Research On Welding Procedures And Welded Joint Properties Of Domex700MC HSLA Steel By Dioxide Gas Shielded Arc Welding Process

Domex700MC steel has both high strength and good plasticity and ductility. So, it has been widely used in the field of mine-machine, bridge and mobile crane and so on. Although the chemical compositions and mechanical properties of Domex700MC steel are known, the welding procedure, choice of the welding material, research for the properties of weld metal and HAZ are not fully studied. The object of our work is to provide the essential information for the welding practice with welding process and technology.Solid wire ER50-6 and flux-cored wire AWSA5.29 E91T1-B3 are chosen according to "low strength match", and the welding procedure of Domex700MC steel is made. weld tests are conducted using solid wire CO₂ arc welding on condition of no preheat, no post-heat treatment, and heat input is 8.5-12kJ/cm.On the other hand, preheat post-weld heat treatment is used, more weld tests are carried out at 12-15kJ/cm heat input using flux-cored wire CO₂ arc welding. The microstructure of welded joints obtained in two types of welding procedures above-mentioned is analyzed. The comparison of the mechanical properties of different welded joints is made by means of tensile test, impact test and hardness test. The relation of microstructure and mechanical properties of welded joints is discussed.The results show that Domex700MC steel has good weldability. Good quality weld joints can be obtained by both solid wire CO₂ arc and flux-cored wire CO₂ arc welding process. But the microstructure and mechanical properties of welded joints by flux-cored wire CO₂ arc welding process are better than those of the joints by solid wire CO₂ arc welding process. There is a metal hardened zone to some extent in HAZ by both solid wire CO₂ arc welding and flux-cored wire CO₂ arc welding process because of the welding thermal cycle effect. The welding parameters and filler metal composition have a main influence to the number and the shape of ferrite in welded joint metal.