PCD刀具切削石材的切削力研究

本文通过用聚晶金刚石刀具切削两种不同硬度石材的实验，总结出切削力随进给量，切削深度，切削速度，以及冷却条件不同时的变化规律，并从理论上进行了初步分析与探讨。     

PCD刀具切削加工硬脆材料时负切削力现象的研究

本文以辉长岩为全和聚晶金刚石（ＰＣＤ）刀具进行了硬脆材料切削加工试验,在时域和频域内对切削力信号进行了数字信号分析处理,提出,硬脆材料切削为可分为成切削力趋势量切削力随机量两部分。硬脆材料的组成结构特点和切削中刀具的振动是硬脆材料切削力出现负值现象的主要原因。     

PCBN刀具断续干式切削ADI时切削力与寿命的研究

选用DBW85、DBC50、BN250、BN700四种牌号的PCBN复合片刀具断续干式车削等温淬火球墨铸铁(ADI),测定了在相同几何参数下的切削力和在不同速度下的刀具寿命。试验结果表明:(1)在所选用四种牌号PCBN刀具中,高CBN含量的BN700和DBW85断续加工ADI的性能,要优于低CBN含量的BN250和DBC50,其中DBW85性能最好。(2)高CBN含量的BN700和DBW85加工ADI时,切削速度可选择偏高一些,一般要大于130m/min,低CBN含量PCBN刀具加工ADI时,切削速度要选择偏低一些,在100m/min左右。(3)黏结剂中添加W元素可以有效抑制PCBN刀具切削ADI时的化学磨损,改善刀具韧性,有利于ADI的断续切削。     

陶瓷刀具断续车削淬硬钢切削力和切削温度的有限元分析

为揭示Al2O3/(W,Ti)C陶瓷刀具断续车削淬硬钢时的切削力、刀具温度以及刀具应力的变化规律及相互关系,采用有限元方法进行金属切削仿真。仿真结果表明,断续车削过程中,刀具承受十分明显的周期性机械载荷冲击与热载荷冲击;单个切削周期内机械载荷与热载荷的变化规律体现了两者的密切相关性以及时间上的不一致性;由于剪切角偏转的影响,刀具最大主应力显著增大,所以切出过程对刀具破坏的作用尤为严重。     

铣削大理石切削参数对PCD刀具磨损的影响

目的探索PCD刀具磨损机理,以延长刀具使用寿命。方法设计正交试验,研究不同加工参数切削大理石对刀具磨损的影响情况。分析主轴转速、进给速度与切削深度对PCD刀具磨损量的影响规律,以优化切削参数来减小刀具磨损量。根据经验公式,建立单位时间刀具磨损量和固定行程磨损量模型。通过对试验过程刀具振动情况记录,结合刀具实际磨损情况,给出了刀具磨损等级。结果主轴转速的提高可以减少刀具磨损量,进给速度的增大会加剧刀具磨损,而切削深度小于1 mm时,其对刀具磨损量的影响很小,但切削深度大于1 mm时,继续增大切削深度会使刀具快速磨损。利用预测模型能够很好地对刀具磨损情况进行预判,根据磨损等级,得出刀具与机床发生共振时磨损最为严重,在刀具表面产生了明显的犁沟、磨损以及金刚石颗粒脱落。结论在实际加工中,通过提高主轴转速、降低进给速度以及减小切削深度有助于增强刀具的耐用度,避开共振切削参数可以有效降低刀具磨损,主轴转速、进给速度、切削深度分别为12000r/min、500 mm/min、0.5 mm时的切削效果较佳,有最小的刀具磨损量。     

PCBN刀具和硬质合金刀具切削淬火钢的比较试验研究

本文通过ＰＣＢＮ刀具和硬质合金刀具车削淬火钢的比较试验，总结出切削力和表面粗糙度随切削速度，进给量、切削深度及工件硬度的变化规律，实验中发现，采用ＰＣＢＮ刀具切削时不产生积屑瘤，本文认为产生这一现象的主要原因是由于ＰＣＢＮ刀具的低摩擦系数和高抗粘结性能。同时还讨论了ＰＣＢＮ刀具切削力较低的原因。     

高效铣削铝合金用PCD刀具

近年来，为了减少汽车的总重量和燃油费用，铝合金材料在汽车零部件中的使用越来越多（图1为汽车零部件中铝合金使用量的变化趋势）。为此，加工铝合金汽车零部件用聚品金刚石（PCD）刀具的使用量也在快速增长。PCD刀具寿命长，能实现高效、高速、高精度切削加工。     

PCD切削刀具的性能及合理使用

本文介绍了聚晶金刚石切削刀具的机械物理性能，进一步阐述了聚晶金刚石切削刀具的适应范围以及聚晶金刚石切削刀具在使用过程中应注意的几个问题。     

断续切削中刀具应力的激光检测

用连续激光测试技术测量了切削过程中刀楔内的应力分布规律；同时为了验证这种测量方法的可靠性，对刀具内的应力分布进行了有限元分析；结果表明，光测刀具应力分布规律和有限元计算结果非常一致；激光测试技术是一种测量刀具应力比较有效的新方法，这为进一步研究切削过程中的刀具破损和其它动态问题提供了坚实的基础。     

