New Vitrified Bond Diamond Grinding Wheel for Grinding the Cylinder of Polycrystalline Diamond Compacts

In this work, a kind of new vitrified bond based on Li2O-Al2O3-SiO2 glass ceramics was used to bond the diamond grains, which is made into grinding wheel and the cylindrical grinding process of polycrystalline diamond compacts （PDCs） by using the new vitrified bond diamond grinding wheel was discussed. Several factors which influence the properties of grinding wheel such as amount of vitrified bond and the kinds and amount of stuff in grinding wheel were also investigated. It was found that the new vitrified bond can firmly combine diamond grains, when there are only diamonds and vitrified bond in the structure of grinding wheel, the longevity of the grinding wheel is about 2.5-3 times as that of resin bond grinding wheel for processing PDCs. The grinding size precision of PDCs can be improved from 4-0.03 mm to 4-0.01 mm because of larger Young＇s modulus of vitrified bond than resin bond. The grinding time of a PDC product can be 1.75-2.0 min from 3.25-3.5 min, so this kind of grinding wheel can save much time for processing PDCs. Also, there is hardly noise when using this new vitrified bond diamond grinding wheel to process PDCs. The amount of vitrified bond in grinding wheel influences the longevity of grinding wheel. When the size of diamond grains is 90-107 μm, the optimal amount of vitrified bond in grinding wheel is 21% （wt pct）. When the amount of vitrified bond exceeds 21%, there are many pores in grinding block, which will decrease the longevity of grinding wheel. The existence of addition stuff such as Al2O3 or SiC can reduce the longevity of grinding wheel.     

精细陶瓷材料的金刚石砂轮磨削性能

本文探讨了精细陶瓷材料的金刚石砂轮磨削性能的共同特点以及不同种类陶瓷和不同磨削方式的影响。研究结果表明：陶瓷材料磨削时，砂轮磨损大，磨削比小，磨削力大、磨削效率低，磨后陶瓷零件使用寿命大大降低；必须根据陶瓷种类的不同选择不同的磨削方式。     

陶瓷结合立方氮化硼磨削工具材料制备研究

陶瓷结合立方氮化硼(CBN)磨削工具是一类用于磨削加工的新型陶瓷/玻璃复合材料。本文作者从复合材料制备理论角度探讨了这类材料的制备原则,并进行了试验研究。研究结果表明:CBN磨具的烧成温度以低于800℃为宜;陶瓷结合剂与CBN磨料的热膨胀系数匹配性对磨具强度有较大影响,具有较小热膨胀系数和较高强度的C₁结合剂较适合CBN磨具制备。在一定温度范围内,适当提高烧结温度,有利于提高陶瓷结合剂桥相本身强度及结合剂与CBN磨料颗粒的结合强度。     

振动辅助磨削——压电平台的设计与制造

旨在研究振动辅助磨削．首先综述了用于不同条件下的振动辅助磨削以及利用振动辅助抑制砂轮堵塞的现象．还论述了振动辅助磨削的优点，例如降低磨削力和磨削温度，提高磨削效率和工件质量等．为了实现振动辅助磨削，设计和制造了一个由平行四连杆机构和压电驱动元件组成的压电平台，并且使用该压电平台进行了陶瓷材料的振动磨削实验．给出了振动磨削实验的初步结果并对结果进行了讨论．     

Ni-金刚石复合涂层的结构优化及基础磨削性能

采用电沉积技术在304不锈钢基体上制备了Ni-金刚石复合涂层。通过金刚石掺入量、加厚镀时间优化了金刚石复合涂层结构,利用球-盘式摩擦磨损试验仪研究了优化后的金刚石复合涂层对不同材料偶件(GCr15、SiC、304不锈钢)的磨削性能。结果表明:金刚石掺入量为1.5g/L时,金刚石上砂均匀且密集;加厚镀15min时,金刚石埋入率约为2/3,附着强度较好,适合磨削加工;GCr15、SiC、304不锈钢3种材料偶件的磨损体积依次减小,分别为:0.353 76mm~3、0.315 90 mm~3、0.194 01 mm~3,金刚石复合涂层对GCr15有较好的磨削性能;金刚石复合涂层磨削GCr15、SiC、304不锈钢均发生了磨粒磨损,此外,GCr15还发生了微弱的化学磨损,不锈钢发生了较明显的化学磨损和粘着磨损。     

