整体硬质合金刀具磨削裂纹的原因分析及其工艺改进

对整体硬质合金刀具磨削裂纹的产生原因进行了分析和探讨,并提出了有效防止整体硬质合金刀具磨削裂纹的工艺改进措施。     

硬质合金刀具的电化学磨削

<正> 由于不重磨硬质合金刀具的耗费量日益增大,因此,许多金属加工公司又在重新恢复使用可重磨的单刃硬质合金刀具,这种刀具通常的磨削方法是速度慢,刀片易于产生热裂纹,且金刚石砂轮消耗大。而电化学磨削硬质合金刀具是速度快(0.030时/分～0.060时/分),不产生磨削热,同时金刚石砂轮的消耗量可降低90%。     

焊接硬质合金车刀裂纹的产生与对策

焊接硬质合金车刀裂纹的产生与对策本文以我厂使用的焊接式硬质合金曲轴成形车刀为例，从金属性能、设计、焊接、磨削等方面进行了研究和分析，并提出了减少裂纹的工艺方法，提高了刀具的成品率。１．刀片产生裂纹的原因１）硬质合金与４５钢的热膨胀系数（α×１０－６／...     

硬质合金刀具刃磨质量的研究

选用绿色碳化硅砂轮刃磨硬质合金刀具进行试验 ,找出砂轮粒度、线速度等因素与刀具表面粗糙度之间的关系 ,对磨削时刀具表面产生的裂纹与烧伤等进行分析 ,提出降低刀具表面粗糙度和避免刀具表面产生裂纹的方法。     

硬质合金螺旋立铣刀磨削裂纹的防止

硬质合金螺旋立铣刀与高速钢螺旋立铣刀相比较,具有耐磨性好、红硬性高等一系列优点,但是由于硬质合金螺旋刀片几何形状复杂,磨削加工裂纹率高,它的应用受到一定限制。磨削裂纹是硬质合金刀具制造中常见的缺陷,也是目前国内硬质合金刀具制造中待解决的难题之一。我厂生产的硬质合金螺旋立铣刀如图1所示:它由     

硬质合金刀具的电解磨削

过去刃磨硬质合金刀具一直采用普通机械磨削,常常产生裂纹、崩刃,粗糙度也达不到要求。硬质合金刀具的磨削成为生产中的关键。我们改制一台简易电解磨床,经十余年实践,成功地用于生产,解决了生产中的关键问题。     

硬质合金刀具钎焊工艺的改进

我厂机加工刀具大多采用硬质合金钎焊刀具,由于采用传统的钎焊方法,使机加工刀具极易在磨削和使用过程中脆裂,造成了很大的经济损失。通过分析刀具产生裂纹的原因,我们改进了刀具钎焊工艺,使刀具的使用寿命得到了延长。现将该方法介绍如下。     

制造硬质合金刀具的体会

我厂于去年生产了好几种硬质合金刀具,如硬质合金扩孔钻硬质合金套式锥柄端铣刀和硬质合金钻头等。在这些刀具的施工中我们碰到过不少问题,其中最困难的是在焊接以后的工序。对这些工序如果控制不当,就会引起裂缝、断裂、以及刃口有锯齿形等现象。现根据我们的体会提出几点意见。 (1)硬质合金刀片本身的质量,对硬质合金刀具的加工及使用寿命都有一定的影响。如果其本身已有隐蔽的裂痕或气孔,则在焊接或磨削时就会加速裂纹的产生。或虽未被发现,但在使用中也会大大缩短其寿命。硬质合金刀片在压铸时的内应力也是促使刀片加工后产生网状裂纹的…     

负刃刃磨法

在刃磨硬质合金时,最容易产生裂纹。为防止裂纹的产生,我厂采用了负刃刃磨法。所谓负刃刃磨法,就是在刀具刃磨前,先在前刀面或后刀面上磨出一条负刃带(附图),以提高刀片强度,增强抗振性,防止大量磨削热导向刀片。经实践证明效果良好,如刃磨YT15类刀片,刃磨后产生裂纹的仅占10％,刃磨YG8类刀片,刃磨后产生裂纹的仅占3％。 硬质合金刀具刃磨时产生裂纹的原因,是由于砂轮振动,使刀具受到冲击载荷及刃磨时产生热应力而     

