微细液态添加剂对电火花加工性能影响的实验研究

研究了微细液态添加剂对电火花加工中放电过程的影响。与单纯工作液中的放电过程相比,微细液态工作液中单位时间内有效脉冲数增多,平均击穿延时缩短,而火花维持电压相对较低,表明加入了微细添加剂的工作液在提高电火花加工性能方面具有潜力。实验结果显示,微细液态添加剂能有效提高工件的材料去除率,显著降低表面粗糙度值,并明显减少了加工表面的显微裂纹。     

混粉超声振动对电火花加工Ti-6Al-4V表面结构及力学特性的影响

研究混粉超声振动对电火花加工Ti-6Al-4V表面结构及力学特性的影响,对传统电火花加工、混粉电火花加工及混粉超声振动电火花加工后Ti-6Al-4V试件的表面粗糙度、表面残余应力和显微硬度进行了测量,采用SEM对3种加工方法的加工试件表面重熔层及微裂纹进行了观察,采用能谱分析仪对加工表面进行了能谱分析,探讨了Al粉、SiC磨料超声振动对电火花加工表面结构和力学性能的影响机理。结果表明:在混粉电火花加工基础上,工作液中加入20 g/L的SiC颗粒,电极施加轴向超声振动,可使电火花加工表面粗糙度值Ra降低0.5μm、重熔层厚度减薄40μm、表面残余应力降低50 MPa、表面显微硬度由7650 MPa提高到9870 MPa。     

基于微纳乳液的Inconel718电火花成形加工工艺实验研究

采用自制的微纳乳液作为工作液,利用电火花成形加工镍基高温合金(Inconel718),选取峰值电流、脉冲宽度、脉冲间隔及单次加工时间等参数进行十字正交试验,研究分析这些参数对电火花成形加工Inconel718的表面粗糙度和材料去除率的影响,并对比了在微纳乳液与煤油工作液中加工的工件表面微观形貌。结果表明:峰值电流对材料去除率影响显著,单次加工时间对表面粗糙度影响显著;与煤油工作液相比,采用微纳乳液进行电火花成形加工的工件表面质量更好。     

硅电极电火花表面改性的研究

以工业纯硅为电极,通过电火花放电对试样进行表面改性处理.电火花设备型号为EDM7125,工作液为普通煤油,电极材料含硅99.6%,工件材料为45钢和球铁.采用扫描电镜及金相显微镜对试样表面形态进行了研究,对试样表面进行了能谱分析,对试样进行了耐蚀及表层结合强度等试验.结果表明:试样加工后表面形成一层含硅超过16%的合金层.电火花加工球铁石墨基本未脱落,但石墨周围易产生或扩展显微裂纹.高硅层结合强度非常高,进行永久变形时,无剥离和裂纹产生.而且,经电火花加工过的试样耐蚀性得到极大提高.另外,电火花加工,当参数合理时,可达到粉末混入加工的目的,试样可获得好的表面质量.     

一种新的混粉电火花加工添加剂

混粉加工是指借助于特殊的过滤系统、控制软件及辅助系统 ,在电火花加工工作液中添加某些粉剂材料进行加工的方法。采用这种加工方法可以在更短的时间内加工出更优质量的工件表面。一些机床制造商已先后开发出混有硅、铬、铝等粉末的工作液 ,而日本牧野公司推出的一种名为 μＳＣ的半导体混粉材料 ,具有理想的商业实用价值。1　常用电火花成形加工电极的局限紫铜是一种优异的电极材料 ,但要加工像镜面这样高精密要求的表面 ,则电极面积只能小于 90 0ｍｍ2 。这是因为加工表面越精密 ,电极与工件之间的放电间隙就应越小。紫铜的膨胀系数比较…     

钛合金电火花多次切割表面气体强化研究

分析了采用电火花线切割多次切割工艺对钛合金进行表面气体强化处理的可行性,前几次切割采用复合工作液为冷却介质,最后一次采用压缩空气或氮气作为放电介质,对钛合金加工表面进行强化.对比实验表明,以气体作为强化介质时,加工表面硬度得到明显提高,采用氮气进行强化的表面显微硬度达到2 050 HV,是基体的486%,形成了氮化钛组分,且表面基本不存在电解微孔洞和显微裂纹,表面完整性也得到明显改善.     

