液氮低温切削钛合金实验研究

针对钛合金难加工特点,将液氮作为冷却介质直接喷向切削区进行钛合金TC4低温车削加工,测量其切削力、表面粗糙度和刀具磨损,并与干切削在相同实验条件下对比,分析低温切削对钛合金的影响。实验结果表明:低温切削钛合金,主切削力有所增大,但进给方向力减小,刀具磨损状况与表面质量得到改善,断屑相对容易。     

钛合金高速切削加工试验研究进展

钛合金因优越的性能而被广泛应用于航空航天和武器装备等领域,但由于切削加工性较差,在高速切削中易出现切削力大、切削温度高和刀具磨损严重等问题,因此,学者们针对钛合金高速切削加工进行了大量试验研究.本文对近年来钛合金高速切削领域的国内外研究进展进行了总结,重点分析了在锯齿形切屑、切削力、切削温度、加工表面质量和刀具磨损方面...     

液氮冷却下大进给铣削TC4钛合金的试验研究

钛合金是现代飞行器的主要结构材料之一,是一种典型的难加工材料。针对切削加工钛合金时刀具磨损快、表面质量不易控制等难题,将TC4钛合金作为研究对象,以液氮作为冷却介质,进行了TC4钛合金的大进给铣削试验,测试了液氮冷却条件下大进给铣削TC4钛合金的铣削力、铣削温度以及刀具磨损等,并与乳化液和低温冷风条件下的测试结果进行了对比分析。结果表明:在以较大的切削速度和每齿进给量铣削TC4钛合金时,采用液氮冷却比使用乳化液能更有效地降低切削力和切削温度;比采用低温冷风冷却能更有效地延长刀具寿命。     

逆-顺铣方式对钛合金TC4高速切削过程影响的比较研究

本文采用仿真软件模拟了PCBN对TC4钛合金进行高速干式切削过程,研究了逆铣-顺铣对钛合金高速切削过程量的影响规律。结果表明,逆铣时的切屑更易卷曲,相较于顺铣多30%,但不易断屑,易于产生毛刺;与逆铣相比,顺铣时的切削温度较低,利于断屑、刀具寿命及零件表面质量;在主切削力和切削热累积双重作用下,逆铣后期刀具抗弯强度很不利,而逆铣时次切削力方向呈y正向不利于切削过程的平稳性。     

低温液氮冷却下高速切削淬硬钢的切屑形成及刀具磨损

针对低温液氮冷却下淬硬钢高速车削过程中切屑形成及刀具磨损机理尚缺乏相关研究的问题,开展了液氮冷却下的淬硬钢高速切削研究,并与干切进行了对比.分析了切削力、切削温度、切屑特征以及刀具磨损特征,讨论了冷却润滑、切屑形成及刀具磨损机理.结果表明:与干切相比,各组实验中低温液氮冷却切削的切削温度降低了6.9％～9.9％,因材料...     

整硬麻花钻横刃轴向前角对TC4钛合金钻削性能的影响研究

TC4钛合金在钻削加工过程中存在切削力大、切削温度高、刀具磨损严重以及寿命短等问题,属于典型的难加工材料。采用三款不同横刃轴向前角的整体硬质合金麻花钻对TC4钛合金进行钻削实验,分析不同轴向前角对切削力、切屑形态、刀具磨损与寿命的影响。结果表明：正轴向前角的钻头切削更锋利,切削阻力小;正轴向前角钻头的寿命高于0°轴向前角和负轴向前角钻头。在TC4钛合金的钻削加工中,横刃轴向前角取正值可以提升刀具寿命。     

TC4钛合金切削刀具磨损对切削过程影响的研究

通过建立的钛合金切削加工仿真数值模型,研究了刀具磨损对钛合金切削过程中切削力、切削温度及切屑形态的影响规律,并对这些影响的产生机理进行了讨论。结果表明:随着磨损程度的增大,切削力及切削温度会迅速增加;月牙洼磨损会引起切削力的剧烈震荡且振幅随磨损的增大而增大,后刀面磨损将增大切削力;锯齿形切屑的变形程度在加大,但是锯齿产生的频率在降低。     

