氮化铬铝涂层PCBN刀具旋风硬铣切屑宏观特征研究

氮化铬铝具有比氮化钛铝更高的硬度和抗氧化性,能否作为PCBN刀具的涂层需要进行试验研究验证.通过对氮化铬铝涂层PCBN刀具在硬态旋风铣削淬硬钢GCr15平均硬度为63.5HRC)加工中,选用不同的切削参数、冷却方式和刀具个数的研究,从而得出氮化铬铝涂层PCBN刀具旋风硬铣加工的特点和应用范围,对涂层刀具的研究和切屑预报研究提供了依据.     

The influence of the microstructure of hardened tool steel workpiece on the wear of PCBN cutting tools

Due to the recent developments of advanced cutting tool materials in the superbarasive family, such as cubic boron nitride (CBN) tools, the interest in cutting hardened steels has increased significantly. High flexibility and ability to manufacture complex workpiece geometry in one set up is the main advantage of hard turning compared to grinding. The focus of this study is to investigate the performance and wear behavior of CBN tools in finish, dry turning of four different hardened steels, treated to the same hardness R_c = 54. The following four materials were machined: X155CrMoV 12 cold work steel (AISI D2), X38CrMoV5 (AISI H11) hot work steel, 35NiCrMo16 hot work steel and 100Cr6 bearing steel (AISI 52100). A large variation in tool wear rate was observed in the machining of these steels. The tool flank grooves have been correlated to the microstructure of these steels, namely the presence of various carbides. The chip study reveals that there is presence of different amounts of white layers in machining these steels.     

硬质合金刀具正交车铣TC4钛合金磨损形貌及机制分析

在车铣复合加工中心Mazak Integrex 200Y上,切削速度为v=150、200 m/min及干式切削条件下,采用硬质合金刀具H13A对钛合金TC4进行正交车铣(顺铣)磨损试验。研究表明高速正交车铣钛合金时,正常磨损阶段前刀面出现不同程度切屑黏结及积屑瘤,后刀面主要以黏结磨损为主,磨损相对均匀;急剧磨损阶段,前刀面切屑黏结加剧,形成连续切屑,缠绕刀具;后刀面由于黏结作用刀具材料被切屑黏结物带走,形成黏结凹坑。刀具磨损的主要原因为黏结磨损、氧化磨损,通过X射线电子能谱(XPS)证明刀具磨损表面有TiO_2、WO_3和Co_3O_4等氧化物生成,分析其对刀具磨损的影响。     

PCBN刀具断续车削淬硬钢的试验研究

为了探索PCBN刀具在断续切削条件下刀具的破损规律,选用两种不同的PCBN刀具,在不同强度的断续方式及不同的切削速度下,对淬硬钢进行车削试验研究。根据试验条件,观察了刀具前、后刀面的磨损及破损情况,分析了刀具的失效机理,比较了刀具的切削寿命。结果表明：断续强度严重影响PCBN刀具的使用寿命,断续强度越高,刀具寿命越低;在相同强度的断续条件下,切削速度影响刀具的使用寿命,切削速度越高,刀具的寿命越低;本实验所用的断续条件下,刀具的失效判据为崩刃。     

Tool life and tool wear in the semi-finish milling of inclined surfaces

Functional die and mold components have complex geometries and are made of high hardness materials, which make them difficult to machine. This work contributes to a better understanding of this type of process and of the wear mechanisms of tools used in semi-finishing operations of hardened steels for dies and molds. Several milling experiments were carried out to cut AISI H13 steel with 50 HR_C of hardness using the high-speed milling technique. The main goal was to verify the influence of workpiece surface inclination and cutting conditions on tool life and tool wear mechanisms. The main conclusions were the inclination of the machined surface strongly influences tool life and tool wear involves different mechanisms. At the beginning of tool life, the wear was caused mainly by abrasion on the flank face plus diffusion and attrition on the rake face. At the end of tool life, the mechanisms were adhesions and microchipping at the cutting edge.     

