矿浆电解的研究现状及展望

矿浆电解工艺(Slurry Electrolysis Process)是一种新的湿法冶金技术。目前,矿浆电解在处理黄铜矿、方铅矿、复杂银精矿、铋矿、多金属硫化矿等领域得到广泛的研究,其中在处理铋矿、复杂银精矿及金精矿方面取得突破,相继实现了工业化生产。它高效、环保的独特优点使矿浆电解具有广阔的应用前景。综述了矿浆电解的发展过程及研究现状,介绍了矿浆电解发展的历史、优缺点及当前它的机理研究、介质研究、设备研究、实验室研究现状和工业应用现状,并对矿浆电解的发展方向进行展望。     

基于Buckingham方程的大倍线充填料浆输送优化与应用

大倍线充填料浆管道输送困难及输送浓度偏低等问题是影响矿山充填效益的关键因素,如何低成本实现大倍线高浓度充填料浆的输送,是充填管道输送研究的重要课题。基于宾汉流体(B-H)的Buckingham方程,开展高浓度尾砂浆大倍线自流输送管道优化研究,结合安庆铜矿马头山矿段充填浓度低和输送倍线大的实际情况,采用分段计算、局部优化的方式,以较低的成本实现了安庆铜矿马头山矿段充填管线的优化工作,通过优化改造,输送效果得到明显改善,充填浓度提高了2%,为矿山创造了良好的综合效益。     

Microstructural Evolution of A356 Al Alloy During Flow Along a Cooling Slope

Cooling slope (CS) has been used in this study to prepare semi-solid slurry of A356 Al alloy, keeping in view of slurry generation on demand for Rheo-pressure die casting process. Understanding the physics of microstructure evolution during cooling slope slurry formation is important to satisfy the need of semi-sold slurry with desired shape, size and morphology of primary Al phase. Mixture of spherical and rosette shaped primary Al phase has been observed in the samples collected during melt flow through the slope as well as in the cast (mould) samples compared to that of dendritic shape, observed in case of conventionally cast A356 alloy. The liquid melt has been poured into the slope at 650?°C temperature and during flow it falls below the liquidus temperature of the said alloy, which facilitates crystallization of ??-Al crystals on the cooling slope wall. Crystal separation due to melt flow is found responsible for nearly spherical morphology of the primary Al phase.     

Modeling of the Effect of Path Planning on Thermokinetic Evolutions in Laser Powder Deposition Process

A thermokinetic model coupling finite-element heat transfer with transformation kinetics is developed to determine the effect of deposition patterns on the phase-transformation kinetics of laser powder deposition (LPD) process of a hot-work tool steel. The finite-element model is used to define the temperature history of the process used in an empirical-based kinetic model to analyze the tempering effect of the heating and cooling cycles of the deposition process. An area is defined to be covered by AISI H13 on a substrate of AISI 1018 with three different deposition patterns: one section, two section, and three section. The two-section pattern divides the area of the one-section pattern into two sections, and the three-section pattern divides that area into three sections. The results show that dividing the area under deposition into smaller areas can influence the phase transformation kinetics of the process and, consequently, change the final hardness of the deposited material. The two-section pattern shows a higher average hardness than the one-section pattern, and the three-section pattern shows a fully hardened surface without significant tempered zones of low hardness. To verify the results, a microhardness test and scanning electron microscope were used.     

Modified metal injection moulding process of 316L stainless steel powders using thermosetting binder

Abstract

A modified metal injection moulding (MIM) process of 316L stainless steels powders using an acrylic thermosetting resin has been developed. Gas and water atomised 316L powders were used. In order to optimise the mixing and moulding steps, different volume fractions of the two components were investigated. Mixing of metal powder and binder was carried out at room temperature and immediately moulding was performed by pouring the slurry in the moulds. It was then heated at 90°C to permit the polymerisation and cross linking of the resin. Different heating cycles, rates, and atmospheres were studied by means of thermogravimetrical analysis. The data obtained were used to establish the best debinding cycle. The debound samples were sintered at different temperatures and high densities (98% of theoretical) were obtained. Materials in as moulded (green part), debound (brown part), and sintered conditions were examined by means of SEM.     

