【作者】 庞子瑞；

【导师】 王宛山；

【作者基本信息】 东北大学 ， 机械制造及自动化， 2009， 博士

【摘要】 超高速磨削技术被喻为“现代磨削的最高峰”,已被国际生产工程学会列为面向21世纪的中心发展方向。德国Junker公司1994年开发的超高速点磨削技术是超高速磨削又一新的应用形式,是集数控柔性加工技术、CBN超硬磨料、超高速磨削三大先进技术于一身的先进加工工艺。超高速陶瓷CBN砂轮技术是超高速点磨削关键技术之一,陶瓷结合剂CBN砂轮因其优良的磨削性能和制作过程的绿色、环保、节能、低耗被公认为是高速、高效、高精、低成本、低环境污染的高性能砂轮,是近年来世界各国竞相开发的热点。本文从超高速点磨削的机理分析入手,针对超高速点磨削陶瓷CBN砂轮的结构特点,按照磨削理论和合成材料的制备原则,对其各组成部分及其关键技术、制造工艺进行了较为系统的研究,并对研发的超高速点磨削砂轮进行了磨削性能实验。总结全文,本论文的工作概括如下：(1)概述了超高速磨削技术及其理论研究领域的发展历史。系统论述了超高速陶瓷CBN砂轮磨削的优越性及国内外的发展状况。阐明了本课题的研究目的和意义。(2)从砂轮、工件接触弧长和未变形切屑厚度这两个基本参数入手,论述了两个变量角α和β对超高速点磨削机理的影响。在此基础上建立了点磨削力、磨削温度、磨削表面粗糙度理论数学模型。通过对各数学模型的MATLAB仿真,从磨削机理的角度分析了点磨削变量角及其他磨削参数对磨削力、磨削温度和表面粗糙度的影响规律。(3)在高速、超高速砂轮应力分布的基础上,借助ANSYS软件,以径向膨胀量最小为目标函数,分析了超高速点磨削砂轮基盘形状、材料、尺寸等的选择,进行了最终截型的优化。(4)为了研发良好的超高速点磨削砂轮,对国内外8种有代表性的CBN磨料进行了常温性能、高温性能和耐腐蚀性能进行了对比实验,并对不同材料工件和加工需要对磨料的种类和粒度进行了探讨性选择；然后根据低温高强陶瓷结合剂的要求,设计了三组结合剂配方。通过对三种结合剂的成分、耐火度、抗折强度、热膨胀系数、物相、微观形貌的实验分析、对比,研制出了符合超高速点磨削砂轮要求的低温高强结合剂。(5)由于砂轮节块对于点磨削砂轮的制作和磨削性能很重要,所以,利用ANSYS软件对目标200m/s,直径Φ370mm的超高速点磨削陶瓷CBN砂轮节块进行了优化分析。根据优化节块的尺寸和强度结果,为了确保点磨削砂轮的安全性,提出了砂轮节块的最低强度要求。然后,以前面分析的CBN磨料和陶瓷结合剂为基础,对多组烧结砂轮样条进行了强度校核、分析,最后得出了高强度砂轮样条所需磨料的微观形貌、粒度、浓度等参数特点和要求。(6)在前面实验的基础上,根据超高速点磨陶瓷CBN砂轮的制作工艺研发、制作了超高速点磨削陶瓷CBN砂轮一块,并在东北大学超高速点磨削实验台和北京机械工业学院凸轮轴高速磨削实验台上,对点磨削砂轮的磨削性能进行了实验分析。实验表明：点磨削力随砂轮速度的增加而降低,随工件速度、磨削深度、纵向进给速度的增加而升高；磨削温度随砂轮速度的增加而降低,随工件速度、磨削深度、纵向进给速度的增加而升高；水平变量角的增大有利于磨削力、磨削温度的降低,但是,牺牲了表面粗糙度值。当变量角αβ都为+5°或-5。时,被磨工件的粗糙度Ra值略有增大,但工件表面的金相组织中无白层出现,被磨工件表面为残余压应力；当变量角αβ都为0°时,Ra值虽有所降低,但工件表面的金相组织中出现了有害的白层组织,即磨削温度高于727℃,被磨工件表面为残余拉应力。同时进行的磨削比表明：以被磨工件表面粗糙度Ra≤0.4μm、表面不出现残余拉应力为磨钝标准,超高速点磨削砂轮的磨削比G=170。同批次的陶瓷CBN砂轮生产中的磨削性能达到了进口砂轮的水平。(7)在超高速点磨削陶瓷CBN砂轮磨损机理分析的基础上,完成了超高速点磨削陶瓷CBN砂轮的修整实验。实验表明：当金刚石滚轮与CBN砂轮的速比为j=0.428时,修整后的砂轮地貌最好。更多还原

