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。     

铣削方式对高速铣削TC4钛合金刀具磨损的影响

为研究高速铣削TC4钛合金时不同铣削方式对刀具磨损的影响,在铣削速度为200m/min时采用硬质合金刀具对工件分别进行顺铣、逆铣和交替铣的切削试验。分析了不同铣削方式下刀具磨损的特点和形貌,并对刀具耐用度进行了对比。结果表明:在此铣削速度下,硬质合金刀具在不同铣削方式下的磨损特征主要表现为前刀面刃口处的塌陷及后刀面的沟槽磨损。刀具耐用度在顺铣方式下较好,交替铣、逆铣时的刀具耐用度则大大低于顺铣,且交替铣比逆铣刀具耐用度稍好。     

TC4钛合金高速铣削加工刀具失效机理研究

以TC4钛合金为试验材料,采用超细硬质合金PVD涂层刀具进行高速铣削加工,研究刀具在铣削TC4材料时的失效机理。试验通过采用扫描电子显微镜(SEM)和元素能谱检测(EDS),分别对失效刀具的刃口区域、前刀面区域、后刀面区域的磨损进行失效形貌检测和合金元素成分的分析测试。研究表明:超细晶粒硬质合金PVD涂层刀具进行TC4钛合金高速铣削加工时,刀具的失效形式在不同加工区域各有不同,刃口以黏结磨损失效和热—机械疲劳磨损失效为主,前刀面和后刀面以黏结磨损失效为主,刃口的热—机械疲劳裂纹扩展到前刀面和后刀面,并加剧了刀具的崩缺失效。     

切削速度对轴向车铣TC4钛合金刀具磨损的影响

为研究高速轴向车铣TC4钛合金时硬质合金刀具的磨损特性,选择S30T硬质合金刀片分别在100m/min、150m/min和200m/min三种切削速度下对TC4进行了轴向车铣试验,分析了不同切削速度对刀具使用性能的影响。研究结果表明:高速轴向车铣TC4钛合金外圆时刀具磨损主要发生在刀片的刀尖刃口及后刀面;磨损形式以粘结磨损为主;刀具的磨损速度随着速度的增加而增大;S30T刀片在100m/min的切削速度下具有较好的刀具耐用度,在150m/min、200m/min的切削速度刀具磨损较快,不适于实际切削加工。     

钛合金高速旋转超声椭圆振动侧铣削切屑特征和刀具磨损研究

难加工材料钛合金在采用传统铣削方式时,随着切削速度的增加,切削力和切削温度都迅速增加,使得切削条件恶化并加速刀具磨损,从而导致刀具过早失效。将超声椭圆振动加工技术引入到高速铣削中,进行了钛合金高速旋转超声椭圆振动侧铣削试验。从切屑特征以及刀具后刀面磨损两个方面研究了高速超声椭圆振动铣削参数匹配对钛合金加工的影响。首先基于高速超声椭圆振动铣削过程中刀具-工件的运动学特点推导出高速超声椭圆振动铣削加工参数与振动参数间的匹配关系,然后利用本实验室自行研制的超声椭圆振动铣削装置进行了不同参数匹配关系下的验证性切削试验。试验结果表明：合理的参数匹配使得超声椭圆振动铣削在高速条件下依然能够实现分离型断续切削加工。相比普通铣削加工,分离型的高速超声椭圆振动铣削能够获得更加微细的切屑,切削热能够被及时地带走;良好的切削条件使得刀具的后刀面磨损均匀而缓慢,从而延长刀具的使用寿命;高速超声椭圆振动铣削能够有效地提高生产效率。     

