高频感应钎焊多晶CBN超硬磨粒自锐性能研究

发布时间：2018-04-26 04:33

本文选题：高频感应钎焊 + 多晶CBN磨粒　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：多晶立方氮化硼(CBN)磨粒是由CBN微晶颗粒与AlN粘结剂通过高温高压烧结而成的聚晶体超硬磨粒,它既具有单晶CBN磨粒的高硬度和高耐磨性,又具有各向同性的特征,在磨削时通过磨粒微破碎自锐能够确保砂轮长时保持高锋利度。此外,采用高频感应钎焊技术制作单层超硬磨料砂轮,能够有效解决真空炉中钎焊制造砂轮产生的基体变形问题,在确保钎焊砂轮牢固把持磨粒的同时,也能显著提升砂轮精度。因此,感应钎焊单层多晶CBN砂轮的制造与应用研究具有重要理论意义和实用价值。然而,现阶段对感应钎焊多晶CBN磨粒的内部应力分布特征、以及磨粒自锐性能及其机理仍缺乏深刻认识,导致多晶CBN砂轮的优异磨削潜能难以充分发挥。有鉴于此,本文提出开展高频感应钎焊多晶CBN超硬磨粒自锐性能研究,以揭示感应钎焊多晶CBN砂轮制造过程的温度场特征为基础,阐明多晶CBN磨粒内部残余应力与磨削应力的影响因素与分布规律,再结合单颗磨粒磨削实验阐释多晶CBN磨粒的微破碎行为,以此揭示磨粒自锐机理。研究成果有利于深化对高频感应钎焊单层多晶CBN超硬砂轮制造与应用相关机理的认识。本文的主要研究工作与取得的成果如下:(1)采用实验和仿真相结合的方法,研究了高频感应钎焊制造单层CBN砂轮时加热微区的温度分布特征,阐明了感应电流大小、电流频率、加热间隙以及扫描速度对感应钎焊最高温度的影响规律。研究发现,在感应电流频率为1MHz和加热间隙2mm的条件下,感应电流幅值和扫描速度分别为19A和0.5mm/s、20A和1mm/s、以及21A和1mm/s时,感应钎焊的温度分布适合制作单层多晶CBN砂轮。(2)采用泰森分割方法建立了多晶CBN磨粒的微结构模型,分别计算了多晶CBN磨粒的钎焊残余应力分布与磨削合应力分布,揭示了包埋深度、磨粒粒径以及磨削力等参数对磨粒内部应力分布的影响规律,优选了包埋深度。通过单晶与多晶CBN磨粒钎焊残余应力的对比分析,以及钎焊多晶CBN砂轮的磨削试验,验证了钎焊应力计算结果的准确性。(3)通过单颗磨粒磨削钛合金TC4试验,从多晶CBN磨粒的磨损形貌及其分形维数两方面阐明了磨削用量对磨粒微破碎自锐行为的影响规律与作用机理。进一步研究发现,不同于单晶CBN磨粒容易出现大块破碎和断裂,多晶CBN磨粒由于更容易发生微破碎,因而磨削性能更加稳定。
[Abstract]:Polycrystalline cubic boron nitride (CBN) abrasive particles are polycrystalline superhard abrasive particles sintered by CBN microcrystalline particles and AlN binders through high temperature and high pressure. It has the characteristics of high hardness and high wear resistance of single crystal CBN abrasive particles, and also has the characteristics of isotropy. The grinding wheel can be kept high sharpness when grinding by micro-crushing and self-sharpening. In addition, using high-frequency induction brazing technology to make single-layer super-hard abrasive grinding wheel can effectively solve the problem of matrix deformation caused by brazing and manufacturing grinding wheel in vacuum furnace. It can also improve the precision of grinding wheel. Therefore, the manufacture and application of induction brazing monolayer polycrystalline CBN grinding wheel has important theoretical significance and practical value. However, there is still a lack of deep understanding of the internal stress distribution characteristics of induction brazed polycrystalline CBN abrasive particles, as well as the self-sharpening properties and mechanism of the abrasive particles, which makes it difficult to give full play to the excellent grinding potential of polycrystalline CBN grinding wheels. In this paper, the self-sharpening properties of high-frequency induction brazing polycrystalline CBN superhard abrasive particles are studied, which is based on revealing the characteristics of temperature field in the manufacturing process of induction brazed polycrystalline CBN grinding wheels. The influencing factors and distribution of residual stress and grinding stress in polycrystalline CBN abrasive particles are expounded, and the micro-breaking behavior of polycrystalline CBN abrasive particles is explained in combination with the grinding experiment of single abrasive particle, so as to reveal the self-sharpening mechanism of polycrystalline CBN particles. The research results are helpful to deepen the understanding of the manufacturing and application mechanism of high frequency induction brazing monolayer polycrystalline CBN superhard grinding wheel. The main research work and results obtained in this paper are as follows: (1) by using the method of experiment and simulation, the characteristics of temperature distribution in the heating microzone of high-frequency induction brazing manufacturing single-layer CBN grinding wheel are studied, and the magnitude and frequency of inductive current are clarified. The effect of heating gap and scanning speed on the maximum temperature of induction brazing. The results show that when the inductive current frequency is 1MHz and the heating gap 2mm, the amplitude and scanning velocity of the induced current are 19A and 0.5mm / s respectively, 20A and 1mm / s, and 21A and 1mm/s, respectively. The temperature distribution of induction brazing is suitable for making monolayer polycrystalline CBN grinding wheel. The microstructure model of polycrystalline CBN abrasive particles is established by Tyson partition method. The residual stress distribution and grinding stress distribution of polycrystalline CBN abrasive particles are calculated respectively. The influence of the parameters such as embedding depth, particle size and grinding force on the stress distribution of abrasive particles is revealed, and the embedded depth is selected. Through the contrast analysis between single crystal and polycrystalline CBN abrasive soldering residual stress, and the grinding test of brazed polycrystalline CBN grinding wheel, the accuracy of the calculation results of brazing stress is verified. The effects of grinding amount on the self-sharpening behavior of polycrystalline CBN abrasive particles were discussed from the aspects of wear morphology and fractal dimension. It is found that compared with the single crystal CBN abrasive particles, the grinding properties of the polycrystalline CBN abrasive particles are more stable because they are more prone to micro-crushing.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG580.1

【参考文献】