Influence Of Heat Treatment Process On Fracture Behavior Of Remanufactured EA4T Axle

With the rapid development of railway transportation in my country,high-speed trains have put forward higher requirements for railway transportation safety.As a very important core component of trains,train axles need to bear complex loads for a long time during operation,so that the axles may suffer fatigue,hot cuts,cold cuts,and other damages.If you choose to scrap it directly,it will not only increase the cost of train transportation,but also violate the economic policy of sustainable development.Remanufacturing the axle to achieve or even exceed the performance before the repair is the key to the repair of the axle.This article uses laser cladding technology to cladding and remanufacture EA4T axles.Taking remanufacturing EA4T axles as the research object,the heat treatment process is determined by finite element and differential thermal analysis methods;and OM,SEM,EDS and XRD are used to pre-heat treatment The microstructure and phase structure of each micro-area of the remanufactured sample after the heat treatment are analyzed;the fracture behavior of the remanufactured axle before and after the heat treatment is carried out through the microhardness test,the Charpy impact test and the plane strain fracture toughness test.Researched.The main research contents of the thesis are as follows:(1)The finite element software Sysweld was used to establish the finite element model of the remanufactured EA4T axle,and the finite element simulation of the annealing treatment test at 550?was carried out.The test results and simulation results were compared and analyzed to verify the feasibility of the finite element method.The stress-relieving annealing process route for remanufactured EA4T axles was determined;the differential thermal analysis experiment(DSC)was used to analyze the alloys in the cladding layer of remanufactured EA4T axles.Carbide re-dissolution temperature was measured and analyzed,and the heat treatment process route of secondary normalizing plus stress-relieving annealing and homogenizing annealing reinforcement solution treatment for remanufactured EA4T axles was determined.(2)After EA4T remanufactured samples are treated by secondary normalizing and stress relief annealing,the cladding layer is composed of austenite and M₇C₃ carbide,and the heat-affected zone is composed of ferrite and tempered sorbite.The matrix structure It is ferrite and pearlite.Compared with untreated,the microhardness of each micro-area of the remanufactured sample after heat treatment is significantly reduced,and the average impact energy is increased to 64 J,which has good mechanical properties.(3)After EA4T remanufactured specimens are treated by homogenization annealing,strengthening and solution treatment,the cladding layer is composed of austenite,Fe Cr₃ and M₇C₃ carbides,and the heat-affected zone and matrix are mainly composed of lath martensite.The average impact energy of the remanufactured samples after heat treatment is 28 J,the impact performance remains unchanged,and the mechanical properties are equivalent to those before heat treatment.(4)After the EA4T remanufactured sample is subjected to stress relief annealing treatment,the cladding layer is composed of austenite,M₂₃C₆ carbide and Cr B,the heat-affected zone structure is lath martensite and tempered sorbite,and the matrix structure is Ferrite.After stress relief annealing at 550?,the microhardness of the remanufactured samples decreased significantly,and the average impact energy increased to 51 J.(5)The three-point bending test method was used to test the plane strain fracture toughness of the specimens remanufactured after 550?stress relief annealing treatment.According to the load-displacement(P-V)curve,the fracture toughness value K_IC of the specimens remanufactured after heat treatment was calculated from 48.1 MPa·m^1/2 increased to 71.5MPa·m^1/2.