二氧化钛粉体的硅包膜研究

为提高二氧化钛的产品性能,以硅酸钠作为包膜剂,利用化学液相沉积法对二氧化钛初品进行了致密的二氧化硅包膜。使用X射线衍射分析法分析了样品的物相结构,并研究了包膜过程中钛浆料浓度、pH值、浆料温度和硅的含量,对其白度、光泽度和吸油量的影响。得到包覆硅氧化物的优化工艺条件为：TiO2浆料的浓度为166.67g/L,pH值为10,温度为70℃,硅的比例占钛的1%。经过硅包膜的样品的白度、吸油量和耐候性等性能得到了明显改善。     

分级细尾砂胶结充填体早期水化放热及强度演化特性

对分级细尾砂胶结充填体的早期水化反应及力学演化特性进行研究，对不同灰砂比充填体料浆进行水化放热及电阻特性测试，并根据扫描电子显微镜对早期水化产物进行微观形貌特征分析，最后在单轴压缩力学试验结果的基础上，分析早期水化反应进程及产物对充填体强度演化的影响。研究表明，灰砂比越大，水化放热速率及放热量越大，生成水化产物越多，体积电阻率越大。同时水化反应速率直接决定了充填体自身强度形成的快慢，生成的Ca(OH)₂减小了料浆体积电阻率，加快充填体自身强度的增长；随后生成的钙矾石（Aft）导致颗粒间孔隙更加致密，抑制了离子的溶解，减缓放出热量速率，从而阻碍了充填体强度的增长；当水化反应进行14 d基本结束后，充填材料凝结固化成为一个整体，强度基本稳定。充填体强度的变化呈现先迅速增加随后增加趋势逐渐减小直至稳定的趋势，为矿山采用分级细尾砂进行井下采空区充填、控制深部采场温度提供理论支撑及科学指导。      

Simulation of Cooling of Liquid Metal in an Inclined Slope to Predict the Condition for Semi Solid Forming and Its Experimental Validation

In semi solid processing, the preparation of slurry with globular microstructure is very important. A recent technique named the inclined slope casting, to produce the semi-solid metal slurry, has been evolved. The microstructure of casting depends on several process parameters like initial temperature of liquid metal, length of the slope, cooling rate and the rate of flow of liquid metal. In the present work numerical modelling of cooling of liquid was carried out. Modelling was done for different mass influx velocities, temperature of pouring and different inclinations of the slope set-up. In this work, a CFD model based on finite volume method for simulating flow along the inclined slope was carried out. Heat transfer, fluid flow and solidification were studied by varying the process parameters like slope angle and inlet pouring rate. The numerical results were verified with experiments for same conditions.     

Preparation of Semisolid Slurry for Stainless Steel 1Cr18Ni9Ti

The preparation of nondendritic semisolid slurry for stainless steel 1Crl8Ni9Ti was studied. The experiments show that when stirred for 2--3 min under the test condition, the semisolid slurry with solid of about 50% and spherical primary austenite in size of 100--200μm can be obtained, and besides the slurry is easy to flow out through the bottom hole of thestirring chamber. More homogeneous temperature fields and solute fields of stainless steel 1Crl8Ni9Ti melt appear because of the electromagnetic stirring, which restrains the formation of large primary austenitic dendrites and creates a base to form spherical crystals of primary austenite. The stronger temperature fluctuation in the melt containing many stirring-initiated rosette primary austenitic grains, together with the simultaneous remelting of the secondary arm roots primarily account for the deposition of the spherical primary austenitic grains.     

Semisolid Slurry Preparation of Die Steel with High Chromium Content

The semisolid slurry preparation of die steels Cr12 and Cr12MoV with high chromium content was studied. The results show that the semisolid slurry of both steels with solid of 40%-60% can be made by electromagnetic stirring method and is easy to be discharged from the bottom little hole of the stirring chamber. The sizes of the spherical primary austenite in the slurry of die steels Cr12 and Cr2MoV are 50-100 μm and 80-150μm, respectively. The homogeneous temperature field and solute field for both steel melts are obtained. The strong temperature fluctuation in the melt with many fine primary austenite grains occurs and the remelting of the secondary arm roots at the same time is accelerated because of the electromagnetic stirring. These are the most important reasons for deposition of spherical primary austenite grains.     

