Effect Of Cold Rolling And Annealing Process On Microstructure And Properties Of Chromized 304 Stainless Steel

304 austenitic stainless steel is a widely used high chromium nickel austenitic stainless steel.It has been widely used in various fields because of its good corrosion resistance,heat resistance and good mechanical properties.However,the defects of low hardness and poor wear resistance of 304 austenitic stainless steel make the surface wear failure of workpiece easily affect its service life,which greatly limits the wider application range of 304 austenitic stainless steel.Current research shows that alloying elements infiltration on stainless steel surface is a very effective surface protection method,which can improve the surface hardness,wear resistance and corrosion resistance of 304 stainless steel.In this paper,the modified chromizing layer was successfully prepared on the surface of 304 austenitic stainless steel by the embedding powder chromizing technology through induction heating,and the coarse grains of the matrix organization caused by diffusion were refined by introducing rolling deformation and annealing.Finally,the surface hardness and wear resistance of 304 austenitic stainless steel were improved,and the corrosion potential was increased.The hardness of the matrix austenitic organization was also improved through fine grain strengthening,and the overall performance of 304austenitic stainless steel was improved.The main work is as follows:(1)Under the condition of heating 1000°C for 1h,the infiltration layer of induction heating and box furnace heating were compared,and the microstructure of Cr infiltration was studied.The formation mechanism of the infiltration layer was explored,and the hardness,wear resistance and corrosion resistance of the infiltration layer were tested.(2)The samples with chromized layer were rolled with different rolling deformations of 21%,31%,35%,40%,46%,50%and 68%,and the changes of microstructure of the chromized layer and the matrix were studied.The relationship between rolling deformation and deformed martensite was discussed,and the microhardness of the rolled sample was tested.(3)The samples with 21%and 31%rolling deformation were annealed at 800°C and 850°C for 5 min,and the microstructure changes of the layer and the matrix were studied.The properties of the layer were tested.Through the above research,the following conclusions are drawn:(1)The induction heating chromizing efficiency is higher and the chromizing quality is better.The microstructure of the chromizing layer is mainly composed of?-Fe-Cr solid solution and alloy carbides(Cr,Fe)₂₃C₆and(Cr,Fe)₇C₃.The hardness,wear resistance and corrosion resistance of 304 austenitic stainless steel after chromizing were improved.(2)With the increase of rolling deformation,the bonding between the infiltration layer and the substrate still remains dense without cracks and spalling.The content of deformed martensite increases with the increase of rolling deformation.(3)After annealing the rolled sample,the microstructure of the infiltrated layer becomes Fe-Cr solid solution near the matrix and the composition of Cr₂₃C₆,Cr₇C₃,Cr₂C and Cr₃C₂.The surface hardness of the infiltration layer reaches about 1100 HV,the wear quality is further reduced,the corrosion voltage increases,but the corrosion rate increases.