Study on Oxygen Content, Inclusions and Fatigue Properties of Bearing Steels Produced by Different Processes

The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continuous casting (CC) and electroslag remelting (ESR) have been investigated. The main results obtained are as follows: (1) Due to low oxygen content and dispersion inclusions in steel, the fatigue life of LF-VD-IC or CC is three times as high as that of EAF steel; (2) The oxygen content in steel produced by CC process is about 9.0× 10-6, the carbon segregation (C/C0) is from 0.92 to 1. 10 and the fatigue life of CC steel is equal to that of ladle refining ingot casting steel; (3) Although the amount of inclusion and oxygen in ESR steel is higher than that of LF-VD-IC or CC steel, the fatigue life of ESR steel is higher than that of the latter because of its fine and well dispersed inclusions.     

钛合金真空自耗电弧熔炼技术发展

目前,生产钛及钛合金铸锭的基本方法仍为真空自耗电弧熔炼方法。讨论了真空自耗电弧熔炼钛合金的常见铸锭缺陷和预防措施。回顾了近代真空自耗电弧熔炼（VAR）技术的发展。较详细地介绍了为获得更高质量的铸锭,当前对VAR熔炼过程控制技术所作的努力及取得的进展。指出了未来真空自耗电弧熔炼控制技术的发展方向。     

5Cr5MoWSI（A8）工具钢锻材的研制

介绍了采用中频炉熔炼－电渣重熔－锻造流程生产５Ｃｒ５ＭｏＷＳＩ（Ａ８）工具钢锻材的研制工艺。     

Mechanism of Slag Composition Change During Electroslag Remelting Process

 The mass loss rate of CaF2-CaO-Al2O3-SiO2-MgO slag system originated from ANF-6 was studied with CaF2, CaO, Al2O3, SiO2 or MgO content as variables. The method of quadratic regression orthogonal design was used for the design and analysis of the experiment. The experimental results indicated that mass loss rate of slag can be increased by 6% with CaF2 changing from 50% to 65%. Mass loss increases with SiO2, Al2O3 and MgO adding and decreases with CaO content increasing. Because of the reaction between oxide and fluoride in the slag pool, apparent mass loss of CaF2-Al2O3-CaO-SiO2-MgO slag system appears at melting point. This will cause obvious composition change of electroslag. In addition, the segregation occurs in the slag skin forming process. This is another reason causing the composition change of electroslag.     

电渣重熔与连铸轴承钢中的夹杂物

研究了电渣重熔前后钢中氧及夹杂物的变化,结果表明:用电渣重熔工艺生产轴承钢,虽然氧含量比连铸钢高,但其大颗粒夹杂物数量少,尺寸较小,分布均匀,因此疲劳寿命高.     

Microstructure and Mechanical Properties of Modified M2 High-Speed Steel by Adding La2O3 in the Electroslag Casting Process

An electroslag casting method is used to add rare-earth La to M2 high-speed steels by adding La₂O₃ into the molten slag. The effects of the La content on the microstructure and mechanical properties of M2 high-speed steel are studied. The results show that rare-earth La is effectively added to steel by taking advantage of the decomposition of La₂O₃. The rare-earth La partially modifies the pre-existing oxide and sulfide inclusions into small and spherical rare-earth oxysulfide inclusions. By adding an appropriate amount of La, the as-cast iron dendrite matrix and coarse eutectic carbides can be refined, the carbide content is reduced, the carbide network is broken, and the decomposition of M₂C into M₆C and MC is promoted. After heat treatment, the network breaking and spheroidalization of the carbides are further facilitated, and the carbide content is reduced. The impact toughness and bending strength of the studied samples are improved by modifying the inclusions and optimizing the microstructure.     

高速钢选择与应用探讨

简要分析了高速钢市场变化，介绍了国内高速钢生产概况及电炉冶炼和电渣重熔高速钢的优缺点，针对高速钢销售服务和选择应用过程中出现问题的指出：选择高速钢应重视生产供应商（品牌）的选择，并对改善高速钢品质和热处理提出建议。