Microstructure and properties of sandwich panels T-joints in flux bands constricting arc welding

960 MPa high-strength steel sandwich plates were welded by a new method of flux bands constricting arc welding in order to solve the problem of poor fusion of core plate and panel T-joint in laser welding of sandwich plate. The forming of arc combustion and the change process of metal droplet transfer were studied with high speed camera technology. Microstructure and mechanical properties of the T-joints were studied through microstructure analysis,hardness test,micro-zone tensile test and T-joint axial tensile test. The results show that the welding flux can compress and stabilize the arc to improve the welding heat efficiency and promote the transition of the droplet in the process of welding,and that T-joint with good fusion of weld and core plate can be obtained. Microstructure of the coarse-grained zone in heat-affected zone of the welded joints is coarse lath martensite and blocky ferrite,and the fine-grained zone in heat-affected zone of the welded joints is fine lath martensite and granular bainite. The microstructure of the weld is mainly acicular and blocky ferrite distributed along the grain boundary of the prior austenite. Hardness distribution of the welded joint is uneven,the average hardness distribution is heat-affected zone ＞ base metal zone ＞weld zone. In the micro-zone tensile test of the welded joint,weld zone is the weakest area of the joint for mechanical properties. In the T-joint tensile test,cracks first produced at fusion line and then extended to weld zone,finally,the joint fractured in weld zone,and the fracture shows ductile fracture characteristics.