离子型稀土矿浸出过程微细颗粒迁移规律及调控

离子型稀土矿在浸出过程中浸出剂与矿石表面水合机制较为复杂,颗粒间的桥式胶结因离子吸附交换过程中存在多种作用力与分散作用而容易发生断裂,从而使微细颗粒发生迁移和重新排列,并在孔喉处沉淀,产生堵塞现象,影响离子型稀土的浸出效率。为揭示离子型稀土矿在原地浸出过程中微细颗粒的迁移规律,并找到适宜的调控方法,以龙南足洞离子型稀土矿为研究对象,采用实验室柱式溶浸法,考察了浸出剂质量浓度、黏度、流速、水力梯度、矿体高度及矿体含水率对微细颗粒迁移的影响。结果表明,离子型稀土矿浸出过程微细颗粒的迁移是影响浸出效率的重要因素之一。在外力的作用下,微细颗粒在浸出过程中易随浸出剂发生迁移运动。当调控浸出剂质量浓度低于4%,浸出剂黏度不超过1.5 mPa?s,水力梯度小于0.75,浸出剂流速低于3 mL/min,原矿含水量大于11%时,矿体中微细颗粒迁移率较低,矿体渗透性保持良好,有利于浸出液的渗流和稀土离子的浸取。     

Deformation Behaviour of Iron‐Rich Iron‐Aluminium Alloys with Ternary Transition Metal Additions

The hardness and yield stress at room temperature and the brittle‐to‐ductile transition temperature of Fe‐Al alloys with 16 at.% Al, which is in the range of the so‐called K‐state with possible short‐range ordering reactions, and ternary additions of 0.5 and 4 at.% of the transition metals Cr, Mo, Mn, V, Ti and Ni were studied with respect to possible hardening effects of the ternary additions. The addition of Cr, Mo and Mn to the Fe‐Al alloys produce solid‐solution hardening which corresponds to the hardening effect of Al. Only Ti, V and Ni produce extra hardening effects which cannot be related to solid‐solution hardening. This extra hardening is attributed to possible fine NiAl precipitates in the Fe‐Al‐Ni case and to possible enhanced short‐range ordering and/or fine carbide precipitates in the cases of Fe‐Al‐V and Fe‐Al‐Ti.     

Slow Hot Rolling in Direct Linkage with Thin Slab and Strip Continuous Casting: Effect on the Evolution of Austenite Grain

This work was carried out in context with the development of strip casting with the single‐belt process. In this new process the hot rolling is performed in‐line with considerably lower velocity than in conventional hot rolling. It is of interest to study the effect of low rolling speed on the material properties. Based on a finite element model used to predict the thermomechanical behaviour of the strip in tandem mills, the microstructural evolution of austenite was computed. In order to take account of the non‐isothermal conditions in industrial hot rolling, the material equations for recrystallization and grain growth are modified. The parameter studies were carried out over a wide range of volumetric flow rate extending from that in thin slab casting to that in conventional finishing rolling. They demonstrate that the “slow hot rolling” can produce a fine grain of austenite. Austenite grain evolution was computed for conventional rolling with a seven stand mill and for in‐line hot rolling of strip produced by the single‐belt process. It is found that the final grain size of austenite is about the same for the two processes under the condition that strip thickness behind the last stand is the same.     

Rotary Blanking ‐ a New Manufacturing Process

Rotary blanking is a method of blanking and punching with rotating tools whereby the cutting tools are fixed to a pair of rollers performing a continuous blanking operation on a strip of sheet metal. The purpose of this paper is to outline the determining conditions under which the rotary blanking process takes place and to discuss advantages, restrictions, applications and optimization of this technology.     