硬质合金刀具的电解磨削

硬质合金刀具在金属切削加工上日益广泛地被应用,对如何提高硬质合金刀具的刃磨质量,不断提高生产率和零件加工质量,已成为迫切需要解决的问题。目前各厂采用碳化硅或金刚石砂轮进行硬质合金刀具的粗、精磨削,砂轮损耗大,刃磨工序繁,磨削时产生热,容易使刀片出现裂纹、烧伤、崩刃等现象,且刃磨质量差,效率较低。金刚石砂轮磨削时虽能获得较高的表面质量,但砂轮价格贵,有一定的局限性。硬质合金刀具的电解磨削是克服机械磨削缺点,稳定获得▽▽▽▽10以上光洁度的一种有效加工方法。现介绍如下。     

Edge chipping mechanism and failure time prediction on carbide cemented tool during drilling of CFRP/Ti stack

To investigate the edge chipping during drilling of the CFRP/Ti stack with carbide cemented tools, a drilling experiment was carried out and a tool failure model was proposed. Thrust force, drilling temperature, and tool wear were analyzed. A tool stressing model and a tool failure model of edge chipping were constructed respectively. On the basis of these, the prediction model on the edge chipping was established to forecast the failure time. Drilling temperature, Vickers hardness, and cutting speed were considered during the prediction model building. The results demonstrate that adhesive wear has a great influence on the edge chipping. The damage of adhesive wear for tool rake face leads to the load variation on rake face and the initial crack. Under the action of shear stress, the crack starts at rake face and then expands to the flank face, resulting in tool edge chipping. The affinity interaction (between titanium alloy with carbide cemented) and the thermal residual stress are two critical factors for tool edge chipping. Tear easily occurs inside the binding phase or at the boundary between hard phase and binder phase. As the drilling temperature increases, the hardness of the carbide cemented will gradually decrease. The prediction result of failure time is similar to the experimental result, and the effectiveness of the prediction model is verified.     

一种新型工具钢冷焊焊缝的研究

利用扫描电镜 (SEM)、透射电镜 (TEM)及X射线衍射等方法研究了一种新型工具钢冷焊焊缝的微观组织 ,认为加入强碳化物元素可获得在低碳马氏体基体上弥散分布碳化物颗粒的冷焊焊缝 ,该焊缝硬度高、韧性好 ,可同时满足工具钢对耐磨性和抗裂性的要求     

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.     

重型切削过程硬质合金刀片的冲击破损行为

应用机械冲击理论分析重型硬质合金车刀冲击断裂过程,并确立其产生冲击断裂的临界条件;采用有限元仿真的方法,分析研究重型硬质合金车刀冲击断裂产生机理及破损形式,并通过冲击试验揭示硬质合金车刀冲击断裂规律。对重型硬质合金车刀疲劳行为进行研究,通过有限元仿真分析方法,提出动态载荷下硬质合金疲劳断裂产生机制,并给出硬质合金疲劳断裂的载荷条件;通过断续切削试验,研究分析导致硬质合金刀具疲劳行为产生的本质原因,以期为预防硬质合金刀具过早出现失效提供理论支持和借鉴。     

表面残余应力对涂层硬质合金刀具磨损影响的研究现状

涂层硬质合金刀具具有良好的抗机械和抗热载荷冲击性能,以及较低的摩擦因数,在常温及高温下耐磨损性能优异,广泛应用于难加工材料的精密、半精密加工。对涂层硬质合金刀具进行表面处理后,刀具表面残余应力会发生演变,并会对刀具磨损产生影响。介绍了针对以上问题的国内外研究现状,并对高性能涂层硬质合金刀具的未来发展进行了展望。     

硬质合金车刀钎焊机

通过结构、工作原理、操作方法等介绍了一种非焊接工人也可操作使用的硬质合金刀片与刀杆焊接的车刀钎焊机.该机采用短路通电的方式加热,使钎料熔化,断电后钎料凝固,刀片与刀杆便焊接在一起;通过及时保温,可获得比火焰加热钎焊质量好的硬质合金车刀.     

