Microstructure and Mechanical Properties of Q690D GMAW Multi-Pass Welding Joint

Under the condition of no preheat and post-weld heat treatment, the multi-pass welding test of 20 mm thick Q690D TMCP steel plate was carried out by using gas metal arc welding (GMAW)and cored welding wire CHW-80C1.The microstructure transformation characteristics and impact properties of the welded joint were analyzed. The results show that excellent welding joint can be obtained by using CHW-80C1 welding wire. The weld metal microstructure of each pass of Q690D are all composed of granular bainite, a small amount of acicular ferrite and proeutectoid ferrite.The heat affected zone consists of granular bainite, acicular ferrite, proeutectoid ferrite and M-A components. The impact absorption energies of the weld metal (WM)and fine grained heat affected zone (FGHAZ)are lower than that of base metal.The fracture modes of the WM and FGHAZ are ductile fracture.