陶瓷结合剂金刚石砂轮磨削超细晶粒硬质合金的表面粗糙度研究

本文结合单因素实验和正交实验,研究了从低速到高速磨削条件下,砂轮速度、进给速度、磨削深度、最大未变形磨削厚度以及磨削方式(顺磨或逆磨)对陶瓷结合剂金刚石砂轮磨削超细晶粒硬质合金表面粗糙度的影响规律,分析了影响超细晶粒硬质合金表面加工质量的原因。研究表明,总体来说磨削参数的变化对超细晶粒硬质合金表面粗糙度的影响程度不大。高速磨削时的表面粗糙度相比低速磨削得到了比较明显改善。逆磨时的粗糙度比顺磨大,随砂轮速度增加下降更快。相比传统硬质合金,磨削WC颗粒更细、强度更高的超细晶粒硬质合金的表面粗糙度更低。磨削参数对表面粗糙度的影响程度从小到大依次是磨削深度、砂轮速度和进给速度,实际加工时为同时获得较高的磨除率和表面质量,宜采用高砂轮速度、低进给和大切深的磨削组合。     

超硬涂层磨削工艺实验研究

针对核主泵关键部件材料镍基碳化钨涂层,采用三种磨粒粒度金刚石砂轮进行平面磨削试验,研究工艺参数、磨粒粒度对涂层材料磨削力、表面粗糙度和表面残余应力的影响规律。实验结果表明:不同粒度砂轮磨削时,随着磨削深度和工件进给速度增加,法向磨削力和切向磨削力均逐渐增大,表面粗糙度值呈现先增大、后减小再增大的趋势,平行和垂直磨削方向的表面残余压应力逐渐增大,且垂直磨削方向应力值更大。综合考虑磨削力、表面粗糙度、磨削表面残余应力和磨削加工效率,600目砂轮具有较好的加工效果,其对应的优化磨削参数为:磨削深度为10μm,工件进给速度为8 m/min。     

基于放电修锐的粗金刚石砂轮干式镜面磨削技术

为解决超硬金刚石砂轮修锐效率较低以及环境友好性等问题，采用干式接触放电修锐(ECD)技术对粗金刚石砂轮进行修锐，获得较高的磨粒出刃，可以实现硬质合金和模具钢等高强高硬材料的高效精密镜面磨削加工。对46#金属结合剂粗金刚石砂轮进行机械修锐和干式ECD修锐，再利用修锐后的粗金刚石砂轮对硬质合金和模具钢进行干式轴向磨削加工，对比分析两种修锐条件下磨削工艺参数对硬质合金干磨削力、磨削表面粗糙度和磨削力比的影响。实验结果表明：硬质合金的干式轴向磨削力及其表面粗糙度随砂轮速度的增大而减小，随进给速度和切削深度的增大而增大；与机械修锐相比，干式ECD修锐能够获得更高的磨粒出刃和更好的表面质量，以及更小的磨削力和磨削力比；硬质合金和模具钢的干磨削表面粗糙度Ra分别可达0.058μm和0.022μm。     

钢结硬质合金的ELID高效磨削实验研究

在基于大量实验的基础上,对磨削钢结硬质合金时磨削力的变化规律进行了详细分析,并将磨削力、磨削表面粗糙度与普通磨削进行了比较.结果表明,采用铸铁结合剂金刚石砂轮进行ELID磨削时磨削力几乎不随时问的变化而变化,而采用普通磨削方式进行磨削时的磨削力随时间的变化不断增大,在线电解修整使砂轮在磨削过程中始终保持良好的磨削性能,有利于节省砂轮修整时间,提高加工效率.在ELID磨削中,采用微细砂轮进行磨削可以获得很低的表面粗糙度,实现了对钢结硬质合金的超精密镜面磨削.     

有序化砂轮磨削表面粗糙度仿真

为改善砂轮的磨削性能,将有序排布理论引入到电镀砂轮磨粒排布中。分别探讨了叶序、错位、无序排布砂轮在不同磨削参数下对工件表面粗糙度的影响,同时建立叶序、错位、无序排布电镀砂轮磨削表面粗糙度数学模型,并利用MATLAB软件进行仿真。在砂轮缓进给磨削过程中,叶序排布砂轮所获得的工件表面粗糙度值低于其他排布方式的砂轮。且工件表面的粗糙度值随着磨削速度比的增大而减小,随着磨削厚度的增大而增大。这为实际磨削工件表面粗糙度分析提供了很好的辅助和验证方法。     

超细硬质合金磨削残余应力仿真与实验研究

本文进行了金刚石砂轮平面磨削超细硬质合金残余应力有限元仿真,通过ANSYS软件中的APDL参数设计语言,完成了对超细硬质合金材料建模、网格划分、加载、求解的整个过程,并对超细硬质合金磨削表面残余应力进行了实验论证,得出了不同磨削参数下的磨削残余应力值,对比了不同目数砂轮和不同WC晶粒硬质合金在同一磨削参数下的残余应力值。研究发现,目数小的砂轮磨削时产生的残余应力值要大,WC晶粒度越小,磨削的残余应力值越大。结果表明,实验结果与有限元模拟大致相同。     

