面向窄深槽结构的风冷式单层CBN砂轮超高速磨削冷却换热机理的研究

Narrow-deep-groove is a type of structure which is appeared in the key special components of aeronaut, automobile and hydraulic, and grinding is the terminal finishing process for this structure. Sudden burns to the workpiece and severe wear to the grinding wheel were caused by its narrow and deep specificity. By studying heat transfer mechanism of grinding narrow-deep-groove at ultra-high speed, depth-to-width ratio structure coefficient of narrow-deep-groove section is introduced. W.B.Rowe heat source allocation model is expended, and heat distribution ratio theory model is built. Combing airflow filed distribution specificity of ultra-high speed grinding and grinding heat hysteresis effect of ultra-high speed grinding, the mapping relation of grinding heat hysteresis response time and wind outlet intervals of grinding wheel base were established. In grinding contact area, “hot and cold synchronization were appeared in the same time, and instant improved-heat-transfer design theory was generated in the process when grinding wheel is rotating at ultra-high speed is formed. By analyzing internal flow characteristic of non-grinding area flow barrier field around grinding wheel, lateral flow barrier break technology is researched, and rotating wind cooling of the tool in non-grinding area is generated .Dual cooling effect to tool and workpiece in the ultra-high speed grinding process of narrow groove structure is achieved. Air cooling and dry grinding of narrow-deep-groove are formed, and the produce bottleneck of key parts in major components is overcome. .The project research results will develop and enrich heat transfer theory in grinding process and offer theory and technology support to the efficient dry grinding and air cooling of narrow-deep-groove structure.

窄深槽是航空、汽车、液压等行业关键零部件上一种特殊结构，磨削常成为它的最后加工工序，其结构的特殊性易引发工件磨削烧伤以及砂轮的剧烈磨损。通过研究超高速磨削窄深槽热交换机理，引入窄深槽截面深宽比结构因数，对W.B.Rowe热源分配模型进行拓展，构建窄深槽磨削区域热分配比理论模型，结合超高速磨削区域气流场分布特性以及超高速磨削热滞后效应，建立磨削热滞后响应时间与砂轮基体出风口间隔的映射关系，形成砂轮在超高速旋转过程中磨削区域“热冷同步”及时强化换热的设计理论。通过分析非磨削区域砂轮周围气流屏障场内部流动特性，研究侧向气流屏障破除机制，形成非磨削区域对工具的旋转给风冷却，达到超高速磨削过程中对工具与工件的双重冷却效能，实现窄槽类结构的风冷干磨削，解决重大装备中关键零部件生产的瓶颈。.项目研究成果将发展和丰富磨削过程传热理论，为窄深槽结构类零件的高效风冷干磨削提供理论和技术支持。

窄深槽是指深宽比大于2，且槽宽一般小于4mm的一种特殊结构，常见于航空、汽车、液压元件等零部件上。窄深槽的传统加工方法存在刀具磨损严重、工件成品率低、加工精度低、成本高等问题。深切缓进给磨削工艺为窄深槽结构磨削提供了一种新途径，但限于窄深槽磨削区域位于工件内部，其磨削区域的冷却润滑非常困难。实现深切缓进给磨削窄深槽工艺的工业化推广应用的关键是解决窄深槽磨削过程中的冷却和提高砂轮耐磨性。.本项目针对窄深槽深切缓进给磨削过程中磨削烧伤和砂轮磨损问题，提出了风冷式单层CBN砂轮超高速磨削窄深槽的同步冷区强化换热新工艺理论。基于窄深槽磨削区划分理论，分析了窄深槽侧面、槽底面和圆角区域的磨削热流密度分布，建立了窄深槽不同磨削区磨削热分配理论；设计了风冷式单层CBN砂轮，利用CBN磨粒的超硬特性提高砂轮耐磨损性能，设计离心式涡轮导风结构和内夹气流道的砂轮基体结构，实现窄深槽磨削区的强化换热冷却；针对砂轮高速旋转产生的气流屏障问题，仿真研究了砂轮高速转动环境气流压力和流速分布特性，通过大直径砂轮磨削窄深槽气流场压力分布特性研究，建立起气流屏障位置和强度的评价机制，研究了砂轮参数及磨削工艺参数对气流屏障位置和强度的影响规律，在此基础上设计了风冷式砂轮上卡盘的出风口结构，实现了窄深槽磨削气流屏障破除技术；根据窄深槽磨削热分配比理论，进行了风冷式砂轮的“热冷同步”设计，优化了涡轮叶片的叶型参数、砂轮基体气流道的形状参数及出风口、对流凹槽、内置的冲液平衡环等结构，建立起面向窄深槽结构的风冷式单层CBN砂轮“热冷同步”设计理论；进行了多种材料的窄深槽磨削，研究了磨削工艺参数对窄深槽表面完整性的影响；完成了基于分子动力学的单晶硅和单晶镍切磨削机理研究，进一步丰富了窄深槽磨削理论体系。.风冷式单层CBN砂轮深切缓进给磨削窄深槽新工艺是解决当前窄深槽结构类零件加工难题的有效途径，在简化工序的基础上保证窄深槽的高表面完整性精密加工，其风冷特性使磨削工艺步入了绿色制造技术行列，对我国高精密产品的中国制造提供了有力支撑。