Characterisation and sintering studies of mechanically milled nano tungsten powder

Abstract

Elemental tungsten powder was mechanically milled by planetary mill for 100 h. Particles were thinned down to nanometre scale. The shape of the milled powders was flat cylindrical with average diameter and length 12˙5 and 46˙5 nm respectively. The corresponding crystallite size obtained by X-ray diffraction (XRD) was 26˙96 nm. The results obtained by XRD and small angle X-ray scattering were well supported by transmission electron microscopy and high resolution transmission electron microscopy results. The maximum shrinkage of the compact has been observed at ～1500 K, which has been used as a guideline for sintering experiments. The powders sintered at 1773 K have resulted in 96% relative density.     

路易斯·康的公共住宅设计——评费城MILLCREEK住宅区

路易斯·康（LOuisIKahn．1901-1974）这位现代主义建筑史上的哲匠，以其带有神秘的宗教色彩的建筑哲学理论以及富于情感的建筑空间闻名于世。在相当长的一段历史时期。他着力于对社会贫困人群住宅设计的研究。该文通过介绍康所设计的费城MILLCREEK住宅区，来论证康的平民建筑思想，以及这一思想对他后期建筑理论所产生的影响．     

HYDROSTATIC PRESSURE CALCULATION AND OPTIMIZATION FOR DESIGN OF BEAM ＆ SLIDE-REST GUIDEWAYS IN HEAVY DUTY CNC VERTICAL TURNING MILL

Aiming at the approximate error of commonly used methods on calculation of hydrostatic pressures of closed hydrostatic guideways with multiple pockets, a more accurate solution is proposed. Taking design of beam & slide-rest guideways for a heavy duty CNC vertical turning mill as an example, under an assumption that stiffnesses of guideways and their jointing structure are sufficiently large, the pressures of the pockets can be attained by adding a co-planarity equation that con strains pocket centers. Then, an optimization model is built to minimize the highest pocket pressure under additional constraints that are posed on the highest seal margin pressure, the highest levitating pressure of the pockets, and the maximum deformation of the guideways. The optimization problem is solved sequentially by using the methods of design of experiments and adaptive simulated annealing on iSIGHT software platform. The results show significant improvements to the original design. Optimized maximum hydrostatic pressure meets the requirement of hydraulic system.     

Recycling of steel plant mill scale via iron ore pelletisation process

Abstract

Mill scale is an iron oxide waste generated during steelmaking, casting and rolling. Total generation of mill scale at JSWSL is around 150 t/day and contains 60–70%FeO and 30–35%Fe₂O₃. To recover the iron, the mill scale must be smelted in a blast furnace or other reduction furnace; however, it is usually too fine to use without previous agglomeration such as via pellet or sinter mix. JSWSL operates a 4·2 Mtpa pellet plant to produce pellets for Corex and BF ironmaking units. The aim of this study is to determine the effect of mill scale on pellet properties. Detailed laboratory basket trials were conducted using up to 40% of mill scale in the pellet mix. The addition of mill scale up to 10% is considered to provide the optimum balance of chemical, physical and metallurgical properties of the pellet.     

SINUMERIK802D数控铣床系统中Power MILL后处理设置

Power MILL自动生成的加工程序不能直接用于数控铣床SINUMER IK 802D系统,因此文中以fanuc15m为后处理原文件进行分析与修改,并对生成的NC代码进行验证。     

Pro/E及Power MILL软件在基座零件制造中的应用

以CAD/CAM技术的应用为前提,以基座零件为例,介绍了Pro/E及Power MILL等相关软件在数控加工中的具体应用,阐述了Pro/E的造型过程,以及运用Power MILL,对基座零件进行自动编程的操作步骤、加工策略、工艺参数、仿真及程序的后置处理等相关过程。实际生产情况表明,其显著提高了产品的加工质量及效率,缩短了零件的制造周期。     

大枣酸性多糖ZJ-6的化学研究

大枣用乙醇回流脱脂,80～100℃温水浸取,提取液减压浓缩,乙醇分级沉淀,三氯乙酸脱蛋白,透析,透析内液减压浓缩,再醇沉得到三个级分ZJ-A,ZJ-B,ZJ-C,ZJ-B经DEAE-Cellulose柱、sepchcryls-300柱分离纯化,得大枣多糖ZJ-6,HPGPC法测定其分子量为4206,光谱和色谱分析(1HNMR,13CNMR,HPLC)表明,ZJ-6是以α-D-(1→4) -半乳糖醛酸为主链,葡萄糖、木糖、阿拉伯糖在末端或支链相连的酸性杂多糖。     

Simulation of thermal history of work rolls of finishing stand in hot strip mill: a numerical approach

Abstract

The work rolls in the finishing stands of any hot strip mill (HSM) experiences thermal shock owing to changes in temperature from initial boundary conditions. The thermal expansion owing to the change of temperature is a major contributing factor to the final shape or the profile of the strip generated at different stands of finishing stands of the HSM. A mathematical model has been developed for the prediction of temperature profile for the surface and the inner depth of the roll in the finishing stand of a HSM. The numerical result from the model calculates the temperature profile in each stand of six finishing stands of the HSM and the corresponding thermal expansion at different stands. The temperature profile and the thermal expansion of the work rolls for a complete rolling schedule have been found from this model. The measurement of the thermal expansion has been found to match closely with the calculated one.     

Synthesis of ultrafine TiC1–X and Ti(CN) powders via planetary milling

Abstract

Ultrafine TiC_1-X and Ti(C,N) powders 100-200 nm in size were synthesised through mechanical alloying for cutting tool applications. Elemental titanium and carbon were processed by a high energy planetary mill in air, argon and nitrogen atmosphere. With variations in the Ti/C ratios, the characteristics of synthesised powders were investigated. Of three atmospheres, argon was effective in synthesising pure TiC_1-X powders. However, the presence of oxygen seemed to interfere with carbon and nitrogen diffusion into TiC lattice. Nitrogen exhibited a stronger affinity with titanium than carbon in forming the Ti(C,N) phase. This study shows the parameters used to determine the final compositions of synthesised TiC_1-X and Ti(C_1-XN_X).     

Numerical determination of heat transfer coefficient for boiling phenomenon at runout table of hot strip mill

Abstract

The heat transfer coefficient during film boiling at the runout table of the hot strip mill is usually determined by experimental methods. Described in the present paper is a finite difference based model for analysis of the thermal behaviour of the strip during cooling at the runout table of the hot strip mill at Tata Steel, India. The model, developed for the prediction of strip temperature, is used to determine the heat transfer coefficient at the water/strip interface while water cooling occurs. A simple form of polynomial as a function of the strip surface temperature is proposed to describe the heat transfer coefficient at the water/strip interface. Good correlation has been found between model predicted temperatures considering the polynomial type heat transfer coefficient and the actual coiling temperature.