磨削油在硬质合金刀具高质量磨削过程中的应用研究

为研究磨削油对硬质合金刀具高质量磨削的影响,通过对两种不同磨削油的清洗性、渗透性及冷却性等基本性能进行测试,分析磨削硬质合金刀具时对机床负载、砂轮工作表面、硬质合金刀具磨削表面质量以及磨削温度的影响规律。试验结果表明：砂轮表面形貌变化、砂轮磨耗磨损和机床负载主要受磨削油清洗性能的影响,磨削油的清洗性能越好,WC在砂轮工作表面黏附越少,砂轮表面形貌变化、砂轮磨耗磨损和机床负载越小;硬质合金刀具圆周刃崩边大小及前刀面粗糙度主要受磨削油渗透性能的影响,其渗透性能越好,磨削区越易形成油膜,圆周刃崩边大小及前刀面粗糙度值越小;磨削区温度主要受磨削油冷却性能的影响,其冷却性能越好,带走的磨削热越多,磨削区温度越低。     

磨削过程模拟及磨削机理研究（上）

在前人磨削理论基础上对砂轮结构做了更接实际的随机性假设,应用计算机数字模拟技术对磨削全过程进行了模拟,获得了磨削过程和磨削表面的许多重要数据和结果,给出了砂轮表层的磨料中中切削的磨粒数目和切屑的长度、厚度和体积。在研究砂轮结构的基础上得出砂轮磨粒分布的随机性是磨削加工能产生表面低粗糙度的重要因素。对砂轮磨料粒度及砂轮修整的定量研究表面,要获得超低粗糙度值磨削表面不仅需要选择较细磨粒,而且需要对砂轮     

酚醛树脂含水率对金刚石砂轮磨削硬质合金的影响

采用不同含水率的酚醛树脂金刚石砂轮,对硬质合金YG8进行了平面磨削试验,研究了含水率变化导致的砂轮磨削性能变化对磨削比、磨削功率和工件表面粗糙度的影响规律,并对砂轮磨削后表面形貌进行了观测,揭示了酚醛树脂金刚石砂轮磨削性能随含水率变化的规律。试验结果表明:含水率越高,砂轮的组织均匀性就越差,机械性能和磨削性能不稳定且总体趋势变差。磨削比、Ra值在一个耐用度周期内波动较大,不适合精密磨削加工。为了获得良好且稳定的粗糙度表面,应选用含水率小于0.3%的树脂原材料制作砂轮。含水率较低时(<0.3%)磨削功率相对稳定,砂轮表面磨粒脱落率低。但不是含水率越高时磨削性能越差,砂轮的磨削比、磨削钝化速度、粗糙度与含水率不是线性关系。     

磨削参数对陶瓷结合金刚石砂轮磨削硬质合金表面粗糙度的影响

采用因素分析法,研究了不同条件下磨削参数的变化对陶瓷结合金刚石砂轮磨削硬质合金表面粗糙度的影响,分析了影响硬质合金表面加工质量的原因,并提出提高硬质合金表面加工质量的方法。     

单层钎焊金刚石砂轮的精密修整及效果评价

单层钎焊金刚石砂轮作为一种新型的磨削工具,具有磨粒固结强度高、磨粒出露大、容屑空间大等优点,比较适合高效率大切深的强力磨削,然而这种工具对高性能的脆性材料的精密磨削却比较困难。本文通过两种精密的修整工艺,使得加工表面质量大大提高。通过观察砂轮磨粒形态的变化可知,磨粒在修整过程中存在有磨损钝化、破碎、表面粘附等现象;通过对砂轮轮廓的激光测量可知,砂轮的磨粒等高性在修整过程中是明显改善的。通过修整磨粒粒径300μm的钎焊砂轮磨削氧化锆的表面粗糙度达到了Ra0.2μm。     

SUBSURFACE DAMAGE IN GRINDING TITANIUM ALUMINIDE

Abstract

This paper reports on an experimental investigation of grinding-induced subsurface damage in gamma titanium aluminide (γ-TiAl). Grinding was carried out with resin-bond diamond wheels having the same concentration but different grit sizes, and with a vitreous-bond silicon carbide wheel using various depths of cut. The extent of the subsurface damage was determined by a bonded interface technique and optical microscopy. The grinding-induced damage beneath the ground surfaces was found to consist of plastic deformation and microcracks. The severity and depth of the subsurface damage zone increased with an increase in the abrasive grit size and the depth of cut. Microcracks were observed when grinding was performed with the silicon carbide wheel at a depth of cut of 100 and 125 μm.     

