工程陶瓷小砂轮轴向大切深缓进给磨削加工的砂轮磨损分析

小砂轮轴向大切深缓进给磨削以较大切深实现了较高的材料去除率,且使用的砂轮直径比常规磨削用砂轮小很多,我们针对这一特点开展了研究。实验通过改变砂轮转速、工件转速和磨削深度等加工参数,对轴向大切深缓进给磨削加工后的砂轮表面进行了形貌观测和磨损分析。分析表明,砂轮各部分的磨损形式与其在磨削过程中所起的作用有关:砂轮端面是磨削加工的主磨削区,磨粒和结合剂主要发生较大程度的磨损;砂轮圆周面主要对已加工表面进行修磨,因而结合剂和磨粒磨损为主要磨损形式;砂轮拐角作为过渡磨削区,承受的磨削力也比较大,而且由于磨粒与结合剂的结合力相对较小,因此易发生磨粒和结合剂的脱落。     

Investigation of the heat partitioning in high efficiency deep grinding

The grinding heat partitioning in the high efficiency deep grinding (HEDG) process has been investigated. The ratios of heat partition to the different heat sinks, i.e. workpiece, chips, fluid and grits, have been calculated, based on both theoretical analysis and experimental data. The heat partitioning ratio to the grinding chips increases with the material removal rate and takes most of the grinding heat away from the grinding zone under HEDG conditions where very high material removal rates apply. The heat partition to workpiece decreases when increasing the material removal rate. Cooling fluid is especially important for the conditions of creep feed grinding when using low feed rates, with over 90% of heat convected away by the grinding fluid. Under HEDG conditions, only 5–10% of the grinding heat is taken away by the grinding fluid. Very high material removal rates can be achieved with good surface integrity, when using an optimised selection of process parameters.     

Limit charts for high removal rate centrelessgrinding

An experimental investigation of the high removal-rate centreless grinding process applied to steel and cast-iron has allowed the investigators to present “limit-charts”. These limit charts illustrate the characteristic diagram for boundaries of operation where the grinding variables are infeed rate, workpiece speed and grinding wheel speed. The boundaries determined in this investigation were formed by burn, chatter, or available power (75 kW). It was not possible to achieve an excessive wheel wear condition although this might have been possible if more power had been available. The shape of the diagram means there is an optimum point of operation within the region enclosed by the boundaries. This forms the basis of a control strategy.Kinematic characterisation of the grinding process is developed by attention to the concept of a ‘speedeffect”, a “size effect” and a “shape effect”. Results for the speed effect are distinguished and presented separately from results for the size effect and shape effect to avoid mixed causes for the differing physical effects.A two-dimensional surface is presented showing the variation of grinding energy with variations in infeedrate, workpiece speed and grinding wheel speed. Because speed, shape and size effects are separated on the surface it is possible to read the optimum grinding wheel speed for minimum energy. For these experimental conditions, the optimum grinding wheel speed was found to be approximately 50 m/s. In the region of the optimum speed, specific energy is relatively insensitive to variations in operating speeds and feeds which is a useful feature when devising an automatic control strategy.     

Modelling of specific energy requirement during high-efficiency deep grinding

Grinding is a multi-point cutting operation. The specific energy or the energy expended for unit material removal in grinding is very high, typically one or two orders higher than the machining specific energy. Such high specific energy required in grinding can be attributed to the irregular and random geometry of the abrasive grits, which induce a lot of rubbing and ploughing actions along with the chip formation by shearing process. Also the effective angle in grinding is highly negative which is again responsible for such high-specific energy requirement in grinding. In grinding, a number of notable phenomena occur during the chip formation process, which actually consumes a significant percentage of energy. Such main energy consumers in grinding are:

• Chip formation due to shearing

• Primary rubbing

• Secondary rubbing

• Ploughing

• Wear flat rubbing

• Friction between the loaded chip and workpiece

• Friction between bond and workpiece, etc.

The present paper tries to analytically predict the specific energy consumed during high-efficiency deep grinding (HEDG) of bearing steel by monolayer cBN wheel. During the HEDG process, energy is spent mostly for shearing, rubbing and ploughing processes. The other energy consumers have insignificant role in such high-speed grinding process. So, models which take into account the processes of shearing, primary rubbing, secondary rubbing and ploughing process can reasonably be used to predict the energy requirement in such HEDG process. The total specific energy value obtained from the model has been validated with those experimentally observed values. A good trend matching of the modelled and experimental values have been observed and the root mean square error values have been found to vary between 7% and 11%.     

