PCBN刀具负倒棱对其硬态切削性能研究

发布时间：2018-03-14 00:36

本文选题：PCBN刀具负倒棱　切入点：粉末冶金气门座圈　出处：《合肥工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：采用粉末冶金技术制备的气门座圈以其良好的耐磨性及耐高温性得到广泛使用,但这种气门座圈硬度高,难以加工,且其内部结构多微孔,切削过程中对刀具的冲击大,使用普通的硬质合金刀具进行切削加工时,刀具耐用度低。近年来,采用聚晶立方氮化硼(Polycrystalline Cubic Boron Nitride,简称PCBN)刀具硬态切削粉末冶金气门座圈,大大提高了加工效率,降低了加工成本,且能获得较高的加工表面质量。本文旨在探究在硬态切削粉末冶金气门座圈时PCBN刀具负倒棱对刀具切削性能的影响,为PCBN刀具负倒棱参数及其他工艺参数的选择提供参考,具有较大的理论价值和实践意义。主要研究内容及成果如下：首先使用PCBN刀具对粉末冶金气门座圈进行了外圆硬态切削试验,利用Kistler9257B型三向测力仪测量切削力,发现了切削力随着PCBN刀具负倒棱角度和负倒棱宽度及进给量的变化规律。研究发现：切削过程中主切削力Fz始终大于Fx和Fy；随着负倒棱角度的增加,切削力Fx,Fy和Fz都出现增大的趋势；而随着负倒棱宽度增加,切削力Fx,Fy和Fz呈现先增大后减小最后再增大的规律,其中切深抗力Fy变化较为明显。然后通过测量气门座圈已加工表面粗糙度研究了PCBN刀具负倒棱角度和负倒棱宽度及进给量对于加工表面质量的影响规律。结果表明：随着PCBN刀具负倒棱角度增大,工件表面粗糙度增大；随着负倒棱宽度增加,工件表面粗糙度呈先增大后减小最后增大的趋势；对于不同负倒棱宽度的PCBN刀具,进给量对已加工表面粗糙度的影响并不一致。最后试验研究了PCBN刀具负倒棱角度和负倒棱宽度对于刀具耐用度的影响,总结了生产中PCBN刀具的主要失效形式,观察了PCBN刀具的磨损形态,并对其磨损机理进行了分析。结果表明：PCBN刀具失效形式有正常磨损和破损失效；主要磨损形式为微崩刃、后刀面磨损以及前刀面磨损,磨损机理主要为磨粒磨损、粘结磨损、扩散磨损和氧化磨损；破损失效主要形式包括崩刃、剥落和碎断等。
[Abstract]:The valve seat ring made by powder metallurgy technology has been widely used for its good wear resistance and high temperature resistance. However, the valve seat ring is hard to be machined because of its high hardness, and its internal structure has many micropores. In recent years, the polycrystalline cubic boron nitride Cubic Boron nitride (PCBN) tool has been used to cut hard the powder metallurgy valve seat ring in hard state, which greatly improves the machining efficiency. The machining cost is reduced and the machining surface quality is obtained. This paper aims to investigate the influence of negative chamfering of PCBN tool on cutting performance of the cutting tool in hard cutting of powder metallurgy valve seat. It provides a reference for the selection of negative chamfering parameters and other technological parameters of PCBN cutting tools. It has great theoretical value and practical significance. The main research contents and results are as follows: firstly, the outside circle hard cutting test of powder metallurgy valve seat ring is carried out by using PCBN tool, and the cutting force is measured by Kistler9257B three-way dynamometer. The variation law of cutting force with negative chamfering angle, negative chamfering width and feed rate of PCBN cutting tool is found. It is found that the main cutting force Fz is always larger than FX and Fyin cutting process, and with the increase of negative chamfer angle, The cutting forces Fxy and Fz both tend to increase with the increase of the width of negative chamfering edges, and the cutting forces FxFy and Fz increase at first and then decrease at last. The change of tangent resistance Fy is obvious. Then the influence of negative chamfering angle, negative chamfering width and feed rate on the surface quality of PCBN cutter is studied by measuring the machined surface roughness of the valve seat ring. With the increase of the negative inverse angle of the PCBN tool, The surface roughness of workpiece increases with the increase of negative chamfering width, the surface roughness of workpiece increases first and then decreases and then increases. For PCBN tool with different negative chamfering width, The effect of feed rate on the machined surface roughness is not consistent. Finally, the influence of the negative chamfering angle and the negative chamfering width of the PCBN cutter on the tool life is studied, and the main failure modes of the PCBN tool in production are summarized. The wear pattern of PCBN tool is observed and its wear mechanism is analyzed. The results show that the failure mode of PCBN tool has normal wear and damage failure, and the main wear forms are micro-disintegrating edge, back face wear and front tool surface wear. The wear mechanism is mainly abrasive wear, bond wear, diffusion wear and oxidation wear, and the main failure modes include breakage, flaking and breaking.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG506

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