外加物理场对激光熔化沉积内部缺陷控制

激光熔化沉积技术是基于“分层—叠加”原理，在高能激光束作用下、按照预定的路径，将同步送给的 金属粉末逐层熔化并快速凝固成形的先进制造技术，具有成形精度高、加工柔性好、内部组织均匀、力学性能 优异、适用难加工金属材料制备等优点，在航空航天等领域具有广阔的应用前景。但是激光熔化沉积过程中 容易产生未熔合、微裂纹、气孔等缺陷，限制了这项技术的大规模应用。其中，激光熔化沉积构件的微观组织 存在明显的各向异性，沉积过程中的快速加热和冷却使构件内部产生较大的残余应力从而导致其变形和开 裂。学者就如何改善激光熔化沉积构件的内部缺陷进行了广泛研究。因此，综述了通过在成形过程中外加温 度场、超声场、电磁场以及复合场的方法改善激光熔化沉积制件的内部组织和性能，以期为激光熔化沉积构件 综合性能的提高提供指导。     

Dissolution of Platinum in Hydrochloric Acid Under Industrial-Scale Alternating Current Polarization

The electrochemical behavior of platinum in a hydrochloric acid solution under polarization by an industrial-scale alternating current has been investigated. For the electrical dissolution of platinum, titanium is used as an auxiliary electrode, which increases the yield of platinum dissolution by 12.5 pct. The influence of the concentration of hydrochloric acid, the current densities of the platinum and titanium electrodes, and the temperature of the electrolyte on the efficiency of the process of dissolving platinum have all been studied.     

激光熔覆涂层的浆体磨损特性及其应用研究

采用激光熔覆技术在４５钢试样表面获得镍基合金和ＷＣ颗粒增强的镍基合金复合材料涂层。研究了激光涂层工艺、熔覆层的组织结构和水平－煤－石英砂浆体的磨损特性,并将研究成果成功地应用于矿用渣浆泵平衡盘等零件。     

Preparation of A357 Alloy Slurry by Pulsed Magnetic Field Processing

Pulsed magnetic field (PMF) processing was employed for preparing semi-solid A357 alloy slurry in this study. The effects of pouring temperature and vibration power on the microstructure of the primary phase in semi-solid A357 alloy slurry were studied, and some characteristic parameters characterized the morphology and the grain size of the primary ??-Al particles were obtained. The results show that the primary ??-Al particles became finer and rounder with the decrease of pouring temperature and/or the increase of vibration power. However, over a certain vibration power, coarse structures appeared again. The slurry with the primary ??-Al particles of average diameter of approximately 92 ??m and average shape factor of 0.56 can be prepared under the action of a PMF at a vibration power of 250?W with pouring temperature of 903?K (630 °C). It was feasible to use PMF processing to prepare semi-solid alloy slurry because of its strong forced convection within the whole bulk melt.     

Al2O3 Mo金属陶瓷测温套管凝胶注模成型工艺

 采用凝胶注模成型工艺制备Al2O3 Mo金属陶瓷。预混液中单体丙烯酰胺AM和交联剂N,N′ 亚甲基双丙烯酰胺MBAM质量比为35∶1,总量为干坯质量的539%时,干坯强度相对较高。分散剂加入量在065%~090%时,浆料粘度为35~36 Pa·s,适于凝胶注模。对烧结金属陶瓷试样作体积密度测定及线扫描分析,结果表明,凝胶注模成型Al2O3 Mo金属陶瓷烧结后体积密度为425 g/cm3,而模压成型、同等条件制备的Al2O3 Mo金属陶瓷体积密度仅为372 g/cm3。烧结试样断口各成分分布比较均匀,没有出现明显的偏析现象。制备出的Al2O3 Mo金属陶瓷测温套管可成功应用于高温合金测温。     