AgCuTi合金钎焊单层立方氮化硼砂轮

为研制我国新一代单层钎焊CBN(立方氮化硼 )磨料砂轮 ,尝试Ni-Cr和Ag -Cu-Ti两种活性钎料 ,在真空炉中钎焊。试验结果表明 ,Ni-Cr合金钎料对CBN磨料不浸润 ,钎焊后CBN磨料全部脱落 ;而Ag -Cu -Ti合金钎料对CBN则表现出良好的浸润性并将CBN牢牢钎焊住。借助扫描电镜、X射线能谱和X射线衍射对界面微区组织的分析研究表明 ,钎焊过程中Ag -Cu -Ti合金钎料中的Ti向CBN磨料界面富集 ,并与CBN磨料表面的N和B元素反应生成TiN和TiB ,这是实现Ag -Cu -Ti合金钎料与CBN磨料高结合强度的关键因素。断口形貌的分析研究表明 ,CBN与Ag -Cu -Ti合金钎料间的断口发生在Ag -Cu -Ti合金钎料层 ,说明CBN磨料与Ag -Cu -Ti合金钎料的结合强度已超过了Ag-Cu -Ti合金钎料本身强度。最后将研制出的单层钎焊CBN磨料砂轮与传统电镀CBN砂轮进行了重负荷磨削对比试验 ,钎焊砂轮表现出明显的优势     

Improved monolayer CBN wheel for load free grinding

A galvanically bonded wheel made of a monolayer of CBN grits may not always ensure free cutting action when a large volume of chips is to be handled because of the fact that about two thirds or more of the grit height has to be covered by the matrix for effective anchorage. The present study shows that the problem of chip accomodation during grinding is further aggravated when the CBN wheel has some surface defect like growth of the galvanic layer in the space between the grits. In order to utilize more effectively the extraordinary capability of CBN grits, a new kind of monolayer CBN wheel has been developed, using a special bonding technique (patent pending). This technique keeps the level of the bond material low but sufficient to hold the grits during grinding. Performance of this CBN wheel relative to that of a galvanically bonded wheel, with particular reference to its grinding capability while grinding unhardened 100 Cr6 steel is discussed in this paper.     

CBN砂轮磨削镍基高温合金磨削温度实验研究

磨削高温是限制磨削技术发展的主要瓶颈之一,因而研究磨削过程中产生高温的机理及磨削温度的变化规律十分重要。采用260 mm的单层钎焊有序排布CBN砂轮,对镍基高温合金GH4169进行不同速度下的磨削实验。实验过程中,保持砂轮线速度和工件进给速度的比值不变,从而保持单颗磨粒最大未变形切屑厚度不变,发现比磨削能得到有效控制,磨削温度的上升主要由材料去除率的提高所导致;随着砂轮线速度的增加,磨削弧区热量分配关系发生显著变化,传入工件的能量增加;磨粒排布方式对传入工件的热量有影响,同一磨削工艺参数下,磨粒斜排布的砂轮磨削温度要低于磨粒直排布的砂轮,最佳磨粒排布方案还有待进一步的研究。     

CBN杯形砂轮端面磨削轧辊的磨削几何学分析

本文建立了CBN(立方氮化硼)杯形砂轮端面磨削轧辊的几何模型，从磨削几何学的角度研究了杯形砂轮端面磨削轧辊的磨削特性和输人参数对切人线长度和宽度的影响，分析了端面磨削外圆时的磨削接触弧的特点，结果表明，当切深较小时，砂轮与轧辊为点接触；已加工表面的粗糙度主要取决于砂轮外缘的磨粒密度；磨削效率的高低取决于砂轮内缘的磨粒密度；在磨削过程中，应根据其他参数的变化调节砂轮轴线与轧辊间的偏移量H；提高砂轮转速有利于磨削效率的改善。     