Development of Fine‐Grained High‐Carbon Steel in High Reduction Low Temperature Rolling

After blanking and bending to form parts with the desired shape, high‐carbon steels are quenched and tempered to produce various machine parts. Thus, the spheroidization, formability and hardenability are very important properties for high‐carbon steels. Thermo‐Mechanical control Process of rolling has been widely used in the steel industry. However, it is difficult to apply this process to high‐carbon steels because of the heavy rolling load. Thus, fine‐grained high‐carbon hot strips were developed through high‐reduction and low‐temperature rolling by using single roll rolling mills with different diameters and laminar flow cooling devices in the finishing train, the grain size of these steels was about 3 microns. Also developed annealed strips with fine homogeneously dispersed spheroidal cementite had many excellent characteristics. For example, burring formability investigated by the hole‐expanding and surface hardness evaluated by laser hardening of the developed high‐carbon annealed steels, were excellent.     

金属薄板滚动冲裁工艺介绍

对变冲压为辊压，变平刃冲切为斜刃剪切，以达到降低口音和提高生产率的滚动式冲裁模具作介绍。     

Effect of Nitrogen and Niobium on the Structure and Secondary Hardening of Super Hard High Speed Tool Steel

High‐speed steels have been used mostly for multi‐point cutting tools and for plastic working tools. High speed steels are ferrous based alloys of the Fe‐C‐X multi‐component system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. The properties of these steels can be improved by modifying their chemical composition or the technology of their production. One of the new trends in modifying the tool steels chemical composition consists in the addition of niobium and nitrogen. In this work, the effects of niobium and nitrogen on morphology of carbides and secondary hardening temperature of investigated high speed tool steels were studied. This experimental work shows that, the conventional ingots have many types of carbides of different shapes and sizes precipitate on the boundary together with thick needle like carbides. On the contrary, for nitrogen steel, the nitrogen alloying leads to form dense, fine and well distributed microstructure. While, on the case of niobium alloying, single carbide (MC), and different types of eutectic carbides were precipitated which have a major effect on the secondary hardening temperature.     

在多向模锻挤压液压机上的型材挤压成形研究

在实验室模拟试验和工厂工业性生产试验的基础上,阐述了在多向模锻挤压液压机上实现挤压的工艺特点,找出了分离压余的理想方法－冲切法,给出了冲切间隙的计算方法。为减小挤压型材的弯扭畸变,建立了局部挤压比、挤压带系数的概念。给出了挤压筒中心与挤压模孔型中心距离的计算方法。     

Heating Rate Effects on Recrystallized Grain Size in Two Al-Zn-Mg-Cu Alloys

A method has previously been described whereby a fine and stable grain size may be achieved in conventional, heat-treatable aluminum alloy sheet by thermomechanical processing. The present work has examined the final recrystallization stage more closely. In particular, the effects of heating rate on recrystallized grain size have been determined and explained. It has been shown that heating rates greater than about 5 K . s^-1 should be employed in the final recrystallization stage in order to obtain maximum benefit from the fine grain processing technique. The coarser recrystallized grain sizes obtained with slower heating rates are mainly due to early activation of the most highly favored nucleation sites. Thermal recovery of the matrix defect structure below the recrystallization temperature is an additional, though less significant, effect. The influence of the degree of cold work and the volume fraction of insoluble particles on recrystallized grain size is discussed in relation to the heating rate.     

Optimal control of an aluminum casting furnace: Part II. Fuel optimization

In this second of a two-article series, the simplified model of the aluminum casting furnace presented in Part I is used to solve a fuel-optimal control problem. Basically a Lagrange problem with equality and inequality constraints, it is formulated through variational calculus into a two-point boundary-value problem with known initial and final conditions and specified final time. It yields an optimal solution with a time-vary ing fuel flow rate that gives 10.9 pct fuel economy over the conventional nonoptimal constant fuel flow rate. This shows that variational calculus can be used to solve optimal control problems for the aluminum casting furnace and for other similar thermal systems commonly encountered in the metallurgical industry.     

