高速磨削用单层钎焊CBN砂轮及其磨削性能

针对钎焊砂轮存在的热变形导致精度降低的问题,提出基于局部加热的超高频感应钎焊工艺方法制备高速磨削用单层钎焊CBN砂轮,采用三坐标测量仪对砂轮及其钎焊前后的尺寸进行测量,最后对该砂轮高速磨削镍基高温合金磨削性能进行评价。三坐标测量结果显示,钎焊CBN砂轮基体的变形量小于16μm,在高速重负磨削镍基高温合金试验中,加工表面未见裂纹和烧伤,表面粗糙度可达Ra0.4μm,砂轮表现为正常磨耗磨损。表明超高频感应钎焊工艺制备的单层钎焊砂轮在高速磨削具有应用潜力。     

钛合金Ti6Al4V高速磨削试验研究

为实现难加工材料钛合金的高效磨削,进一步发挥高速磨削的潜力,开展了钛合金Ti6Al4V高速磨削工艺试验研究,对磨削过程的磨削力、磨削比能以及磨削温度随单颗磨粒最大切屑厚度agmax的变化特征进行了分析。研究结果表明：不同砂轮线速度vs条件下,磨削力、磨削比能及磨削温度三者随单颗磨粒最大切屑厚度agmax变化的特征曲线略有不同,具体表现为,单颗磨粒最大切屑厚度agmax一定条件下,磨削力及磨削比能随着磨削速度的提高呈减小趋势,磨削温度则呈上升趋势,同时钎焊CBN砂轮的磨削力、磨削比能低于陶瓷结合剂及电镀CBN砂轮的磨削力、磨削比能,因此,利用钎焊CBN砂轮磨料有序排布的优势,选择合理的单颗磨粒最大切屑厚度,可在提高砂轮线速度的同时提高进给速度,从而提高磨削效率,实现钛合金的高速高效磨削。     

新型小直径端面CBN砂轮开发及其磨削性能研究

基于电镀小直径端面CBN砂轮磨削沟槽的试验结果,为减小沟槽底面与侧面过渡圆弧半径,开发了一种新型小直径端面CBN砂轮,在试验研究其磨削性能的基础上提出了改善措施,取得了良好的磨削效果。新型端面CBN砂轮加工沟槽的过渡圆弧半径达到0.2mm以下,比电镀CBN砂轮减小60%以上。新型端面CBN砂轮磨削过程中,由于有效CBN磨粒发生的后面磨损及其破碎,使磨粒切削刃凸出高度降低,而砂轮表面所有CBN磨粒均先后依次成为有效磨粒,因此提高单个CBN磨粒的耐磨性和韧性,减小破碎,是提高新型CBN砂轮寿命的有效措施。选用多晶强韧的CBN磨粒(通用电器GE550型产品)使砂轮寿命提高到了原来的6.75倍。     

金属结合层包覆单列磨粒小直径CBN砂轮端面磨削过程研究

金属结合层包覆单列磨粒小直径CBN砂轮在端面磨削过程中突出高度不同的CBN磨粒相继发生后面磨损、切削刃破碎和脱落,产生了砂轮自锐效应。砂轮磨削力呈现低频起伏和高频波动变化的特征,这是由于磨削过程中CBN磨粒后面磨损钝化使磨削力增大以及随后磨钝磨粒破碎变得锐利使磨削力减小的综合作用结果。砂轮磨削过程受到CBN磨粒性能及其切削刃状态的支配,多晶强韧CBN磨粒(BORAZON550,GE产品)耐磨性改善、磨粒微细破碎保持了砂轮的锐利性,延长了单个磨粒服务时间,突出高度不同的磨粒加入磨削过程的批次效应显著,磨削力低频起伏明显,单晶CBN磨粒(BORAZON500,GE产品)破碎范围大有效降低了磨粒切削刃突出高度、新磨粒加入磨削的过程具有连续性,磨削力高频波动明显。     

