SULFIDE STRESS CRACKING OF HEAT-AFFECTED SUBMERGED-ARC WELD METALS

Sulphide stress cracking (SSC) susceptibility of submerged arc weld me tals hardened by successive welding was investigated using four point bending tests. The chemical compositions of weld metals studied includ ed variations in carbon, silicon, manganese, molybdenum, chromium, nic kel, copper, boron, and oxygen concentrations. Testpieces for SSC prev iously stressed were held in NACE TM-01-77 solution for 21 days. The o bservation of SSC revealed that addition of oxygen to a weld metal red uced the SSC susceptibility while addition of all other elements incre ases SSC susceptibility. The critical hardness to avoid occurrence of SSC is then dependent on the chemical composition of the weld metal an d is well estimated by the carbon equivalent as a measure of the harde nability of the weld metal.