The Experimental Study And Simulation On Grind-hardening Of GCr15 Steel By CBN Grinding Wheel

With the development of the mechanical processing fild,grinding processing gradually develops in the direction of green,energy saving and high efficiency.Grind-hardening technology actively uses the heat and grinding force generated in dry grinding to directly harden the workpiece surface to produce the hardened layer surface of the workpiece material.Grind-hardening technology integrates surface heat treatment with parts manufacturing and production,which is both environmentally friendly and can increase production efficiency.It is a green manufacturing process and is in line with the development trend of modern manufacturing.In this paper,under the study of the grind-hardening process,through the test of cBN grinding wheel hardening GCr15 steel and the simulation of the grinding temperature field,the temperature curve of the part is used to combine the surface hardness measurement of the material and the metallographic structure and observation of the microscopic morphology reveals the hardness distribution and structure transformation distribution of the hardened layer that affects the surface of the grinding parts,and the wear resistance of the hardened layer is tested by the friction and wear test.The main work and innovative research results are as follows:(1)The surface grind-hardening test of GCr15 steel was carried out with cBN grinding wheel.The hardness of the cut-in area,middle area and cut-out area of the workpiece hardened layer surface after grind-hardening and the hardness of the cross section of the hardened layer were measured.The metallographic structure and surface micro-morphology of the workpiece before and after hardening.The above measurement data is simply processed,and the hardness and surface morphology of the hardened layer of the workpiece are compared through different grinding conditions tests,and the rules are summarized.The results show that:according to the degree of hardness increase,it can be judged that the workpiece has hardened during grinding,which is conducive to improving the performance of the workpiece.The surface hardness of the workpiece gradually increases as the grinding depth of the grinding wheel increases,and gradually increases as the feed rate of the workpiece increases.The hardness distribution has a greater consistency along the width distribution.In the feed direction of the grinding wheel,that is,the grinding direction of the workpiece,the hardness has a tendency to gradually increase.The transformation of the microstructure of the workpiece is the main factor affecting the hardness uniformity of the hardened layer during the grinding process.The depth and width of the wear scar increase with the increase of the grinding depth and the feed rate of the workpiece.Properly reducing the workpiece speed can increase the Surface Quality.Cryptocrystalline martensite appears in the grind-hardening layer of the workpiece,and the matrix structure remains unchanged.However,due to the grinding force,the ferrite fracture phenomenon occurs.(2)Conduct friction and wear experiments on GCr15 steel before and after grinding.Different load strengths are used to compare the wear resistance of the hardened layer,and to compare the differences in friction and wear characteristics of the workpiece surface before and after grinding.Studies have shown that:the overall friction coefficient decreases with increasing load;compared with the workpiece before grinding-hardening,the friction coefficient of the hardened layer of the workpiece after grinding is significantly reduced;under the same load state,the grinding hardened layer is less than the unhardened The surface wear scar width and depth of the workpiece are small,and the amount of wear is also small;the surface roughness of the three areas of the hardened workpiece from the cutting area to the cutting area gradually increases,the grinding depth increases,and the surface roughness increases;the feed speed increases,The roughness is reduced.(3)The finite element simulation model of the temperature field of cBN grinding GCr15 steel was established.The equilibrium conditions of the grinding temperature field during the grind-hardening process are proposed,and the temperature field changes during the grinding and hardening process are simulated by Abaqus software.Through simulation,the temperature distribution of the grind-hardening zone at different time steps and the temperature change of the grinding node are obtained.The depth of the hardened layer is roughly estimated based on the temperature of the node,and compared with the experimental value,the error is 1.6%.The hardness of different areas of the hardened layer is calculated according to the empirical formula and compared with the test.The results show that the error between the thickness of the simulated grinding hardened layer and the data measured in the test is about 3%,and the accuracy of the test is verified.