1988 年 37 巻 412 号 p. 24-29
An application of slow strain rate tensile (SSRT) test to evaluation of sulfide stress cracking (SSC) susceptibility of low alloyed steel was investigated. A ductility loss parameter of IL=(L0-L)/L0×100% was used, where L0 is the elongation to failure in air and L is that in H2S containing media.
The dependece of IL on strain rate in the range of 10-4 to 10-7s-1 was influenced by test temperature. IL increased with decreasing strain rate below 50°C, while the maximum embrittlement was attained at 10-5s-1 when the test was performed at 80°C. This phenomenon might suggest the importance of an interaction between dislocation and hydrogen.
The ductility loss IL showed a significant correlation with strength level and microstructure. IL increased with increasing strength level, and the limiting strength, above which extremely poor ductility was obtained, became higher as the homogeneity of microstructure was improved. These behaviors were in good agreement with the results of conventional uniaxial tensile type SSC tests.