Analysis Of Impact Energy Difference For Butt Weld Metal And Deposition Metal

Properties of welding electrode are estimated by properties of its deposited metal and butt joint. For some kinds of welding electrodes, such as ZS60A, WE960, 903, 907 A, 945 welding electrodes, under the same condition of welding technology, compared with deposited metal, impact energy of butt welded metal at -50℃decreases in big extent and the decrease extent commonly beyond 30%. For argon-arc welding wire with yield strength of 590 MPa, decrease extent even beyond 50%. In this paper, researches are done on this problem.Results of instrumented impact energy test indicate that: (1) ductile-brittle transition temperature of butt welded metal is higher than that of deposited metal; (2)in ductile-brittle transition zone, impact energy of butt welded metal is lower than that of deposited metal, and difference of crack formation energy for butt welded metal and deposited metal is about 10J, but difference of crack extension energy for butt welded metal and deposited metal is variational and the biggest can reach 40J. Difference of impact energy for butt welded metal and deposited metal is mainly resulted in by crack extension energy.Results of chemical analysis indicate there is not big difference for butt welded metal and deposited metal. Results of microstructure test and fracture analysis indicate that: (1) there are a large number of troostite in butt welded metal, but there is only a few in deposited metal, so there are many ferrite-troostite component, which makes crack form easier at ferrite-troostite boundary, and crack formation energy of butt welded metal is lower than that of deposited metal. (2) for butt welded metal, there are coarse crystal zone and fine crystal zone, but for deposited metal, there is mainly fine crystal zone and only small local coarse crystal zone, so compared with deposited metal, crack extension resistance is more lower, which makes crack extension energy of butt welded metal is more smaller than that of deposited metal.Difference of structure for butt welded metal and deposited metal is resulted in by its difference on bead arrange, which makes effect of reheat for subsequent bead to former bead is different. So impact property of butt welded metal is worse than that of deposited metal.