模具钢高速切削表面粗糙度的试验研究

用硬质合金刀具对NAK80模具钢进行了高速精密切削试验,研究了切削条件、切削用量对加工表面粗糙度的影响。切削试验结果表明:提高切削速度与减小进给量有利于改善模具钢工件的加工表面质量;当切削速度超过某一范围后,随着切削速度的进一步提高,加工表面粗糙度的降低并不明显。     

高效切削钛合金Ti-6Al-4V硬质合金刀具扩散磨损研究

钛合金化学活性高,在切削过程中与硬质合金刀亲和性大,导致刀具易于发生扩散磨损。在使用硬质合金刀具切削钛合金Ti-6Al-4V试验及切削仿真分析基础上,采用SEM的EDAX研究刀具的扩散磨损,通过研究切削温度及刀-屑/工件接触区压力对扩散磨损的影响,并借助相图分析刀-工件之间的元素亲和力,进而研究扩散磨损的形成机理。结果表明:钛合金切削温度高,并且随着切削速度的增加,切削温度上升;在刀-屑以及刀-工件接触区,最高温度处于刀尖部位靠前刀面的位置。钛合金的加工回弹,造成刀-工件接触面摩擦加剧,使得整个接触区域的最高压力位置位于刀尖附近靠近后刀面的位置。在接触区的高温高压下,硬质合金刀具前、后刀面均发生元素扩散,且前刀面扩散现象比后刀面较为严重;随着切削速度的增加,加剧了扩散现象的发生。     

高速铣削工件表面粗糙度的预测

表面粗糙度是衡量工件表面质量的重要指标。采用正交试验方法,利用圆环面铣刀对模具钢NAK80进行了高速铣削试验,测量了不同工艺参数下的工件表面粗糙度。将试验结果与人工智能中的BP神经网络结合,建立了表面粗糙度预测模型,用于预测不同主轴转速、进给速度、切削深度、切削行距、刀具倾角时被加工工件的表面粗糙度,并通过MATLAB图形用户界面设计了表面粗糙度预测软件。结果表明,该预测模型及其封装后的软件可用于加工前工件表面粗糙度的预测。     

陶瓷刀具切削加工时的磨损和润滑及其与加工对象的匹配研究

分析了陶瓷刀具发展及其应用过程存在的问题，综合评述了陶瓷刀具切削加工时的磨损和润滑的研究进展，提出了陶瓷刀具与加工对象存在合理的匹配问题。指出了在实际应用中，应根据所加工的工件材料选择合适的陶瓷刀具材料，并应根据陶瓷刀具组分中是否含有高温下易与工件发生扩散及化学作用的组分来确定合理切削用量。     

蜂窝状铝合金高速加工刀具粘附行为及其作用机理研究

通过高速铣削试验方法对蜂窝状铝合金高速铣削刀具的粘附行为及粘附机理进行了研究。结果表明,由于初期铝屑粘附在刀具表面上,致使后期切削加工中的铝切屑与刀具表面的化学活性近似,使得铝屑进一步强化粘附在刀具表面,且由于高速加工中产生的高温和高压作用,使得粘附层材料发生变形。后续切屑划擦初期的粘附层,使粘附层出现变形和犁沟现象,加剧刀具与工件间的摩擦状态。同时,铝合金高速加工中高的塑性变形特征是发生粘附磨损的另一重要作用机制。此外,切屑表层材料受到剧烈剪切变形引起表面积增加,使切削形成的金属表面膜破裂,在与刀具表面紧密接触的近乎为真空环境下刀具不断切削新的表面,活性非常高,极易发生摩擦化学反应,较高摩擦化学反应形成的表面厚度达到临界值时将发生磨损,导致刀具粘附磨损加剧。     

金属切削刀具和工件的波段发射率标定

使用红外热像仪对切削加工中常见的工件材料碳钢和模具钢、常用的刀具材料硬质合金和涂层硬质合金在300～900 ℃进行表面发射率的标定,并考虑加热箱内环境热辐射对试样的作用,分析温度、表面结构、几何形状对试样表面发射率的影响。结果表明钢材表面发射率随温度升高而增大,但模具钢在较宽的温度范围内保持较小的表面发射率;试样表面平整性影响表面发射率;涂层刀具的表面发射率在比较宽的温度范围内一直稳定在相当低的值。     

涂层刀具切削淬硬H13模具钢的切削性能研究

基于有限元方法选取4种不同涂层材质的刀具进行切削淬硬H13模具钢仿真加工,研究涂层材质和切削速度对刀具切削性能的影响。从切削力和切削温度两个方面考虑,在相同切削条件下,Ti Al N涂层刀具的切削性能最优,Al_2O_3涂层刀具引起的已加工表面塑性变形最小;随着切削速度的提高,切削力和切削温度不断增加,工件材料已加工表面的塑性变形也逐渐增大。     