冷却方式对H13A硬质合金切削性能试验分析

在MAZARK车铣加工中心和高速铣床上选用切削速度150m/min和200m/min进行顺铣干/湿切削加工,采用H13A硬质合金刀具对TC4钛合金进行高速车铣和高速铣削加工试验。分别对比分析两种加工方式下冷却方式不同时的刀具磨损形态,结果表明:干切削时,无论正交车铣或高速铣削,刀具都是以粘结磨损为主;正交车铣干切削时,刀具表面有较多的切屑粘结物,易形成积屑瘤;切削液条件下,刀面粘结物相对减少,切屑粘走刀具材料,形成较多的粘结凹坑;铣削干切削时,粘结到刀面的切屑较正交车铣少,但切屑粘走刀具材料更为严重,前刀面出现较深的月牙洼,采用切削液时前刀面出现层状剥落。试验表明,当金属切除率一定时,正交车铣干切削金属切出总量最大,刀具寿命最长,湿切削加工时刀具寿命较短,切削液对刀具磨损形态和刀具寿命影响较大,可能与热交变应力和Co元素流失有关。试验结果表明,H13A刀具正交车铣钛合金干切削时切削性能较好。     

硬质合金刀具高速车铣和铣削TC4钛合金磨损试验对比

采用H13A未涂层硬质合金刀具对TC4钛合金进行高速正交车铣和铣削试验,并从刀具磨损破损形态、磨损机理及其寿命等方面进行对比分析。研究表明:高速正交车铣和铣削钛合金时,前、后刀面主要以粘结磨损为主,车铣加工时在切削刃口易形成积屑瘤及连续切屑,但对刀具材料粘结较轻;高速铣削时,对刀具材料粘接较重,在前刀面刃口附近形成凹坑及崩刃;后刀面最大磨损的位置不相同。试验对比了相同切削条件时刀具使用寿命,结果表明采用正交车铣加工可以获得更长的刀具使用寿命。     

陶瓷刀具高速车削铸铁切削性能实验研究

针对陶瓷刀具和铸铁材料的切削特点,从切削力、切削温度、表面粗糙度、切屑形态和刀具磨损5个方面进行铸铁高速车削实验研究。首先采用单因素实验,分析切削参数对切削力、切削温度、表面粗糙度的影响,并对切屑形貌进行分析探讨;进而采用正交实验进一步分析切削参数对切削加工性能影响的显著程度,并优选出最佳切削参数;最后在正交实验的基础上,对刀具磨损情况进行分析,证明陶瓷刀具高速车削铸铁的合理性。实验结果为进一步研究铸铁的高效切削、刀具磨损以及切削参数优化、新型陶瓷刀具的开发提供技术支持。     

钛合金TC11车削中已加工表面质量试验研究

为了研究车削钛合金TC11时切削速度和刀具磨损对已加工表面质量的影响,选用涂层硬质合金刀片CNMG120408在不同切削条件下进行车削试验,分析后刀面磨损量随切削时间的变化规律;对比磨损刀具与新刀具切削的工件表面,观察表面粗糙度、表面形貌、显微硬度以及表层微观组织情况,分析切削速度和刀具磨损对已加工表面质量的影响规律。试验结果表明:在刀具磨损初期,即新刀具切削时,切削速度从60m/min增加到100m/min,刀具磨损程度增大,表面粗糙度值降低,硬化层深度减小,加工硬化程度略微增大,表面塑性变形层深度减小;在刀具磨损终期,不同切削速度下的表面粗糙度增大,表面形貌变差,硬化层深度和加工硬化程度增加,表面变形程度增大,塑性变形层深度增加。     

高硅铝合金切削性能的试验研究

由于Al-Si合金比重小、强度高、导热性好和便于回收利用等优点,广泛应用于飞机、汽车和电子科技等行业产品中。因其切削加工过程中易发生刀屑粘结、刀具磨损严重和划伤已加工表面等问题,难以获得良好的表面质量和较高的加工精度。为研究高硅铝合金的切削性能,本文以切削力和切削温度为研究对象,采用正交试验法试验,分析切削速度、进给量、铣削宽度和背吃刀量对铣削力和温度的影响。通过本研究,期望改善生产中刀具磨损严重和加工表面质量差的状况。     

低温氮气射流对钛合金高速铣削加工性能的影响

在钛合金的高速切削过程中，切削区温度很高，加速了刀具的磨损，限制了切削速度的进一步提高。为降低切削区温度、防止刀具的氧化磨损，提出在低温氮气射流条件下进行钛合金的高速铣削加工。在干铣削、浇注切削液、常温氮气油雾、低温氮气射流和低温氮气射流结合微量润滑等冷却润滑条件下进行了钛合金的高速铣削对比试验。试验结果表明，低温氮气射流结合微量润滑能够最有效地降低铣削力，抑制刀具磨损。借助扫描电镜的检测手段，研究了不同冷却润滑条件下刀具的失效形式。指出在低温氮气射流条件下高速铣削钛合金时，只要热裂纹的形成与扩展未引起刀具的崩刃及刀面的剥落，进一步降低低温氮气的温度将提高刀具的使用寿命。     