基于激光超声技术的刀具检测系统实验研究

针对合金刀具制造和切削过程中产生表面缺陷的无损检测问题,建立激光超声实验装置。实验结果表明,该系统能有效检测刀具表面裂纹,检测效率高,实验装置简单,经济成本低,且易于实现完全非接触式检测。     

The effect of a weak W/SiC interface on the strength of Sigma silicon carbide monofilament

Fractography studies have shown that the strength-determining flaws in silicon carbide monofilaments are generally at the core/silicon carbide interface or in the vicinity of the outside, carbon-based coating. In tungsten-cored monofilaments like DERA Sigma, the W/SiC flaws primarily determine the strength. Fracture is accompanied by brittle failure of the tungsten. The crack propagates simultaneously outwards through the silicon carbide, inwards through the tungsten and also around the W/SiC interface before being deflected into the tungsten or out through the silicon carbide. Experiments depositing boundary layers between the tungsten and silicon carbide have resulted in significantly different fracture behaviour. The tungsten fails in a ductile manner and the strength-determining flaws are located predominantly at the outside surface of the silicon carbide. This behaviour is discussed in terms of models proposed by E. Martin and W. Curtin. It is thought that the work will ultimately lead to a significantly stronger, tungsten-based monofilament.     

Investigate on effect of cryogenic cooling on oxidation wear of WC-Co carbide tool milling titanium alloy

Abstract

For titanium alloy at high cutting speed, the severe tool wear will ineluctably take place diminishing the available tool life because of the high instantaneous temperature rise. Especially the WC-Co material in carbide tool will be reacted with the oxygen element in the air and generate oxide, and the tool oxidation wear is inevitable. In milling Ti–6Al–4V alloy operations, this article presents the first comprehensive investigation on the oxidation wear effect of cryogenic cooling on carbide tool compared with the conventional cooling. Based on the Gibbs free energy of the chemical reaction, the machining characteristics of the oxidation reactions were analyzed in detail. A series of machining testes were executed adopting controllable cryogenic cooling milling system. The surface and cross-section morphology and phase composition characteristics of tool were measured by SEM and XRD measuring equipments, as well as the oxidation wear mechanism of tool in cryogenic cooling. The results show that the thermal oxidation degree of the elements of WC-Co is higher in the conventional cooling processing. After cryogenic cooling intervention, oxidation reactions in tool are reduced significantly. Even the most probable reaction is disappeared, and the oxidation degree is decreased. When the temperature drops to 180 K, it has the best cooling effect. In cryogenic, the effective binding of WC crystal particle to the adhesive phase Co is a major factor for inhabiting oxidation wear of tool. The investigations indicate that the cryogenic cooling method can effectively inhibit the oxidation effect of carbide tool in milling titanium alloy process, and it improves the resist oxidation ability of tool.     

基底组织对酸蚀预处理工艺及金刚石薄膜特性的影响

采用原子吸收光谱(AAS)标准曲线法对YG系列硬质合金刀具酸蚀后浸蚀溶液中的Co浓度进行了定量测试;采用洛氏硬度(HRC)计跟踪测试了不同酸蚀时间后刀具硬度的变化;采用扫描电子显微镜(SEM)观察了硬质合金刀具酸蚀前后的组织变化及金刚石薄膜的组织形貌。结果表明:YG类硬质合金刀具基底含Co量越高,基底晶粒越粗大,酸蚀速度越快,酸对基底组织刻蚀能力越强;随着酸蚀时间的延长,硬质合金刀具硬度不断降低,YG6、YG6X、YG8刀具分别在刻蚀300秒、420秒、180秒后出现刀具硬度急剧下降。镀膜结果显示,YG6、YG6X刀具最佳酸蚀预处理时间分别为300秒和420秒;对于YG8刀具,只有增加酸蚀时间以消除或减弱Co的不利影响,但这将导致刀具机械性能显著下降。