PCD刀具切削天然大理石的磨损特性研究

通过PCD刀具切削天然大理石的试验研究,分析了在不同加工参数条件下对PCD刀具切削性能的影响以及刀具的磨损机理。试验结果表明:PCD刀具在加工过程中的磨损机理主要表现为磨粒的磨损、剥落,聚晶层的破损与结合剂破坏等;刀具主轴转速为12 000 r/min、进给速度为1 000 mm/min、切削深度为0.5 mm时,刀具的磨损量最小;且磨损量随刀具主轴转速的增加而降低,随刀具的进给速度和切削深度的增加而增加。     

PCD刀具加工氮化硅陶瓷孔的试验研究

使用PCD刀具对氮化硅陶瓷内孔进行切削试验,首先研究氮化硅陶瓷材料的去除机理,主要包括脆性去除和塑性去除,且以脆性去除为主。其次,研究刀具前角、切削速度、背吃刀量和进给量对切削力的影响。结果表明:刀具前角对切削力的影响不明显;随切削速度、背吃刀量和进给量的增加,切削力均增大,且背向力大于进给力和主切削力。最后,重点研究各参数对内孔侧壁表面粗糙度的影响。结果表明:进给量对表面粗糙度的影响最显著,其次是背吃刀量和切削速度,刀具前角几乎没有影响,且当刀具前角为-5°,切削速度为32.97m/min,背吃刀量为0.10mm,进给量为0.08mm/r时,可以得到较好的表面粗糙度和刀具寿命的综合效益。      

Analysis of stresses during exit in interrupted cutting with champfered tools

This paper presents an analysis of the stresses in the workpiece and tool during exit in interrupted cutting with chamfered tools. An elastic-plastic finite element model is developed to examine the stress fields in the workpiece for various chamfer forms and exit angles. Eight different cases are considered. The workpiece material considered is low carbon steel (203.4 N/mm² yield stress). The geometric conditions considered include cases where the thickness of the cut h₁ is rather small (h₁ = 0.04 mm) compared to the chamfer width (L_c = 0.2 mm), as well as cases where L_c = h₁ = 0.3 mm. Chamfer angles of 5 and 20° are considered, while the exit angle is taken as 60 and 90°. For the various conditions considered, the loads on the tool are obtained and then used to analyze the stresses in the tool nose. An elastic, plane-strain finite element model is developed for the tool with a very fine mesh near the cutting edge. The material of the tool carbide inserts is considered to be homogeneous and isotropic.

The results indicate that the presence of the chamfer does not prevent the dangerous rotation of the workpiece shear angle in the negative direction. For the cases where the thickness of the cut is small compared to the chamfer width (L_c = 5h₁), the magnitude of the shear stresses near the cutting edge increases significantly when the chamfer angle is increased from 5 to 20°, and also these stresses reach levels corresponding to the shear flow strength of sintered carbides. For the cases where the thickness of cut is equal to the chamfer width, the results suggest that the build up material which is formed on the chamfer decreases the probability of tensile failure in the tool.     

恒温时间对PCD刀具焊接性能的影响

本文通过PCD复合片与YG8硬质合金的高频感应钎焊试验,研究了恒温时间对PCD刀具钎焊接头强度及钎缝宽度的影响,并用扫描电镜观察了钎焊接头的显微结构,用电子探针分析了接头界面元素分布情况。试验结果表明：随着恒温时间的增加,钎焊接头的剪切强度先增大后减小,而钎缝宽度先减小后增大。当恒温时间为16S时,剪切强度达340MPa,钎缝宽度仅有25μm。No2试样中钎料元素发生了不同程度的扩散,Mn元素的氧化和Zn元素的挥发不明显,C元素有一定程度的扩散,说明钎焊工艺参数选择合理。     

Experimental study on ultrasonic elliptical vibration cutting of hardened steel using PCD tools

Diamond tools cannot usually be applied for machining hardened steels while applying conventional cutting technique. As an alternative, ultrasonic elliptical vibration cutting (UEVC) technique was successfully applied for obtaining mirror surface on such steels using single crystal diamond (SCD) tools. In order to reduce production cost without compromising mirror surface quality, polycrystalline diamond (PCD) tools may be tested against highly expensive SCD tools. However, study on machining of hardened steel using PCD tools applying the UEVC technique has not yet been reported. The current research presents an experimental study on UEVC of hardened stainless steel (a typical Stavax, hardness 49 HRC) using the PCD tools. Face turning experiments were carried out to investigate the effects of three machining parameters: nominal depth of cut, feed rate, and nominal cutting speed on output performances such as cutting force, tool flank wear, surface roughness, and chip formation. Experimental results show that nominal cutting speed has very strong influence on the output performances, compared to the other two parameters. The surface roughness improves with a decrease in cutting speed. A mirror-like surface of approximately 804 mm² with a roughness value R_a of 11 nm was achieved at a lower cutting speed. Theoretical explanations have been given to support the results drawn from the UEVC experiments. It can be concluded that, while applying the UEVC technique, the inexpensive PCD tools instead of the SCD tools can be effectively applied to obtain optical surface for producing precise molds from the hardened steel.     

