| Welding of large cross-section dissimilar metals is an important subject of dissimilar metals welding.In this paper,the diffusion welding process with temperature of 950～1000℃,pressure of 20～25 MPa,vacuum degree of 0.6 Pa and heat preservation time of 30～45 minutes used to realize the welding of 45 steel with diameter of 350 mm and 304 stainless steel ingot.OM and SEM were used to analyze the microstructure of the weld and its vicinity,and tensile,bending,impact,hardness and fatigue tests were used to study the mechanical properties of the welded joint.Research shows that:(1)45 steel and 304 stainless steel achieve good metallurgical bonding at the interface.Ferrite region exists in the range of about 50 μm from weld,grain refinement occurs near weld of 304 stainless steel.It was found that Fe diffusion from 45 to 304 stainless steel was about 6 μm,Cr and Ni diffusion from 304 stainless steel to 45 steel was about 5μm and 2 μm,respectively.(2)The tensile strength of the welded joint specimen is 568.8 MPa and the elongation is 25.4%.the welded joint specimen fails to 304 stainless steel far away from the weld under the action of tensile stress;The impact work of the welded joint sample is 52.23 J,the impact work of the 45 steel base material is 32.95 J,and the welded joint sample fails on the 45 steel side;Through the bending test,there is no obvious crack on the inside and outside of the welded joint.(3)The fatigue strength limit of welded joint specimens is 216.7 MPa.The reliability was 90%,the specified life was 107 times,the survival rate was 90%and 99%,the fatigue limit of welding joint specimens was 204.4 MPa and 195.8 MPa,respectively. |
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