【Abstract】 Ultra-high speed grinding is regarded as "the highest peak of modern grinding technology" and listed as one of main development directions in 21st century. In 1994, ultra-high speed point grinding is developed by Junker Company in Germany. It is a new application form of ultra-high speed grinding. Ultra-high speed point grinding is an advanced processing technique which includes flexible numerical control machining technology, CBN super-hard abrasives and ultra-high speed grinding and so on. Vitrified bond CBN wheel is an important part of quick-point grinding, and called as high performance grinding wheel. Its characteristics are high speed, high efficient, high precision, and low cost, low environment pollution. Now, it is a development focus all over the world.In the paper, by using grinding mechanism of ultra-high speed point grinding and structural characteristics of ultra-high speed vitrified CBN wheel, and according to grinding theory and preparation principle of compose material, the key technologies of all parts of CBN wheel and manufacturing processes are systematically studied. Eventually, a vitrified bond CBN wheel is developed. Grinding performance of vitrified bond CBN wheel is tested on experiment table of quick-point grinding. The main works of the paper includes the following aspects:(1) The characteristics, key technologies and development status at home and abroad of vitrified bond CBN wheel and quick-point grinding are discussed. Research background and meaning of the thesis are introduced.(2) By undeformed chip thickness and contact arc length between grinding wheel and workpiece, the paper discusses grinding mechanism of ultra-high speed point grinding based on variable angleα&β. The theory mathematics models such as ultra-high speed point grinding force, grinding temperature and surface roughness are educed according to ultra-high speed point grinding mechanism. By MATLAB simulation, the effect of variable angleα&βand some grinding parameters on grinding force, temperature and surface roughness were analyzed.(3) Considering the security of CBN wheel, stress distribution characteristics of high speed and ultra-high speed grinding wheel are presented. Taking the distributing radial expansion volume of wheel base as objective function, selection of wheel hub shape, material, size and optimization of section shape are analyzed by using ANSYS software.(4) In order to develop an excellent ultra-high speed point grinding wheel, the paper does some comparative experiments for five kinds of home-made CBN abrasives and three kinds of foreign CBN abrasives, and analyzes their normal temperature characteristics, high temperature characteristics and resistant to corrosion. Different abrasive materials and grain sizes are tentatively selected to meet different workpiece material and machining requirements. Three kinds of vitrified bonds are configured based on request of low temperature high intensity vitrified bonds. These bonds’component, refractoriness, coefficient of thermal expansion, strength, mineral phase and micro-topography are verified by experiments. At last, the kind of low-temperature high-strength vitrified bond is selected.(5) The segment of CBN wheel plays the most important role on grinding wheel performance. Thus, considering the strength of the segment and its forming process, the size of wheel segment of ultra-high speed point grinding wheel withΦ370mm,vs=200m/s is optimized by ANSYS software. Considering the security of wheel, the minimum segment strength is obtained according to strength of segment optimized. Afterward, the wheel sample configured by different abrasives and bonds selected before are sintered. By the measurements of strength, grain size, concentration and micro-topography of the abrasive and bond are determined for samples with high strength.(6) Based on the experiment research before, the ultra-high speed point grinding CBN wheel is made according to its manufacture techniques. And the performances of the CBN wheel are tested on NEU ultra-high speed point grinding test-bed and high speed camshaft grinder made by Beijing Mechanism College. Experimentation shows that point grinding force decreases with the wheel speed increases, and with workpiece speed, grinding depth, longitudinal feeding speed increases, the grinding force increases too; the grinding temperature decreases with the wheel speed, and with workpiece speed, grinding depth, longitudinal feeding speed increases, the grinding temperature increases too; the grinding forece and temperature decreases with level variable angle increases, but surface roughness decreases. Whenα&β=±5°, although the surface roughness value (Ra) increases, but surface of workpiece present residual compress stress and without white layer and phase transformations; whenα&β=±0°, although the surface roughness value(Ra) decreases, but surface of workpiece present residual tensile stress and having white layer and phase transformations. When taking workpiece surface roughness value Ra≤0.4μm and workpiece surface without residual stress as grinding blunt standard, the grinding ratio (G) of ultra-high speed point grinding wheel is 170 in experiment. The performance of the wheel approach importation grinding wheel level in production.(7) The paper analyzed wear mechanism of ultra-high vitrified bond CBN wheel. Dressing experimentation of vitrified bond CBN wheel is completed. The experimentation indicates that wheel topography is best when velocity ratio j=0.428 between the diamond rotary and CBN wheel.更多还原