The Reheated Zone Toughness of Multipass Weld Metal (Report 1) : Comparison of Reheated Zone Toughness between Si-Mn System and High Strength Low Alloy System Weld Metals

Abstract

The weld construction using heavy section steel and/or high strength low alloy steel is made by multipass welding. In that case, weld metal is reheated to various temperatures by welding heat of the subsequent pass. This result will lead to both microstructural change and through thickness toughness variation in weld metal.In this work, an investigation was carried out about the reheated zone toughness in weld metal.It is found by this work that, for simple Si-Mn system weld metal, the reheated zone toughness is improved as compared with as-welded touhgness, and increases with the ratio of reheated structure to aswelded structure. This improvement is caused by both the disappearance of columnar structure and the refinement of microstructure.While, for high strength low alloy system weld metal, the reheating shows the complex effect. The reheated zone toughness in this system deteriorates at peak temperature range between 750°C and 950°C, although the remarkable optical microstructural change is not observed.The reheating effect to the toughness of high strength low alloy system weld metal shows the inverse phenomenon as compared with that to the toughness of simple Si-Mn system weld metal.