Papers by Keyword: Grind-Hardening

Abstract: Based on orthogonal experiments, the influences of grinding process parameters including depth of cut (a_p), workpiece infeed velocity (v_w) and transverse regrinding value (C_r) 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 a_p, followed by v_w and C_r 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.

Abstract: The grind-hardening test of 42CrMo steel was carried out on a forming grinding machine. The macrostructure, microstructures, micro-hardness and the depth of the hardened layer were measured and analyzed by optical micro-scope, scanning electron microscope and digital micro-hardness tester. The influences of original microstructure on the grind-hardened layer of 42CrMo steel were studied. The results show that the acicular martensite and a small amount of undissolved carbide appear in the surface layer, and slightly coarse martensite and a small amount of undissolved carbide appear in the middle layer of the completely hardened zone. Microstructure of the transitional zone varies with original structure. The microstructures and micro-hardness of the completely hardened zone have no obvious change under different original organizations, and the micro-hardness is 620HV0.5-700HV0.5. However, the distance from the slightly coarse martensite and the depth of the hardened layer increase with the uniformity improvement of the original microstructure.

Abstract: The grinding hardening workpiece deformation caused by high temperature leads to the variation of the grinding force. Grinding force of dynamic variation affects the grinding depth of hardened layer distribution. So it is necessary to study the variation rule of grinding hardening force. Through grinding arc temperature analysis and deformation analysis, the influence factor for grinding arc temperature and workpiece deformation on grinding force is analyzed. The analysis results are compared with the experimental results.

Abstract: External grind-hardening is a new technology combing grinding and quenching. Hardening tests are carried out according to 3-level and 3-factor orthogonal method for 40Cr steel, and metallographic observation and hardness measurement are put forward. Martensite is found in the surface layer structure, which hardness reaches HV647.4~719.4 and depth is about 0.22~1.1mm. The practicability of the new technology is confirmed. Orthogonal analysis is proceeded successively for the acquirements of influencing pattern and significance of factors based on the hardening results.

Abstract: Grind-hardening is a green efficient processing technology that focus on surface harden. The paper simulated the traverse cylindrical grinding with establishing a finite element model, which revealed the thermal gradient while processing in history. And the research confirmed the possibility of prediction of the harden layer, and summarized the properties of traverse cylindrical grind-hardening.

Abstract: A new manufacturing technology, external grind-hardening, is put forward and orthogonal tests are carried out with 3-level 3-factor aimming at 40Cr steel and 45 steel. A certain depth of Martensite layer is found on the hardened surfaces of both materials by metallographic observation and the hardness values meet the design requirement, which demonstrates the practicability of the new technology. Orthogonal analysis is proceeded successively for the acquirements of influencing pattern and significance of factors, and comparative study is carried on the hardening effect and feature for the both materials.

Abstract: Grind-hardening experiments of 40Cr steel were carried out on the external grinder, and the hardness and hardened-depth of the samples were measured and analyzed. Experimental results showed that the external grind-hardening was feasible and could take the place of high-frequency induction hardening. Moreover, dynamic temperature field was simulated and analyzed based on the finite element analysis, and the simulation results were in a good accordance with these of experiment values.

Abstract: The grinding process is currently used for machining the parts requiring for good precision. However, the apparition of some damage related to this process is still uncontrolled, in which the major deterioration is from the residual stress. Through grinding and hardening test, the residual stress distributions under different grinding speeds are obtained, and then numerical simulation for thermal stress of the workpiece surface is carried out by finite element software ANSYS to deduce the distribution of phase transformation stress under different grinding speed.

Abstract: The grind-hardening method suitable for external grinding is proposed in this paper and the experiments are carried out on MI432B grinding machine.The hardened layer of the workpiece with cut depth 0.3mm and speed 0.2 m/min is analyzed.The result indicates the metallurgical structure of the hardened layer is martensite and the top hardness value is 754 HV(about 620 HRC).At the same time,the grinding force,one of the most important factors of grind-hardening process is modeled, and the measurement method is provided with elastic core clampers.The measurement result shows that the values of both the tangential force and the normal force increase when the cut depth increases,and the top value is 146 N and 656 N with the cut depth value of 0.4 mm respectively.

Abstract: By using ANSYS, the temperature distribution in workpiece of steel 48MnV under the actions of a moving thermal source, is first carried out by FEM for non-linear transient temperature field. On this basis, the residual stress distribution in the workpiece under the action of temperature variation and moving grinding loads is determined by FEM for thermo elastic-plasticity. The result shows that the existent residual stress on surface of grinding hardening is press. The reason of this is discussed. The difference between the simulated value and measured value of grind-hardening stress is acceptable.