超声滚压参数对18CrNiMo7-6齿轮钢表面性能的影响

目的研究在不同加工参数下,对18CrNiMo7-6齿轮钢进行超声滚压加工后表层质量的变化,并得出其显著性顺序。建立表面粗糙度的解析模型,研究进给量、滚压次数和初始表面粗糙度对表面质量的影响,并与试验结果作对比。方法采用车刀将固定在车床卡盘上的18CrNiMo7-6齿轮钢棒状材料的端面进行精车后,采用超声滚压试验装置对精车后端面进行加工处理。采用三维形貌测量仪等专用设备,对加工完成后的试样表面表面粗糙度、表层显微硬度、表面二维形貌和表层残余应力等进行检测,然后利用正交试验,寻找对试样表面粗糙度影响的显著性因素,建立表面粗糙度的解析模型,对比试验数据和解析模型数据,研究超声滚压对表面粗糙度、表面二维形貌、表层显微硬度和表层残余应力的影响。结果得到的显著性顺序为进给量、主轴转速、次数、振幅、静压力,并且前述给出的粗糙度解析模型可以较好地预测超声滚压后的表面粗糙度,计算得到的理论数据与试验数据较为接近。试样表面的粗糙度Ra由车削加工的3.003μm减小为0.468μm,齿轮钢表层形成了明显的加工硬化层,其深度约为260μm;表层显微硬度从未处理的360.9HV升至417.6HV,比率为15.7%;表层内形成了勺形分布的残余应力,在距离表层60μm处,最大残余压应力形成,为–790.97 MPa,残余压应力层深度达到了800μm。结论超声滚压加工可以显著提高18CrNiMo7-6齿轮钢试样的表面性能,其中以滚压进给量的影响最为显著。

Effect of Ultrasonic Rolling Parameters on Surface Properties of 18CrNiMo7-6 Gear Steel

The paper aims to study the effects of different ultrasonic rolling parameters on the surface quality of 18CrNiMo7-6 gear steel and its significance sequence.It also aims to establish an analytical model of surface roughness to research the influences of feed rate,repeat processing numbers and initial surface roughness on surface quality and compare them with the experimental results.The specimen was clamped on the blade adapter.The end face of 18CrNiMo7-6 gear steel rod material was turned first,and then processed by ultrasonic rolling.The surface roughness,surface microhardness,surface two-dimensional morphology and surface residual stress were measured by special equipment such as three-dimensional topography measuring instrument.Then orthogonal experiment was carried out to find the factors of significant effect on the surface roughness of the sample.An analytical model of surface roughness was established,and the analytical model data were compared with the experimental data to obtain the influence of ultrasonic rolling process on surface roughness,surface two dimensional morphology of ultrasonic rolling,surface microhardness and surface residual stress.The order and significance of the effect of ultrasonic rolling process parameters on surface roughness was:feed rate,spindle speed,repeat processing numbers,vibration amplitude,static pressure;and the analytical model of surface roughness can better predict the surface roughness after ultrasonic rolling.The calculated theoretical data was very close to the experimental data;after ultrasonic rolling,the surface roughness of the sample was reduced from the turned Ra 3.003μm to Ra 0.468μm.The obvious work hardening was obtained on the surface layer of the gear steel,and its depth was about 260μm;the surface microhardness was increased from 360.9 HV to 417.6 HV,increased by 15.7%.A spoon-shaped residual stress was formed in the surface layer.The maximum compressive residual stress,which was about–790.97 MPa,appeared in the depth of 60μm from the machined surface and the compressive residual stress layer reached 800μm.As a result,ultrasonic rolling process can remarkably improve the surface performance of 18 CrNiMo7-6 gear steel specimen,and the feed rate is the most significant factor.