微量润滑在GH4169高温合金车削加工中的应用

为提高GH4169高温合金的可加工性,引入了微量润滑（MQL）技术开展该材料的车削加工试验。以表面粗糙度和切削温度为性能指标,分析干切削和MQL切削条件下工艺参数对已加工表面粗糙度和切削温度的影响规律。结果表明：工件表面粗糙度值均随转速的增加而降低,随进给量的增加而增大,随背吃刀量的增加而增大;切削温度则随工件转速、进给量、背吃刀量的增加而上升;相比于干切削加工,MQL切削加工能够获得粗糙度值更小的工件表面,且切削温度更低。该研究方法对于提升GH4169高温合金产品质量和实现绿色切削具有积极的作用。     

基于UG模型分析的两刃球头铣刀开发与试验

用球头铣刀加工模具和叶片零件时,球头刃的轮廓度和切削参数决定了零件的精度。采用UG软件对整个球头铣刀的圆弧轮廓度和球头前角进行分析,并结合切削理论找出球头铣刀加工的薄弱点,开发了新结构的球头铣刀,并对模具钢NAK80和叶片材料GH4169进行了切削试验。结果表明:新结构的球头铣刀比原结构更适合模具钢、叶片材料的端铣加工,刀具轮廓精度等级和耐用度更高;在模具加工方面,给出了不同加工精度的切削参数,为模具的高效加工提供参考依据。     

金刚石切削黑色金属时刀具磨损机理的摩擦磨损试验

为了降低黑色金属金刚石切削过程中的刀具磨损,提高表面加工质量和精度,对刀具磨损机理进行了研究.通过黑色金属金刚石摩擦磨损试验,模拟了实际切削过程中的刀具磨损行为;分别采用扫描电镜(SEM) 、X射线能谱仪(EDS)以及拉曼光谱仪(RS)对工件表面形貌、实验前后工件表面化学组分变化以及金刚石磨损表面的晶体结构转变进行了检测,同时提出了用石墨化程度作为试验过程中评价金刚石磨损的指标.试验结果表明:金刚石的磨损主要与机械力和温度有关,摩擦速度和工件材料中的含碳量对其影响相对较小;石墨化磨损、扩散磨损和氧化磨损等磨损机理共存,其中石墨化为导致金刚石磨损的主要原因.结合红外热像仪测温和热传导理论推算,近似获得了摩擦界面的真实温度,且随着温度升高15％,金刚石石墨化程度显著加剧83％.作者提出,应当综合考虑热-力耦合作用下的刀具磨损机理,以便进一步探寻抑制刀具磨损的工艺措施.     

高速铣削近α钛合金的切削温度研究

切削温度不仅直接影响刀具的磨损和耐用度,而且也影响工件的加工精度和已加工表面质量。由于钛合金导热性差和化学亲和性强等原因,通常在其切削加工时切削温度高、刀具磨损严重,致使切削速度难以进一步提高。本文重点对钛合金高速铣削时的切削温度进行试验研究,阐明夹丝半人工热电偶法测温原理和所测热电势信号的物理意义。试验选用了3种不同类型的硬质合金刀具,系统地研究了切削用量、冷却条件及刀具磨损等因素对近α钛合金高速铣削时切削温度的影响。     

Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool's adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.     

Investigation on diffusion wear during high-speed machining Ti-6Al-4V alloy with straight tungsten carbide tools

During high-speed machining Ti-6Al-4V alloy, high-temperature at the tool–chip interface and the concentration gradient of chemical species between tool material and workpiece material support the activation of diffusion process, and therefore the crater wear forms on the rake surface of the cutting tool at a short distance from the cutting edge. In this paper, the diffusion analysis was theoretically proposed. The constituent diffusion at the contact interface between tool material and Ti-6Al-4V alloy at high-temperature environment, the crater wear on the rake surface of the tool, and the chips collected from high-speed milling Ti-6Al-4V alloy with straight tungsten carbide tools were analyzed by the scanning electron microscope with energy dispersive X-ray spectroscopy. The constituents inside the tool could diffuse into the workpiece and the diffusion layer was very thin and close to the interface. Compared with the diffusion of tungsten and carbon atoms, the pulling out and removing of the tungsten carbide (WC) particles due to cobalt diffusion dominated the crater wear mechanism on the rake surface of the cutting tool.     

