Effect Of Alloy Element And Heat Treatment Process On Microstructure And Properties Of Welded Seam Of FV520(B) Steel

Martensitic precipitation hardening stainless steel FV520(B)was used in the production of centrifuge fan because of its excellent comprehensive performance,but the production was often fracture failure due to lack of toughness of welded joint and improper heat treatment process.For the problem of insufficient toughness of FV520(B)steel welded joint,through analyzing effect of heat treatment process on the properties of steel FV520(B),found that austenite content was the main factors affecting its toughness.This paper tries to improve the FV520(B)steel weld seam toughness by control austenite content in the weld seam with coating transferring alloy elements Mn and Ni and different heat treatment process after welded.With the help of microstructure observation,tensile,impact and XRD test,analyzed effect of alloy element and heat treatment process on microstructure and properties of welded seam of FV520(B)steel.By add carbon ferromanganese and nickel powder in acidic and basic coating to transition austenite alloy elements Mn and Ni to welded seam,the experimental results suggest that basic coating transition alloy elements was better,welded joint toughness was better with basic coating.The microstructure of FV520(B)steel welded seam was dominated by tempering martensitic,with the increase of alloying elements,the microstructure became finer;By coating transition Mn,Ni elements,can improve welded seam austenitic.Adding 5%of the carbon ferromanganese and 5%of nickel powder in basic coating,austenite content in FV520(B)welded seam increased to 25.2%,impact absorbing energy of weld seam increased to 79J.Coating transition alloy elements can improve the impact toughness of welded seam by increasing the amount of austenite.The Ni element was better than Mn element to improve toughness of FV520(B)welded seam.By the test of heat treatment with different intermediate temperature and aging temperature of FV520(B)welded joint,the test results showed that:The microstructure of welded joint was smaller and distributes more homogeneous with the intermediate and aging treatment,intermediate treatment can significantly increase austenite content in welded seam.With the processing of intermediate treatment,strength and hardness of welded joint was decreased,while the plasticity and toughness was better;intermediate treatment can improve corrosion resistance of welded joint and base metal.Austenite content in welded seam increased with the aging temperature increasing,and strength and hardness of welded joint decreased,but the plasticity and toughness was better.The impact absorbing energy of weld seam improved with the increased of austenite content in welded seam,with adding intermediate treatment,toughness of welded seam improved significantly.With 1050 ? solid solution +850 ?intermediate +620? aging treatment,the welded joint has good comprehensive performance;with 1050? solid solution +750? intermediate +620? aging treatment,austenite content of welded seam was the highest,the impact toughness of welded seam was the best.