Crystal growth in liquid steel during secondary metallurgy

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.     

粉末冶金在钢铁企业的应用及发展前景

概述了粉末冶金的技术特点以及含铁粉尘在钢厂的应用情况;分别阐述了钢铁企业直接还原铁在炼钢中的应用、以及还原铁粉和雾化铁粉的生产过程;列举了JFE、神户制钢公司开发的粉末冶金制品及其应用领域,以及我国武钢、莱钢粉末冶金技术的进步;分析了铁基粉末冶金行业发展的影响因素,汽车工业的发展、以及切削刀具行业对高速钢性能要求的提升,促进了铁基粉末冶金零部件种类和数量需求的快速增长;指出了钢铁企业在当前的困境条件下,应加速发展铁基粉末冶金技术,发掘企业新的利润增长点,并实现资源的综合利用。     

Niobium-Alloyed high speed steel by powder metallurgy

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.     

高摩擦力矩值钢纤维增强粉末冶金摩擦材料

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.     

粉末冶金渗铜钢的摩擦磨损性能

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。     

我国钢铁工业冶金石灰技术进步回顾与展望

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.     

易切削高硫钢的冶炼工艺探讨

探讨了硫在易切削钢中的作用，还原期造渣工艺和硫的加入方法对硫回收率的影响。     

Modern trends in the development of ladle metallurgy and the problem of nonmetallic inclusions in steel

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.     

Effect of furnace atmosphere on sintering process of chromium-containing steel via powder metallurgy

During a powder metallurgy process such as sintering,the primary role played by the atmosphere in furnace is to prevent an excessive oxidation of powder compact...     

粉末冶金制备高氮不锈钢的研究进展

概述了加压冶炼制备高氮不锈钢存在的问题,介绍了粉末冶金制备高氮不锈钢的发展现状,其中包括高压气雾化法、机械合金化法等高氮不锈钢粉末制备技术,和注射成形、热等静压成形、热挤压、粉末包套烧结–自由锻造、等离子烧结成形等高氮不锈钢粉末致密化及成形技术,指出了粉末冶金制备高氮不锈钢存在的问题,并对其未来的发展趋势进行了预测。     

15Cr-15Mn-0.4N不锈钢冶金缺陷分析

结合现场生产工艺,分析了15Cr-15Mn-0.4N不锈钢棒材圆心部位点状偏析形成的机理.结果表明,点状偏析是由于存在大量的含Nb析出物以及聚集的大量夹杂物而形成的.调整AOD吹氮工艺,加强钢液的吹氩搅拌操作,以及在加入合金后保持充分的冶炼时间,有利于减少此类偏析现象和夹杂物缺陷的发生.     

制动条件对粉末冶金航空刹车副钢对偶金相组织的影响

欧美飞机常使用的粉末冶金航空刹车副选用粉末冶金刹车材料和钢对偶材料配对作为摩擦偶以达到制动目的,而其钢对偶材料组织在使用过程中的变化一方面反映了航空刹车副所经历的刹车过程累计状况,另一方面也将影响刹车副的正常制动性能.作者研究了不同制动条件如正常着陆刹车、中止起飞、极限磨损状态中止起飞等3种条件下,粉末冶金航空刹车副钢对偶材料30CrSiMoVA的组织变化情况,并初步比较了不同组织状况下刹车副的摩擦磨损性能.研究结果表明,在3种条件下,表面均形成了塑性变形区.在正常着陆条件下,内部组织由回火索氏体转变为板条状马氏体;而在中止起飞和极限磨损状态中止起飞条件下,钢对偶材料组织则发生更为显著的变化.体现在恢复性试验中,刹车压力需求明显增大.