陶瓷cBN砂轮磨料性能实验及建模仿真研究

采用扫描电镜、冲击韧性测定、能谱分析等方法对8种国内外cBN磨料进行了高温焙烧后微观形貌、冲击韧性、纯度的性能分析。结果表明,国产部分单晶cBN磨料性能已达到较高的水平,甚至超过了国外产品的性能。在进一步实验观测的基础上,不同于传统的表面实际测量、映射方法或简化磨粒形状建模方法,模拟工业生产中磨粒切割原理,作者使用随机切分平面方法切分模拟出了随机形状及分布磨粒模型,为三维磨削仿真研究提供了一种更具有相似性的有限元模型。     

The relation between the traverse dressing of vitrified grinding wheels and their performance

A new model of the dressing of grinding wheels by diamond blade or single point tools is proposed. It is based on the statistics of brittle fracture of bonds and grits, and on the geometrical interaction between the grits and the dressing tool. It successfully predicts the measured topography of wheels dressed in various different ways, and in combination with a model of abrasive wear, can successfully predict the forces in surface grinding tests, and the resulting workpiece roughness. There is much scope for using the model in its present state as a means of assessing the likely effects of changing process parameters on the performance of a grinding process, but with better measurements of the input parameters it requires, its accuracy and effectiveness could be improved.     

基于控制研磨深度的金刚石研磨质量分析

为了探究金刚石器件在机械研磨过程中原子层面的材料表面成形和亚表面损伤机制,利用分子动力学（molecular dynamics,MD）方法建立金刚石多磨粒研磨金刚石工件的模型,仿真研究金刚石材料表面成形的过程,并对比不同研磨深度对研磨力、材料回弹率和材料亚表面损伤的影响规律。分析表明：堆积在磨粒之间的切屑原子具有微研磨的作用,磨粒之间的相变区在研磨的作用下逐渐融合在一起,形成金刚石材料的加工表面;分别以h=0.36 nm、0.71 nm、1.07 nm、1.43 nm的研磨深度进行研磨,研磨深度超过0.71 nm后才能有效抑制金刚石晶体材料回弹,但增大研磨深度会增加金刚石工件表面堆积原子,不能改善其表面研磨质量;研磨深度在0.71 nm范围内的金刚石亚表层损伤较小且稳定,超过0.71 nm的研磨深度会使损伤快速增大,且会出现超过3.00 nm的大纵深损伤。     

陶瓷刚玉磨料行星磨干法造粒研究

本文对陶瓷刚玉磨料干凝胶颗粒进行形状控制的造粒工艺进行了研究,对影响造粒的主要参数进行了讨论.采用扫描电子显微镜(SEM)对磨料的颗粒形貌进行了观察,采用筛分法对磨料的粒度分布进行了测定.研究结果表明:合适的料球比既能使干凝胶颗粒受到磨介的充分作用,又能避免过粉碎;磨介形状和大小的级配对颗粒形状的控制有着重要影响;合理的球磨转速使磨介对干凝胶颗粒的作用得到充分的发挥;通过对造粒工艺参数的适当选择,获得了粒度分布范围集中的等积形陶瓷刚玉干凝胶颗粒粉料.     

单颗钎焊金刚石磨粒磨损试验研究

采用单颗磨粒试验方法,以碳钢碟轮为修整工具,研究金刚石和CBN磨粒修整过程中的磨损特征。结果表明:砂轮和修整碟轮的相对速度对金刚石磨粒的磨损有重要影响;相对速度为51.9 m/s时,金刚石磨粒的磨损高度为50.1 μm;相对速度为17.3 m/s时,金刚石磨粒的磨损高度显著减小,为19.5 μm。通过相同条件下金刚石与CBN磨粒的磨损特征对比,表明金刚石磨粒在磨损过程中同碟轮之间发生化学作用,加速金刚石磨粒的磨损;对试验后金刚石磨粒进行拉曼光谱分析,并未检测到石墨物质。      

单颗金刚石磨粒磨削SiC的磨削力实验研究

选取两种不同锥度角的金刚石磨粒,分别用其对SiC陶瓷和单晶SiC进行了单颗磨粒磨削实验,检测了磨削过程中的磨削力大小,分析了磨削参数对磨削力的影响。实验结果表明:磨削力随着切削深度的增大而增大,随磨削速度的减小而增大;随着磨粒顶锥角的增大,磨削力明显增大;磨削单晶SiC(6H)的磨削力大于磨削SiC陶瓷的磨削力。     

