Simulation of Surface Integrity for Nanopowder-Mixed Dielectric in Micro Electrical Discharge Machining

The use of powder-mixed dielectric for electrical discharge machining (PMD-EDM) and micro-electrical discharge machining (PMD micro-EDM) has been shown to reduce machined surface roughness and surface defects, such as, recast layer thickness. However, these were mainly empirical studies which had limited capacity to elucidate the physics and characteristics of the PMD-EDM process. In the current study, a new numerical model has been developed to describe the PMD micro-EDM process. The model has taken into account the larger expansion of the plasma channel and reduction in heat flux distributed to the workpiece because of the presence of powder particles. It has been analyzed using finite element methods (FEMs) and based on the multiple discharge approach. The heat source expansion factor due to the presence of powder particles has been estimated to be 1.07 at 0.02 g/L powder concentration. The fraction of heat flux to the workpiece has been found to decrease from 0.24 at 0.02 g/L to 0.11 at 0.2 g/L powder concentration. For model validation, simulated R _max and recast layer thickness values were compared with their corresponding measured values. The simulated and measured results varied with the same general trend which suggested that the proposed process model for PMD micro-EDM was fundamentally sound.     

Surface Characteristics and Hardness Variations in Electrical Discharge Machining of Enhanced Nitrogen in Vanadium Steels

Metallurgical and Materials Transactions B - Enhanced nitrogen in steels containing vanadium causes fine precipitates of vanadium nitride, which improve the hardenability properties. However,...     

中和温度对电解二氧化锰产品放电性能的影响

在不同的温度条件下对电解二氧化锰进行中和处理，用半电池模拟放电试验（half—cell）检测其放电情况，进而探讨中和温度对电解二氧化锰电性能的影响。     

金属原型零件渗铜烧结及其放电加工行为

研究了激光烧结快速成形技术制备金属原型零件的渗铜烧结处理工艺。通过放电加工试验以及对原型零件表面组织结构的分析，讨论了原型零件的放电加工行为，结果表明，经渗铜烧结处理的原型零件可获得与常规电极相近的加工性质，并且表现出优于常规电极的特性。     

How Suspended Particles Affect Surface Morphology in Powder Mixed Electrical Discharge Machining (PMEDM)

The effect of SiC powder mixing into the dielectric liquid on surface topology and structure of interstitial free (IF) steel has been studied. Four process parameters, namely pulse duration, pulse current, concentration of powder, and type of dielectric liquid material, have been selected as varying parameters. Surface modifications due to suspended SiC particles were identified by using optical, scanning electron microscopy, and X-ray diffraction analysis. It was observed that suspended particles around discharge column accelerated and gained sufficient velocity to penetrate to the molten pool before solidification by means of electrophoresis and negative pressure induced after cessation of a discharge, which leads a surface embedded with added fine particles under that prevent formation of penetrating cracks during machining. However, surface cracks that formed due to high transformational stresses developed during solidification were found to be unaffected by means of mechanical action of the particles.     

稀土钨电极在高强度气体放电灯中的应用研究

通过对单元稀土钨合金材料和多元稀土钨合金材料的研究及稀土钨电极的制备,并组装成不同功率的照明金卤灯和汽车金卤灯,测定其发光性能,经对比分析,可知用稀土钨电极的灯的主要性能达到钍钨电极灯的水平,能部分取代传统的有放射性污染的钍钨电极,实现环保条件和材料性能的双替代。     

空气加湿对烧结性能指标的影响

为了探索空气加湿对钒钛磁铁精矿烧结性能的影响,在实验室进行了烧结料层表面空气加湿试验,其结果为,增产效果最好的是点火后18 min喷水0.4%,利用系数达到1.31 t/(m2·h),与基准期对比增产率达到15.94%;其次是不喷水的二次点火烧结,利用系数1.281 t/(m2·h),增产率13.40%。综合评价效果最好的是点火后18 min喷水0.4%,综合指数达98.54,其次是实行二次点火烧结(不喷水)综合指数98.50,第三是点火后18min喷水0.3%,其综合指数97.33,这三种组合的综合效果均高于基准期96.25。     

不同淬火介质对铝合金电工圆杆性能的影响

通过KHR-A便携式冷却介质性能检测仪对淬火介质的淬火冷却性能进行了测量,研究了水、淬火油及不同浓度的PAG淬火介质对铝合金电工圆杆性能的影响。510℃×6h固溶试样经过13%PAG淬火后,试样组织较为均匀,晶粒内基本无白色颗粒物析出,只有在晶界上有少量白色颗粒物析出,试样的综合性能较好,抗拉强度为112 MPa,延伸率为10%、导电率达55.90%IACS。     