钛合金铣削过程刀具前刀面磨损解析建模

钛合金Ti6Al4V作为典型的航空航天难加工材料,在其铣削过程中硬质合金刀具的磨损会降低加工过程稳定性,进而影响加工效率和已加工表面表面质量。刀具前刀面磨损会导致刀具刃口强度降低,并影响切屑的流向和折断情况。针对前刀面磨损机理进行分析并构建了月牙洼磨损深度预测模型。首先运用解析方法构建了前刀面应力场模型,得到切屑在前刀面滑动过程中的刀具前刀面应力分布情况及磨损位置。基于刀-屑接触关系的基础上建立了前刀面温度场模型。然后,基于所得刀具前刀面应力与温度分布,构建综合考虑磨粒磨损、粘结磨损与扩散磨损的铣刀月牙洼磨损深度预测模型,获得月牙洼磨损预测曲线;结合铣刀月牙洼磨损带沿切削刃方向分布的特点,建立了随时间变化的铣刀前刀面磨损体积预测模型。最后通过试验验证了切削宽度对前刀面磨损的影响规律,预测结果与试验测量值具有较好的吻合性。结果表明随着切削宽度的增加,月牙洼磨损深度及前刀面磨损体积都随之增加。研究结果为钛合金铣削用刀具的设计和切削参数的合理选择提供了理论基础。     

高速车削钛合金时PCBN刀具寿命的研究

采用对角正交回归试验法,研究了用PCBN刀具高速车削钛合金TC4时切削用量对刀具寿命的影响,并分析工件已加工表面粗糙度。通过扫描电镜观察分析,证实刀具的磨损机理主要是前后刀面的粘结磨损及氧化磨损、后刀面磨损以及切削深度线处的沟槽磨损。     

陶瓷刀具车削TC4钛合金磨损特性的研究

为研究陶瓷刀具切削钛合金的磨损机理,采用CC6060陶瓷刀片对TC4钛合金进行了干式车削试验。结果表明:陶瓷刀具干式切削TC4钛合金时,磨损形貌以前刀面月牙洼磨损、后刀面沟槽磨损和刀尖破损为主,磨损机理主要是粘结磨损和氧化磨损。随着切削速度的增加,刀具磨损加剧,刀具寿命降低。CC6060陶瓷刀片干式切削钛合金时的使用寿命很低,不适于干式切削钛合金。     

高速铣削Ti-10V-2Fe-3Al的刀具磨损试验研究

针对切削加工Ti-10V-2Fe-3Al钛合金时刀具磨损迅速、加工效率低的问题,开展硬质合金刀具高速铣削Ti-10V-2Fe-3Al的刀具寿命试验,以研究刀具的磨损机理,分析刀面磨损的发展以及对切削力的影响。利用扫描电子显微镜观察了后刀面磨损区域的微观形貌并对元素成分进行了能谱分析。实验结果表明：高速铣削Ti-10V-2Fe-3Al时硬质合金刀具的磨损形式为后刀面带状磨损与局部崩刃,伴有明显的切屑黏附与热裂纹;磨损区域有工件材料的元素向硬质合金内扩散的迹象出现;切屑流的黏附与撕扯导致硬质合金的颗粒脱落,切削刃逐步退化为洼形区域,其与后刀面交界的棱边代替原切削刃进行切削直至剥落。     

高速轴向车铣45钢刀具磨损的研究

介绍了轴向车铣加工的特点,通过试验得到了高速轴向车铣加工45钢时刀具的磨损曲线,分析了在水冷和干切削时TiN涂层和金属陶瓷刀具的磨损特点,得出采用干切削更有利于延长刀具使用寿命,且TiN涂层刀具比金属陶瓷刀具更适合高速轴向车铣加工45钢.     

Cutting performance of coated carbide tools in high-speed face milling of AISI H13 hardened steel

In the present study, high-speed face milling of AISI H13 hardened steel was conducted to investigate the cutting performance of coated carbide tools. The characteristics of chip morphology, tool life, tool wear mechanisms, and surface roughness were analyzed and compared for different cutting conditions. It was found that as the cutting speed increased, the chip morphology evolved in different ways under different milling conditions (up, down, and symmetric milling). Individual saw-tooth segments and sphere-like chip formed at the cutting speed of 2,500 m/min. Owing to the relatively low mechanical load, longest tool life can be obtained in up milling when the cutting speed was no more than 1,000 m/min. As the cutting speed increased over 1,500 m/min, highest tool life existed in symmetric milling. When the cutting speed was 500 m/min, owing to the higher mechanical load, the flaked region on the tool rake face in symmetric milling was much larger than that in up and down milling. There was no obvious wear on the tool rake face at the cutting speed of 2,500 m/min due to the short tool-chip contact length. In symmetric milling, the delamination of tool material, which did not occur in up and down milling, was caused by the relatively large cutting force. Abrasion had great effect on the tool flank wear in symmetric milling. With the increment of cutting speed, surface roughness decreased first and then increased rapidly. Lowest surface roughness can be obtained at the cutting speed of about 1,500 m/min.     

