Effect of Ti addition on microstructure and mechanical properties of laser welds
Kurosawa Nobutaka; Maeda Hiroki; Kobayashi Kojiro F
Abstract:The effect of Ti in low carbon high strength steels on the microstructures and mechanical properties of laser welds was investigated. The addition of Ti content up to 0.06mass% scarcely increased the hardness of weld metal. However, Ti addition inhibited the decrease in hardness by heat treatments at 773 - 1073K because of TiC precipitation. Using Johnson Mehl equation, the decrease in hardness of Ti free steel after the heat treatments can be approximately estimated as a function of temperature and time. Further, in the steels with Ti addition, the effect of TiC precipitation, on hardness being evaluated, the decrease in hardness after the heat treatments can be also estimated. In tensile test, the elongations of laser welded specimens were lower than those of the base metals in as welded condition. They increased to the same level as the base metal by a heat treatment at 973K. Key Words:high strength steel, microstructure, laser welding, TiC, precipitation, heat treatment, activation energy, tensile strength, elongation