Microstructure and mechanical properties of rolled composite plate and welded joint

To better guide the development of the welding process of composite material, the welding was carried out by three welding methods: self-fusing plasma arc welding, submerged arc welding and tungsten inert gas welding. After welding, the microstructure, interfacial element distribution, microhardness and tensile properties of rolled composite plate and joint were studied by metallographic microscope, scanning electron microscope, X-ray energy spectrum. The result showed the base material and cladding material (check the corrosion resistance of the material) interface element diffusion layer thickness was about 10 µm, because of the existence of carburization layer and the decarburization layer, microhardness values incrensed and decreased accordingly, and tensile strength was 665 MPa, The fracture morphology showed mixed fracture characteristics of toughness and brittleness. After welding, the thickness of the diffusion layer at the interface of the base material and transition layer weld was about 5 µm, and the thickness of the diffusion layer at the interface of the base material and cladding layer weld was about 3 µm; The ferrite content of the first cladding weld reached 65% and the average microhardness was about 380 HV0.2 due to the action of multi-pass welding heat. Compared with the composite plate, the tensile strength of the joint was reduced by about 11%,, the size and depth of the dimple were clarity reduced, and the fracture location was at the weld.