基于ABAQUS有限元仿真的硬质合金刀具磨损机制研究

钛合金在切削过程中会产生严重的加工硬化现象,导致切削性下降、刀具磨损加剧,直接影响工件的加工质量。为研究钛合金切削性能和刀具磨损机制,利用ABAQUS软件建立了钛合金的有限元模型,对其切削过程进行仿真分析,研究硬质合金刀具磨损机制;设计Ti6Al4V钛合金车削实验,研究不同加工参数对刀具磨损程度的影响规律。研究结果表明:在切削钛合金时,刀具的磨损主要发生在刀尖和后刀面位置,刀具的磨损长度随车削速度的增加而变大,随车削深度的增加而减小,随进给量的增加呈现出先减小后变大的情况,实验和仿真结果趋于一致,平均误差在6%以内。     

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.     

Effects of Fe intermetallics on the machinability of heat-treated Al–(7–11)% Si alloys

The need for bridging the divide between the casting process and the machining process provides a strong motivation for examining the various aspects affecting the machinability of Al–Si casting alloys, given that these alloys constitute about 85% of all aluminum castings produced. Strontium-modified, grain-refined, T6 heat-treated 396 alloys (containing ～11% Si), and B319.2 and A356.2 alloys (containing ～7% Si) were selected, with a view to studying their machinability characteristics. Three 396 alloy compositions were selected (M1, M3, M4) such that different iron intermetallic phases were obtained in each case. Drilling and tapping operations were both carried out using a Makino A88E machine under fixed machining conditions. The machinability criteria relates to forces and moment analysis as well as to tool life, chip configuration, and built-up edge (BUE) evolution. The effects of Fe-intermetallics (α-Fe, β-Fe, and sludge) on the machining characteristics of these alloys were investigated and a comparison was made between the three 396 alloys in terms of mean total drilling forces, mean total tapping forces, tool life, and chip configuration. The results demonstrate that the presence of sludge has a significant effect on cutting forces and tool life. The tool life of the 396-M3 alloy (containing sludge) decreased by 50% compared to the base alloy 396-M1 (containing α-Fe intermetallics). Increasing the Fe-content from 0.5% to 1% in the M1 alloy (i.e., M4 alloy) produces a distinct improvement in the alloy machinability in terms of cutting forces and tool life. The addition of Fe and Mn appears to have no discernible effect on the built-up-edge (BUE) width and chip configuration as compared to the base alloy. The dominant type of wear which leads to drill failure and breakage is outer corner wear; there is, however, no evidence of crater-wear. Fan-shaped chips were obtained during machining of the 396, B319.2 and A356.2 alloys, where the latter alloy yielded the largest chips. As far as the alloy Si content was concerned, it was found that the 396 alloys produce drilling results similar to those of the B319.2 and A356.2 alloys, in terms of the number of holes drilled (cf. 2160 with 2100 and 2285 holes drilled in the B319.2, and A356.2 alloys, respectively). During tapping tests, however, the B319.2 alloy yielded the longest tool life, i.e., more than twice that of 396 alloy and four-and-half-times that of the A356.2 alloy.     

Comparison of the machinabilities of Ti6Al4V and TIMETAL® 54M using uncoated WC–Co tools

Single-point turning tests of cylindrical bars were undertaken to analyse and compare the machinability of Ti6Al4V, the most common titanium alloy, and TIMETAL^® 54M, a newly developed alloy with similar mechanical properties as Ti6Al4V but with better machinability. Conventional cooling and uncoated WC–Co tool inserts were used in the study, because they are the most recommended for machining these materials. The feed and the depth of cut were maintained constant, and only the cutting speed was varied because it is the most affecting parameter. Adhesion of workpiece material in the form of a built-up edge appeared in all the cutting inserts after machining both alloys, which was removed for flank- and crater-wear measurements. Lower wear rates were observed for the Ti54M alloy, especially at high cutting speeds. In the same manner, cutting-force measurements showed lower specific cutting- and feed-force values for the Ti54M alloy. Adiabatic shear bands, a typical feature in the machining of titanium alloys, were observed in chips from both alloys under all cutting conditions. Finally, scanning electron microscopy observations were carried out to analyse the adhered material on the cutting edges of the worn tools where signs of diffusion and attrition were detected.     

Machining of hardened steel—Experimental investigations,performance modeling and cooling techniques: A review

The researchers have worked on many facets of machining of hardened steel using different tool materials and came up with their own recommendations. Researchers have tried to investigate the effects of cutting parameters, tool materials, different coatings and tool geometry on different machinability aspects like, the tool life, surface roughness, cutting forces, chip morphology, residual stresses and the tool–chip interface temperature under dry and/or semi-dry and/or flood cooling environment during machining of hardened steels while many of them have ventured to characterize the wear phenomenon. Good amount of research has been performed on an analytical and/or numerical and/or empirical modeling of the cutting forces, tool–chip interface temperature, and tool wear under orthogonal/oblique cutting conditions during machining of hardened steels. This paper presents a comprehensive literature review on machining of hardened steels using coated tools, studies related to hard turning, different cooling methods and attempts made so far to model machining performance(s) so as to give proper attention to the various researcher works.     