烧结型耐磨耐热堆焊焊条抗磨损性能的研究

对烧结型耐磨耐热堆焊焊条在高速摩擦磨损的工况下使用时,焊层合金的抗磨损性能进行了研究。实验结果表明,该焊条具有良好的抗磨损性能,适于在高速摩擦磨损工况下使用。     

����̼�������µ͹��ս���϶�ֲ��Ķ��ط����о�

The pore distribution of low silica sinter samples with different C was measured by pressure mercury, and the fractal characteristic of pore distribution was calculated with multifractal theory. With the amount of C increasing, ???? is the least when the mass percent of C is 3. 7%, furthermore, the value of ??f(??) changes from negative to positive in the vicinity 3. 7%, the number of maximum probability element increases relatively, so the sinter has good multiple fractal structure and fractal features. If the amount of C continues increasing, the size of pores will drop, then fractal features will becomes less pronounced. The results also show when the mass percent of C is 3. 7%, its metallurgical properties is optimal.     

阳极氧化工艺条件对氮化钽烧结体电性能的影响

用纳米氮化钽粉末烧结制备了氮化钽烧结体,分析了烧结体的物相结构,研究了形成液种类、形成液浓度、温度、电流密度以及赋能电压等条件对氮化钽阳极氧化膜电性能的影响。结果表明,该烧结体是由纯氮化钽组成的,氮化钽阳极块体阳极氧化过程的最佳赋能工艺:磷酸溶液浓度0.01%,形成液温度55℃,电流密度40mA/g,形成电压小于16V。     

MgO含量对高铝烧结矿冶金性能的影响

为了改善高铝烧结矿对高炉冶炼不利的影响,本文在实验室条件下研究了Mg O含量对高铝烧结矿冶金性能的影响。实验结果表明:当烧结矿中Mg O含量为2.5%左右时,烧结矿的转鼓指数、低温还原粉化指数为最高,分别达到了了68.24%和72.58%;烧结矿的成品率较高,粒度分布合理;烧结矿的软熔区间较窄,对高炉生产有利。     

Influence of Dielectric Type on Porosity Formation on Electrical Discharge Machined Surfaces

This work presents a comparative study on the performance of three types of dielectrics at different electrical discharge machining (EDM) parameter combinations favorable for generating porosity. The characteristics of the porosity formation in the recast layer formed in water/oil emulsions (W/O) were investigated by comparing them with those present in the recast layer formed in kerosene and deionized water dielectric. The results showed that the porosity characters were influenced significantly by the dielectric type. The formation mechanism of the porosity in different dielectrics is presented in this article.     

烧结型耐磨耐热堆焊焊条抗热腐蚀性能的研究

对烧结型耐磨耐热堆焊焊条在高温腐蚀气体工况下使用时,焊层合金的抗热腐蚀性能进行了研究。实验结果表明,该焊条具有良好抗热腐蚀性能,适于在高温腐蚀工况下使用。     

Electrochemical Corrosion Behavior of Nd-Fe-B Sintered Magnets in Different Acid Solutions

Electrochemical corrosion behavior of Nd-Fe-B sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied. Potentiodynamic polarization curves and immersion time dependence of corrosion rates of Nd-Fe-B sintered magnets in different acid solutions were tested. Microstructures of corroded Nd-Fe-B sintered magnets were investigated by means of SEM and AFM. The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl 〉 H3SO4 〉 HNO3 solution and Nd-Fe-B sintered magnets are passivated in phosphate acid and oxalic acid. Within 25 min, the corrosion rates of Nd-Fe-B sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising. And in H2C2O4 solution, weight of the magnets increases. The brim of Nd-Fe-B sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid. The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.     

烧结型耐磨耐热堆焊焊条抗高温氧化性的研究

对烧结型耐磨耐热堆焊焊条在高温腐蚀气体的工况下使用时,焊层合金的抗高温氧化性能进行了研究.实验结果表明,该焊条具有良好的抗高温氧化性能,适于在高温腐蚀工况下使用.     

电工用铜线杆加工性能研究

连铸连轧低氧铜杆和上引连铸无氧铜杆由于制造工艺的不同,导致在组织结构和机械性能方面不同,最终体现在下道加工性能上。文章从拉制性能,退火性能和铜材的表面质量3方面对两种铜杆进行了对比和分析.