Effect of Hardness and Hydrogen Concentration on Critical Stress of Cold Cracking in Welded Joint

Abstract

The implant cold cracking test has been made to investigate the effect of the residual diffusible hydrogen content, which remained in the specimen subjected to thermal cycle, and the maximum hardness in the neighbourhood of fusion boundary in heat affected zone on the critical stress of weld cold cracking. The relation between critical stresses and the common logarithm of residual diffusible hydrogen content was indicated by two straight lines. When the residual hydrogen became under 2 ppm, the change of hydrogen content effected extremely on the critical stress. However, when the residual hydrogen became above 3 ppm, the change had some influence on the critical stress. When the residual diffusible hydrogen con tent remained unchangeable, the critical stress was related with the linear equation of the maximum hardness. Equations for estimation of the critical stress of the cold cracking were derived from the maximum hardness, cooling time and fused metal hydrogen content.