Sulphide stress cracking of heat affected submerged arc weld metals

Sulphide stress cracking (SSC) susceptibility of submerged arc weld metals hardened by successive welding was investigated using four point bending tests. The chemical compositions of the weld metals studied included variations in carbon, silicon, manganese, molybdenum, chromium, nickel, copper, boron, and oxygen concentrations. Testpieces for SSC previously stressed were held in NACE TM–01–77 solution for 21 days. The observation of SSC revealed that addition of oxygen to a weld metal reduces the SSC susceptibility while addition of all other elements increases SSC susceptibility. The critical hardness to avoid occurrence of SSC is then dependent on the chemical composition of the weld metal and is well estimated by the carbon equivalent as a measure of the hardenability of the weld metal.