Properties of fine metal powders produced by the formate pyrolysis method

Conclusions Optimum parameters have been determined for the processes of preparation of fine copper, nickel, and cobalt powders by the pyrolysis of formates in a protective argon atmosphere. Use of fine copper, nickel, and cobalt powders prepared by this method as interlayers in the vacuum diffusion welding of copper and steel parts enables the temperature of the process to be substantially lowered. Copper coatings can be applied to metallic and nonmetallic materials in the course of the pyrolysis of copper formate.Translated from Poroshkovaya Metallurgiya, No. 3(207), pp. 1–6, March, 1980.     

Activation of the sintering process of iron powders by introducing nanodispersed additives

The results of studying of the effect of additions on nanodispersed iron powder (Fe-NP) obtained by the electrical explosion method on the formation and sintering of industrial coarse-grain iron powder are presented. The effect of amount of Fe-NP added to the charge material on compactibility and moldability of compacts, properties, microstructure, and phase composition of sintered material is analyzed. Electrically explosive Fe-NP is shown to be low-technologic. Charges based on the coarse-grained iron powder that contain up to 20% Fe-NP have good compactibility and moldability. It is established that introduction of Fe-NP into the charge causes activation of sintering and is favorable for obtaining the sintered samples with fine-grain crystalline structure and increased physicomechanical characteristics. The effect of amount of the Fe-NP addition to effective activation energy of sintering is evaluated.     

Properties of iron and low-alloy powders produced by the Sulinsk Metallurgical Plant

Translated from Poroshkovaya Metallurgiya, No. 2(350), pp. 101–106, February, 1992.     

PREP法制备球形NiTi合金粉末的特性及显微组织

以NiTi合金棒材为原料,采用PREP法(plasma rotating electrode process,等离子旋转电极雾化法)制备球形镍钛(NiTi)合金粉末,粉末粒度主要分布在60~125μm之间。通过扫描电镜(SEM)、X射线衍射(XRD)与差示扫描量热分析(DSC)等,对不同粒度的NiTi粉末显微组织进行表征。结果表明,粒径较大颗粒(≥178μm)的冷凝组织为胞状晶组织,小尺寸颗粒(≤40μm)表面光滑,无明显结晶组织;大尺寸颗粒主要以B2相为主,同时含有少量Ni_3Ti、NiTi_2二次相,随粉末粒度减小,二次相的生长受到抑制;不同粒径的NiTi合金粉末由于冷却速率不同最终导致相变点温度不同,粒度≥178μm的大颗粒粉末由于发生共析反应生成二次相,使得B2-NiTi相内Ni含量减少,最终导致该粉末的相变点温度高于粒度≤40μm粉末的相变点温度。     

High-dispersion iron powders produced by the thermochemical method

The problem of producing high-dispersion iron powders is very complicated because of the fact that these powders are highly pyrophoric and, consequently, the number of methods of production of these powders is limited. Another difficulty is that the majority of these methods do not make it possible to vary the properties of microcrystals in the required range and this greatly restricts the application of powders. Institute of Colloidal Chemistry of Water, National Academy of Sciences of the Ukraine. Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 1–4, May–June, 1998.     

铁矿烧结过程微细颗粒物排放行为

 采用ELPI+设备(荷电低压撞击器)对铁矿烧结过程微细颗粒物进行在线检测与采样,利用场发射扫描电子显微镜(FESEM EDS)对采集的颗粒物形貌特征进行分析,研究铁矿烧结过程中微细颗粒物的排放行为。研究结果表明,PM10大量释放集中在烧结升温段,且颗粒物质量浓度与数目浓度在粒径分布上有较大差异,其中质量浓度峰值区间为5.37～10.00 μm,数目浓度峰值区间为0.10～0.16 μm;形貌特征上,微细颗粒物呈规则的球形、方块形和片状;不同粒径物质组成差异明显,其中颗粒物中的K、Na主要以KCl和NaCl的形式存在,含量随颗粒物粒级的增大而略有降低。     

Study of the sintering of nickel powders produced by different methods

Conclusions It was established in this investigation that, in the temperature range 500–700°C, carbonyl nickel powder is subject to more intensive sintering than electrolytic nickel powder. The theory of diffusional viscous flow is unsuitable for this case, and needs revision.It is shown that crystal lattice distortions, as determined by x-ray diffraction methods, do not cause an increase in the rate of sintering. Hypotheses are put forward for the possible mechanism by which diffusional mobility is increased in the case of carbonyl nickel.     

铁矿烧结过程烟气中微细颗粒污染物的特性

铁矿烧结过程分为点火段、中间段(点火结束至烟气温度升温前)和升温段(烟气温度开始上升至达到最高温)3个阶段,通过烧结杯模拟实验研究了各阶段烟气中微细颗粒污染物的排放浓度及其特性.研究结果发现,点火段、中间段微细颗粒污染物的质量浓度较低,在升温段则显著上升;各阶段切割粒径d50=0.7μm粒级颗粒表面形貌也存在着差异,其中点火段和中间段的颗粒主要是由球形颗粒组成,颗粒轮廓清晰没有明显的聚结现象,而升温段d50=0.7μm粒级颗粒主要为不规则的絮状体,颗粒之间易聚结形成团聚状;升温段d50=0.7μm粒级颗粒中F、S、K、As、Pb元素的含量明显高于点火段和中间段的含量,而Fe元素则在点火段和中间段的含量较高,在升温段含量相对较低.     

铁精矿粉粒度对精控还原工艺的影响

本文以河北承德地区的铁精矿粉为原料,选用模拟隧道窑还原工艺制备海绵铁粉,研究了铁精矿粉粒度对精控还原工艺的影响。结果表明:铁精矿粉粒度对其还原工艺影响很大,并直接影响海绵铁粉的产品性能。在既定试验条件下,随着铁精矿粉粒度的增大,其精控还原所需最优还原温度随着增加,最佳配碳量先减少后增大,而最佳还原时间随粒度的增大呈现出先增大后减小的变化趋势。究其原因为粒度过小导致的粉体烧结和粒度过大导致的粉体芯部不易还原均会阻碍还原过程的进行。45~75μm粒度区间铁精矿粉最适合作为制备优质海绵铁粉原料,其在配碳量0.8、还原温度1150℃、还原时间4.5 h的精控还原工艺下可制得的海绵铁粉的铁含量高达97.88%。     

Permanent magnets from fine iron and iron-cobalt alloy powders

Conclusions It has been established that, to obtain the optimum, magnetic properties in isotropic materials from fine iron and iron-cobalt alloy powders, the powders should be heat-treated for 4 h at a temperature of 280°C and compacted under a pressure of 15–16 kbar. Heat treatment tends to destroy dendritic axes of the second and third orders on the powder particles, heal structural defects, and increase the flowability of particles during pressing, thereby ultimately improving the magnetic properties of the resultant components. The maximum magnetic energy is 4.6 kJ/m³ for isotropic magnets from iron powders and 8.6 kJ/m³ for magnets from iron-cobalt alloy powders.Translated from Poroshkovaya Metallurgiya, No. 10 (142), pp. 61–63, October, 1974.