Influence of melt treatments and turning inserts on cutting force and surface integrity in turning of Al-12Si and Al-12Si-3Cu cast alloys

The microstructures, machinability and surface characteristics of Al-12Si and Al-12Si-3Cu cast alloys were studied after various melt treatments like grain refinement and modification. Results indicate that combined grain refined and modified Al-12Si-3Cu alloys have microstructures consisting of uniformly distributed α-Al dendrites, eutectic Al-silicon and fine CuAl₂ particles in the interdendritic region. These alloys exhibited better machinability and surface characteristics in the cast condition compared with the same alloy subjected to only grain refinement or modification. Performances of the turning inserts (un-coated, PVD and Polished CVD diamond coated) were evaluated in machining Al-12Si and Al-12Si-3Cu cast alloys under dry environment using a lathe. The Polished CVD diamond coated insert outperformed the un-coated or PVD-coated cutting inserts which suffered from sizeable edge buildup leading to higher cutting force and poor surface finish. The Polished CVD diamond coated insert shows a very small steady wear without flaking of the diamond film during cutting. This paper attempts to investigate the influence of grain refinement, modification and combined action of both on the microstrutural changes in the Al-12Si and Al-12Si-3Cu cast alloys and their machinability and surface finish when different turning inserts used.     

Ti6Al4V车削加工时硬质合金刀具磨损的数值模拟

为研究硬质合金刀具车削加工钛合金过程中的刀具磨损,刀具选择刚性模型,工件选择塑性模型,利用有限元软件对切削过程的刀具磨损进行了模拟。运用正交试验分析了在不同刀具参数组合下刀具磨损量的变化情况。结果表明:在固定的工艺参数下,刀具的前角和后角的交互作用对刀具的磨损量影响较大;单一参数因素的变化对刀具磨损量的变化影响较小。分析结果对降低硬质合金车削加工钛合金时的刀具磨损提供了参考。     

Effects of minimum quantity lubrication on turning AISI 9310 alloy steel using vegetable oil-based cutting fluid

This paper presents the effects of minimum quantity lubrication (MQL) by vegetable oil-based cutting fluid on the turning performance of low alloy steel AISI 9310 as compared to completely dry and wet machining in terms of chip–tool interface temperature, chip formation mode, tool wear and surface roughness. The minimum quantity lubrication was provided with a spray of air and vegetable oil. MQL machining was performed much superior compared to the dry and wet machining due to substantial reduction in cutting zone temperature enabling favorable chip formation and chip–tool interaction. It was also seen from the results that the substantial reduction in tool wears resulted in enhanced the tool life and surface finish. Furthermore, MQL provides environment friendliness (maintaining neat, clean and dry working area, avoiding inconvenience and health hazards due to heat, smoke, fumes, gases, etc. and preventing pollution of the surroundings) and improves the machinability characteristics.     

Refrigerated cooling air cutting of difficult-to-cut materials

One approach to enhance machining performance is to apply cutting fluids during cutting process. However, the use of cutting fluids in machining process has caused some problems such as high cost, pollution, and hazards to operator's health. All the problems related to the use of cutting fluids have urged researchers to search for some alternatives to minimize or even avoid the use of cutting fluids in machining operations. Cooling gas cutting is one of these alternatives. This paper investigates the effect of cooling air cutting on tool wear, surface finish and chip shape in finish turning of Inconel 718 nickel-base super alloy and high-speed milling of AISI D2 cold work tool steel. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry cutting, minimal quantity lubrication (MQL), cooling air, and cooling air and minimal quantity lubrication (CAMQL). For this research, composite refrigeration method was adopted to develop a new cooling gas equipment which was used to lower the temperature of compressed gas. The significant experimental results were: (i) application of cooing air and CAMQL resulted in drastic reduction in tool wear and surface roughness, and significant improvement in chip shape in finish turning of Inconel 718, (ii) in the high-speed milling of AISI D2, cooling air cutting presented longer tool life and slightly higher surface roughness than dry cutting and MQL. Therefore, it appears that cooling air cutting can provide not only environment friendliness but also great improvement in machinability of difficult-to-cut materials.     

