【作者】 徐正亚；

【导师】 徐鸿钧；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 金刚石磨料具有硬度高、导热性、耐磨性好等优良的性能,因此金刚石工具在石材、硬质合金、玻璃、陶瓷等硬脆材料的加工中获得了广泛的应用。然而传统的多层烧结与单层电镀金刚石砂轮由于结合剂对金刚石磨粒的把持强度低且容屑空间小,金刚石工具的优势未得以充分发挥。钎焊金刚石工具由于实现了金刚石与活性钎料的冶金结合,因此钎料对金刚石磨粒有很强的把持力,且磨粒间容屑空间大。本课题利用感应钎焊工艺研制了磨粒有序排布的单层钎焊金刚石砂轮。本文完成的研究工作主要包括:(1)研制了一套感应钎焊工艺试验装置,根据感应加热设备与线圈间阻抗匹配的要求,通过实验测量及理论计算设计了相应的感应加热线圈,制作了感应钎焊气体保护装置。在分析强磁场干扰下热电偶输出电势信号的基础上设计了相应的信号调理电路,获得了准确的钎焊温度信号,结合模糊控制方法开发了基于虚拟仪器的感应钎焊温控系统,为研究金刚石感应钎焊工艺奠定了基础。(2)利用扫描电镜、能谱仪和X射线衍射仪分析了钎焊工艺参数对金刚石界面化合物和微观结构的影响,结合不同钎焊工艺时金刚石磨粒的静态抗压强度及钎焊试样磨削花岗石的研究,获得了优化的钎焊工艺,磨削花岗石的实验同时也表明感应钎焊金刚石工具比炉中钎焊金刚石工具有更优异的加工性能。(3)研制了局部感应加热条件下连续感应钎焊金刚石砂轮的装置,利用带导磁体的平面线圈实现钎焊部位的局部加热,结合工件的连续旋转完成了金刚石砂轮的感应钎焊过程,该工艺的特点是砂轮表面钎料熔化区域窄,金刚石磨粒在钎焊时不易发生移位,易于获得磨粒有序排布的金刚石砂轮。(4)利用感应钎焊金刚石砂轮进行了硬质合金的磨削试验研究,并与同规格的电镀金刚石砂轮进行了对比实验。结果表明,单层钎焊金刚石砂轮较为锋利,相对于电镀金刚石砂轮有更长的工具寿命。对磨削过程中金刚石磨粒的磨损状态进行跟踪观察,结果发现钎焊金刚石的磨损机理主要是磨耗磨损,试验中未出现磨粒脱落,表明采用感应钎焊工艺制作的单层金刚石砂轮对磨粒有很强的把持力,有助于充分发挥超硬磨料本身的加工性能。更多还原

【Abstract】 Diamond tools have been extensively utilized in grinding hard and brittle materials such as stone, tungsten carbide, glass and ceramics, because of the excellent performances of Diamond abrasive, including extremely high-hardness, high-thermal conductivity, high-wearing feature and so on. However, owing to the limited storage space for chips and poor bonding force between diamond grits and matrix, it is not cost-effective with traditional multiplayer sintered and monolayer electroplated Diamond tools. Due to the chemical metallurgical reaction between grains and matrix, brazing diamond tools have sufficient storage space for chips and high bonding strength between diamonds and brazing filler. The monolayer diamond grinding wheels with rhythmed grain distribution are developed with induction brazing.The main contents in this paper are as follows:1. Experiment platform for high-frequency induction brazing diamond has been established, including inductor suitable to induction heating power, inertia gas protecting device. Based on the analysis of signal characteristics of thermocouple under strong electromagnetic disturbance, a real thermal potential representing the brazing temperature was obtained through the processing of signal conditioning circuit designed to regulate the measured signal, a temperature control system based fuzzy-control and virtual instrument was developed, the preparative work laid foundation of induction brazing process.2. The reaction products and the interfacial microstructure under the different conditions have been detected by scanning electron microscope (SEM), energy dispersion spectrometer (EDS), and X-ray diffraction (XRD), which combining with the tests of grinding granite and the compressive strength of the grain, processing parameters are recommended for brazing diamond with Ni-Cr filler alloy under high frequency induction heating. Performance of an induction brazed diamond wheel is remarkable than furnace brazed diamond tool while machining granite.3. Experiment devices have been designed and illustrated for induction brazing of diamond wheels, the method of local heating combine with continual revolving of the workpiece was adopted to fabricate the grinding wheel by plane inductor fixed with magnetic flux concentrator. During the process of induction brazing, small melting area of brazing filler alloy on the grinding wheel was achieved, the diamond grains could hardly be removed from their original position, which was key to acquire the monolayer diamond grinding wheels with rhythmed grain distribution.4. Experiments of grinding tungsten carbide were conducted to measure the grinding forces under different grinding parameters, and compared with the electroplated Diamond wheel. The experiment results illustrated the lower grinding force, and longer life could be reached with induction brazing diamond wheel than electroplated grinding wheel. Worn behaviour of the brazing diamond grits are traced in the whole grinding process, the fallout of Diamond grits was not found and the abrasion wear was the leading worn patterns of diamond grits, which indicates that the strong joining to the grains has been realized in the induction brazing, it will benefit to utilize the outstanding machining ability of Diamond superabrasive grains.更多还原