Effect Of Heat Treatment Process On Microstructure And Properties Of 25CrMo48V High Strength Steel Under Magnetic Field

High strength steel is widely used in aerospace,shipbuilding,energy transportation,automobiles and other fields due to the excellent mechanical properties and low cost.In recent years,with the continuous upgrading of industrialization in various industrial fields,higher requirements have been placed on the comprehensive properties of high strength steel.The studies found that the magnetic fields heat treatment is of great significance to the research and development of high quality and high strength steel.The magnetic field heat treatment process can optimize the toughness and toughness of the material by controlling the phase transformation and carbide precipitation.Based on this,this article takes 25Cr Mo48V high strength steel with Nb,V,Ti and other microalloying elements as the research object,using metallographic microscope,scanning electron microscope,transmission electron microscope,EBSD,mechanical properties and corrosion resistance testing and other technical methods.The effect of magnetic field tempering heat treatment process on the microstructure,carbide evolution law,mechanical properties and corrosion resistance of 25Cr Mo48V microalloyed high strength steel was systematically studied.The main research contents and results are as follows:(1)To clarify the microstructure and precipitation phase evolution behavior of25Cr Mo48V microalloyed high strength steel under different tempering temperatures under the action of 1 T magnetic field.The results show that with the increase of tempering temperature,the width of martensite laths in 25Cr Mo48V steel gradually becomes thicker and the proportion of large-angle grain boundaries gradually increases.There are six different types of carbides precipitated in the matrix,which are rich-Nb MC,rich-Ti MC,M₃C,M₂₃C₆,M₂C,M₇C₃,and two kinds of MC carbides can exist stably with little size change.Compared with conventional tempering conditions,the application of a magnetic field can inhibit the merging of martensite laths and promote the premature precipitation of M₂₃C₆and M₇C₃.(2)The microstructure and carbides evolution of 25Cr Mo48V microalloyed high strength steel under the action of 1 T magnetic field is clarified in the different tempering time.The results show that the martensite laths in the untempered sample are arranged in parallel,and the martensite recovery degree is low.After tempering,the martensite laths are arranged at a certain angle,and the lath width increases with the tempering time..The size of the M₂₃C₆in the matrix gradually increases with the tempering time,and the size of the M₂C has little change.The size of M₇C₃remains unchanged for 10 min to 180 min after tempering,and then gradually increases with the tempering time extending to 240 min.(3)Electrochemical impedance spectroscopy,potentiodynamic polarization curve and corrosion morphology observation were used to investigate the effect of different tempering conditions on the corrosion resistance of 25Cr Mo48V microalloyed high strength steel under magnetic field.The results show that the self-corrosion potentials of samples under different tempering conditions is basically the same,and the corrosion morphology is mainly pitting corrosion.With the tempering temperature increasing,the corrosion resistance of 25Cr Mo48V steel gradually decreases.In different tempering time ranges,the corrosion resistance of tempered samples is higher than that of the non-tempering samples.and the corrosion resistance of other tempered samples gradually decreases with tempering time.