Analysis and control of laser weld crack

Abstract

During laser welding of titanium alloy, it is easy to absorb nitrogen, oxygen and hydrogen in the surrounding air, and react with them to form a gap solid solution, which hinders the movement of dislocations between grain boundaries and significantly improves the hardness of the weld, but its plasticity will deteriorate, resulting in the embrittlement of the whole welded joint. Because of the low thermal conductivity of titanium alloy, the weld pool continuously transfers the heat to the heat affected zone in the way of heat conduction, which keeps the heat affected zone at a high temperature all the time. In this way, the volume of hydride precipitated rapidly expands, resulting in a large local stress. When the local stress exceeds the yield limit of the material, cracks will occur. The quality of welding joint determines the reliability and economy of welding structure to a great extent. The defects of welded joints often destroy the performance of components, and in some cases, accidents will occur. Therefore, the control of weld defects is particularly important.