THE PROPERTIES OF PLATINUM-COBALT MAGNETS PRODUCED BY POWDER METALLURGY

Abstract

Improved and more consistent magnetic properties can be obtained from platinum-cobalt alloys produced by powder-metallurgy techniques. The importance of heat-treatment is emphasized, and for optimum permanent-magnet properties it is shown that the equiatomic stoichiometric alloy should be employed. Magnetic measurements demonstrate that energy products < 10 × 10⁶ gauss-Oe, and coercive forces up to 4900 Oe can be achieved.     

EFFECTS OF PARTICLE SIZE ON THE SINTERING KINETICS IN TUNGSTEN POWDER

Abstract

An experimental study has been made of the effects of initial particle size on sintering kinetics in tungsten powder within the temperature range 1100–1500°C. Particle size, compacting pressure, sintering time and temperature all influence the rate of sintering. Isothermal changes in density and volume have been measured. The results indicate grain-boundary diffusion as the mechanism principally responsible for material transport in the case of particle sizes <4 μ Surface diffusion appears to bethe mechanism of material transport in compacts with particle sizes of 14– 16 μ The temperature-dependence of the rate of sintering is characterized by activation energies of 101± 2 and 72± 2 kcal/mole for fine particles (< 4 μ) and coarse particles (14–16 μ), respectively.     

INFLUENCE OF TIN POWDER CHARACTERISTICS ON THE SINTERING OF IRON-TIN-COPPER POWDER COMPACTS

Abstract

In view of increasing industrial interest in the use of tin additions as an aid to the sintering of iron-based powder compacts, an examination has been made of the influence of the characteristics of the tin powder on sintering performance.

The effect of additions of narrow size-range fractions of atomized tin powder on the dimensional changes and tensile properties obtained on sintering Fe-Sn-Cu compacts made with –100 mesh (–152 μm) or – 300 mesh (– 53 μm) sponge iron and – 300 mesh (– 53 μm) atomized copper powders has been determined. The compacts contained tin and copper in the ratio 2:3. The narrow size fractions were separated from – 300 mesh tin powder by air elutriation. It was found that the use of coarse tin powder reduced the tensile strength of – 300 mesh iron-based Fe–1% Sn–1 ½% Cu compacts, but had no influence when this mixture was based on –100 mesh iron powder, or when the mixture composition was Fe–2% Sn–3% Cu. The effects have been examined in relation to the sintering mechanism by scanning electron microscopy and by X-ray microanalysis.     

邢钢烧结配加白云石粉的探讨

介绍了邢钢4台28m^2烧结机配加白云石粉代替轻烧白云灰的工业试验,在保持烧结矿MgO不变的条件下,分析了白云石粉对烧结生产、质量和冶金性能的影响。     

注射成形在NdFeB烧结永磁体中的应用

比较了用快淬法、HDDR法、机械合金化法、和气体雾化法生产NdFeB水磁体的制备方法及其特点，指出采用气体雾化制备的磁粉较适宜于注射成形生产；对注射成形生产烧结NdFeB水磁体时枯结剂、成形及取向、脱脂和烧结工艺参数进行了总结，介绍了热塑性体系和水溶性体系枯结剂在注射NdFeB烧结磁体中的应用；将注射成形和传统模压成型的NdFeB磁体性能进行了对比；在分析现状的基础上，指出了现阶段存在的问题和发展方向。     

粉末冶金烧结炉的结构设计及发展趋势

介绍了用于粉末冶金机械零件生产的不同类型烧结炉的结构和设计,包括炉体构件、传输方式和机构、各温度带的功能、气氛及其控制,并着重介绍了步进梁式烧结炉的特点,同时简述了烧结炉某些新技术的发展。     

加入纳米Ni粉对微米级Fe粉试样烧结工艺及性能的影响

进行了真空状态下微米级Fe粉试样以及加入纳米Ni粉的微米级Fe粉试样的烧结试验。得出如下结论:添加1%纳米Ni粉的微米级Fe粉试样在900℃真空烧结2h的烧结体强度(289.61MPa)比微米级铁粉试样的烧结体强度(255.47MPa)提高13.4%。在保持烧结性能不降低的前提下,添加1%纳米Ni粉可使微米级Fe粉的烧结温度降低100℃或烧结时间缩短1h。     

THE INFLUENCE OF VAN DER WAALS FORCE ON THE SINTERING OF GLASS

Abstract

The contribution of van der Waals forces to the sintering of glass particles has been estimated. The contribution appears to be small relative to surface-tension forces in practical cases, but may be of importance in the formation of the initial bond during sintering.     

THE DRIVING FORCE FOR SHRINKAGE IN COPPER POWDER COMPACTS DURING THE EARLY STAGES OF SINTERING

Abstract

The shrinkage behaviour of compacts from irregular copper powder during the initial stages of sintering has been determined by a dilatometric method. The effects of compacting pressure and of external load during sintering at a constant heating rate of 3°C/min upon shrinkage were observed. The residual stresses present on the surface of compacts heated at the same rate to temperatures of 200, 300, 400, 500, and 600°C were also measured. It was observed that shrinkage starts at temperatures where considerable residual stresses in the surface of the compacts are still present, and that this temperature also depends upon the external stress applied during sintering. Residual and externally applied stresses complement each other in shifting the temperature of start of shrinkage to lower values with increasing stress. It is concluded that, in the low-temperature range up to 400°C, residual and externally applied stresses, rather than surface-tension forces, cause shrinkage.     