Wear and tool life of tungsten carbide, PCBN and PCD cutting tools

The wear mechanisms of cutting tools made of tungsten-carbide (WC), PCBN and PCD were investigated using the tool life and temperature results available in the literature. For tool/work combinations WC/steel and PCBN/hardened-steel, under practical conditions, tool wear was found to be greatly influenced by the temperature. It was concluded that the most likely dominant tool wear mechanism for WC is diffusion and that for PCBN is chemical wear. For PCD, more experimental results and hence further research is required to determine the dominant wear mechanism.     

Machinability study of tungsten carbide using PCD tools under ultrasonic elliptical vibration cutting

Sintered tungsten carbide (WC) is an extremely hard and brittle material extensively used in tool manufacturing industries. However, the current cutting technologies for shaping this typical hard-to-machine material are still cost ineffective. In this study, polycrystalline diamond (PCD) tools are used to study the machinability of sintered WC (~15% Co) by applying the ultrasonic elliptical vibration cutting (UEVC) technique. Firstly, it presents the UEVC principle and the effects of speed ratio (i.e. the ratio of the nominal cutting speed to the maximum tool vibration speed in the cutting direction) on the tool–workpiece relative motion as the cutting speed greatly influences the UEVC performance. Then UEVC experiments are carried out to analyze the cutting force, tool-wear progression, chip formation and surface quality against the cutting time at different speed ratios. The results show that when the speed ratio decreases, the resultant cutting force and the tool flank wear decrease while the surface finish improves. Average surface roughness, R_a, in a range between 0.030 and 0.050 μm is achieved at speed ratios less than 0.107. The experimental findings suggest that the commercial PCD tools can be used to machine sintered WC to achieve ultraprecision surface by applying the UEVC technique, which will be cost effective for miniature cutting technologies in future.     

PCD和CVD金刚石刀具切削性能对比及失效机理初探

通过切削实验,观察切削前后刀具的表面和刃口形貌、金刚石刀片组成成分、以及被加工工件表面粗糙度,比较两种刀具的切削性能,探讨其失效机理。结果表明:在同等条件下,CVD金刚石刀具的切削性能要明显优于PCD刀具。在车削过程中,PCD刀具的失效机理主要是结合剂与被加工材料中化学成分发生化学反应使结合剂流失,导致刀具结构疏松,从而导致磨粒团脱落。CVD刀具的失效机理为产生变质层磨损。切削过程中随着加工时间的进一步延长,切削区温度不断升高,当达到热化学反应温度时,就会在刀具表面形成变质层,从而带来切削过程中刀具的磨损;同时高温状态下CVD金刚石的晶界疲劳破坏,也可能会造成CVD金刚石刀具的磨损失效。     

Hard turning in continuous and interrupted cut with PCBN and whisker-reinforced cutting tools

PCBN (polycrystalline cubic boron nitride) is the most widely used material for tools employed in hardened steel turning applications due to its high hardness, wear resistance and thermal stability. However, its high costs severely limit its use. Alumina-based ceramics reinforced with whiskers, an alternative and less expensive material for these tools, has been used successfully in turning interrupted surfaces. The objective of this work is to investigate the conditions under which PCBN and ceramic tools can promote optimal results in the turning of hardened steel with continuous and interrupted surfaces. These tools were used in the radial turning of hardened steel with three types of surfaces: continuous surfaces and surfaces with 4 and 8 interruptions. The results indicated that, in continuous turning, the longest tool life was achieved using PCBN, but similar tool longevity was attained in interrupted turning using both PCBN and ceramic. In terms of roughness, the PCBN tools showed better results for continuous and interrupted surfaces.     

Turning of interrupted and continuous hardened steel surfaces using ceramic and CBN cutting tools

In the machining of hardened steel surfaces, turning instead of grinding has been employed increasingly due to several advantages it offers, such as flexibility and the possibility of dry cutting. The main tool materials used for this purpose are CBN and ceramic due to their high hardness and, in the case of some grades of these materials, high chemical stability with iron. However, when interrupted surfaces are turned, the tool requires not only these properties but also sufficient toughness to resist impacts against workpiece interruptions. Therefore, the main goal of this work is to compare CBN and ceramic tools in continuous and interrupted cutting. To this end, several turning experiments were carried out on continuous surfaces (in this case, CBN with an added ceramic phase and a mixed ceramic were compared, due to their high chemical stability and hardness) and on interrupted surfaces (here, a high CBN content and a SiC-reinforced ceramic were compared due to their good ability to withstand impacts), applying different cutting speeds. The main conclusions of this work were that in both continuous and interrupted cutting, the CBN tools exhibited a much better performance with respect to both tool life and workpiece surface roughness than the ceramic tools.