聚晶立方氮化硼刀具磨损与寿命研究综述

聚晶立方氮化硼(PCBN)是一种超硬刀具材料,由于其具有硬度高、化学稳定性和热稳定性好等优点,已经被广泛应用于汽车、航空航天、能源等领域的机械零部件加工。文中分析了PCBN刀具的主要磨损形式及其原因,并从刀具材料构成和几何形状、工件材料以及切削条件3个方面总结了影响PCBN刀具磨损和寿命的主要因素,最后介绍了切削参数优化和添加涂层等方法在提高刀具耐磨性与寿命方面的应用。     

Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.     

PCBN微型铣刀的制备及应用

聚晶立方氮化硼(PCBN)刀具具有高硬度、高耐磨性、较好的导热性、较低的摩擦系数,同时又具有优良的化学稳定性、热稳定性及加工红硬性,可以以铣磨方式高效加工高硬度、高强度、耐腐蚀性钢材并获得高表面加工质量。在分析PCBN微型铣刀的设计特点与加工难点基础上,成功制备了颈部缩颈3 mm,直径0.2 、0.4 、0.6 以及1.0 mm的PCBN微型球头双螺旋刃铣刀,并使用直径0.4 mm的微型铣刀进行铣削实验。结果表明:制备的PCBN微型铣刀可以高质量、高效率地加工硬度50 HRC的模具钢模具,模具的表面粗糙度R_a值可达0.101 μm,且无阴阳面,满足其表面最终加工要求。      

Wear behavior of Al2O3/Ti(C,N)/SiC new ceramic tool material when machining tool steel and cast iron

Design, fabrication and application of ceramic cutting tools are one of the important research topics in the field of metal cutting and advanced ceramic materials. In the present study, wear resistance of an advanced Al₂O₃/Ti(C,N)/SiC multiphase composite ceramic tool material have been studied when dry machining hardened tool steel and cast iron under different cutting conditions. Microstructures of the worn materials were observed with scanning electronic microscope to help analyze wear mechanisms. It is shown that when machining hardened tool steel at low speed wear mode of the kind of ceramic tool material is mainly flank wear with slight crater wear. The adhesion between tool and work piece is relatively weak. With the increase of cutting speed, cutting temperature increases consequently. As a result, the adhesion is intensified both in the crater area and flank face. The ceramic tool material has good wear resistance when machining grey cast iron with uniform flank wear. Wear mechanism is mainly abrasive wear at low cutting speed, while adhesion is intensified in the wear area at high cutting speed. Wear modes are dominantly rake face wear and flank wear in this case.     

Tool wear mechanism of WC–5TiC–10Co ultrafine cemented carbide during AISI 1045 carbon steel cutting process

WC–5TiC–10Co ultrafine and conventional cemented carbides were prepared and used for AISI 1045 carbon steel cutting tool inserts. The microstructure and mechanical properties were characterized, and cutting tests were conducted with different cutting parameters. Tool wear mechanism was analyzed by SEM and EDS. Ultrafine inserts possess higher hardness and transverse rupture strength. There were adhesive wear on the rake and slight abrasive wear on the flank of ultrafine inserts. As for conventional inserts with the same composition but with medium grain size, there were combinations of more serious abrasive and adhesive wear on the rake and flank.     

PcBN刀具连续车削淬硬钢性能的研究

为了研究PcBN刀具在干式连续车削条件下刀具的性能,选用两种不同的PcBN刀具,在不同切削速度及不同工件硬度条件下,对淬硬钢进行车削试验。在此基础上,对刀具前、后刀面的显微形貌特征进行了观察,分析了刀具的失效机理。结果表明:切削速度对刀具的切削寿命影响很大,随着切削速度的增加刀具寿命几乎线性下降。硬度也是影响刀具切削寿命的重要因素之一,当v190 m/m in时,刀具切削硬度为(64±1)HRC工件的寿命比相同条件下切削硬度为(61±1)HRC工件的寿命下降约40%~60%。刀尖温度随着切削速度的增加不多,切屑温度要比刀尖温度高出许多。在本试验中,刀具的失效判据为崩刃或后刀面平均磨损超过0.3 mm。     

Chip formation, cutting forces, and tool wear in turning of Zr-based bulk metallic glass