铍铜合金断续切削后刀面磨损机理研究

目的研究断续切削过程温度变化对刀具粘结现象、涂层剥落和刀具磨损的影响。方法搭建了仿铣削加工的断续车削实验平台,采用热电偶法测量了断续切削过程中刀具后刀面在不同速度下的切削温度,利用带有能谱仪(EDS)的扫描电镜(SEM)观察后刀面随速度变化的磨损形貌并分析后刀面磨损区域的元素组成,阐述了后刀面温度和刀具磨损之间的联系,研究了Ti AlN涂层硬质合金刀具断续切削铍铜合金C17200时的后刀面磨损机理。结果随着切削速度的增加,刀具温度在v=500 m/min出现峰值,温度越高,后刀面的涂层剥落和粘结磨损现象越严重,涂层剥落和粘结磨损现象在切削速度为500 m/min时最严重,而后随着刀具温度的降低而减缓,切削速度600 m/min时的涂层剥落和粘结磨损现象相比500 m/min时有所减轻。结论断续切削过程中,刀具持续性地经受"负载-卸载"、"升温-降温"产生的高温、冲击和加工环境的不稳定性,是引起粘结现象、涂层剥落和刀具磨损的主要原因。涂层剥落和粘结磨损是导致铍铜合金断续切削刀具失效的主要磨损形式。     

铝含量对AZ系列镁合金机械加工性能的影响

研究铝含量对AZ系列铸造铝合金机械加工性能的影响。为评价该合金的机械加工性能,测量切削操作过程中的切削力以及表面粗糙度,以及研究显微组织和拉伸性能。结果表明：添加2%铝含量的镁合金具有最佳的拉伸性能。随着铝含量增加到2%以上,由于晶界上析出金属间化合物β-Mg17Al12,切削力会随延展性的降低而降低。切削力也会随着切削速度的增加而增大,这是由于在加工过程中切削工具的尖端有侧面生成。     

Machinability aspects of new Al–Cu alloys intended for automotive castings

This study was undertaken to investigate the machinability aspects of four new Al–Cu casting alloys with regard to the drilling and tapping processes; the base alloy is the 220 Al–2%Cu–1.3%Si–0.4%Mg alloy from which the other three alloys were prepared through the addition of TiB₂ and Zr, Sn, and Bi. The machining performance was evaluated based on the calculation of the total cutting force and moment together with that of the tool life expressed as the number of holes drilled/tapped up to the point of tool breakage. The evaluation range was limited by a predefined targeted tool life of 2520 holes corresponding to 14 machinability test blocks. The results show that more than 2520 holes can be drilled for all the alloys studied without drill breakage. The addition of Sn and Bi decreases the total drilling force over the evaluation range by 14% and 25%, respectively, compared to the base alloy. The total drilling moment was reduced by almost the same ratios. All the alloys studied produce a fan-shaped chip which is considered to be the ideal chip for most drilling applications. The addition of Bi increases chip fragility considerably whereas no distinct change in chip characteristics was caused by the addition of Sn. No significant drill wear or any outstanding change in the built-up edge (BUE) to be observed with the progress of the drilling process. A comparative study was also carried out on the machining behavior of these new alloys, represented by their base 220 alloy, with that of the A206, 356, B319, and A319 alloys. Results revealed that the 220 alloy may be proposed as a promising cheaper and lighter alternative for the machining application of the A206 alloy. Furthermore, the machinability of the 220 alloy may be deemed an acceptable compromise between that of the 356 and B319 alloys, on the one hand, and that of the A319 alloy on the other.     

Machinability improvement of titanium alloy (Ti–6Al–4V) via LAM and hybrid machining

Titanium alloy (Ti–6Al–4V) is one of the materials extensively used in the aerospace industry due to its excellent properties of high specific strength and corrosion resistance, but it also presents problems wherein it is an extremely difficult material to machine. The cost associated with titanium machining is also high due to lower cutting speeds (<60 m/min) and shorter tool life. Laser-assisted machining (LAM) and consequently hybrid machining is utilized to improve the tool life and the material removal rate. The effectiveness of the two processes is studied by varying the tool material and material removal temperature while measuring the cutting forces, specific cutting energy, surface roughness, microstructure and tool wear. Laser-assisted machining improved the machinability of titanium from low (60 m/min) to medium-high (107 m/min) cutting speeds; while hybrid machining improved the machinability from low to high (150–200 m/min) cutting speeds. The optimum material removal temperature was established as 250 °C. Two to three fold tool life improvement over conventional machining is achieved for hybrid machining up to cutting speeds of 200 m/min with a TiAlN coated carbide cutting tool. Tool wear predictions based on 3-D FEM simulation show good agreement with experimental tool wear measurements. Post-machining microstructure and microhardness profiles showed no change from pre-machining conditions. An economic analysis, based on estimated tooling and labor costs, shows that LAM and the hybrid machining process with a TiAlN coated tool can yield an overall cost savings of ～30% and ～40%, respectively.     

