Yin Youkang, Chen Ming
State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Materials (Basel). 2024 Apr 12;17(8):1784. doi: 10.3390/ma17081784.
Creep-feed grinding of high-strength steel is prone to excessive wheel wear and thermal damage defects, which seriously affects the service performance of parts. To solve the above-mentioned issue, a creep-feed grinding test was carried out on high-strength steel using SG and CBN abrasive wheels. The grindability of high-strength steel was scrutinized in terms of grinding force, machining temperature and grinding specific energy. Moreover, the effects of operation parameters and grinder performances on the surface integrity of the workpiece such as surface morphology, roughness, residual stress and hardness were rigorously studied. The results indicate that, when the instantaneous high temperature in the grinding area reaches above the phase transition temperature of the steel, the local organization of the surface layer changes, leading to thermal damage defects in the components. The outstanding hardness and thermal conductivity of CBN abrasives are more productive in suppressing grinding burns than the high self-sharpening properties of SG grits and a more favorable machining response is achieved. The effects of thermal damage on the surface integrity of high-strength steel grinding are mainly in the form of oxidative discoloration, coating texture, hardness reduction and residual tensile stresses. Within the parameter range of this experiment, CBN grinding wheel reduces grinding specific energy by about 33% compared to SG grinding wheel and can control surface roughness below 0.8 µm. The weight of oxygen element in the burn-out workpiece accounts for 21%, and the thickness of the metamorphic layer is about 40 µm. The essential means of achieving burn-free grinding of high-strength steels is to reduce heat generation and enhance heat evacuation. The results obtained can provide technical guidance for high-quality processing of high-strength steel and precision manufacturing of high-end components.
高强度钢缓进给磨削容易出现砂轮过度磨损和热损伤缺陷，严重影响零件的使用性能。为解决上述问题，采用立方氮化硼（CBN）砂轮和陶瓷（SG）砂轮对高强度钢进行了缓进给磨削试验。从磨削力、加工温度和磨削比能等方面考察了高强度钢的磨削加工性。此外，还深入研究了工艺参数和磨床性能对工件表面完整性（如表面形貌、粗糙度、残余应力和硬度）的影响。结果表明，当磨削区瞬时高温达到钢的相变温度以上时，表层局部组织发生变化，导致零件出现热损伤缺陷。与SG磨粒的高自锐性相比，CBN磨料优异的硬度和热导率在抑制磨削烧伤方面更有成效，并且能获得更良好的加工响应。热损伤对高强度钢磨削表面完整性的影响主要表现为氧化变色、涂层纹理、硬度降低和残余拉应力。在本试验参数范围内，CBN砂轮比SG砂轮磨削比能降低约33%，且能将表面粗糙度控制在0.8μm以下。烧伤工件中氧元素的质量分数为21%，变质层厚度约为40μm。实现高强度钢无烧伤磨削的根本途径是减少热量产生并增强热量散逸。所得结果可为高强度钢的高质量加工和高端零部件的精密制造提供技术指导。