The chip light emission and morphology, cutting forces, surface roughness, and tool wear in turning of Zr-based bulk metallic glass (BMG) material are investigated. Machining results are compared with those of aluminum 6061-T6 and AISI 304 stainless steel under the same cutting conditions. This study demonstrates that the high cutting speeds and tools with low thermal conductivity and rake angle activate the light emission and chip oxidation in BMG machining. For the BMG chip without light emission, serrated chip formation with adiabatic shear band and void formation is observed. The cutting force analysis further correlates the chip oxidation and specific cutting energy and shows the significant reduction of cutting forces for machining BMG at high cutting speeds. The machined surface of BMG has better surface roughness than that of the other two work materials. Some tool wear features, including the welding of chip to the tool tip and chipping of the polycrystalline cubic boron nitride (PCBN) tool edge, are reported for turning of BMG. This study concludes that BMG can be machined with good surface roughness using conventional cutting tools.     

PCBN刀具切削性能和磨损机理研究综述

聚晶立方氮化硼(PCBN)刀具是继聚晶金刚石刀具之后的又一种超硬刀具,以其独特的“以车代磨”、“硬态加工”、“干式切削”等方式被誉为21世纪的绿色环保刀具。PCBN刀具在金属切削方面具有广泛的应用,主要用来加工各种淬硬钢、耐磨铸铁等铁基材料。本文介绍了PCBN刀具成分、几何形状、切削参数等对其切削性能的影响,在此基础上分析了不同材料加工时刀具的主要磨损机理,还简单对比了硬质合金和PCBN刀具切削性能上的差异。      

Performance evaluation of pure CBN tools for machining of steel

Ultra-precision machining is one of the most important machining technologies for the manufacture of precision dies and molds. Typically, single point diamond cutting tools are used to machine molds which are coated with electroless nickel (NiP) for such applications. The high cost of diamond cutters and electroless nickel plating, coupled with problems of pre-mature failure of the coating in service and long lead time are negative factors in this approach. Hence, there is a strong need for the direct ultra-precision machining of mold steel and to develop relevant technologies to address the problem of tool wear. In the machining of alloy steel, cubic boron nitride (CBN) has long been used as an ideal cutting tool material but recently binderless CBN or pure CBN (PCBN) with superior mechanical properties has been developed by Sumitomo Electric Industries in Japan. The objective of this paper is to explore the feasibility of using PCBN tools for direct ultra-precision machining of Stavax, a type of alloy steel from ASSAB. The performance characteristics in terms of surface roughness and tool wear of PCBN (Sumitomo IZ900) and conventional CBN (Sumitomo BN600) under different machining conditions were studied and their results were compared. Based on the experimental results, PCBN has been found to perform better in terms of wear resistance compared to conventional CBN tool. It is also able to achieve near mirror finish of less than 30 nm R_a, and hence it appears to be a promising tool for direct cutting of die and mold materials.     

Tool wear when turning hardened AISI 4340 with coated PCBN tools using finishing cutting conditions

Tool wear is one of the most important aspects in metal cutting, especially when machining hardened steels. The present work shows the results of tool wear, cutting force and surface finish obtained from the turning operation on hardened AISI 4340 using PCBN coated and uncoated edges. Three different coatings were tested using finishing conditions: TiAlN, TiAlN-nanocoating and AlCrN. The lowest tool wear happened with TiAlN-nanocoating followed by TiAlN, AlCrN and uncoated PCBN. Forces followed the same pattern, increasing in the same order, after flank wear appears. At the beginning of cutting, there was no significant difference amongst the coated tools, only the uncoated one showing higher cutting force. Ra values were between 0.7 and 1.2 μm with no large differences amongst the tools. Finite element method (FEM) simulations indicated that temperature at the chip–tool interface was around 800 °C in absence of flank wear, independently of coating. In that range only the TiAlN coating oxidize since AlCrN needs higher than 1000 °C. Therefore, due to a combination of high hardness in the cutting temperature range and the presence of an oxidizing layer, TiAlN-nanocoating performed better in terms of tool wear and surface roughness.     

Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and machined material. The high fluid pressure allows a better penetration of the fluid into the tool–workpiece and tool–chip contact regions, thus providing a better cooling effect and decreasing tool wear through lubrication of the contact areas.The main objective of this work is to understand how the tool wear mechanisms are influenced by fluid pressure, flow rate and direction of application in finish turning of AISI 1045 steel using coated carbide tools.The main finding was that when cutting fluid was applied to the tool rake face, the adhesion between chip and tool was very strong, causing the removal of tool particles and large crater wear when the adhered chip material was removed from the tool by the chip flow. When cutting fluid was not applied to the rake face, adhesion of chip material to the face did occur, but was not strong enough to remove tool particles as it moved across the face, and therefore crater wear did not increase.     

Influence of oxygen on the tool wear in machining

High temperatures generated in machining are known to facilitate oxidation wear. A controlled atmosphere chamber was developed to investigate the effects of oxygen on tool wear and high speed machining tests were conducted on air and in argon. Cemented carbide, cermet and cubic boron nitride tooling was used on alloyed steel, hardened tool steel and superalloy Alloy 718. Machining in argon resulted in higher flank wear, higher cutting forces, and larger tool–chip contact length on the rake face. However, in hard machining, argon atmosphere reduced rake cratering. Transmission electron microscopy of tools worn on air showed formation of nanocrystalline Al₂O₃ film on the rake when machining aluminium containing Alloy 718, while no oxide films was detectable in the other cases.     

Machinability of BN free-machining steel in turning

In the past few years, extensive researches have been done to improve the machinability of work materials in order to increase productivity and reduce the effect on the environment. To satisfy these demands, various free-machining steels have been researched and developed. One of them is BN free-machining steel that contains hexagonal boron nitride (h-BN). However, the machinability was not stable. In this study, machining tests were carried out to clarify the machinability of steels and appropriate chemical composition of work material and tool material to achieve high efficient machining. Tested work materials were plane carbon steel JIS S45C and BN free-machining steels. The JIS S45C was used as the standard. The tool wear in turning BN free-machining steel was smaller than that in turning standard steel. In case of turning BN1 with P30 at 200, 300 m/min, the wear progress rate of flank wear and crater depth were about half as much as that in turning standard steel. BN free-machining steel showed slightly lower cutting temperature and smaller cutting force in comparison with standard steel at the tested cutting speeds. Al and N were detected as a layer at the tool wear region of P grade carbide tools after turning BN free-machining steel at high cutting speed. It is thought that one of the main reasons of outstanding machinability of BN free-machining steel is that the deposited layer containing Al and N acts as diffusion barrier at the tool–chip interface. In turning larger Al content BN-added steel with higher Ti content cutting tools, a larger wear reduction was observed. Therefore, it is said that not only added BN but also appropriate Al is necessary in work material.     

高速钢丝锥的切削性能

目前,丝锥主要采用高速钢制作。为了解钢的冶炼工艺和显微组织,如碳化物的尺寸和分布、晶粒度等,对丝锥切削性能的影响,采用喷射冶炼和粉末冶金HSF825K、HOP2030和HSF838高速钢制作了螺旋槽丝锥,检测了丝锥的硬度、显微组织和切削性能。结果表明:3种钢丝锥热处理后的硬度均高于66HRC,钢的碳化物的尺寸、圆整度和分布对丝锥韧性的影响比淬火、回火后的硬度和冶炼工艺的影响大。弥散、细小、圆整、均匀分布的碳化物有利于提高丝锥的韧性和切削性能。采用喷射冶炼的HSF825K钢制作的丝锥的切削性能最佳。     

PCBN刀具高速切削淬硬轴承钢的磨损机理研究

采用美国D.I.公司生产的BZN9000作为刀具材料制成PCBN刀具,在沈阳机床厂生产的CA6140A车床上对GCr15淬硬轴承钢进行高速切削试验。对切削试验后刀具的前、后刀面进行SEM形貌观察和EDS能谱分析,结果表明:PCBN刀具在高速切削过程中,机械磨损、黏着扩散磨损和化学磨损是刀具磨损的主要形式;前刀面磨损主要为月牙洼磨损,切削刃处、月牙洼后、前刀面处的黏着元素扩散比月牙洼底部还要严重;对后刀面的WDS线能谱分析证实,切削刃处的黏着元素扩散比后刀面要严重。