CBN grain wear and its effects on material removal during grinding of FGH96 powder metallurgy superalloy

Grinding with cubic boron nitride (CBN) superabrasive is a widely used method of machining superalloy in aerospace industries. However, there are some issues, such as poor grinding quality and severe tool wear, in grinding of powder metallurgy superalloy FGH96. In addition, abrasive wheel wear is the significant factor that hinders the further application of CBN abrasive wheels. In this case, the experiment of grinding FGH96 with single CBN abrasive grain using different parameters was carried out. The wear characteristics of CBN abrasive grain were analyzed by experiment and simulation. The material removal behavior affected by CBN abrasive wear was also studied by discussing the pile-up ratio during grinding process. It shows that morphological characteristics of CBN abrasive grain and grinding infeed direction affect the CBN abrasive wear seriously by simulation analysis. Attrition wear, micro break, and macro fracture had an important impact on material removal characteristics. Besides, compared with the single cutting edge, higher pile-up ratio was obtained by multiple cutting edges, which reduced the removal efficiency of the material. Therefore, weakening multiple cutting edge grinding on abrasive grains in the industrial production, such as applying suitable dressing strategy, is an available method to improve the grinding quality and efficiency. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00412-2     

On the Surface Integrity of Precision-Ground Steel Cylindrical Parts

The effects of traditional corundum and boron-nitride (CBN) wheels on the surface integrity of internally and externally ground steel parts has been investigated in respect to microhardness, residual stresses, and change of texture. The microhardness and residual stress components of the surface layer of HSS tools ground with CBN wheels have been measured and texture has been also investigated. Case-hardened steels have been ground with mainly traditional wheels. The change of microhardness, residual stresses, and texture depends to a large extend not only on grinding parameters but also on the grade of sharpness of the wheel. The difference between grinding with sharp and worn wheels is significant. These facts prove the importance of different continuous wheel dressing processes. The effect of the coolant on the surface quality has also been examined.     

铝基结合剂金刚石制品的组织观察

为研究Ti、Ni、Co对铝基结合剂性能的影响及结合剂对金刚石包裹情况,用热压烧结的方法制备了金刚石磨轮,采用扫描电镜研究了磨轮的断口形貌、结合剂与金刚石的界面结合以及元素的分布情况.研究表明:Al-Sn-Ti-Ni-Co是较好的结合剂体系,300℃烧结断口平坦,金刚石颗粒局部黏附有结合剂;Ti、Ni在结合剂中偏聚或形成独立相,可降低结合剂的塑性,改善结合剂的可磨削性;Co在结合剂中总体上分布均匀,有利于提高结合剂对金刚石的把持力.Al-Sn-Ti-Ni-Co结合剂对金刚石包裹较好,Ti、Ni、Co起到了改善结合剂性能的作用.     

Ductile Regime Mirror Finish Grinding of Ceramics with Electrolytic In-process Dressing (ELED) Grinding

Advanced structural ceramics, such as silicon nitride based materials, are of interest owing to their unique physical and mechanical properties. However the cost of grinding these ceramics, which is an integral part of their fabrication, is very high. Moreover, grinding can result in surface and sub-surface damage in the material and these defects can significantly reduce the strength and reliability of the finished components. Grinding damage is sensitive to grinding parameters. Two types of silicon nitride based ceramic materials were ground with Electrolytic In-Process Dressing (ELID) using different grit sized metal bonded diamond grinding wheels. With the application of ELID technology, mirror surface finish was realized with a #4000 mesh size wheel (average grain size = 4μm). Differences in ground surface topography caused by wheel grain size were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM studies reveal that material was predominantly removed in the ductile mode when ELID grinding was performed with a #4000 grit size wheel or finer.     