声波耦合旋流对转炉一次烟气细颗粒物的去除

针对钢铁厂转炉一次烟气含尘浓度高、颗粒物细的特点,提出一种声波耦合旋流除尘新技术,用于降低转炉一次烟气细颗粒物浓度。采用单因素试验和响应面法研究了声压级、声频率、停留时间及烟气进气方式对颗粒物浓度降低率的影响。单因素试验结果表明,转炉一次烟气颗粒物团聚效率随声压级升高而增大,但存在最佳团聚频率。相比单一声波团聚,声波耦合旋流除尘技术对细颗粒物有很好的团聚效果。响应面法优化试验得出,当声压级为140 dB、声频率为1 400 Hz、停留时间为8 s时,采用旋流进气方式颗粒物浓度降低率最高,达33%。研究结果为提高转炉一次烟气中细颗粒物的去除效率及工艺开发提供参考。     

Short‐term Creep Behavior of an X 37 Cr Mo V 5‐1 Hot‐work Tool Steel with almost Bainitic and fully Martensitic Microstructures

In this study two different heat treatments were conducted on an X 37 Cr Mo V 5‐1 hot‐work tool steel, resulting either in a tempered fully martensitic matrix or a matrix almost consisting of tempered bainite. Short‐term creep tests were performed at a high stress level of 800 MPa and at temperatures in the range from 450 °C to 500 °C. Creep specimens consisting of a tempered fully martensitic microstructure exhibited a three times longer creep‐to‐rupture time, than those consisting of a tempered almost bainitic microstructure. Microstructural investigations of creep specimens were performed by transmission electron microscopy. Results of these investigations revealed that due to a lower cooling rate, which is necessary to form bainite, the tempered bainitic microstructure consists of large former bainitic plates, whereas tempered martensite shows fine former martensitic laths. Tempered bainite also exhibits a higher number density of large M₃C, M₇C₃ and MC carbides than tempered martensite. Small M₂C carbides appear in both microstructures in the same quantity, however, nanometer‐sized MC carbides could only be found in tempered martensite. Thus poor short‐term creep behavior of the tempered almost bainitic microstructure can be explained by the lesser amount of strengthening relevant precipitates, a smaller size‐effect due to distance of bainitic interfaces as well as lower solid solution hardening.     

巴西Vale低硅铁矿粉烧结性能研究

采用最优实验设计方法,在实验室条件下进行了巴西Vale低硅粉矿配加低硅铁精矿的烧结杯实验,研究了该粉矿配比对烧结主要技术经济指标及烧结矿冶金性能的影响。通过优化其它铁料、燃料配比及混合料水分,确定了在巴西Vale低硅粉矿配比为19．35％、水分为6．9％-7．1％时,可获得较好的烧结性能指标。     

Behaviour of Surface Defects in Wire Rod Rolling

Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape.     

Water Distribution Network Renewal Planning

This paper provides an overview of the writers' previous work in formulating a comprehensive approach to the important problem of water distribution network renewal planning, with a particular emphasis on the computing aspects involved. As pipes in a water distribution network age in service, they are characterized by increased frequency of breakage and decreased hydraulic capacity. The resulting service failures incur utility costs for the repair or rehabilitation of the pipe systems and consumer costs for degraded system performance. The challenge to the decision maker is to determine the most cost-effective plan in terms of what pipes in the network to rehabilitate, by which rehabilitation alternative and at what time in the planning horizon, subject to the constraints of service requirements (system reliability, service pressure, etc.) A dynamic programming approach, combined with partial and implicit enumeration schemes, was used to search the vast combinatorial solution space that this problem presents. A computer program was written to implement these concepts. A hydraulic network solver is used by the program to assure the network conformance to hydraulic constraints during the search for a solution. The outcome is a strategy that identifies, for each pipe in the network, the optimal rehabilitation∕renewal alternative and its optimal time of implementation. The significance of this method is in its ability to identify an optimal rehabilitation strategy while considering the deterioration of both structural integrity and hydraulic capacity of the entire network. The best current heuristic method is limited in practical studies to a network of up to 15–20 pipe links. A more efficient heuristic method is required for implementing these principles in a larger-scale water distribution system and is the subject of current research.     

