硬质合金可转位浅孔钻优化设计及CAD原型系统研究

以提高浅孔钻加工性能、促进浅孔钻批量化生产为目标,对刀体上装有两个等边不等角六边形硬质合金可转位刀片的浅孔钻进行研究。采用向量矩阵法建立切削部分几何模型;采用经典斜角切削理论和经验公式相结合的方法建立浅孔钻的力学模型;基于上述数学模型,以径向合力与扭矩最小为优化目标建立优化程序;在给定已知条件下求出不同切削用量、不同直径条件下的浅孔钻内、外刀片的最优空间位置,并进行分析;最后,基于理论分析与实验数据,建立可转位浅孔钻的参数化CAD原型系统。     

现代刀具材料系列讲座（四）：新型硬质合金——添加钽、铌的硬质合金

主要介绍了添加钽、铌硬质合金的种类和性能,并引入一些切削试验数据。     

硬质合金角度组合铣刀设计

为满足用户生产需求设计了此组合刀具,此组合刀具由两个刀盘和调整垫组成,用螺栓及销子将它们连接在一起,在保证产品质量的同时又提高了生产效率。     

现代刀具材料系列讲座（六）新型硬质合金——表面涂层硬质合金

主要介绍了涂层硬质合金的性能、类别和涂层工艺,并列出一些试验数据。     

硬质合金刀具干切削TC4钛合金耐用度的研究

通过对YT15、YG8、YW2这3种牌号的硬质合金刀具干切削TC4钛合金的试验,分析了3种刀具的磨损形貌及特征,并研究了切削速度对刀具耐用度的影响,建立了刀具耐用度T与切削速度v之间的泰勒公式.结果表明,随切削速度增加YT15刀具耐用度降低最快,YG8刀具的耐用度次之,YW2刀具的耐用度降低最慢.     

凿岩球齿钎头硬质合金的失效形式

根据国内外凿岩球齿钎头硬质合金失效形式的研究,指出球齿合金在凿岩过程中出现的磨粒磨损、热疲劳、剥落、内部裂纹、固齿部断裂、剪切断裂、表面裂纹等7种主要失效形式及其应对措施,对钎钢钎具和矿用硬质合金生产企业的产品质量控制具有指导作用。     

Processes involved in the wear of cemented carbide tools

Studies were made of the initial cratering wear and subsequent wear propagation of WC-(Ti, Ta, W)C-Co tools used to cut carbon steel. Using mechanically polished tools and short cutting times (1–11 s), microstructural and chemical changes involved in the initial wear process were identified and used as a basis for evaluating several wear models. Making use of iron-coated and diffusion-annealed tools, the wear propagation process was similarly evaluated in tests of up to 6 min duration.Microscopic examination shows that WC grains fracture intragranularly, consequently generating fine WC wear debris. Analysis of chip material reveals the size of WC wear debris to be an order of magnitude less than the original grain size. The (Ti, Ta, W)C wear debris size was found to be of the order of the original grain size. Adhesion seems to be the most likely mechanism of wear. Abrasive wear seems to be inconsistent with the observed similarity between results for inclusion-containing 52100 steel and 1045 steel relatively free of inclusions. Despite evidence of substantial diffusion, diffusional wear models seem inapplicable owing to the relative wear rates of coated and uncoated tools and to the absence of intergranular failure. Dissolution models seem inconsistent with the observed coexistence of the iron coating and the WC particles.     

纳米WC-Co硬质合金研究现状

综述纳米硬质合金的研究开发概况及应用。重点介绍纳米WC和WC-Co粉体的制备方法和烧结工艺,指出要成功地制备纳米硬质合金,关键在于抑制烧结过程中WC晶粒的长大。简要介绍纳米硬质合金的应用前景。     

Failure analyses of cemented tungsten carbide extrusion die

Abstract

In this study, the failure of a cemented tungsten carbide extrusion die (WC–Co) which was designed for the production of 55 000 components but failed during production of third component has been investigated. The die is used for cold extrusion of auto parts components as sizing die. Sizes achieved by forging process are further refined to required fine tolerance. The component size is required to be controlled within ±20 μm. The investigations revealed that the failure is due to abusive machining of cemented tungsten carbide. Detail studies under different electrical discharge machining conditions have been made to investigate the formation of cracks and their morphology. The major cause of the failure is established as abusive electrical discharge machining conditions with higher pulse current, which lead to micro- to macrocracks at the machining stage. These cracks further enlarged under load conditions when extrusion was done. Based on this study experiments were performed under different machining conditions on the WC–Co material. Optimum parameters were established for machining and accordingly new die was designed and fabricated which is performing very well.     