On brazing of cubic boron nitride abrasive crystals to steel substrate with alloys containing Cr or Ti

An investigation has been carried out to gain information about the capabilities of some filler alloys for direct brazing of CBN (cubic boron nitride) grits to a steel substrate. It has been found that a Ni-Cr alloy, known for effective diamond brazing, failed to show satisfactory wetting and bonding characteristics towards CBN under the same brazing conditions as that of diamond. The situation could not be improved either by increasing the wt% of Cr or the brazing temperature. Also, prolongation of the brazing time did not show any significant change. It was further revealed that a Ag-Cu-Ti alloy, which is well established for the brazing of diamond and ceramics, exhibited good wetting and bonding towards CBN at moderate temperature. Based on the thermodynamic properties of various materials, characteristic properties of elements of group IV B to VI B and the physical observations made during the investigation, it is suggested that the transition elements of group IV B, such as Ti or Zr, are preferred to transition elements of group VI B, such as Cr, as an activator to promote the wetting characteristics of the braze alloy towards CBN, which is far more chemically stable than diamond.     

单颗CBN磨粒磨削20CrMo的微观成屑过程研究

为研究20CrMo材料的磨削去除机理与微观成屑过程,采用Johnson-Cook模型作为20CrMo的本构模型,应用有限元软件Abaqus建立了单颗CBN磨粒磨削20CrMo成屑过程的三维有限元分析模型。通过该模型探究不同磨削参数下的微观成屑过程,仿真分析结果表明:磨削速度对成屑过程中的耕犁与成屑阶段影响较大,磨削深度对滑擦与成屑阶段影响较大。设计了单颗磨粒磨削实验装置,对微观成屑进行了实验研究与分析,从磨痕沟槽和磨屑的整体特征来看,实验结果与仿真结果都较为吻合,验证了该三维仿真模型的正确性。     

Grinding of Single-Crystal Silicon Using a Microvibration Device

This paper presents experimental results of grinding of single-crystal silicon using a microvibration device and a diamond grindingwheel. Samples were cut from (100) silicon. The grinding direction was parallel to the [110] direction of (100) silicon. These samples were ground under the same grinding conditions but with different vibration directions, frequencies, and/or amplitudes. The surface roughness and the surface texture of all samples were analyzed for comparison. The R_a, R_q, and R_t values and the microphotographs of the ground silicon surfaces showed the dependency of surface finish on the grinding with vibrations. Samples ground with vibrations had better surface finish compared with the silicon surfaces ground without vibrations. Out of the 12 experiments, the best surface finish was achieved when (100) silicon was ground with horizontal vibrations at a 70-Hz frequency and 6-μm amplitude perpendicular to the grinding direction.     

Parametric Study of Temperature Distribution in Electrodischarge Diamond Grinding

Electrodischarge diamond grinding (EDDG) is a potential process for machining of advance engineering components, but there is no theory to support it. The work reported in this article makes an attempt in this direction. This article reports on determination of temperature distribution in the workpiece due to EDDG using the finite element method. The temperature distribution in the workpiece domain due to EDDG is obtained by superposition of the two temperature distributions for grinding and electrical discharge mechining (EDM) (i.e., 2D for grinding and axisymmetric for EDM). The effects of duty cycle, on-time, current, energy partition, time of machining, and feed velocity while machining are computationally investigated.     