磨料粒度对电镀CBN砂轮磨损影响的有限元仿真分析

以单颗CBN磨粒的磨损为例,对电镀CBN砂轮的磨损进行研究。针对磨削淬硬轴承钢GCr15,将单颗CBN磨粒适当简化成圆锥体,建立楔形滑擦模型,利用Deform 3D软件对单颗CBN磨粒的磨耗磨损进行仿真分析。仿真结果表明:不同粒度磨粒的磨损形式相似,均为前端面磨成弧形月牙洼形,尖端逐渐磨成平台;相同条件下磨粒的最大磨损量随着磨料粒度号的增大而减小。同时也说明了细粒度的电镀CBN砂轮的磨损较小。研究结果对进一步研究电镀CBN砂轮制造工艺有指导意义。     

磨粒有序化排布外圆砂轮磨削TC4的粗糙度实验研究

为了了解有序化砂轮磨削钛合金的表面质量,将叶序理论引入到CBN电镀砂轮磨粒的设计当中来,采用紫外线感光干膜作为掩膜感光层来实现在砂轮表面磨粒的排布,利用光刻技术和复合电镀工艺技术制造出磨粒有序排布外圆砂轮,并对钛合金TC4进行磨削实验研究,获得了不同的进给速度及磨削深度对磨粒叶序排布,错位排布,无序排布砂轮磨削表面粗糙度的影响规律.实验结果表明:在相同的磨削条件下,与其它排布砂轮相比,磨粒叶序排布砂轮磨削工件表面得到的粗糙度值最小。     

超声辅助磨削碳化硅陶瓷的工具磨损试验研究

为探究超声辅助磨削过程中不同工具的磨损特征,采用电镀和钎焊两种金刚石磨头对碳化硅陶瓷进行了超声辅助磨削和普通磨削对比试验,研究了超声振动作用、工具类型对磨粒磨损形式及其变化过程的影响,在此基础上分析了磨粒磨损形式对工件表面质量的影响.试验结果表明:对于电镀磨头,普通磨削和超声辅助磨削过程中的磨粒磨损形式均以磨耗磨损和宏观破碎为主,超声振动作用可有效改善加工表面质量;而对于钎焊磨头,普通磨削的磨粒磨损形式主要是磨耗磨损和宏观破碎,超声辅助磨削的磨粒磨损形式主要是磨耗磨损和微破碎,初始阶段超声振动作用可改善表面质量,但随着磨削行程的增加,微破碎形式的占比增高,超声辅助磨削时的工件表面粗糙度值高于普通磨削时的工件表面粗糙度值.     

金属结合剂杯形小直径CBN砂轮端面磨削沟槽底面时砂轮的自锐效应

金属结合剂杯形小直径CBN砂轮端面磨削沟槽底面时 ,砂轮磨削力不随砂轮累积磨削行程的增加而增大 ,已加工表面粗糙度Rz 稳定在 4μm以下 ,处于持续稳定的正常磨削状态。这缘于磨削过程中CBN砂轮的自锐(Self-dressing)效应 ,即在砂轮磨削的同时砂轮结合剂被连续地去除 (CBN磨粒裸露体积增大 ) ,磨钝磨粒发生龟裂、破碎和脱落 ,不断产生新的磨粒切削刃 ,CBN磨粒切削刃密度保持动态稳定 ,砂轮维持在锋利状态。CBN砂轮自锐效应产生的机理是磨屑与冷却液形成的混合流体对砂轮结合剂产生冲击、冲刷和刻划作用产生了去除砂轮结合剂和梳理磨粒的效果     

自润滑金属结合剂CBN砂轮干式磨削特性分析

针对钛合金难磨削加工性,提出了自润滑金属结合剂砂轮,综合液相烧结与钎焊工艺制备了自润滑金属结合剂立方氮化硼(Cubic Boron Nitride,CBN)砂轮,分析了砂轮强度和微观组织,完成了自润滑CBN砂轮与碳化硅砂轮干式磨削钛合金的性能试验。通过砂轮磨损、工件表面形貌、金相显微组织和显微硬度等特性研究表明:自润滑CBN砂轮干式磨削钛合金切削性能明显优于绿色碳化硅砂轮,在vs=15m/s,vw=2m/min,ap=0.025mm磨削条件下,自润滑金属结合剂砂轮具有较好的磨削性能。     