SUBSURFACE DAMAGE IN GRINDING TITANIUM ALUMINIDE

This paper reports on an experimental investigation of grinding-induced subsurface damage in gamma titanium aluminide (γ-TiAl). Grinding was carried out with resin-bond diamond wheels having the same concentration but different grit sizes, and with a vitreous-bond silicon carbide wheel using various depths of cut. The extent of the subsurface damage was determined by a bonded interface technique and optical microscopy. The grinding-induced damage beneath the ground surfaces was found to consist of plastic deformation and microcracks. The severity and depth of the subsurface damage zone increased with an increase in the abrasive grit size and the depth of cut. Microcracks were observed when grinding was performed with the silicon carbide wheel at a depth of cut of 100 and 125 μm.     

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel,workpiece characteristics,and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.     

Grinding damage of BK7 using copper-resin bond coarse-grained diamond wheel

Coarse-grained wheels can realize high efficient grinding of optical glass. However, the serious surface and subsurface damage will be inevitably introduced by the coarse-grained wheels. In this paper, the grinding damage of a copper-resin bond coarse-grained diamond wheel with grain size of 150μm was investigated on optical glass BK7. The wheel was first properly trued with a metal bond diamond wheel, then pre-dressing for the wheel and grinding experiments are carried out on a precision grinder assisted with electrolytic in process dressing (ELID) method. The surface roughness (Ra) of ground surface was measured using an atomic force microscope (AFM) and the surface topography were imaged by a white light interferometer (WLI) and the AFM. The subsurface damage level of ground surface was evaluated by means of both MRF spot method and taper polishing-etching method, in term of the biggest depth of subsurface damage, distribution of micro defects beneath the ground surface, the cluster depth of subsurface damage, relationship between subsurface damage (SSD) and PV surface roughness (SR), propagating distance and pattern of cracks beneath the ground surface. Experimental results indicate that a well conditioned copper-resin bond coarse-grained diamond wheel on a precision grinder can generate good surface quality of Ra less than 50nm and good subsurface integrity with SSD depth less than 3.5ε for optical glass BK7.     

硬质合金YG8高速磨削工艺试验研究

采用树脂结合剂金刚石砂轮,对硬质合金YG8进行了高速磨削工艺试验研究,测得了不同砂轮线速度、磨削深度和工作台速度条件下的磨削力和表面粗糙度,并对磨削的表面形貌进行了观测,揭示了硬质合金YG8高速磨削的材料去除机理。试验结果表明:将高速磨削技术应用于硬质合金材料的加工是一种切实可行的加工方法,能得到较好的表面质量并提高加工效率。随着砂轮线速度的增加,或者工作台速度和磨削深度的减小,磨削的最大未变形切屑厚度减小,磨削力减小,材料的比磨削能增加,使得工件的加工表面质量得到改善。     

The experiment of high-speed grinding of a gemstone: cubic zirconia

Grinding is one of the major machining processes of gem manufacturing. The largest gemstone in the jewelry market is the cubic zirconia (CZ) which is ground in the same fashion as diamonds. This study was interested to investigate the influence of parameters on grinding CZ gemstone. The parameters were grinding speed, depth of grinding, and abrasive grit size of diamond electroplated disc. The results could conclude that the surface finish was improved when increasing grinding speeds and abrasive grit size. The grinding time was decreased with an increase in grinding speeds. Examination of the surface texture of the ground surface on CZ was analyzed and reported.     

单层钎焊金刚石砂轮的修整实验研究

为满足单层钎焊金刚石砂轮高效精密加工的性能要求,对磨粒有序排布单层钎焊金刚石砂轮的修整进行了实验研究。采用磨粒有序排布的钎焊金刚石修整工具对钎焊砂轮进行了修整,该修整方法通过修整工具粒度的变化以及修整速比的调整来控制砂轮形貌,从而使氧化锆的磨削表面粗糙度达到了精密加工的水平。对砂轮形貌进行了观测统计,数据表明,砂轮磨粒的等高性得到明显改善且避免了磨粒端部的严重钝化。     

工件旋转法磨削硅片的磨粒切削深度模型

半导体器件制造中,工件旋转法磨削是大尺寸硅片正面平坦化加工和背面薄化加工最广泛应用的加工方法。磨粒切削深度是反映磨削条件综合作用的磨削参量,其大小直接影响磨削工件的表面/亚表面质量,研究工件旋转法磨削的磨粒切削深度模型对于实现硅片高效率高质量磨削加工具有重要的指导意义。通过分析工件旋转法磨削过程中砂轮、磨粒和硅片之间的相对运动,建立磨粒切削深度模型,得到磨粒切削深度与砂轮直径和齿宽、加工参数以及工件表面作用位置间的数学关系。根据推导的磨粒切削深度公式,进一步研究工件旋转法磨削硅片时产生的亚表面损伤沿工件半径方向的变化趋势以及加工条件对磨削硅片亚表面损伤的影响规律,并进行试验验证。结果表明,工件旋转法磨削硅片的亚表面损伤深度沿硅片半径方向从边缘到中心逐渐减小,随着砂轮磨粒粒径、砂轮进给速度、工件转速的增大和砂轮转速的减小,加工硅片的亚表面损伤也随之变大,试验结果与模型分析结果一致。