Structural and morphological investigations of an atomized iron powder

Conclusions The surfaces of the particles of a powder subjected to decarburizing-reducing annealing consist of masses of interwoven fibrous metallic formations, thanks to which the powder exhibits good compactibility. The fibrous formations have been found to have structural features suggesting that a gaseous phase participates in their growth. Material transfer is apparently effected by transport reactions. The transporting agent is carbon monoxide forming as a result of oxidation of carbon in the atomized particles by the oxygen of oxide phases during annealing. Growth of the fibrous formations is due to the carbonyl process, made possible by the structural features of the starting powder, which enable high gas pressures to be generated.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 16–22, August, 1985.The authors wish to thank S. P. Gordienko for assistance with the mass-spectrometric investigation and E. I. Givargizov and S. M. Solonin for their interest in the work.     

Choice of oxygen-to-carbon ratio in an atomized cast iron powder in iron powder manufacture

Conclusions The supply to the reactor of a reducing gas for the reduction-decarburization of an atomized cast iron powder has no effect on the width of the range of permissible O/C ratios in the resultant powder. Industrial self-reduction in cases where no reducing atmospheres are available should be carried out, using an atomized jast iron powder with an O/C ratio of 1.4±0.25, in continuous annealing furnaces provided with lock chambers at their charging and discharging ends.Translated from Poroshkovaya Metallurgiya, No. 8(248), pp. 103–105, August, 1983.     

Structural and morphological investigations of an atomized iron powder. I. Investigation of particles of a starting powder

Conclusions The particles of practically all fractions of a pig iron powder generally have internal voids and a conchoidal structure. The voids in the particles form as a result of a carbon oxidation reaction taking place during the atomization of molten metal, which is accompanied by evolution of gaseous products. The degree of oxidation of fine atomized powder particles is greater than that of large ones. The oxide phase in the powder is composed of almost pure iron oxides: FeO, Fe₃O₄, and, to a smaller extent,-Fe₂O₃.Translated from Poroshkovaya Metallurgiya, No. 7(271), pp. 7–11, July, 1985.     

Kinetics and thermodynamic characteristics of the reduction-decarburization-carburization of an atomized cast iron powder in converted gas

Conclusions An investigation into the kinetics and thermodynamic calculations of the reduction-decarburization-carburization of an atomized cast iron powder in a converted gas stream (heating to 1000 or 1100°C), together with a comparison of these annealing processes with each other and with a self-reduction process (heating to 1000 °C), have shown the following. The highest rates of reduction and decarburization are attained simultaneously, but both maxima are displaced to an earlier stage by supplying a converted gas stream to the reactor (as opposed to self-reduction under the same temperature and time conditions) and to an even earlier stage by raising the temperature from 1000 to 1100°C (under the same conditions of supply of a converted gas stream to the reactor). In annealing with heating to 1000°C the realized percentage of the reducing power of the carbon contained in the powder and of the converted gas is twice as high as in annealing with heating to 1100°C. Self-reduction under the same temperature and time conditions is characterized by the highest percentage realization of thermodynamic reducing power, which is 1.5–2.2 times that in the annealing of the powder in a converted gas. After 20-to 30-min annealing in a converted gas the material is characterized by the lowest carbon content, and increasing the duration of annealing raises its carbon content to a level closer to that of the carbon potential of the surrounding gas phase. During annealing in a converted gas with heating to 1000°C the true carbon content of the sponge quite quickly approaches the carbon potential of the gas, whereas during annealing with rapid heating to 1100°C the process of secondary carburization of the sponge is strongly inhibited, probably as a result of densification both of the surface of the sponge itself and of the surface layers of the sintered powder particles forming the sponge. In annealing in a converted gas raising the temperature from 1000 to 1100°C is not beneficial from the point of view of intensity of reduction, but markedly decreases the intensity of undesirable carburization.Translated from Poroshkovaya Metallurgiya, No. 2(254), pp. 12–19, February, 1984.     

棒磨工艺对水雾化铁粉松装密度的影响

为了更加合理有效地控制水雾化铁粉的松装密度，研究了水雾化铁粉棒磨系统棒头的转速、棒头的长度和筛底空隙宽度对粉末松装密度的影响。发现：将棒头的转速从700r／min提高到1100r／min时，松装密度由2．76g／cm^3提高到3．17g／cm^3，棒头长度从22cm加大到26cm时，松装密度由3．24g／cm^3降低到2．76g／cm^3；筛底空隙宽度从0．6cm增加到3．0cm时，松装密度由3．24g／cm^3降低到2．81g／cm^3。结果表明：上述3个因素的合理调配能较好地满足各种不同使用条件对雾化铁粉松装密度的要求；将该方法使用于生产中来控制松装密度，不仅能提高生产效率、降低生产成本，而且为产品的稳定性提供了可能。     

Properties of high-speed steel blanks produced by hot exteusion of atomized powder

Conclusions Hot extrusion of high-speed steel powder enables metal of 100% density to be obtained. The quality of P/M 10R6M5K5 high-speed steel produced by hot extrusion of powder, as assessed by all the indicators investigated, is comparable to that of the same steel produced by hot gasostatic pressing followed by forging.Translated from Poroshkovaya Metallurgiya, No. 9(213), pp. 23–27, September, 1980.