电镀CBN锥砂轮磨削齿面残余应用的研究

从磨削表面生成过程出发,对电镀CBN锥砂轮磨齿表面残余应力进行了定性分析,并对其与陶瓷CBN锥砂轮在不同工艺参数组合下磨削后齿面残余应力状态做了对比试验。结果表明,电镀CBN锥砂轮磨削后齿面处于残余应力状态,且在相同金属去除率时电镀CBN锥砂轮比陶瓷CBN锥砂轮磨削后齿面的残余压应力值更大。     

Wear behavior and mechanism of single-layer brazed CBN abrasive wheels during creep-feed grinding cast nickel-based superalloy

Wear behavior and mechanism of single-layer brazed CBN abrasive wheels during creep-feed grinding nickel-based superalloy K424 was investigated. Grinding force and temperature acting on the abrasive wheels were measured. Optical microscopy and scanning electron microscopy were utilized to detect grain protrusion and wheel wear morphology. The normal distribution of the protrusion height of the brazed CBN grains on the wheel surface was determined. The results show that, though the grinding zone temperature is merely about 180°C during creep-feed grinding nickel-based superalloy, the grinding heat still has an important effect on the grain wear owing to the high temperature of the individual grain up to 500–600°C. Wear patterns of brazed wheels are composed of mild wear (attritious wear and grain micro-fracture) and severe wear (grain macro-fracture, erosion of the bonding layer). Strong joining of brazed CBN grains and Ag–Cu–Ti bonding layer improves significantly the resistance to grain pullout.     

Ni—Cr合金Ar气保护炉中钎焊金刚石砂轮的研究

用活性行钎料钎焊单层金刚石砂轮与传统电镀砂轮相比具有磨锋利，寿命长等优异性能。利用Ar气谷护炉中钎焊的方法，用Ni-Cr合金粉末做钎料，迁当控制钎焊温度，保温时间和冷却速度，实现了金融石与钢基体的牢固连接，利用扫描电镜和X射线能谱，结合X射线衍射结构分析，发现在钎焊过程中Ni-Cr合金中的Cr元素分离出在金刚石界面形成富Cr层并与金刚石表面的C元素反应生成Cr3C2和Cr7C3，这是实现合金与金刚石有较高结合强度的主要因素，重负荷磨削实验表明金刚石为正磨损，没有整颗金刚石脱落。     

Study on textured CBN grinding wheel by laser cladding

In this investigation, in order to improve bonding strength between superabrasive/metal matrix/grinding substrate, life span of grinding wheel, and grinding using small grits in continuous grinding simultaneously to fit for high speed and high precision machining in industry, coaxial powder feeding laser cladding method with CAD/CAM technology is introduced to manufacture textured CBN/CuSnTi–grinding wheels. The morphology of CBN grit on laser-cladding layer under optimized laser-cladding parameters and a pit created by fallen-off CBN on laser-cladding layer with lower laser–cladding energy density are observed by scanning electron microscope (SEM). The element distributions of interfaces of CBN/CuSnTi/AISI 1045 are analyzed by SEM and energy disperse spectroscope (EDS). The morphology and elements distribution of residual resultants on the surface of CBN grits etched by nitric acid are analyzed by SEM and EDS. Comparative-grinding process between laser cladding–grinding wheel (LCGW) and customized electroplated grinding wheel (EGW) is analyzed with grinding forces and temperature aspects respectively. The wear morphology of CBN grits on LCGW after grinding is observed by SEM. The results show that CBN grit with integrate cutting edges can protrude 50% height of its diameter on laser-cladding layer under optimized laser–cladding parameters. Fe, N, Ti, and B segregates attached to the interfaces of CBN/CuSnTi/AISI 1045 with Cu and Sn distributed uniformly in the laser-cladding layer. Residual resultants on CBN can be divided into two parts based on the distances from the surface of CBN grits. The grinding forces (Fz and Fy) and grinding temperature from LCGW are lower than those from EGW. The wear conditions of CBN on laser cladding are three parts: microfracture, cleavage plane, and wear-out.     