Tool wear mechanism in turning of novel wear-resisting aluminum bronze

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合金灰铸铁成分对切削刀具磨损的影响

利用正交试验法研究了合金灰铸铁中碳、铜、铬、锡含量变化对切削刀具(硬质合金)磨损的影响。结果表明,C、Cu、Cr、Sn等元素对刀具磨损影响大小的顺序是:C>Cu=Cr>Sn。其中,随着C含量升高,刀具磨损降低,但超过3.0%后变化不大;Cu和Cr含量增加都使刀具磨损明显上升,而Sn对刀具磨损的影响很小。获得了使刀具磨损最低的各元素的含量:C为3.00%,Cu为0.30%,Cr为0.20%,Sn为0.055%。阐明了C含量对刀具磨损影响的原因。     

高铝锌基合金粉末冶金材料及其摩擦学特性初探

初步研究了高铝锌基合金的粉末冶金工艺及其材料的摩擦磨损性能。通过气喷气冷法制取合金粉末，用压制后真空烧结的方法制备高铝锌基合金粉末冶金材料。实验结果表明，高铝锌基合金的粉末冶金试样在干摩擦和油润滑条件下的磨损率及摩擦系数均小于同一合金的铸造试样，但其压溃强度有待提高。在实验的基础上还探讨了该材料的耐磨减摩机理     

Machinability of titanium alloys (Ti6Al4V and Ti555.3)

Near-beta titanium alloys like Ti555.3 are increasingly being used in aeronautics replacing in some critical applications the most common Ti6Al4V. However, these near-beta titanium alloys have a poor machinability rating which needs to be overcome so as to maintain at least the same productivity levels as in Ti6Al4V.This paper presents the machinability results carried out for Ti555.3 compared with the commonly used Ti6Al4V. The aim of this research work is to understand tool wear mechanisms when machining Ti555.3. Analysis of variables such as cutting forces, chip geometry and tool wear shows that: (I) greater difficulty is encounterd when machining Ti555.3 alloy compared with Ti6Al4V alloy which can be machined at higher speeds up to 90 m min^?1; (II) there was a correlation between the mechanical properties of work material, tool wear, and component forces; (III) the occurrence of the diffusion process leads to the formation of a layer of adhered material composed of Ti and TiC on the tool's rake face for both Ti alloys.     

Effects of copper and sulfur additions on machinability behavior of high performance austenitic stainless steel

Flank wear, cutting force, the number and area of sulfides, and shear strain rate were measured to elucidate the synergistic effects of Cu and S additions on machinability of high-performance austenitic stainless steels with a basic composition of Fe-18 %Cr-21 %Ni-3.2 %Mo-1.6 %W-0.2 %N. As Cu and S content increased, flank wear and cutting force decreased. While Cu and S content increased, shear strain rate and shear angle increased. The tool life for an alloy with 3.1 %Cu + 0.091 %S was about four times longer than that of an alloy with 0.06%Cu + 0.005 %S due to high shear strain rate generated by Cu addition, lubricating films of ductile (Mn, Cr)S sulfides adhering to tool surface and low cutting force resulting from thinly and lengthily continuous sulfides formed in chips during machining.     

Experimental study on turning of TC9 titanium alloy with cold water mist jet cooling

Titanium alloys, as difficult-to-cut materials, have poor machinability due to their superior mechanical properties, heat resistance and corrosion resistance. High cutting temperature that will greatly accelerate tool wear often occurs in titanium alloy cutting process. In this paper, cold water mist jet (CWMJ) cooling method, an eco-friendly cooling method, was used to obtain a lower cutting temperature during TC9 titanium alloy turning process. The effects of CWMJ were mainly discussed as compared with cold air jet and flood cooling methods. A comprehensive evaluation on the cooling effects of CWMJ was carried out by hydrodynamic tests, heat transfer tests and turning tests, respectively. Experimental results indicated that CWMJ had better cooling effects as compared with other two cooling methods. Cutting temperature was greatly reduced, and tool life was improved with CWMJ during TC9 turning process. Machined surface quality and chip morphology were also acceptable.     

Hard turning of an alloy steel on a machine tool with a polymer concrete bed

Finish turning of 39NiCrMo3 alloy steel in the hardened state has been widely investigated under dry, minimum quantity of lubricant and wet cutting conditions, using inserts in ceramic and PCBN materials, on turning centers equipped with polymer concrete and cast iron beds. The progress of workpart surface roughness and tool wear with cutting time has been measured and the results analysed and discussed in detail. It has been observed that dry cutting leads to the lowest values of tool wear and surface roughness, whilst the minimal quantity of lubricant technique does not provide advantages regarding to dry turning. Furthermore, the PCBN inserts are characterised by a longer tool life than the one exhibited by the ceramic inserts. Finally, the outstanding damping and high rigidity of the polymer concrete bed has a beneficial effect on both tool wear and workpiece surface finish.