机械活化对Mo-Cu粉末烧结行为的影响

对机械活化粉末施以液相烧结制备了Mo-Cu合金,经后续处理后达到了完全致密化。结果表明,机械活化可以显著促进该体系的液相烧结,大大缩短了烧结致密化所需要的时间。随机械活化时间的延长,促进液相烧结的效果越明显。     

奥氏体不锈钢粉末压坯的液相烧结

综述了添加元素对奥氏体不锈钢粉末压坯液相烧结行为及材料性能的影响。加铜可以改善材料的耐腐蚀性并提高其力学性能；加硅可以提高材料的力学性能，特别是韧性；加铝影响材料的致密化行为。     

首钢京唐烧结配加阿特拉斯粉的试验

随着优质铁矿粉供应量的逐年减少及其性价比的降低,扩大高性价比进口矿品种及用量成为必然趋势。首钢京唐公司根据烧结生产的原料条件,进行了配加阿特拉斯粉的工业试验。试验结果表明:在目前烧结原料条件下,阿特拉斯粉配比不超过8%时,烧结矿中的SiO_2、Al_2O_3、TFe含量变化不大,烧结矿的粒度控制较好,可获得较好的综合烧结指标。     

用煤粉代替焦粉的烧结实践

广钢的烧结燃料是焦粉,燃料成本偏高。为降低燃料成本,决定用价格较低的无烟煤粉代替焦粉,在烧结杯实验的基础上,进行了生产试验,取得了降低烧结燃料成本的成效。研究与实践表明,煤粉配入比例占燃料的40%左右比较合适。     

预混合粉材料烧结

深入了解预混合粉材料的烧结,对促进铁基粉末冶金零件产业的发展具有重要作用.这涉及到固态烧结与液相烧结两个方面.本论文讨论了添加下列合金元素粉末的预混合粉材料的烧结:(1)石墨粉;(2)镍粉与石墨粉;(3)铜粉与石墨粉;(4)磷铁粉状的磷;(5)硼铁粉状的硼.另外,还讨论了这些材料的显微组织与力学性能.     

SINTERING KINETICS OF OXIDE-FILMCOATED COPPER POWDER

Abstract

The sintering kinetics of pure copper powder and of copper powder coated with a critical oxide (CU₂O) film thickness (～,500Å), has been studied by following the densification of the compacts as a function of temperature and time in pure dry hydrogen and in vacuum. The activation energy for the sintering of pure copper powder in hydrogen was 55,000 cal/mole, suggesting that the volume self-diffusion mechanism predominates during the sintering process. In the case of the oxide-coated powder the corresponding value was 37,000 cal/mole. The high rate of sintering of the coated powder in hydrogen and in vacuum is explained in terms of an activated sintering mechanism.     

THE INFLUENCE OF SILICON AND OTHER ELEMENTS IN CONTROLLING INTERPARTICLE FRICTION AND SINTERING OF BERYLLIUM POWDER

Abstract

The effect of small additions of activating elements such as silicon on the consolidation behaviour of beryllium powder has been investigated. Evidence is given that compacts of activated powder have more uniform high density than those produced from non-activated material. Studies carried out on prepared beryllium discs show that silicon modifies the micro-structure of the surface layer of beryllium oxide and, in consequence, affects its sliding behaviour and bonding characteristics.

From these results a model is proposed to account for the observations made on both sintered and hot-pressed beryllium which leads to the conclusion that, in addition to interparticle bonding, some measure of metal particle rearrangement is necessary for maximum densification. Activating elements may, in modifying the surface characteristics of the individual powder particles, assist in achieving an improved balance between particle sliding on the one hand and interparticle bonding on the other. In taking into account the bulk consolidation characteristics as well as the micromechanics of the process, the model also explains the observed influence of particle-size distribution on porosity in the compact.

The extent to which friction and sliding can influence compaction has been demonstrated by using a system of coloured Plasticine balls to simulate individual powder particles. Analysis of the behaviour of the Plasticine compacts substantiates the proposed model of the hot pressing of beryllium powder.     

承钢钒钛矿“100％外配焦粉烧结”工艺的应用研究

承钢烧结厂采用“100％外配焦粉烧结”,提高了钒钛矿强度和烧结机生产率,降低了固体燃耗。     

配加澳大利亚Mac^TM粉矿的烧结杯试验

进行了烧结混匀料配加澳大利亚Mac^TM粉矿的试验，增大Mac^TM粉矿配比烧结矿转鼓强度和成品率没有明显变差，但需要增大烧结料水分以保证较高的成球率；由于Mac^TM粉矿含有5％左右的结晶水、烧损较高，随其配比加大，烧结矿的烧成率逐步下降。     

配加澳大利亚MacTM粉矿的烧结杯试验

进行了烧结混匀料配加澳大利亚MacTM粉矿的试验,增大MacTM粉矿配比烧结矿转鼓强度和成品率没有明显变差,但需要增大烧结料水分以保证较高的成球率;由于MacTM粉矿含有5%左右的结晶水、烧损较高,随其配比加大,烧结矿的烧成率逐步下降.