Dynamic reliability sensitivity of cemented carbide cutting tool

Influence of geometric and cutting parameters of cemented carbide cutting tool on reliability of cutting tool has become more and more mature, yet influence of its physical and material parameters on reliability is still blank. In view of this, cutting test and fatigue crack growth test of YT05 cemented carbide cutting tool are conducted to measure such data as the original crack size, growth size, times of impact loading, number and time of cutting tool in failure, and stress distribution of cutting tool is also obtained by simulating cutting process of tools. Mathematical models on dynamic reliability and dynamic reliability sensitivity of cutting tool are derived respectively by taking machining time and times of impact loading into account, thus change rules of dynamic reliability sensitivity to physical and material parameters can be obtained. Theoretical and experimental results show that sensitive degree on each parameter of tools increases gradually with the increase of machining time and times of impact loading, especially for parameters such as fracture toughness, shape parameter, and cutting stress. This proposed model solves such problems as how to determine the most sensitive parameter and influence degree of physical parameters and material parameters to reliability, which is sensitivity, and can provide theoretical foundation for improving reliability of cutting tool system.     

Failure of cemented carbide tools in intermittent cutting

The nature and mode of cemented carbide tool failure has been examined by considering the effects of thermal and mechanical loads to which a tool is subjected during intermittent cutting. Interrupted cutting tests were performed on a lathe, using a specially designed slotted workpiece fixture and several grades of cemented carbides were used to machine mild steel. Experimental results indicate that the mechanism of tool failure changes with the cutting parameters; these must therefore be carefully chosen to optimise tool performance.     

高速车削钛合金时硬质合金刀具和涂层刀具的寿命分析

采用硬质合金刀具和硬质合金TiMN涂层刀具对Ti-6Al-4V钛合金进行高速干车削正交试验,并通过多元线性回归分析得出硬质合金刀具和涂层刀具的寿命经验公式.分析表明:随着所选用的切削参数值的升高,刀具的使用寿命急剧减少,其中速度v对刀具使用寿命的影响最大.涂层刀具在低速切削加工钛合金时其寿命优于未涂层刀具,随着速度的提高,涂层刀具的优势迅速减小.当切削速度低于85 m/min,刀具寿命经验公式可以作为数控机床自动换刀的刀具寿命标准.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

硬质合金内圆工件磨削的在线检测系统的设计

针对M2110型内圆磨床在磨削硬质合金等高硬度内孔时,加工精度低,加工效率不高等问题,通过实时在线测试加工工件的余量,控制步进电机的进给,形成在线的闭环控制系统,从而提高了硬质合金内孔的加工精度和效率。     

整体硬质合金枪钻在特深小孔钻削中的应用

本文分析了特深小孔及其钻削特点,对研制特深小孔钻床和钻头提出了一系列技术要求,并介绍了使用时的钻削参数,同时指出了钻削加工中应注意的几个技术问题。     

钨资源在硬质合金刀具行业中的可持续发展

针对我国钨资源日益紧缺的形势,在硬质合金刀具行业中以刀具的全生命周期为基线,从发展高档硬质合金刀具提升刀具使用性能,提高刀具材料利用率,回收利用废旧刀具材料,研发新刀具材料及推广应用其他刀具材料几个方面来论述减少钨资源消耗的措施,为钨资源在硬质合金刀具行业中的可持续发展提供思路和方法.     

Fabrication and cutting performance of cemented tungsten carbide micro-cutting tools

We have developed cemented tungsten carbide (CTC) micro-cutting tools of 3 μm diameter by electrical discharge machining (EDM). Microdrilling and micromilling were carried out using the developed tools, and their cutting performance was investigated. Cutting was performed in free-cutting brass plates. Ultrasonic oscillation was employed to lower the cutting resistance. As a result, holes and a slot of 3 μm depth were successfully fabricated using tools made of CTC with 0.6 μm grain size, indicating that successful cutting with 3 μm-diameter tools was accomplished for the first time. Furthermore, CTC with 90 nm grain size was used as a tool material to improve the tool breakage resistance and tool form accuracy. The drilling performance of tools made of this ultrafine-grain-sized CTC was also investigated and found to exhibit a considerably improved average tool life.     

基于CUDA的硬质合金可转位刀片缺陷检测方法研究

在精密加工中,刀片的质量直接影响产品的加工精度.对于刀片生产厂家来说,在刀片生产过程中,快速有效地对其进行在线缺陷检测的需求已非常迫切.鉴于此,针对硬质合金可转位刀片,专门研究设计了一种采用机器视觉技术基于统一计算设备架构(CUDA)方案的缺陷检测方法.     

Resistance of a binderless cemented carbide to abrasion and particle erosion

A binderless cemented carbide has been evaluated in abrasion and erosion tests. The binderless carbide was compared with: SiC, Al₂O₃ and two conventional cemented carbides with 6% Co and different WC grain sizes (1 and 7 μm). In the abrasion tests, the materials were ground with silica, silicon carbide and diamond particles in the size range of 5–15 μm. The erosion tests were performed with 80, 200 and 600 μm silicon carbide erodents. The angle of impingement was 45° and the erodent velocity 70 m/s. In all tests, the conventional cemented carbides showed the highest, the binderless cemented carbide an intermediate and the ceramics the lowest wear resistance. Scanning electron and atomic force microscopy of the abraded surfaces revealed that the binderless cemented carbide was worn by a preferential removal of TiC grains. In erosion, the wear mechanism was largely plastic for the cemented carbides, whereas the ceramics were worn by micro-fracture. The SEM analysis also showed an impact scaling effect for the cemented carbides in erosion. This revised version was published online in August 2006 with corrections to the Cover Date.