurities phosphorus and nitrogen to grain boundaries during the stress relief heating cyle. It is shown that for a comprehensive assessment of stress relief cracking susceptibility, cracking response should be monitored throughout the entire postweld heat treatment cycle and not just at the peak temperature.