Computational Fluid Dynamics Study of a Noncontact Handling Device Using Air-Swirling Flow

The vortex gripper is a recently developed pneumatic noncontact handling device that takes advantage of air-swirling flow to cause upward lifting force and that thereby can pick up and hold a work piece placed underneath without any contact. It is applicable where, e.g., in the semiconductor wafer manufacturing process, contact should be avoided during handling and moving in order to minimize damage to a work piece. For the purpose of a full understanding of the mechanism of the vortex gripper, a computational fluid dynamics (CFD) study was conducted in this paper, and at the same time, experimental work was carried out to measure the pressure distribution on the upper surface of the work piece. First, three turbulence models were used for simulation and verified by comparison with the experimental pressure distribution. It is known that the Reynolds stress transport model (RSTM) can reproduce the real distribution better. Then, on the basis of the experimental and numerical result of RSTM, an insight into the vortex gripper and its flow phenomena, including flow structure, spatial velocity, and pressure distributions, and an investigation into the influence of clearance variation was given.     

高强钢冲裁断面质量模具间隙敏感性分析

高强度汽车板应用越来越多,其成形边裂问题一直是研究的热点。冲裁间隙对冲压件断面质量有着重要的影响,以S550MC、S315MC和SPFH590等3种高强钢板为研究对象,以冲孔、扩孔和电镜扫描等物理试验为研究手段,分析了冲裁间隙对断面质量、冲裁力和扩孔率的影响。结果表明,对于高强钢来说,随着光亮带宽度的增加,扩孔率并不一定增加;对于S550MC来说,适当增加冲裁间隙不仅有利于降低冲裁力,且有利于提高板料的扩孔性能。     

高炉煤气全干式精脱硫工艺路线探讨

针对高炉煤气含硫特性及气量大、下游用户多而分散等特点,简要分析了煤气精脱硫技术现状.采用源头控制方式,提出"预处理+水解催化+干法脱硫"精脱硫技术路线,根据实际工况可选择将预处理及水解系统置于余压发电(TRT)之前或之后.工艺路线采用全干式处理单元,可保证煤气热值,同时降低末端治理压力,实现超低排放.其中,预处理单元可...     

Measurement of Subsurface Unsaturated Hydraulic Conductivity

Measurement of unsaturated hydraulic conductivity is needed for precise control of water and solutes in the vadose zone. Because of the spatial variation of soils, a large number of surface and subsurface measurements are needed to characterize a field. In this work, permeameters were developed and tested for estimating subsurface unsaturated hydraulic conductivity. The permeameters apply water under tension; they are easy to use and have adequate accuracy. Unsaturated hydraulic conductivity was determined by measuring the steady flow rates for various values of negative pressure. Tests using a soil of known hydraulic conductivity showed that the permeameters provided valid measurements. Two types were used, a porous cloth model that was inflated against the soil and a porous ceramic cup that was rigid. The field testing determined that a rigid design using a ceramic cup coupled to the soil by a layer of fine sand was easier to use, was reliable, and provided good results.     

Synthesis and characterization of porous Fe–25 wt.% Al alloy with controllable pore structure

Porous Fe–25 wt.% Al alloy is synthesized by reactive synthesis with Fe and Al powders as the raw materials. Various processing parameters such as the final sintering temperature, pressure during cold pressing, and powder size are investigated to control the pore structure of the alloy. It has been shown that the optimal final sintering temperature is around 950–1050°C. When the pressure is higher than 110 MPa, the variation of the pore structure is mainly caused by the change of the pore nature in the as-pressed compact. In addition, the pore structure of porous Fe–25 wt.% Al alloys depends on the size of the raw powders and the weight fraction of different-sized raw powders.