Fe-Mn-Si系烧结钢显微组织的观察与分析

观察了含硅锰母合金烧结钢的组织变化和合金元素锰、硅的分布情况。发现:添加硅锰母合金后,在1100℃以上为液相烧结,但只有小尺寸母合金颗粒熔化后留下的孔洞趋于球形,较大尺寸母合金颗粒则在其周围留下环形孔洞。那些较大的原硅锰母合金颗粒的组织随温度的升高而变化。合金元素锰硅向基体内扩散的过程会由于液相的出现而大大地加快。     

Modeling Chemical Vapor Deposition of Silicon with Local Equilibrium Consideration at the Substrate

The purpose of this article is to present a general purpose mathematical model for describing the transport phenomena and the resulting rate of deposition in chemical vapor deposition (CVD) reactors. The model employs a finite difference scheme to solve the governing partial differential equations in order to predict the velocity field, temperature distribution, and concentration profiles of various gas species in a CVD reactor. The model predicts the rate of deposition for CVD reaction whose rate is mass transport controlled, for example, silicon deposition by the reaction of silicon tetrachloride and hydrogen at temperatures above 1050 °C. Silicon deposition by reaction of SiCl₄ and H₂ in a vertical CVD reactor with a rotating substrate is studied to compare the predicted and the experimental deposition rates. The effects of inlet gas composition, reactor pressure, and speed of substrate rotation on the rate of silicon deposition have been studied to verify the model's predictions. Local equilibrium and flux balance concepts have been used to determine the partial pressures of species at the substrate as well as the consequent deposition rate of silicon. The effects of thermal diffusion, grid size, and etching by HC1 on the deposition rate have also been studied. The results show that implementation of the local equilibrium concept and the flux balance principle, use of sufficiently small grid size above the substrate, thermal diffusion of SiCl₄ away from the substrate, and etching of deposited silicon by HC1 are all very important in evaluating the rate of silicon deposition in the mass transport-controlled regime. With all of the above-mentioned effects taken into consideration, model predictions agree well with the experimental data over a wide range of operating conditions for the system considered. Finally, use of the optimized design of a flow control device (FCD) in the reactor shows that once properly validated, the model can be used as a tool in computer-aided process optimization.     

充填料浆流动温变性研究

为解决矿山充填料浆堵管事故频发的问题,以具有代表性的不同配比充填料浆为研究对象,通过安东帕MCR102高级流变仪获取并分析相关数据,重点研究了充填料浆的温度对高浓度充填料浆流变特性的影响,探索温度变化对充填料浆流动性能的影响。研究结果表明：（1）高浓度全尾砂充填料浆的流变性能会随着料浆的温度变化而发生变化;（2）随着温度的升高,高浓度全尾砂充填料浆黏度系数降低,屈服应力先下降再升高;（3）温度为10 ℃时高浓度全尾砂充填料浆流变性能最好。根据本研究结果,矿山在使用高浓度全尾砂充填料浆时,可适当调节充填料浆温度,使充填料浆达到流变性能最优状态,进而减少充填料浆堵管事故的发生。     

Effects of Solid–Liquid Mixing on Microstructure of Semi-Solid A356 Aluminum Alloy

The desired starting material for semi-solid processing is the semi-solid slurry in which the solid phase is present as fine and globular particles. A modified solid–liquid mixing (SLM) is reported wherein semi-solid slurry can be produced by mixing a solid alloy block into a liquid alloy, and mechanical vibration is utilized to enhance the mixing. Effects such as liquid alloy temperature, mass ratio, and mixing intensity on the microstructure and the cooling curves during SLM were evaluated. 2D and 3D microstructure analysis of treated A356 aluminum alloy shows that microstructure can be refined significantly with a considerable morphology change in primary Al phase. It is critical that the temperature of mixture after mixing is lower than its liquidus temperature to obtain a valid SLM process. Specially, mixing intensity is identified as a primary factor for a favorable microstructure of semi-solid slurry.