高速切向车铣对18CrNiMo7-6钢表面完整性的影响

Effects of High Speed Tangential Turn-milling on Surface Integrity of18CrNiMo7-6 Steels

为提高18CrNiMo7-6齿轮钢的抗疲劳性能,进行了高速切向车铣试验。结果表明:高速切向车铣可获得接近于磨削的三维表面粗糙度S_(a),工件转速nw和铣刀转速n_(c)对S_(a)的影响较为显著,且S_(a)随着n_(c)的增大而减小,随nw的增大而增大;高速切向车铣(逆铣)已加工表面均为残余压应力,n_(c)及轴向进给量f_(a)对表面残余应力有显著影响;随着n_(c)的增大,轴向残余应力σ_(x)和切向残余应力σy均呈先增大后减小的趋势,随着f_(a)的增大,σ_(x)和σy显著减小;最大残余应力出现于已加工表面,且在距已加工表面40~60μm之内逐渐减小,之后趋于稳定;轴向进给量f_(a)对表面完整性综合影响最大,随着f_(a)的增大,表面质量迅速变差。在高速切向车铣正交试验条件下,得到的最优试验参数组合为:n_(c)=6500 r/min,n_(w)=75 r/min,f_(a)=0.02 mm/r,径向切深ap=0.1 mm。在最优参数切削条件下,S_(a)为0.30μm,σ_(x)为-400.5 MPa,σy为-415.9 MPa,残余应力影响层深度为60μm。高速切向车铣获得的表面完整性优于传统车削,该切削方法可为外圆表面的加工提供一种更好的加工方式。

In order to improve the anti-fatigue performance of 18CrNiMo7-6 gear steel,high-speed tangential turn-milling experiments were conducted.Results show that with high-speed tangential turn-milling,the three-dimensional surface roughness value S_(a) are close to those with grinding.The influences of workpiece rotating speed n_(w) and milling cutter rotating speed n_(c) on S_(a) are significant.The Sa decreases with the increase of n_(c),and increases with the increase of n_(w).There are residual compressive stresses on the machined surfaces of high-speed tangential turn-milling(up milling).The n_(c) and axial feed f_(a) have significant effects on surface residual stress.With the increase of n_(c),the axial residual stressσx and the tangential residual stressσy show the trends of increasing at first and then decreasing,and with the increase of f_(a),σx andσy decrease significantly.The maximum residual stress appears on the machined surfaces,decreases gradually within 40~60μm thickness from the machined surface and then stabilizes.The f_(a) has the greatest overall impact on the surface integrity and the surface integrity deteriorate rapidly with the increase of f_(a).Under the orthogonal test conditions of high-speed tangential turn-milling,the optimal test parameter combination obtained is as n_(c)=6500 r/min,n_(w)=75 r/min,f_(a)=0.02 mm/r,radial depth of cut a p=0.1 mm.Under the conditions of optimal cutting parameters,the Sa is as 0.30μm,σx is as-400.5 MPa,σy is as-415.9 MPa,and the depth of residual stress affected layer is as 60μm.The surface integrity with high-speed tangential turn-milling is better than that with conventional turning.The cutting method herein provides a better machining method for machining external cylindrical surfaces.