1993 Volume 33 Issue 12 Pages 1275-1280
Cold-working is known to be detrimental to sulfide stress cracking (SSC) resistance. However, whether the increase in strength due to cold-working or cold-working itself deteriorates SSC resistance is not clear. In this paper, the effect of cold-working on SSC resistance was investigated using a constant load SSC test for low alloy martensitic steels cold-worked by tensile deformation. Threshold stress for SSC (σth) slightly decreases with an increasing cold-working rate. However, the decrease in σth caused by an increase in yield strength resulting from an increasing cold-working rate is much smaller than that caused by lowering the tempering temperature. Fractographic observation reveals that the fracture mode is not affected by cold-working. No intergranular crack appears even at the yield strength where intergranular fracture occurs for as-tempered steels. Because there is a good correlation between σth and the percentage of intergranular fractures, the same fracture mode may give a constant value of σth. It was also clarified that fractographic morphology does not change after cold-working in case of low temperature brittle fracture. From these observations, deterioration in SSC due to cold-working is considered to be caused by an increase in yield strength due to cold-working.
