CBN/纳米硬质合金复合材料纤维微刃螺旋砂轮及其磨削机理研究

During grinding process, grinding fluid is very difficult to penetrate into the grinding zone effectively. Abrasive grains are generally grinding with negative rake angle and the cutting chips usually remove inadequate, which result in a large number of grinding heat, poor surface integrity as well as wear of the grinding wheel. A new type CBN/nano-cemented carbide fibers grinding wheel with spiral groove is proposed in this project. The traditional abrasive grains of the grinding wheel are replaced by CBN/nano-cemented carbide fibers, and the fibers are distributed in spiral belt along the outer circumference of the grinding wheel. The wear resistance property of the grinding wheel is enhanced since the composite combines the merits of the high hardness for CBN and the good toughness for cemented carbide. Furthermore, the grinding heat will be reduced as the fibers are grinding with zero rake angles. In addition, the spiral structure of the grinding wheel is conducive to inject grinding fluid into the grinding zone, and then the lubrication and cooling performance of the grinding zone will be improved. Based on this, the preparation technologies of the composite and sharpening method of the fiber will be researched. The designing theory and manufacture method of the fibers grinding wheel with spiral groove will be established. The stress-strain behavior, the temperature distribution characteristics and the materials removal mechanism of the interface between fiber and workpiece will be studied by the grinding experiment and numerical simulation for single fiber. The grinding experiment of fibers grinding wheel with spiral groove will be carried out and the grinding theory of this new grinding wheel will be established. This work will provide new ideas and theoretical basis for reducing grinding temperature, improving grinding quality and enhancing grinding efficiency.

针对磨削加工时磨削液很难进入磨削区，磨粒往往呈负前角加工，且排屑不畅而导致生成热量多、磨削质量差和砂轮磨损严重等问题，本项目提出了一种新型结构的CBN/纳米硬质合金复合材料纤维微刃螺旋砂轮，其特点是采用CBN/纳米硬质合金复合材料纤维取代传统砂轮磨粒，纤维微刃沿着砂轮外圆周呈螺旋带状排布。复合材料集CBN高硬度和硬质合金高韧性于一体，增强了砂轮的使用性能和寿命；纤维微刃零前角切削可减少磨削热的产生；砂轮的螺旋结构有助于磨削液进入磨削区，增强磨削区润滑冷却性能。在此基础上研究复合材料制备技术、纤维微刃的制备与刃磨方法；建立纤维微刃螺旋砂轮的设计理论和制备方法；通过单纤维微刃磨削实验和数值仿真研究纤维微刃/工件界面的应力/应变行为、温度分布特征和微观材料去除机理；基于纤维微刃螺旋砂轮磨削实验，系统建立新型砂轮磨削加工理论。本项目将为降低磨削温度、改善磨削质量、提高磨削效率提供新思路和理论基础。

针对磨削加工时磨削液很难进入磨削区，磨粒往往呈负前角加工，且排屑不畅等问题，本项目提出了一种螺旋有序排布CBN-WC-10Co复合材料纤维刀具，其特点是采用CBN-WC-10Co纤维取代传统砂轮磨粒，纤维沿着刀具轮毂外圆周呈螺旋排布；复合材料集CBN高硬度和WC-10Co高韧性于一体，增强了刀具的耐磨性能；纤维零前角切削可减少切削热的产生；刀具的螺旋结构有助于切削液进入切削区，增强了润滑冷却性能。在此基础上开展了CBN-WC-10Co复合材料放电等离子烧结方法研究，结果表明CBN颗粒与WC基体具有良好的粘接性能，没有出现CBN向HBN转变现象，随着烧结温度升高或保温时间延长，复合材料的密度、抗弯强度、硬度等物理力学性能增强，然而当烧结温度超过1250℃或保温时间超过7分钟，进一步增大烧结温度或保温时间，材料硬度反而下降。采用激光和电火花技术对CBN-WC-10Co复合材料进行了切割实验，实验发现电火花线切割材料去除机理主要是放电通道产生高温使得材料局部区域熔化或气化，在放电爆炸力作用下被抛出熔池，金属钴会被过量去除并导致WC颗粒脱落，部分CBN颗粒直接从基体脱落并形成凹坑；激光切割时出现了亚表面微观裂纹和HBN转变相。开展了螺旋有序排布纤维刀具的设计理论及制备方法研究，流场仿真发现纤维刀具的切削液有效流量明显增大，增大纤维间距会使得切削液有效流量增大；喷射速度和喷嘴出口高度增大，切削液有效流量增大，但是有效流量利用率反而降低。开展了单纤维切削材料去除机理和微刃磨损机理研究，结果表明与单颗磨粒相比，单纤维划痕两侧的材料堆积现象大为减轻，单纤维的材料去除率高达99.1%，纤维磨损率有了较大减轻。开展了螺旋有序排布CBN-WC-10Co纤维刀具切削实验研究，实验发现螺旋有序排布纤维刀具的切削表面形貌可以与普通树脂结合剂CBN砂轮相媲美，纤维刀具的表面粗糙度略大于CBN砂轮，纤维刀具的切削力、切削温度和比切削能均有了明显降低。本项目为降低切削温度、改善切削质量、提高切削效率提供了新思路和理论基础。