An Overview on Effect of Preheating on Cold Cracking of Low Alloy steel and Stainless Steel Weld Joint

Weldability of alloy steel and stainless steel is having major consideration of hydrogen induced cracking or cold cracking. During welding metal is heated above melting point and cooled at very high speed. So contraction forces are developed in weld joint and HAZ. The microstructure of weld joint is also different in various zones of weld joint. Production of hard and brittle microstructure like martensite, high carbon and other alloying elements present in parent metal, restraint in welding and diffused hydrogen develop the hydrogen induced crack in various areas of weld metal and HAZ. HIC cracks are generally sub surface and difficult to detect but sometimes it propelled towards the surface also. HIC crack is observed both in weld metal and HAZ. Effect of preheating on cooling rate and alloying elements on development of HIC in low alloy steel and stainless steel metal welding is reviewed in this paper. It was found that by applying preheating, cooling rate of weld metal is reduced and solidification time is increased. Cold cracking can be reduced by selecting proper preheating temperature which depends on carbon equivalent, diffusive content of hydrogen, weld heat input, joint restraint, yield strength of weld metal and thickness of parent metal.