纤维油石在超声波抛光中的应用

（树脂结合剂陶瓷）纤维油石是我们国家磨具的一个新品种,被广泛应用于超声波抛光中,它适合对硬质合金、钢模具进行地粗、半精磨削,尤其适用于磨削模具的边缘、曲面及圆弧面;选择纤维油石的尺寸和性能取决于工件的材质、磨削效率、工件的表面粗糙度、磨料粒度和磨削液的品种等。     

Wire electro discharge trueing and dressing of fine grinding wheels

In this paper fundamental investigations are presented regarding the capabilities of Wire-EDM for trueing and dressing of fine grained metal bonded diamond grinding wheels. These wheels are often used for precision grinding operations of hard and brittle mould materials like ceramics or cemented carbides. They are characterised by high profile constancies and wear resistances. Due to the electrical conductivity of the bond material, Wire-EDM offers an efficient and powerful alternative to conventional trueing and dressing. Achievable grit protrusion and possible thermal damage to smallest diamond grits are theoretically and experimentally examined. Additionally, machining strategies for high profile accuracy are presented.     

陶瓷磨削中新型多孔金属结合剂金刚石砂轮磨损特征研究

在磨削Al2O3工程陶瓷材料过程中,利用三维视频显微镜跟踪观察了新型多孔金属结合剂金刚石砂轮,金刚石的磨损过程以及砂轮表面形貌的变化。分析了新型砂轮中金刚石磨损的主要形式及原因,砂轮工作表面的状态变化特征。试验结果表明：新型多孔金属结合剂金刚石砂轮在加工过程中,金刚石的磨损形式包括磨耗磨损,破碎及脱落等磨损过程,其中以磨耗磨损为主;同时,随着结合剂的不断磨除,砂轮深层磨料能够不断出露,取代表面钝化失效、脱落的金刚石,且砂轮表面孔隙结构,随磨损过程呈交替更迭变化,砂轮具有较好的自锐性。     

基于ELID磨削WC-Co硬质合金表面机械研抛研究

本文采用ELID磨削和机械研磨抛光复合技术,对WC-Co硬质合金表面进行了超精密加工实验研究。首先采用ELID磨削对WC-Co硬质合金表面进行预加工,获得表面粗糙度Ra18 nm的精密加工表面。在此基础上对其进行机械研磨抛光加工,研抛盘转速设定为150～200 r/min,研抛压力控制在0.2～0.5 N/cm2范围;机械研抛时,首先采用含W1金刚石磨粒的研抛液,对ELID磨削后的表面进行加工100min左右,以达到快速去除的目的。再用含W0.5金刚石磨粒的研抛液,进行机械研抛约100 min,最后获得Ra4 nm的超精密表面。同时,针对机械研磨抛光过程,本文深入研究了磨料种类、粒度、抛光液溶剂、研抛压力、研抛加工时间等因素对加工表面粗糙度的影响。     

高温钎焊立方氮化硼界面微结构

以Ag-Cu-Ti合金为钎料采用真空钎焊的方法在优化的钎焊温度和时间下，实现了立方氮化硼(CBN)与砂轮基体的牢固连接。运用扫描电镜(SEM)、X射线能谱仪(EDS)及X射线粉末衍射仪(XRD)对连接界面的微观组织以及CBN表面生成物的三维形貌、化学成分、物相结构进行了综合分析。结果表明，钎料中的元素Ti向CBN表面扩散富集，生成了针状TiB2和TiN，在磨粒与钎料界面形成化学冶金结合，这是CBN与Ag-Cu-Ti钎料间有良好浸润性和高结合强度的主要原因。磨削对比试验表明钎焊CBN砂轮比电镀CBN砂轮具有更高的磨粒把持强度。     

界面理论在树脂超薄切割砂轮制做中的应用

本文从界面浸润理论、界面黏接理论分析出发,探讨一种有可能改善磨料与黏结树脂之间的表界面性能,提高黏结能力,提高砂轮磨削性能的混料工艺及其作用机理。通过加热、抽真空等手段对磨料进行处理,获得了清洁的表面;通过正交试验和方差分析对所制砂轮切割试验结果进行数据处理,结果表明:抽真空和加热均能提高砂轮的磨削性能,抽真空对提高砂轮磨削性能的影响更显著。通过抽真空和加热可改善磨料与黏结树脂之间的表面-界面性能,可提高其黏结能力,提高砂轮的磨削性能。该结论对树脂砂轮的制造具有较好的指导意义。