Study On The Mechanical Properties And Microstructural Of WDB620 Steel And Welded Joint

High strength low carbon bainitic steel WDB620 is a kind of steels which is a new generation high-strength steel of low susceptibility to welding crack made in China, the performance fully meet the large steel structure on the low susceptibility to welding crack the requirement. It can substitute with the import CF62 steel and has been used extensively in pressure Hydropower pressure containers such as steel pipe structure. WDB620 were used in the Wa Wushan Hydropower Station's penstock at large, but we found some impact energy unsteady and less than the relevant specifications and design requirements in the mechanical properties testing of the steel and welded joints. This has led to rejecting the bifurcation which was assembled to be welded , Causing heavy economic losses.This paper studies on the mechanical properties and microstructure of high strength low carbon bainitic steel WDB620 and welded joints. Through micro-shear test of the 62 mm thick WDB620 especially Z direction and multi-passes welding joints ,the paper make gradient performance curve of WDB620 and welding joints in different depth. And through optical metallographic microscope ,this paper analyze of the microstructure differences of the steel and welding joint ,find out the reasons for mechanical properties instability. Some significant recommendations to ensure the plate microstructure and mechanical properties uniform was given.This paper also collect together the high strength low carbon bainitic steel's micro-shear test's shear energy and the impact energy data of impact test ,use probability and mathematical statistics method, obtain the curve regression experienced formula.