Failure mechanisms of a PCD tool in high-speed face milling of Ti–6Al–4V alloy

High-speed milling tests were carried out on Ti–6Al–4V titanium alloy with a polycrystalline diamond (PCD) tool. Tool wear morphologies were observed and examined with a digital microscope. The main tool failure mechanisms were discussed and analyzed utilizing scanning electron microscope, and the element distribution of the failed tool surface was detected using energy dispersive spectroscopy. Results showed that tool flank wear rate increased with the increase in cutting speed. The PCD tool is suitable for machining of Ti–6Al–4V titanium alloy with a cutting speed around 250 m/min. The PCD tool exhibited relatively serious chipping and spalling at cutting speed higher than 375 m/min, within further increasing of the cutting speed the flank wear and breakage increased greatly as a result of the enhanced thermal–mechanical impacts. In addition, the PCD tool could hardly work at cutting speed of 1,000 m/min due to the catastrophic fracture of the cutting edge and intense flank wear. There was evidence of workpiece material adhesion on the tool rake face and flank face in very close proximity to the cutting edge rather than on the chipped or flaked surface, which thereby leads to the accelerating flank wear. The failure mechanisms of PCD tool in high-speed wet milling of Ti–6Al–4V titanium alloy were mainly premature breakage and synergistic interaction among adhesive wear and abrasive wear.     

低温微量润滑高速铣削PH13—8Mo刀具磨损试验研究

针对高强度不锈钢材料加工性能差、刀具耐用度低的问题,进行了硬质合金刀具在低温微量润滑条件下高速铣削高强度不锈钢PH13—8Mo的刀具磨损试验,结果表明：WSP45刀片比WXM35适合加工PH13—8Mo,低温微量润滑（cMQL）能有效地抑制刀具磨损,提高刀具耐用度;两种刀具在铣削过程中前、后刀面同时发生磨损,最终因刃口严重崩刃而失效。     

A FINITE ELEMENT ANALYSIS OF BURR FORMATION IN FACE MILLING OF A CAST ALUMINUM ALLOY

The research discussed in this article focuses on the effects of tool geometry (i.e., rake angle and cutting edge radius) and flank wear upon burr formation in face milling of a cast aluminum alloy. As to tool edge preparation, the use of a tool with variable cutting edge radius was investigated using FEM, and compared for its cutting performance (i.e., burr reduction and tool life) with a conventional tool with uniform cutting edge radius. In order to evaluate 3D face milling through 2D orthogonal cutting simulations, the cross-sections that consist in the cutting speed direction and chip flow direction were selected at different locations along the tool rounded corner. At these cross-sections, the local value of cutting edge radius and their associated tool rake angles as well as the effective uncut chip thickness were determined for 2D cutting simulations. In addition, 3D face milling simulations were conducted to investigate more realistic chip flow and burr generation. Comparisons were made for burrs produced from 3D simulations with a sharp tool, 3D simulations with a worn tool and face milling experiments. Finally, recommendations for cutting tool design are made to reduce burr formation in face milling.     

涂层刀具前后刀面摩擦下界面应力分析

基于任意拉格朗日欧拉方法(ALE)建立金属正交切削加工的热力耦合的有限元模型,获得不同速度下切削稳定时涂层刀具前后刀面的接触应力、剪应力以及温度场。通过对涂层刀具施加已获得的刀具表面的应力场和温度场,分析了不同速度下摩擦分界点变化的规律以及对涂层基体界面应力的影响。结果表明,随着速度的增大,摩擦分界点逐渐有向前刀面移动的趋势,表明磨损的方式开始从后刀面磨损向前刀面月牙湾磨损转变,这与切削试验结果一致。同时随着速度的增大,涂层界面应力突变更加显著,表明高速条件下涂层更容易破坏,且速度越高,前刀面涂层破坏的几率越大。     