钎焊单层金刚石砂轮的实验研究

单层高温钎焊超硬磨料砂轮具有传统砂轮和电镀砂轮无法比拟的优异磨削性能。利用高频感应钎焊的方法,以Ag-Cu合金和Cr粉为钎料,在一定的钎焊工艺条件下进行了实验研究,实现了金刚石与钢基体间的牢固化学冶金结合。扫描电镜分析发现在Ag-Cu-Cr与金刚石的界面之间形成CrC,与钢基体结合界面之间形成(FexCry)C,这是实现合金层与金刚石及钢基体之间都有较高结合强度的主要因素,并在相同的磨削参数条件下与电镀砂轮进行了对比实验,取得了较好的结果。     

CBN砂轮在轴承套圈内圆磨削中的应用

CBN砂轮以其优异的性能在高效、高精度磨削中具有广阔的应用前景。文中以树脂结合剂CBN砂轮轴承圈内圆磨削为研究对象,采用金刚石滚轮修整器,研究选择合适的修整及磨削参数,使CBN砂轮的性能在轴承磨削中得到充分发挥。通过对修整前后砂轮表面形貌分析,揭示了修整参数对修锐效果的影响,并结合磨削后试件表面的精度获得了合适磨削参数,试验结果对CBN砂轮在轴承圈的大批量磨削中的广泛应用具有重要的指导意义。     

Investigation and development of a molding process for the production of micro-hairs

Cubic boron nitride (cBN) is a unique synthetic material on account of its high hardness, high wear resistance, excellent cutting edge stability and relative chemical inertness compared to diamond. The introduction of monolayer electroplated cBN wheels replaced the complex pre-grinding wheel preparation work (truing and dressing) of composite cBN wheels and thereby extensively facilitating the application in high-efficiency deep grinding, creep feed grinding, etc. The present work has aimed at developing a precisely controlled brazing technique suitable for bonding the cBN grits to a steel substrate in monolayer form with higher bond strength, larger grit protrusion and more uniform grit distribution compared to that in the currently used galvanically bonded wheels. Experimental investigation have clearly demonstrated the potential of the newly developed brazed wheels under varying grinding conditions for processing materials like bearing steel. Improved capability of these wheels over galvanically bonded wheels could be better recognised during dry grinding at high material removal rate and for large stock removal when galvanically bonded wheels were found to suffer from severe wheel loading in grinding bearing steel and from unusual increase in grinding forces due to grit pullout. Creation of wider inter-grit spaces with strong bonding and uniform grit spacing happened to be the essence of the present brazed cBN wheel.     

超高速陶瓷结合剂CBN砂轮关键制备技术的研究

砂轮制备技术是实现超高速磨削的关键之一.本文介绍了超高速陶瓷结合剂砂轮的特点,综述了超高速陶瓷结合剂CBN砂轮的关键制备技术,分析了我国CBN磨料、砂轮结构、陶瓷结合剂、砂轮制备工艺等的研究现状,最后展望了超高速陶瓷CBN砂轮的研究及应用前景.     

Development and performance of monolayer brazed CBN grinding tools

CBN grinding tools have been broadly utilized in machining difficult-to-cut materials in recent years. Grains of the conventional grinding tools, however, are held in the tool matrix just through the mechanical incrustation effect induced by the electroplated or sintered metal, which results in the stochastic grain distribution and limited grain protrusion, in addition to the easy grain pullout and premature tool failure by the strong impact forces generated during machining. These properties and shortcomings of the electroplated or sintered tools have restricted the potential of CBN superabrasive grains. Therefore, a new technology has been developed and introduced in this paper to fabricate successfully monolayer CBN grinding tools, in which the highly protruding grains could be planted in the required uniform pattern through the brazing effect among CBN grains, filler alloy and tool substrate at elevated temperature. Finally, comparative grinding tests performed with the conventional electroplated and newly-developed brazed CBN tools have indicated that highly increased efficiency and prolonged tool lives, as well as low fabrication and use cost could be achieved by applying the brazed CBN grinding tools.