Aim at the issue that the bending crack is easy to generate inside dissimilar welded joint of low alloy steel and stainless steel, a new process of submerged arc welding filled with Ni wire is put forward. The influence mechanism of filling quantity of Ni wire to the joint of microstructure evolutions and mechanical properties is mainly explored based on the contrast test of non-filling Ni wire and three different filling speeds of Ni wire. The experiment results indicate that, the filling process of Ni wire supplies austenite forming element, and alters heat allocation process of molten pool. The filling quantity of Ni wire is the quantitative parameter, it is used to control the transition width between low alloy steel and weld metal, also to adjust the peak temperature and holding time at elevated temperature of molten pool. When the value of the filling quantity of Ni wire is determined, the problem of bending crack in the fusion zone of low alloy steel can be solved, and also the overheat damage can be eliminated. At the same time, the grains of weld metal and heat affected zone are refined. And on this basis the plasticity, toughness and microhardness of welded joint can be guaranteed.
Microstructure and mechanical property of 738 low alloy steel welded joint