Blend of sharpness and strength on a ball nose endmill geometry for high speed machining of Ti6Al4V

The applications of titanium alloys are increasingly common at marine, aerospace, bio-medical and precision engineering due to its high strength to weight ratio and high temperature-withstanding properties. However, whilst machining the titanium alloys using the solid carbide tools, even with application of high pressure coolant, reduced tool life was widely reported. The generation of high temperatures at the tool–work interface causes adhesion of work material on the cutting edges, and hence, shorter tool life was reported. In order to reduce the high tool–work interface temperature-positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose endmill cutting edges. Despite of careful consideration of tool geometry, after an initial working period, the growth of flank wear accelerates the high cutting forces followed by work material adhesion on the cutting edges. Hence, it is important to blend the strength, sharpness, geometry and surface integrity on the cutting edges so that the ball nose endmill would exhibit an extended tool life. This paper illustrates the effect of ball nose endmill geometry on high speed machining of Ti6Al4V. Three different ball nose endmill geometries were configured, and high speed machining experiments were conducted to study the influence of cutting tool geometry on the metal cutting mechanism of Ti-6Al-4V alloy. The high speed machining results predominantly emphasize the significance of cutting edge features such as K-land, rake angle and cutting edge radius. The ball nose endmills featured with a short negative rake angle of value ?5° for 0.05～0.06 mm, i.e. K-land followed by positive rake angle of value 8°, has produced lower cutting forces signatures for Ti-6Al-4V alloy.     

Effect of cutting speed on cutting forces and wear mechanisms in high-speed face milling of Inconel 718 with Sialon ceramic tools

In this paper, a series of milling tests were carried out in order to identify the effects of cutting speed on cutting forces and tool wear when high-speed face milling Inconel 718 with Sialon ceramic tools. Both down-milling and up-milling operations were conducted. The cutting forces, tool wear morphologies, and the tool failure mechanisms in a wide range of cutting speeds (600–3,000 m/min) were discussed. Results showed that the resultant cutting forces firstly decrease and then increase with the increase of cutting speed. Under relatively lower cutting speeds (600 and 1,000 m/min), the dominant wear patterns is notching. Further increasing the speed to more than 1,400 m/min, the notching decreases a lot and flank wear becomes the dominant wear pattern. In general, at the same cutting speed, flaking on the rake face and notching on the flank face are more serious in down-milling operation than that in up-milling operation with the same metal removal volume. However, the surface roughness values for down-milling are lower than that for up-milling.     

Crater and flank wear resistance of cutting tools having micro textured surfaces

We have proposed cutting tools with various textured surfaces to increase cutting tool life. Our previous studies have developed cutting tools having periodical stripe-grooved surfaces on their rake face formed using femtosecond laser technology, which displayed high crater wear resistance in cutting of steel materials. In this study, the mechanism for suppressing the crater wear on the tool surface and the relationship between texture dimensions and wear resistance were investigated to provide a guideline for developing tools with textured surfaces. Furthermore, we newly introduced the textured surfaces into a flank face of cutting tools to improve flank wear resistance. Face milling experiments on steel materials exhibited that the newly developed tool having the textured flank face significantly reduced the flank wear. Moreover, the influences of texture dimensions and cutting conditions on the flank wear resistance were also discussed.     

CN35硬质合金涂层刀具高速车削淬硬钢的磨损与破损形态

借助于扫描电镜照片和能谱分析,对高速车削淬硬45钢时CN35硬质合金涂层刀具的失效形态及其机理进行了观察和分析。结果显示,在高速切削条件下,涂层刀具的失效形态主要分为破损与磨损两种,刀具正常磨损失效过程仍然遵循常规切削条件下三个阶段的程序。刀具破损失效发生在低速切削阶段,且随着切削速度的提高,破损部位由后刀面转移到前刀面;高速切削时,刀具失效形式倾向于后刀面磨损、边界磨损和切削刃斜面磨损,因高热、粘结、疲劳、氧化、扩散和热裂等原因造成刀具切削功能丧失。