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Crystal growth in liquid steel during secondary metallurgy 总被引:1,自引:0,他引:1
Morphology of nonmetallic inclusions depends on their crystallographic structure, the growth conditions, and the presence
of impurities. Inclusions were extracted from industrial aluminum-killed steel samples and investigated under high-resolution
scanning electron microscopy. In this article, the morphology of these aluminum oxide inclusions, including their surface
features, is approached from the viewpoint of crystal growth. Commonly, aluminum oxide inclusions are considered to be corundum,
but some inclusion shapes prove that other aluminum oxide polymorphs are present as well. 相似文献
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A philosophy for the use of strong carbide formers like niobium in high speed steels is described. It follows the concept
of independently optimizing the compositions of the matrix (for maximum secondary hardening potential) and the volume fraction
of the blocky carbides (for protection against abrasive wear). Normally, the two are interdependent through the action of
the solidification equilibria, but separate control becomes possible when the blocky carbides are formed by a strong carbide
former such as niobium. During normal ingot solidification, such strong carbide formers would produce very large primary carbides.
This can be avoided by atomization and powder metallurgical processing. In this way, a steel has been produced whose matrix
composition is similar to that of AISI M2, and whose primary carbides are all of NbC type. Its composition is 1.3C, 2W, 3Mo,
1.6V, 3.2Nb (wt pct). Because of its high stability, NbC is a much more effective obstacle to grain growth than the normal
high speed steel carbides, and this allows substantially higher austenitization temperatures to be used. Despite its leaner
composition, the Nb-alloyed steel matches the cutting performance of AISI M2, and its secondary hardening seems to be more
persistent at high temperatures. 相似文献
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高摩擦力矩值钢纤维增强粉末冶金摩擦材料 总被引:6,自引:3,他引:3
樊毅 《粉末冶金材料科学与工程》2008,13(3)
成功地制备了一种在0.25~0.30 MPa低制动压力和0~2 000 r/min转速下产生高力矩的铜基粉末冶金摩擦材料,通过加入6%~9%(质量分数)的低碳钢纤维有效地提高了该材料摩擦面上的微凸体数量,使偶面始终保持高咬合性,从而极大地提高了室温和热态条件下的摩擦稳定性,且在上述工况范围内工作时偶面上产生的力矩始终保持在24 N·m以上.在热态并接近零转速状态下,于旋转方向垂直悬挂20 kg重物,工作偶面不产生相对位移,可完全满足用户对摩擦材料的特殊要求. 相似文献
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近年来,汽车、建筑等领域对高强度-高塑性金属材料的需求日益增长,为了获得高强度-高塑性的金属材料,粉末冶金技术发挥着越来越重要的作用。通过放电等离子烧结技术(SPS)烧结质量比为2:1的马氏体钢和奥氏体钢混合金属粉末,复合钢的奥氏体相均匀分布于马氏体相当中,试样致密度高达95.5%,并通过后续的热轧处理,提高复合钢的烧结质量,致密度提高至98.9%。热轧后复合钢的屈服强度、抗拉强度、均匀伸长率和总伸长率分别为960 MPa、1 529 MPa、6.7%和6.7%。在热轧的基础上引入冷轧+短时间高温回火处理,粉末冶金复合钢性能进一步提高。其中冷轧30%/500℃回火5 min的复合钢,屈服强度、抗拉强度、均匀伸长率和总伸长率分别为1 899 MPa、1 964 MPa、9.2%和10.0%。 相似文献
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通过压制、预烧和熔渗,制备1种液压零件用粉末冶金渗铜钢。用UMT 3型摩擦磨损实验机评价该材料在边界润滑条件下的耐磨性,研究基体密度对渗铜钢摩擦磨损性能的影响,并与目前常用的耐磨合金进行摩擦磨损性能对比。结果表明:在边界润滑条件下,渗铜量相同,基体材料密度分别为6.40、6.60、6.80 g/cm3的粉末冶金渗铜钢摩擦副的摩擦因数相差不大,4 h的质量磨损量分别为1.70、1.50和3.10 mg;而传统耐磨合金中硬度较低的HMn58 2铜合金磨损量为24.10 mg,磨损较快。 相似文献
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烧结过程控制对粉末冶金整个工艺过程起着至关重要的作用,控制不好,将导致烧结后的零件在尺寸和性能上不稳定或达不到产品设计要求,并可能还会出现氧化、脱碳、渗碳、崩裂和积碳等工业中常见的问题。随着对粉末冶金产品的性能和成本控制要求不断提高,金属Cr因其价格低并具有很好的强化效果,成为粉末冶金工业开拓的重点方向。但是金属Cr容易氧化,对烧结气氛要求较高,因此对烧结工艺提出了挑战。随着烧结炉技术的发展和氮基保护气体广泛使用,在网带炉中烧结含Cr成分的零件已经成为现实。利用热电偶、氧分压和CO分析仪等设备组成的分析系统,评估了以氮氢混合气体作为保护气氛的网带烧结炉的实际烧结情况,分析了几种烧结过程中常见的缺陷及其原因,并提出了相应的改善措施,同时也总结了含Cr材料所需的烧结条件及其控制。 相似文献
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冶金石灰是钢铁生产中不可缺少的、数量最多的熔剂材料,主要消耗在炼钢和烧结生产中.我国是钢铁生产大国,但并非强国.我国钢铁工业实现由大向强转变,仍有许多方面需努力,特别是从提高钢铁产品质量、稳定钢铁原燃料供应、实现节能减排等诸多因素分析,冶金石灰当属需要改进的因素之一.本文总结了"十一五"期间,钢铁工业冶金石灰的生产与消耗变化,提出未来钢铁工业冶金石灰的技术进步方向. 相似文献
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E. Kh. Shakhpazov A. I. Zaitsev A. A. Nemtinov S. D. Zinchenko I. G. Rodionova S. V. Efimov N. A. Rybkin N. G. Shaposhnikov 《Russian Metallurgy (Metally)》2007,(1):1-9
The main trends in the development of the ladle treatment of steel have been analyzed. The most complex problem is shown to be the formation of nonmetallic inclusions having a certain type and a low concentration. The main parameters of the ladle treatment of steel that control the type and amount of nonmentallic inclusions in ready products are analyzed using the data of industrial heats, laboratory experiments, and physicochemical simulation and computation. The principles of control of steel purity in nonmetallic inclusions are formulated, and the main trends in the development of the concepts of nonmetallic inclusions are determined. 相似文献
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《Acta Metallurgica Materialia》1994,42(3):661-665
The magneto-mechanical behaviour of five steels, mild steel, HSLA 80, HY 80, HY 100 and a quenched alloy steel, has been investigated. Magnetic fields of the order of the Earth's field and compressive stresses up to 200 MPa were applied to the steels. The increase in magnetization due to stress cycling in a constant applied field and to field cycling at constant stress was measured. The results show that the differential permeability of the steel largely determines the magnetization increase and that steels with similar microstructures have similar magneto-mechanical response. The strength or hardness of the steel is a less reliable indicator of magneto-mechanical response. 相似文献
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