混粉电火花放电蚀坑及温度场仿真研究

混粉电火花加工是一种新型加工工艺,通过在工作液中添加微细粉末,显著改善加工表面粗糙度。电火花加工表面粗糙度的形成与放电蚀坑大小有直接关系,而放电蚀坑大小与单次脉冲放电温度场有密切联系。为了进一步提高混粉加工表面质量,利用ANSYS软件对放电点温度场进行了模拟与分析,得到了工件表层温度场的分布规律,揭示了材料去除机制,阐明了加工表面粗糙度与温度场的关系,对预测和改善混粉加工表面质量及日后生产实际应用提供了一定的理论依据。     

深微孔电火花加工非电参数工艺规律研究

在深微孔电火花加工中,工作液及电极材料等非电参数的选择对加工效率及加工质量有极大的影响,揭示这些非电参数的工艺规律对提高深微孔电火花加工性能有重要的研究意义.利用煤油和去离子水两种工作液,以加工效率为目标,在不同条件下开展工艺试验,得出最适宜的工作液在加工45钢和紫铜材料工件时为去离子水,加工铝合金材料工件时为煤油;利用黄铜丝、钨丝及钼丝3种电极材料,同样以加工效率为目标开展工艺试验,得出最佳电极材料在加工45钢工件时为钨,加工紫铜材料工件时为钨和钼,加工铝合金材料工件时为黄铜.上述研究在深微孔电火花加工中合理选择工作液及电极材料方面做出了有益的探索,其研究成果为深微孔电火花加工高效率、高质量的开展提供了重要的借鉴.     

工作液对线电极电火花磨削陶瓷表面性能的影响

利用扫描电镜观察、比较碳化硼陶瓷加工表面弹性性能及加工表面变质层.采用不同工作液用线电极电火花放电磨削方法加工工件,得出采用添加铝粉的工作液加工所得工件表面力学性能较好.     

短电弧加工工件表面特性的研究

对短电弧加工工件的表面综合特性进行了研究.通过分析加工后工件表面形貌、显微裂纹和机械性能变化,逐步探索出使短电弧切削技术具有良好工艺特性的加工条件.分析了现有短电弧机床在工作介质和烟尘处理方面的不足,为后续的深入研究指明了方向.     

Influence of silicon powder-mixed dielectric on conventional electrical discharge machining

Electrical discharge machining (EDM) is a technological process with a large industrial implementation. Its use is particularly intense when very complex shapes on hard materials with a high geometrical and dimensional accuracy are required. However, the technological capability of the process has limited its application when the specification of the part surface quality imposes polished and mirror-like characteristics. The addition of powder particles in suspension in the dielectric modifies some process variables and creates the conditions to achieve a high surface quality in large areas. This paper presents a new research work aiming to study the performance improvement of conventional EDM when used with a powder-mixed dielectric. A silicon powder was used and the improvement is assessed through quality surface indicators and process time measurements, over a set of different processing areas. The results show the positive influence of the silicon powder in the reduction of the operating time, required to achieve a specific surface quality, and in the decrease of the surface roughness, allowing the generation of mirror-like surfaces.     

The use of the orthogonal array with grey relational analysis to optimize the electrical discharge machining process with multiple performance characteristics

In this paper a new approach for the optimization of the electrical discharge machining (EDM) process with multiple performance characteristics based on the orthogonal array with the grey relational analysis has been studied. A grey relational grade obtained from the grey relational analysis is used to solve the EDM process with the multiple performance characteristics. Optimal machining parameters can then be determined by the grey relational grade as the performance index. In this study, the machining parameters, namely workpiece polarity, pulse on time, duty factor, open discharge voltage, discharge current, and dielectric fluid are optimized with considerations of multiple performance characteristics including material removal rate, surface roughness, and electrode wear ratio. Experimental results have shown that machining performance in the EDM process can be improved effectively through this approach.     

Electrical discharge machining using simple and powder-mixed dielectric: The effect of the electrode area in the surface roughness and topography

Electrical discharge machining (EDM) is one of the most widely disseminated manufacturing technologies, in particular as regards the generation of accurate and complex geometrical shapes on hard metallic components. Nevertheless current EDM technologies have major limitations when dealing with fine surface finish over large process area. Indeed this is one reason that explains the need of final manual polishing of mould cavities performed by EDM. Recently EDM with powder-mixed dielectric (PMD-EDM) has been a focus of an intense research work in order to overcome these technological performance barriers. This paper presents a research work within the objective to acquire deep knowledge on EDM technology with powder mixed dielectric and to compare its performance to the conventional EDM when dealing with the generation of high-quality surfaces. In particular the analysis of the effect of the electrode area in the surface quality measured by the surface roughness and craters morphology was carried out for both technologies. The results achieved evidenced a linear relationship between the electrode area and the surface quality measures as well as a significant performance improvement when the powder mixed dielectric is used.     

Improvement of surface finish on SKD steel using electro-discharge machining with aluminum and surfactant added dielectric

Electrical discharge machining (EDM) process is widely used to process hard materials in the industry. Electrical discharge distribution effects can be achieved by the addition of Al powder in the dielectric. A fine surface roughness value of the workpiece is thus obtained. However, the electrostatic force among fine Al particles is found to agglomerate the Al powders in the dielectric. A surfactant can be adopted to separate the Al powder in the dielectric homogenously. A better surface even the mirror-like quality of the EDMed workpiece is thus desired. In the study, the effect of surfactant and Al powders added in the dielectric on the surface status of the workpiece after EDM is investigated.It is observed the best distribution effect is found when the concentrations of the Al powder and surfactant in the dielectric are 0.1 and 0.25 g/L, respectively. An optimal surface roughness (Ra) value of 0.172 μm is achieved under the following parameter—positive polarity, discharge current 0.3 A, pulse duration time 1.5 μs, open circuit potential 140 V, gap voltage 90 V and surfactant concentration 0.25 g/L.The surface roughness status of the workpiece has been improved up to 60% as compared to that EDMed under pure dielectric with high surface roughness Ra of 0.434 μm.     

