Effect of particle size on the magnetic properties of powders and finished pieces

Conclusions The properties of individual particles can be used as factors in predicting finished piece properties.Particle size and active surface retain their effect on finished piece properties for different sample treatment regimes.Translated from Poroshkovaya Metallurgiya, No. 1(253), pp. 73–76, January, 1984.     

Effect of high-voltage discharge on the particle size of hard alloy powders

Powder Metallurgy and Metal Ceramics - The effect of high-voltage discharge treatment of Fe–20% TiC and VK6–1% ASUD75 diamond powder mixtures on their particle size and morphology is...     

Effect of composition of copper-tin melts and bronzes on the particle size of powders produced by the electric-pulse disintegration of jets

Conclusions The results are presented of an investigation into the effect of composition of coppertin bronzes on the particle size distribution of powders and granules produced by the electric-pulse disintegration of a jet. On passing from copper to Cu-Sn alloys and then to pure tin, the proportion of fine fractions (< 160 m) grew from 7.5 to 22.7%, the amount of medium fractions also increased, and at the same time that of coarse fractions decreased, which was due to the surface tension of the melts falling from 1350 for pure copper to 540 mJ/m² for tin. Additions of 5% each of zinc and cadmium to Br 0–10 bronze resulted in the yield of fine fractions rising from 10 to 14.4 and 18.8%, respectively. The action of these elements consists in increasing the vapor pressure, which results in the generation of more powerful shock waves in the zone of the electric arcs appearing during breaks in the jet. The addition of phosphorus, which forms with copper a stable compound, has comparatively little effect on the particle size distribution of powders.Translated from Poroshkovaya Metallurgiya, No. 1(289), pp-1–4, January, 1987.     

Effect of cathodic current density on the structure of fine tin powders

Conclusions By varying electrolysis parameters it is possible to substantially change the structure and properties of granular systems based on finely divided electrolytic tin. Raising the cathodic current density from 0.5 to 7 A/dm² increases the mean size of the metal particles and decreases the specific surface of the metal powder.Translated from Poroshkovaya Metallurgiya, No. 10(190), pp. 11–14, October, 1978.     

球磨时间对钨粉粒度分布及形貌影响

通过改变球磨时间,获得不同粒度分布的钨粉颗粒,分析球磨时间对钨粉粒度分布和形貌特征的影响,提高粒度分布在目标区间（5～11 μm）的钨粉颗粒体积分数。结果表明,球磨的前2 h对原料中大颗粒钨粉的影响较大,钨粉颗粒最大粒径由134 μm迅速下降到20 μm左右。随着球磨时间的增加,钨粉粒度分布指标减缓下降,除粒径变小外,颗粒形貌基本无变化,但是在球磨10 h后开始出现团聚现象。综合分析可知,球磨时间的改变对钨粉粒度分布指标影响较大,球磨时间为8 h时,可获得粒度分布最窄的钨粉颗粒,在目标区间的钨粉颗粒体积分数达到75%。     

Effect of chemistry and particle size of cryochemical powders on the properties of humidity sensors

A comparative analysis of various sintered materials based on cryochemical powders was carried out. The electrical resistance of compacts of pure aluminum oxide and its mixtures with CoO, MgO, ZrO₂, and Y₂O₃ were compared with data on the specific surface area, phase composition, and pore size distribution in the sintered ceramics. Conclusions were drawn about the suitability of the materials as humidity sensors. Highest sensitivity was found in sensors based on aluminum—cobalt spinel, and aluminum—magnesium spinel mixed with zirconium oxide. Deceased. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(400), pp. 39–43, March–April, 1998.     