高钛矿渣的粉磨特性研究

由于攀钢高炉渣中含有20%以上的TiO2,使其利用受到很大限制,为使高钛矿渣作为掺合材料应用于混凝土,需首先了解高钛矿渣的粉磨特性。本文中研究了粉磨时间与高钛矿渣细度之间的关系,对比了高钛矿渣与普通矿渣易磨性并分析了助磨剂对高钛矿渣粉磨的影响。结果表明,高钛矿渣的易磨性较普通矿渣差,可使用助磨剂提高高钛矿渣的粉磨效率。     

The effect of silicon dioxide content of natural stones on their strength properties,material removal rate and power consumption in diamond grinding

The paper addresses the influence of silicon dioxide content of natural stones on their Mohs hardness, ultimate uniaxial compression strength, microhardness as well as on the removal rate and power consumption in diamond grinding of these materials. An increase in the amount of this constituent in natural stones is demonstrated to have an effect on strength properties and power consumption in grinding and a considerable effect on removal rate in diamond grinding.     

2D-C/SiC高速深磨磨削特性及去除机制

采用树脂结合剂金刚石砂轮, 通过对2D-C/SiC复合材料高速深磨磨削加工, 并对磨削表面形貌和亚表面损伤进行了观察。提出了2D-C/SiC摩擦层(表面)的磨削力理论公式, 讨论了磨削加工用量对磨削力和磨削力比的影响。实验结果表明, 2D-C/SiC复合材料的高速深磨材料去除机制与其自身的微观结构相关, 既不同于塑性材料, 也不同于普通脆性材料, 而是以脆性断裂去除为主。     

矿物湿法超细磨矿中助磨剂的作用效应及其程度的研究

通过考察硬脂酸钠对重质碳酸钙－水矿浆粘度的影响和因硬脂酸钠在重钙表面吸附而导致的颗粒表面自由能的变化以及由此产生的对湿式搅拌磨细磨重质碳酸钙磨矿效果的影响,研究了助磨剂的各种作用效应及其程度。结果表明,助磨剂对矿物湿法细磨的助磨作用是改善矿浆流变性和吸附降低颗粒表面自由能两种效应综合的结果,其中前一作用较强。     

DG系列双盘式磨粉机制粉系统的开发与应用

采用剪切式粉碎原理,开发了DG系列双盘式磨粉机。该机采用独特的两组动、静盘式机构及简单有效的间隙精密调整机构,通过分析动、静盘间间隙ΔH的作用及影响磨粉数量和粒度的因素,合理选择了相关的工作参数,并设计了相应的磨粉工艺系统。     

Precision grinding of microarray lens molding die with 4-axes controlled microwheel

This paper deals with precision grinding of microarray lens (fly eye) molding die by using a resinoid bonded diamond wheel. An ultra-precision grinding system of microarray lens molding die and new truing method of resinoid bonded diamond wheel were developed. In this system, a grinding wheel was four-dimensionally controlled with 1 nm resolution by linear scale feedback system and scanned on the workpiece surface. New truing method by using a vanadium alloy tool was developed and its performance was obtained with high preciseness and low wheel wear. Finally, the microarray lens molding dies of fine grain tungsten carbide (WC) was tested with the resinoid bonded diamond wheel to evaluate grinding performance.     

MACHINING OF THERMALLY SPRAYED WC-Co COATINGS

This paper reports the research results obtained from machining of thermally sprayed WC-Co coatings. WC-Co coatings are used in marine applications. The machined coatings were obtained by using two thermal spraying processes: arc spraying and high-velocity oxy-fuel (HVOF) spraying. Different techniques were tried to optimize the surface finishing of the thermally sprayed coatings based on surface finish and time required. The machining processes tried for WC-Co coatings were diamond grinding, cubic boron nitride (CBN) grinding, diamond turning, and diamond polishing. Diamond turning had the advantage of speed, however, the surface finish was not as good as that with fine grinding. Polishing should have given the best surface finish, however, this process was slow. It is suggested to reduce the machining time, first by rough grinding or diamond turning to near the final dimensions, and then by fine grinding or polishing to get the required surface finish and dimensions.