Workpiece surface modification using electrical discharge machining

Electrical discharge machining (EDM) is a widely used process in the mould / die and aerospace industries. Following a brief summary of the process, the paper reviews published work on the deliberate surface alloying of various workpiece materials using EDM. Details are given of operations involving powder metallurgy (PM) tool electrodes and the use of powders suspended in the dielectric fluid, typically aluminium, nickel, titanium, etc. Following this, experimental results are presented on the surface alloying of AISI H13 hot work tool steel during a die sink operation using partially sintered WC / Co electrodes operating in a hydrocarbon oil dielectric. An L8 fractional factorial Taguchi experiment was used to identify the effect of key operating factors on output measures (electrode wear, workpiece surface hardness, etc.). With respect to microhardness, the percentage contribution ratios (PCR) for peak current, electrode polarity and pulse on time were ˜24, 20 and 19%, respectively. Typically, changes in surface metallurgy were measured up to a depth of ˜30 μm (with a higher than normal voltage of ˜270 V) and an increase in the surface hardness of the recast layer from ˜620 HK_0.025 up to ˜1350 HK_0.025.     

不同电极电火花加工硬质合金的效率研究

通过实验的方式对采用不同电极电火花加工技术加工硬质合金的效率进行了研究。通过调整加工过程中的脉冲宽度和开路电压，变换加工电极，探讨了不同电极材料、开路电压及脉宽加工硬质合金的加工效率的影响.     

Workpiece surface roughness and integrity after WEDM of Ti-6Al-4V and Inconel 718 using minimum damage generator technology

Following a brief review of EDM and its use on advanced aerospace alloys including workpiece integrity constraints, data are presented after machining Ti-6Al-4V and Inconel 718. Roughing and finishing (multiple trim cut) strategies were employed on two high specification machines with pulse generators designed to provide minimum workpiece integrity damage. Results include productivity, 3D topographic maps of workpiece surfaces, microstructural and microhardness depth profile data. Average recast thickness was <11 μm, several trim passes showing no apparent recast or damage. Similarly, no significant change in workpiece microhardness variation was observed with cracking confined to the recast layer.     

Near dry electrical discharge machining

This study investigates the near dry electrical discharge machining (EDM) process. Near dry EDM uses liquid–gas mixture as the two phase dielectric fluid and has the benefit to tailor the concentration of liquid and properties of dielectric medium to meet desired performance targets. A dispenser for minimum quantity lubrication (MQL) is utilized to supply a minute amount of liquid droplets at a controlled rate to the gap between the workpiece and electrode. Wire EDM cutting and EDM drilling are investigated under the wet, dry, and near dry conditions. The mixture of water and air is the dielectric fluid used for near dry EDM in this study. Near dry EDM shows advantages over the dry EDM in higher material removal rate (MRR), sharper cutting edge, and less debris deposition. Compared to wet EDM, near dry EDM has higher material removal rate at low discharge energy and generates a smaller gap distance. However, near dry EDM places a higher thermal load on the electrode, which leads to wire breakage in wire EDM and increases electrode wear in EDM drilling. A mathematical model, assuming that the gap distance consists of the discharge distance and material removal depth, was developed to quantitatively correlate the water–air mixture's dielectric strength and viscosity to the gap distance.     

Electrical Discharge Surface Alloying of Ti and Fe Workpiece Materials Using Refractory Powder Compact Electrodes and Cu Wire

The paper reviews the use of metal powders dispersed in the dielectric fluid and refractory PM electrodes, to initiate workpiece surface modification during EDM. Experimental work details the effects of EDM parameters (up to 270 V) on the hardness/composition of the white layer following die sink machining of AISI H13 tool steel and roll texturing of 2% Cr steel using partially sintered PM electrodes. Similar data are presented following EDM scanning and wire cutting of standard TI alloy TI-6AI-4V and a y TIAI. With AISI H13, recast layers were 5-20 μm thick and up to ∼ 1350 HK_0.025. When machining TI-6AI-4V with WC/Co electrodes, recast microhardness was 600-2900 HK_0.025. Wire cutting y TIAI generated porous alloyed layers up to 115 μm thick with extensive cracks and no increase in bulk hardness.     

基于ABAQUS的煤油介质中电火花表面强化工艺参数的研究

选取合适的热源模型、热边界条件和放电通道半径公式等,建立了煤油介质中电火花表面强化的热传导模型.在此基础上,利用ABAQUS有限元分析系统,模拟了煤油介质中电火花表面强化的单脉冲瞬态温度场,研究了电流增大对温度场的影响,并对单脉冲条件下的工具电极和工件在不同峰值电流下的温度场进行数值模拟,预测了电火花表面强化的工艺参数...