Control over the particle size of stainless-steel powders

Conclusions Replacing some of the metallic iron by ferric oxide, Fe₂O₃, in the charge for the preparation of Kh18N15 and Kh23N28 stainless-steel powders by the calcium-hydride reduction process increases (two- to threefold) the yield of the fine fraction (-0.063 mm) without affecting the apparent density of the powders (1.4–1.85 g/cm³) or the sponge shape of their particles. At the present time, stainless-steel powders are being manufactured using a charge in which 20–30% of metallic iron has been replaced by the oxide Fe₂O₃.Translated from Poroshkovaya Metallurgiya, No. 2 (134), pp. 1–8, February, 1974.     

Effect of the amount of electrolytic nickel in an iron charge on its distribution on the particle surfaces and on the powder particle size

Conclusions After the passage of 0.16 A · h of electricity per 1 g of the charge investigated, the amount of nickel in the powder was 13–14 wt.%. The surfaces of the powder particles, which had retained their original shape and dendritic structure, were covered with fairly even, 5- to 8-m-thick nickel layers. During nickel plating the powders coarsened as a result of coalescence of separate particles, which was especially pronounced with charges containing large nickel additions (up to 30–50%). Additional comminution of nickel-plated powders increased their fineness. The milling operation virtually restored the original fine particle size of powders containing 13–14% of nickel.Translated from Poroshkovaya Metallurgiya, No. 1(229), pp. 1–4, January, 1982.     

Effect of particle size on the amount of residual austenite in atomized high-speed steel powders

Conclusions The presence of -phase and decomposition of martensite in fine particles as a result of heating by large particles alter the relative intensities of the austenite and martensite lines. Because of this, determination of the amount of residual austenite in a fine fraction by the existing x-ray methods gives low results. A more accurate estimate of the amounts of residual austenite in fine and coarse particles is obtained by measuring the areas of corresponding austenite lines.Translated from Poroshkovaya Metallurgiya, No. 11(275), pp. 6–8, November, 1985.     

Effect of the solidification time on the median particle size of powders produced by water atomisation

Present empirical correlations to predict the median particle size of water atomised powders have a validity restricted to a particular atomiser and alloy family. This work proposes a mathematical function that takes into account the influence of the heat transfer coefficient and, therefore, of the solidification time on the median particle size. This equation is applied in combination with previously proposed empirical correlations to extend their validity to a broader range of alloys. Experiments were conducted with alloys of different melting point (Fe base, Cu base and Sn). Quantitative measurements of the median particle size, tap density and several shape factors, and qualitative observations of the particle shape confirmed the importance of the heat transfer rate. It is shown that the inclusion of the solidification time effect results in a better agreement between calculated and experimental data when both low and high melting temperature alloys are taken together.     

基于离散元的不同粒径配比粉末压制相对密度与力链分析

利用PFC三维数值模拟软件,通过改变粉末颗粒粒径分布建立各组冷压模型,得到压制过程中相对密度变化规律与力链分布情况。在特定粉末粒径配比下,能够得到相对密度最高的压坯。结果表明:在大、中、小粒径颗粒质量比为60:15:25的粒径配比下,压坯相对密度最高,压坯相对密度并不会随着细粉比例不断增加而一直提高;在压制过程中,随着附加细粉占比上升,压制方向上能产生更大应变。侧压系数与泊松比受粉末粒径分布影响较小,且在压制后期,在压坯已获得较高相对密度的情况下,会因缺乏足够的驱动力与位移空间发生下降;混合粒径粉末试样的力链数量远大于单一粒径粉末试样,在强力链数目充足的前提下,结合大量的弱力链能获得更高的压坯相对密度。     

Effect of current source characteristics on powder particle size in electric-pulse atomization

Conclusions Tests of a high-power current pulse source with a capacitive energy accumulator for the atomization of metal jets have shown it to be suitable for the production of very fine powders. Depending on the diameter of the jet being disrupted, there exists some limiting value of capacitor battery capacitance above which the particle size analysis of the powder undergoes no marked changes. Increasing the initial battery voltage at an unchanged battery energy is accompanied by a substantial increase in the yield of fine powder fractions.Translated from Poroshkovaya Metallurgiya, No. 1(265), pp. 5–10, January, 1985.