On the evaluation method of sulfide stress cracking susceptibility of carbon and low alloy steels

Abstract

Characteristic features in various sulfide stress cracking (SSC) evaluation methods [slow strain rate tensile test (SSRT), uniaxial tension load test, four point bent test], are investigated in comparison with an actual pipe biaxial stress loading test. In evaluating materials with homogeneous microstructures, there is consistency among SSC susceptibilities evaluated by different test methods, even though the threshold stress depends upon the method used. An SSRT test is beneficial for shortening the evaluation time. SSC susceptibility of materials with inhomogeneity in strength and microstructure is significantly affected by the test method. In an SSRT test of HSLA steel weldments concentrated plastic deformation at the heat affected soft zone might lead to initiation of SSC, yet the portion with maximum hardness could be the most susceptible to SSC in the actual pipe test as in the four point bend test. Finally, the SSC behavior of welds under uniaxial tension load are discussed in relation to micro-yielding in the specimen.