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。     

Cooling performance of micro-texture at the tool flank face under high pressure jet coolant assistance

Micro-texture at the tool face is a state-of-the-art technique to improve cutting performance. In this paper, five types of micro-texture were fabricated at the flank face to improve the cooling performance under the condition of high pressure jet coolant assistance. By using micro-textures consisted of pin fins, plate fins and pits fabricated 0.3 mm away from the cutting edge, heat transfer from the tool face to coolant was enhanced. The conditions of tool wear, adhesion and chip formation were compared between the micro-textured and non-patterned tools in the longitudinal turning of the nickel-based superalloy Inconel 718. As a result, micro-textured tools always exhibited the reduced flank and crater wear compared with the non-patterned tool, and the rate of tool wear was influenced by the array and height of fin. The energy dispersive spectroscopy analysis of worn flank faces and the electromotive forces obtained from the tool-work thermocouple supported better cooling performances of micro-textured tools. In addition, coolant deposition at flank face evidenced that heat transfer could be promoted by micro-texture near the border of the contact area between the flank wear land and machined surface. Finally, the changes of flow patterns with pit depth are analyzed for pit type tools by computational fluid dynamics. This investigation clearly showed the function of micro-textures for increasing the turbulent kinetic energy and cooling the textured tool face.     

Modeling and analyzing the effects of air-cooled turning on the machinability of Ti–6Al–4V titanium alloy using the cold air gun coolant system

This study provides the mathematical models for modeling and analyzing the effects of air-cooling on the machinability of Ti–6Al–4V titanium alloy in the hard turning process. A cold air gun coolant system was used in the experiments and produced a jet of compressed cold air for cooling the cutting process. The air-cooling process seems to be a good environment friendly option for the hard turning. In this experimental investigation, the cutting speed, feed rate and cutting depth were chosen as the numerical factor; the cooling method was regarded as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology (RSM) was employed to carry out the experimental study. The mathematical models based on the RSM were proposed for modeling and analyzing the cutting temperature and surface roughness in the hard turning process under the dry cutting process and air-cooling process. Tool wear and chip formation during the cutting process were also studied. The compressed cooling air in the gas form presents better penetration of the lubricant to the cutting zone than any conventional coolants in the cutting process do. Results show that the air-cooling significantly provides lower cutting temperature, reduces the tool wear, and produces the best machined surface. The machinability performance of hard turning Ti–6Al–4V titanium alloy on the application of air-cooling is better than the application of dry cutting process. This air-cooling cutting process easily produces the wrinkled and breaking chips. Consequently, the air-cooled cutting process offers the attractive alternative of the dry cutting in the hard turning process.     

基于复合喷雾冷却的TC4钛合金切削温度的研究

钛合金是一种典型的难加工材料,其热传导率低,切削过程温升大而易加剧刀具磨损。本文通过对TC4钛合金的车削试验,研究了在干切削和复合喷雾冷却条件下切削温度随切削速度、切削深度和进给量的变化情况。结果表明:切削温度随着切削速度、切削深度和进给量的增大而增大;采用复合喷雾冷却技术可在TC4钛合金车削过程中取得较好的冷却效果,切削温度明显低于干切削条件下的切削温度。     

Effect of very high cutting speeds on shearing, cutting forces and roughness in dry turning of austenitic stainless steels

Behavior of austenitic stainless steels has been studied at very high cutting speeds. Turning tests were carried out using the AISI 303 austenitic stainless steel. In particular, the influence of cutting speed on tool wear, surface quality, cutting forces and chip geometry has been investigated. These parameters have been compared when performing machining at traditional cutting speeds (lower than 350?m/min) versus high cutting speeds. The analysis of results shows that the material undergoes a significant change in its behavior when machining at cutting speeds above 450?m/min, that favors the machining operation. The main component of cutting forces reaches a minimum value at this cutting speed. The SEM micrographs of the machined surfaces show how at the traditional cutting speeds the machined surfaces contain cavities, metal debris and feed marks with smeared material particles. Surfaces machined at high cutting speeds show evidence of material side flow, which is more evident at cutting speeds above 600?m/min. Tool wear is located at the tool nose radius for lower cutting speeds, whereas it slides toward the secondary edge when cutting speed increases. An analysis of chips indicates also an important decrement in chip thickness for cutting speeds above 450?m/min. This study concludes that there is an unexplored range of cutting speeds very interesting for high-performance machining. In this range, the behavior of stainless steels is very favorable although tool wear rate is also significant. Nevertheless, nowadays the cost of tool inserts can be considered as secondary when comparing to other operation costs, for instance the machine hourly cost for high-end multitasking machines.