磨削用量对灰铸铁HT250磨削淬硬层的影响

Influence of grinding parameters on grinding hardened layer of gray cast iron HT250

在平面磨床上采用白刚玉砂轮对灰铸铁HT250进行磨削淬硬试验,研究磨削用量对灰铸铁HT250磨削淬硬层的影响。结果表明:灰铸铁HT250磨削后淬硬层由表及里依次是熔化层、完全淬硬层、过渡层和基体。熔化层由二次渗碳体、残留奥氏体和碳化物组成;完全淬硬层由马氏体、残留奥氏体和条状石墨组成;过渡层由马氏体、珠光体、残留奥氏体和条状石墨组成。改变磨削用量对淬硬层高硬度区显微硬度值没有显著影响,其硬度在800~900 HV0.2之间。磨削深度增加或者工件进给速度减小,都会使淬硬层深度增大。磨削深度和工件进给速度会对淬硬层的均匀性产生影响,致使切入端、中间端、切出端淬硬层深度不同,在本试验条件下当进给速度v_(w)=0.4 m/min时淬硬层的均匀性较好。

The grinding hardening test of gray cast iron HT250 was carried out on a surface grinder with white corundum grinding wheel,and the effect of grinding parameters on grinding hardened layer of the gray cast iron HT250 was studied.The results show that the hardened layer of the gray cast iron HT250 after grinding is composed of melting layer,completely hardened layer,transition layer and matrix from surface to inside.The melting layer consists of secondary cementite,retained austenite and carbide;the completely hardened layer is composed of martensite,retained austenite and strip graphite;the transition layer is composed of martensite,pearlite,retained austenite and strip graphite.Changing the grinding parameters have no significant effect on the microhardness value of the high hardness area of the hardened layer,and its hardness is between 800 HV0.2 and 900 HV0.2.The increase of grinding depth or the decrease of workpiece feed speed will increase the depth of the hardened layer.The grinding depth and workpiece feed speed will affect the uniformity of the hardened layer,resulting in different depths of the hardened layer at the inlet end,the middle end and the cutting end.Under the test conditions,the uniformity of the hardened layer is better when the workpiece feed speed v_(w)is 0.4 m/min.