精密电成型筛在超硬磨料生产中的应用

本文对超硬磨料粒度检验用精密电成型筛网孔尺寸选择的理论依据进行了简述,并分析了金属丝编织筛和电成型筛网孔允许偏差及两种筛网孔几何形状差异对筛分效果造成的影响。通过对金属丝编织筛网孔有效筛分尺寸的计算,看出两种筛的使用尺寸基本相符,因此,使用金属丝编织筛分级,电成型筛检验粒度是可行的,并通过实践得到了证实。     

金刚石微粉粒度不同检测方法的比较与研究

本文分析比较了不同型号激光粒度分析仪测量同一金刚石样品结果的差异。同时还比较了激光粒度仪与沉降管法对同一样品检测结果的差异。实验发现,由于不同型号的激光粒度分析仪设计原理、数据采集方式、算法不同,导致检测结果有所差别;另外,不同方法检测结果没有可比性。因此使用激光粒度分析仪检测粉状物料时,应注明所使用的仪器型号。该结论对超硬材料和磨料磨具行业微粉粒度组成检测有重要的参考价值。     

标准砂与粒度检验

磨料粒度检验所使用的金属丝编织的筛网,存在着相当大的公差。用尺寸公差不同的两套筛网对同一份样品进行粒度分布检验时,会得到极不相同的结果。这就给粒度分布检验带来了困难。为缩小检验误差我国1971年的标准和外国的一些标准中都规定了使用标准砂。把它当成粒度检验中的“原器”,使筛网公差造成粒度检验结果的差异得到适当的校正。本文是根据笔者的学习和体会,介绍一点外国有关标准砂与粒度检验的方法,以引起国内同行们的讨论。     

人造金刚石形貌分析系统与振筛系统测试金刚石粒度组成的对比研究

对人造金刚石粒度组成进行检测的方法主要有利用筛网筛分和形貌分析系统进行检测两种方法，本文采用这二种方法分别对同一组样品进行三次连续检测，发现采用筛网检测同一个样品基本粒比例的最大值与最小值的差值最大为1个百分点，形貌分析系统测试同一个样品的基本粒比例的最大值与最小值的差值最大为8．7个百分点；筛网检测三个样品基本粒比例的平均值是96．7％，形貌分析系统测试三个样品的基本粒比例的平均值是81．6％，这说明振筛机系统检测金刚石粒度组成的稳定性好于形貌分析系统，形貌分析系统测试的基本粒少于振筛机系统，形貌分析系统测试粒度分布结果受金刚石晶形的完整性、对称性影响较大。     

金刚石磨具的指标及表征

金刚石磨具的指标包括金钢金刚石种类(磨料)、粒度、硬度、结合剂、浓度及工具的形状和尺寸。金刚石磨具的标志方法举例如下: JR 120 Y1 S75 BW 150×35×32×10×3 磨料粒度硬度结合剂浓度形状尺寸(外径×厚度×孔径)(工作宽度—厚度) 1.磨料指金刚石的种类,有天然金刚石和人造金刚石两大类,分别以JT和JR表示。金刚石比重为3.5,一般称量单位为克拉(1克拉等于0.2克)。 2.粒度为金刚石磨料颗粒尺寸大小的标志。粒度号80,即磨料颗粒尺寸为200～160微     

一种新型的筛分设备——之字型电机振动筛

目前,国内许多行业如磨料、机械、化工、医药、煤炭、矿山等,所用的物料筛分设备多数是摇板筛(也称摇动筛),此种筛分设备机械原理落后,结构复杂,筛分效果差,易出现故障。为改变这种状况,国内一些厂家都先后研制了电磁振动筛、概率筛、施振筛等。由于磨料颗粒形状复杂,粒度级别多,每个粒度级的尺寸范围小,且其组成要求严格,比筛分     

激光粒度仪测试金刚石微粉粒度组成的实验研究

使用Malvern MS2000型激光粒度仪对M6/12和M8/16两种规格金刚石微粉的粒度组成进行了检测,通过不同实验室Malvern MS2000型激光粒度仪和不同型号的激光粒度仪对M0.5/1、M1/2、M6/12、M8/16、M20/30、M22/36六种规格金刚石微粉的粒度组成进行了对比检测.实验发现Malvern MS2000型激光粒度仪具有良好的检测重复性,且不同实验室Malvern MS2000型激光粒度仪的检测结果具有可对比性;Malvern MS2000型激光粒度仪与不同型号激光粒度仪之间检测结果的可对比性偏低;同厂家的各型号激光粒度仪检测结果之间的可对比性高于不同厂家激光粒度仪检测结果之间的可对比性.     

固结磨料研磨蓝宝石晶片的工艺优化

为了满足蓝宝石晶片高效低损伤的加工要求,采用亲水性固结磨料研磨垫研磨蓝宝石晶片的工艺,研究基体中碳化硅粒度尺寸、基体类型、金刚石粒度尺寸及研磨液中磨料4个因素对材料去除率和表面粗糙度的影响,并综合优化获得高加工效率和优表面质量的工艺参数。实验结果表明:基体中碳化硅粒度尺寸为10 μm、基体类型为Ⅱ、研磨垫采用F公司粒度尺寸为35~45 μm的金刚石、研磨液中磨料的粒度尺寸为5 μm的碳化硅为最优工艺组合,亲水性固结磨料研磨蓝宝石的材料去除率为431.2 nm/min,表面粗糙度值为R_a 0.140 2 μm。      

人造金刚石的筛分与筛机

人造金刚石生产中的粒度分级；质量检测中粒度检验；以及冲击强度值的最终确定等都离不了筛分与筛机。筛分涉及到筛网、筛机、筛分参数(如投料量、筛时间…)等。要获得精度高、重复性好、效率高的筛分必须全面考虑上述各因素。本文回顾了筛分技术的由来；分析了目前筛分技术存在的问题；介绍了2004年上海——展览会上国外筛机的参展情况。特别是对筛分投料量；筛分工艺安排；标准筛分对筛机的要求等提出了一些看法。     

标准砂在磨料粒度组成检测中的作用分析

磨料粗磨粒粒度组成检测的基本方法为筛分法。本文通过对磨料粒度组成检测时筛分条件对筛分结果的影响进行分析，得出标准砂在粒度组成检测中的两个作用：一是用来选择高精度的试验筛，二是对筛分结果进行校正，达到准确检测粒度组成，统一检测结果的目的。同时论述了标准砂的校正原理，并以实例对标准砂的作用进行了论证。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.