Studies On Interface Structure And Properties Of Explosive Welded 317L Stainless Steel-FH40 Marine Steel Composite Plate

Explosive welding uses the energy of explosive explosion to weld two dissimilar metals,which is one of the most common processes for the fabrication of bimetals composites.The317 L stainless steel-FH40 marine steel composite plate manufactured by explosive welding not only has the seawater corrosion resistance of 317 L stainless steel,but also has the strength and low-temperature toughness of FH40 marine steel,which can withstand harsh polar marine environments,It has good application prospects on polar ice breakers.In this paper,the effect of the interface structure of the explosive welded 317 L stainless steel-FH40 marine steel composite plate on the properties of the composite plate was studied,and the interface structure of composite plates was adjusted by designing a heat treatment process to obtain good comprehensive properties.Firstly,this thesis studies the influence of interfacial structure on mechanical properties of explosive welded composite plate.The research on the interface structure shows that the explosive welding interface presents a waveform structure,and nanograins and elongated grains are generated at the interface due to the strong plastic deformation during explosive welding;Atomic diffusion and metal melting occurred at the interface.The research on the influence of interface structure on mechanical properties shows that the increase in hardness at the interface originates from the grain refinement and work hardening structure at the interface,and the diffusion of C atoms can cause a decrease in hardness at the FH40 side;The corrugated structure improves the bonding strength of the composite interface,and the composite interface does not separate during shear and tensile tests;The fine grain strengthening produced by nanograins at the interface improves the strength of the composite plate,but the elongated grains with higher work hardening level reduce the plasticity of the composite plate.Then,this thesis studies the effect of 550℃-650℃ heat treatment on the interface structure and mechanical properties of explosive welded composite plate.The interfacial structure study shows that recrystallization occurs on the FH40 side after annealing at 600℃,and grain growth occurs after annealing at 650℃.Heat treatment has little effect on the microstructure of 317 L side.The study on the influence of interface structure changes on mechanical properties shows that due to the effects of recrystallization,grain growth,and element diffusion,the increase in heat treatment temperature leads to a decrease in the side hardness of FH40 marine steel;After heat treatment at 600℃ and 650℃,the elongated grains with poor toughness disappear,and the bending performance of the composite plate is better;the interfacial structure of the composite plate remains unchanged after stress relieving annealing at 550℃,and its strength decreases and its plasticity improves.Recrystallization annealing at 600℃ eliminates the elongated grains with large deformation,resulting in an equiaxed grains structure without internal stress and work hardening.The elongation of the composite plate increases significantly(20%→26%),while retaining the presence of nanograins,resulting in the composite plate still having high strength(882MPa).After annealing at 650℃,the grains grow up,nanograins disappear,the strength of the composite plate decreases significantly,and the elongation increases.After heat treatment at 600℃ for 4 hours,the tensile strength of the tensile parts decreased slightly,and the elongation increased significantly.Moreover,the tensile properties of the parent plate and flyer plate were not changed after heat treatment at 600℃,achieving reasonable control of the interface structure and properties.Finally,the low-temperature performance and corrosion resistance of composite plates were studied.Due to the layered structure at the interface,explosive welding composite plates have higher low-temperature toughness than rolling welding;After heat treatment,the bending strength of the composite plate at low temperature decreases;Electrochemical tests and corrosion rate tests indicate that the composite plate has the best corrosion resistance after heat treatment at 650℃;Heat treatment will not cause sensitization of the stainless steel layer.