【作者】 张明亮；

【导师】 刘海涛；

【作者基本信息】 哈尔滨工业大学 ， 机械（专业学位）， 2023， 硕士

【摘要】 8Cr4Mo4V轴承钢因其优异的高温力学性能,目前广泛的应用于我国高端轴承领域。磨削加工作为高端轴承制造过程中的一道重要工序,磨削表面的质量将会影响轴承的性能以及使用寿命,磨削变质层的性能对于磨削表面质量有较大的影响,因此需要进一步对8Cr4Mo4V轴承钢磨削变质层进行深入研究。为了拓展8Cr4Mo4V轴承钢的应用、提高国产高端轴承的磨削技术水平,本文采用有限元仿真与磨削实验相结合的方法,通过建模、分析、测试,进行了8Cr4Mo4V轴承钢磨削变质层微观组织的研究。首先进行霍普金森压杆实验,获得8Cr4Mo4V材料高应变率下的应力应变曲线,根据准静态与动态的力学特性曲线,确定8Cr4Mo4V材料的Johnson-Cook本构方程参数;采用有限元方法,从晶体和相体两个角度,建立了含有晶粒、晶界的多晶体模型和由针状马氏体、碳化物和其他基体相组成的相体模型,研究磨削过程中微观组织的去除和微观缺陷的形成及演化,分析不同磨削参数对磨削力和微观缺陷的影响规律。进行不同磨削参数的磨削实验,得到不同磨削参数条件下的磨削变质层。对磨削变质层进行测试与分析,通过X射线衍射(XRD)分析变质层的物相、微结构,得到不同磨削参数对变质层的奥氏体含量、亚晶粒尺寸以及微观应变的影响;通过超景深显微镜(OM)、扫描电子显微镜(SEM)对变质层进行观测,分析不同磨削参数对变质层厚度以及微观组织的影响;使用电子背散射衍射仪(EBSD)对变质层的梯度性能进行测试,分析变质层不同梯度的晶界、再结晶晶粒以及位错密度的分布情况。基于ABAQUS二次开发,建立具有梯度结构的变质层模型,使用晶体塑性有限元,研究变质层的拉伸性能。不同磨削参数的变质层具有不同的奥氏体含量、晶粒尺寸以及织构强度,将这些作为输入条件,探究变质层拉伸性能的变化规律。最后,通过纳米压痕实验,对变质层模型的结果进行验证。更多还原

【Abstract】 8Cr4Mo4V bearing steel is now widely used in the field of high-end bearings in China because of its excellent high temperature mechanical properties.As an important process in the manufacturing process of high-end bearings,the quality of the grinding surface will affect the performance and service life of the bearings,and the performance of the grinding metamorphic layer has a great influence on the quality of the grinding surface,so it is necessary to further study the grinding metamorphic layer of 8Cr4Mo4 V bearing steel.In order to expand the application of8Cr4Mo4 V bearing steel and improve the grinding technology level of domestic highend bearings,this Thesis adopts a combination of finite element simulation and grinding experiments to study the microstructure of the grinding metamorphic layer of 8Cr4Mo4 V bearing steel through modeling,analysis and testing.Firstly,Hopkinson pressure bar experiments were conducted to obtain the stressstrain curves of 8Cr4Mo4 V material at high strain rates,and the Johnson-Cook principal equation parameters of 8Cr4Mo4 V material were determined based on the quasi-static and dynamic mechanical property curves;the polycrystalline model containing grains and grain boundaries and the phase body model consisting of acicular martensite,carbide and other matrix phases were established from two perspectives of crystals and phase bodies using the finite element method to study the removal of microstructures and the formation and evolution of microscopic defects during grinding,and to analyze the influence law of different grinding parameters on grinding forces and microscopic defects.Grinding experiments with different grinding parameters were carried out to obtain the grinding metamorphic layers under different grinding parameters.The grinding metamorphic layers were tested and analyzed by X-ray diffraction(XRD)to analyze the physical phase and microstructure of the metamorphic layers,and to obtain the effects of different grinding parameters on the austenite content,sub-grain size and micro-strain of the metamorphic layers;the metamorphic layers were observed by ultra-field depth microscopy(OM)and scanning electron microscopy(SEM)to analyze the effects of different grinding parameters on the thickness and microstructure of the metamorphic layers The gradient properties of the metamorphic layers were tested by electron backscatter diffractometer(EBSD)to analyze the distribution of grain boundaries,recrystallized grains and dislocation density in different gradients of the metamorphic layers.Based on the secondary development of ABAQUS,a metamorphic layer model with gradient structure was established and crystal plasticity finite elements were used to study the tensile properties of the metamorphic layer.The metamorphic layers with different grinding parameters have different austenite content,grain size and weave strength,and these are used as input conditions to investigate the variation pattern of the tensile properties of the metamorphic layers.Finally,the results of the metamorphic layer model were verified by nanoindentation experiments.更多还原