Based on the orthogonal experiment, the influences of grinding depth (a
p), the workpiece feeding rate (v
w) and the transverse regrinding value (C
r) on two side-direction burr of 40Cr steel large-plane grind-hardening workpiece were investigated. The results show that, under the coupling of heat and force in the grind-hardening process, the surface metal of the workpiece metal flows toward the unconstrained direction on both sides, resulting in the formation of the burr. The grinding depth and the workpiece feeding rate become leading factors affecting the size of the burr. Moreover, the significance of three factors to the size of the burrs is as follows: the grinding depth (a
p) > the workpiece feeding rate (v
w) > the transverse regrinding value (C
r). The result showed that the maximum size of the first-pass and the second-pass burr would increase with the increasing of the grinding depth and the transverse regrinding value in grind-hardening processes, but it decreases with the workpiece feeding rate. The optimal process parameters are a
p=0.1mm, v
w=0.8m/min, and C
r=1mm under the experiment conditions.
This paper discusses the effects of the depth of cut (ap
), the workpiece speed (vw
) and the grinding wheel speed (vs
) on the structure and hardness of the grind hardening layer on the steel GCr15. It was found that the completely hardened zone of the internal grind-hardened layer on the steel GCr15 mainly contains needle-shaped martensite and a very low amount of carbides and retained austenite. The grinding parameters have no significant effect on the martensite microstructure and hardness of the high-hardness zone in the internal grind-hardening process. An increase of the depth of cut and the grinding wheel speed or a decrease of the workpiece speed, leads to a thicker grind-hardening layer. From the viewpoint of increasing the hardness penetration depth, a larger the depth of cut and the grinding wheel speed and a smaller the workpiece speed should be selected, under the internal grind-hardening experimental conditions.
Based on orthogonal experiments, the influences of grinding process parameters including depth of cut (ap), workpiece infeed velocity (vw) and transverse regrinding value (Cr) on hardened layer depth (HLD) of 40Cr steel are studied in the grind-hardening process. The grind-hardening orthogonal experiments of 3-factors are performed on the 40Cr steel with the L16 (45) orthogonal table and the experimental optimization design theory. To understand quantitatively the effects of three grinding process parameters, the experimental data are modeled by regression. Among three grinding process parameters, the most important parameter is ap, followed by vw and Cr respectively. The experimental results indicate that HLD would increase with the increasing of the depth of cut and the decreasing of the workpiece infeed velocity in grind-hardening process, but HLD would decrease with the increasing of the interaction between the depth of cut and workpiece infeed velocity.
Grind hardening is an alternative process to the conventional quenching process. The heat generated during grinding transforms the surface layer of workpieces into the martensitic structure. In this study, we simulated the temperature distribution during grind hardening to investigate the effects of heat on the changes in hardness and microstructure with different regrinding values using AISI 5140 alloy metal. We also compared the experimental results of single-and double-pass grind hardening processes. The results showed that the regrinding value affected the lateral distribution of hardness on the surface of the metal during grind hardening. The process created a softening width between the first and second ground layers, where a decreased softening width indicated the improved efficiency of grind hardening. It was found that double-pass grind hardening yielded the desired grinding results that reduced the softening width. The results of this study obtained using the AISI 5140 alloy metal also suggest that double-pass grind hardening can be used in high-efficiency quenching for various alloy metals.
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