高强度钢干式铣削替代半精磨的试验研究

采用硬质合金刀片(YW1)和涂层刀片(YB415)进行了高强度钢的干式铣削代替半精磨试验研究。根据试验结果,确定适合加工该型号高强度钢的刀具材料和切削用量。以这两种刀片在不同切削用量条件下的耐用度、加工表面粗糙度和主切削力作为刀具加工性能的评价依据,同时研究了刀片的磨、破损机理和卷、排屑稳定性。试验结果表明:涂层刀片干铣削高强度钢的加工性能优异,工件加工表面质量达到半精磨水平。     

[刀具及切削工艺]高速铣削中TaC（NbC）对硬质合金刀具磨损性能的影响

针对航空航天钛合金加工时硬质合金刀具磨损过快的难题,制备了主元素一致、微量合金碳化物TaC（NbC）含量不同的两种WC-Co基硬质合金材料。采用高温维氏硬度计检测两种材料的高温硬度和高温断裂韧性,并制备相同几何参数的立铣刀对钛合金TC4进行铣削加工试验。试验结果表明：在硬质合金中添加微量合金碳化物TaC（NbC）,可以同时提高材料的高温硬度和高温断裂韧性,在相同的切削条件下,添加微量合金碳化物TaC（NbC）的硬质合金立铣刀比未添加微量合金碳化物的立铣刀耐磨性更好,刃口断裂裂纹更少,刀具使用寿命更长,更适合航空航天钛合金材料的高速铣削加工。     

Performance and wear mechanisms of whisker-reinforced alumina, coated and uncoated PCBN tools when high-speed turning aged Inconel 718

Inconel 718, an efficient superalloy for energy and aerospace applications, is currently machined with cemented carbide tools at low speed (v _c?≈?60 m/min) due to its unfavorable mechanical and thermal properties. The article presents results of a study of superalloy machinability with whisker-reinforced alumina, uncoated and coated polycrystalline cubic boron nitride (PCBN) tools. Turning of age-hardened Inconel 718 (45 HRC) was done under high-speed machining conditions (v _c?=?250…350 m/min). Aspects of tool life, tool wear, and generated surface quality were studied. Application of uncoated PCBN tools resulted in surface quality and force level superior to other tool materials. Considerable sideflow of workpiece material was found to affect surface quality, especially for coated PCBN and ceramic tools. It was found that protective function of the coating, which increases the tool life up to 20 %, is limited only to low cutting speed range. EDX and AFM analyses suggested dominance of chemical and abrasive wear mechanisms. EDX mapping of worn tools pointed absence of diffusional wear for PCBN tools and intensive degradation of whisker reinforcement in ceramic tools due to diffusion of Ni, Fe, and Cr.     

硬质合金铣刀片粘结破损的研究

针对铣削难加工材料时刀具粘结破损问题,进行了用平刀片和自主研发的复杂槽型铣刀片切削3Cr1Mo1／4V高温耐热钢的测温测力试验,同时采用高速摄影观察了铣刀片切入切出时粘结切屑脱落过程,应用有限元法分析了粘结破损时温度场和应力场耦舍后的等效合成应力。理论和试验数据分析结果表明,粘结破损的主要原因是工件和刀具材料的亲合力、铣刀片的等效合成应力大于硬质舍金的强度,改变铣刀片的槽型是提高抗粘结破损的有效方法。为三雏复杂槽型铣刀片槽型的优化和重构技术提供了理论依据和试验数据。     

Effects of tool deflection in the high-speed milling of inclined surfaces

The present paper looks at the dimensional errors resulting from tool deflection in the high-speed milling of hardened steel surfaces. These errors are measured as the difference between the theoretical surface and the high-speed milling machined using ball-end mills. The effect of various factors on this dimensional error is investigated. First, account was taken of the workpiece material and the slope of surfaces; the values chosen were those normally used in injection mould manufacturing. The workpiece materials were of 30 and 50 HRC hardness, with slopes of 15°, 30°, and 45°. In this manner, results may thus be of utility to the mould and die industry. The selected tools were solid ball end mills of sintered tungsten carbide, coated with TiAIN. These were of various diameters and lengths, and accordingly exhibited various degrees of slenderness. A great value for this latter parameter is a restraint on the potential application of the high-speed milling technique. This is the main reason for this work. Tests were carried out using three machining strategies, namely, upward, downward, and z-level (horizontal), as well as with two cutting types, downmilling (also called climb milling) and upmilling (or conventional milling). In all cases the resulting roughness was also measured. Dimensional errors in several flat slope planes were measured, comparing with those obtained by simulation. The results of these tests have been applied to the prediction of error in the high-speed milling of two industrial parts. Knowledge of error magnitude may be useful when NC programs are prepared for the machining of mould complex surfaces, since it may then be attempted to enhance accuracy. Reference is made to various practical problems that were necessary to resolve in order to achieve measurement errors less than 20 μm in a process as complex as that of high-speed milling in three axes machining centres.