粉末冶金钢中的Cu

近年来,粉末冶金已成为一种可制造形状结构复杂、精度高及具有优异力学性能的零件的重要且成本可行的生产工艺。在铁基粉末冶金产品中,除碳外,Cu是应用最广的一种合金化元素。虽然Cu在锻轧钢中具有不良作用,但在粉末冶金钢中却具有显著强化作用。然而,Cu在烧结中会引起胀大,并且在与Fe粉的混合粉中倾向于偏聚,从而导致压坯的各部分组成之间发生变化,致使烧结件的尺寸显著分散。通过不同的方法将Cu粉粘结于Fe粉颗粒上,可有效地防止这种偏聚。本文评定了用不同的含Cu合金化系统得到的零件力学性能与尺寸变化。     

Thermomechanical processing of microalloyed powder forged steels and a cast vanadium steel

The effects of controlled rolling on transformation behavior of two powder forged (P/F) microalloyed vanadium steels and a cast microalloyed vanadium steel were investigated. Rolling was carried out in the austenitic range below the recrystallization temperature. Equiaxed grain structures were produced in specimens subjected to different reductions and different cooling rates. The ferrite grain size decreased with increasing deformation and cooling rate. Ferrite nucleated on second phase particles, deformation bands, and on elongated prior austenite grain boundaries; consequently a high fractional ferrite refinement was achieved. Deformation raised the ferrite transformation start temperature while the time to transformation from the roll finish temperature decreased. Cooling rates in the cast steel were higher than in P/F steels for all four cooling media used, and the transformation start temperatures of cast steels were lower than that of P/F steel. Intragranular ferrite nucleation, which played a vital role in grain refinement, increased with cooling rate. Fully bainitic microstructures were formed at higher cooling rates in the cast steel. In the P/F steels inclusions and incompletely closed pores served as sites for ferrite nucleation, often forming a ‘secondary’ ferrite. The rolling schedule reduced the size of large pores and particle surface inclusions and removed interconnected porosity in the P/F steels. Formerly Postgraduate Researcher in the Department of Metallurgy and Materials Science, UMIST/University of Manchester, United Kingdom     

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.     

铸铁中碳测定方法的改进

碳是铸铁中最重要的元素。因此,在铸造过程中需要经常对碳进行监控。取样过程非常关键,冷凝速度过慢就会产生石墨夹杂。然而,火花直读光谱仪进行测定时需要完全不含石墨的样品才能得到精确的测量结果。本文对这种要求的原因进行了研究和讨论,并对一种测定碳新方法的原理和可行性进行了阐述。该方法改进了测定未达到最佳标准要求的铸铁样品中碳含量的准确性,并能提示取样过程是否恰当。     

粉末冶金低合金钢的制备和性能研究进展

从粉末制备、成形工艺、烧结工艺和组织控制等方面,系统的介绍了国内外粉末冶金低合金钢的制备技术,并对其研究方向和应用前景进行了展望。     

Influence of a metal-oxide modifying mixture in ultrafine powder form on the physicochemical characteristics of IChKh28N2 cast iron

Wear-resistant IChKh28N2 cast iron is investigated by X-ray spectral phase analysis and scanning electron microscopy, with and without the introduction of a modifying mixture (d-metal oxides in the form of ultrafine powder and nanopowder) and cryolite (Na₃AlF₆) reducing agent. The elementary and phase composition is determined; the microstructure of the metal matrix and eutectic is studied. The introduction of a modifying mixture and cryolite reducing agent changes the morphological structure, shifts the ratio of the basic phases, reduces the corrosion rate, and increases the corrosion resistance.     

Substitution of graphite in powder metallurgical steels with carbon from petroleum products

Abstract

This paper reviews the mechanical and microstructural characteristics of hypoeutectoid steels obtained by powder technology, in which various carbonaceous petroleum products provide the carbon constituent. These steels are compared with others of similar composition obtained from graphite.     

Influence of carbon on the formation of structure during mechanical alloying and sintering of powder steels

The structure and properties of steels produced from powders in a thermodynamically nonequilibrium state with an increased dislocation density, cellular substructure, and ground subgrains are studied. A non-equilibrium state of powders was reached using mechanical alloying of iron with carbon. Sintered steels inherited the powder structure, and the physicomechanical properties increased with increasing amount of added mechanical energy and carbon content. The strengthening mechanism is associated with the formation of a cellular dislocation structure in iron in its mechanical alloying with carbon.     

Structure formation in and magnetic properties of a P/M iron-chromium-cobalt alloy

Conclusions A study was made of the dependence of the processes of structure formation in a P/M iron-chromium-cobalt alloy on heat treatment conditions. Optimum magnetic properties are attained in an alloy of this composition after 3-h sintering at a temperature of 1290±10°C, TMT, and stepwise tempering. The alloy investigated and the process developed can be employed for the industrial manufacture of permanent magnets.Translated from Poroshkovaya Metallurgiya, No. 9(237), pp. 60–63, September, 1982.     

高频红外碳硫测定仪测定铸铁中的碳

采用LECO CS-444红外碳硫仪对铸铁中的碳含量进行测定,通过屑状试样与块状试样的对比,证明利用块状制样测定铸铁中的碳含量准确可靠,并对样块大小、助熔剂的种类、助熔剂的加入量等条件进行试验,选择了测定铸铁中碳的最佳条件,解决了含石墨碳的铸铁定碳难的问题.