马钢炼钢污泥直接配入烧结混合料系统的研发及使用

针对马钢炼钢污泥产出量大、处理困难的现状,在研究国内污泥处理方法的基础上,提出滚筒给料,对辊打碎,大批量处理的新方法并立项攻关.经过研发、生产检验,证明该污泥配加系统原理可行,处理量大且不影响烧结生产,效益显著.     

LF精炼及后道工序钢中氮、氧含量控制技术研究

论述了各种不同工艺技术对控制钢中较低氮、氧含量水平的作用.指出,LF炉采用泡沫渣工艺和连铸保护浇铸,可有效降低钢中的氮含量;采用LF炉渣洗工艺及控制钢水的浇铸温度等措施,对降低钢中的氧含量有明显的效果.     

宝钢纯净钢生产技术进步

重点叙述了宝钢在钢中碳、氮、氧、磷、硫以及夹杂物控制方面的技术进步.并介绍了宝钢IF钢、管线钢所达到的纯净度综合水平.     

洁净钢冶炼技术在首钢的应用

以转炉终点控制、LF-VD精炼及连铸过程防止卷渣和二次氧化为主线,简述了首钢近年来在洁净钢冶炼技术方面所取得的一些进展.对钢帘线的[O]、[N]及Al5含量及夹杂物数量和形态控制进行了分析.     

锰球团矿在电炉炼钢中的应用研究

综述了锰矿直接合金化炼钢的研究及应用现状 ,讨论了其原理及工艺 ,重点讨论了锰矿合金化的动力学过程。     

Optimization of power input diagram of 50 t UHP-EAF

In order to improve operation for shortening tap to tap time and saving electrical energy, on the base of no-linear reactance model, the electrical characteristics of the 50 t UHP-EAF in Fushun Special Steel Co. Ltd. were analyzed. Considering steelmaking process conditions, the optimum power-input diagrams were investigated, which can save energy, lower consumption, and raise productivity. This has been verified by production contrast tests. Application of the optimum curve in 50 t UHP-EAF indicates that research method is correct, the 50 t UHP-EAF runs smoothly with lowering electrical energy by 29.35 kW.h/t and shortening power on time by 3 rain. The general steps of making optimum power-input specification is also given.     

Evaluation of Desulphurization Flux in CaO‐Al2O3‐BaO‐CeO2‐MgO System

The flux of the CaO‐Al₂0₃‐BaO‐CeO₂‐MgO system as a desulphurization flux containing no fluorine for the secondary metallurgy process was evaluated in this study. The flux composition was designed using the eutectic compositions of the binary systems. The melting and desulphurization abilities of the fluxes were evaluated by measuring their liquidus temperatures and the distribution ratios of sulphur between the fluxes and the carbon‐saturated iron or stainless steel. The lowest liquidus temperature of 1325°C was obtained by adding 5.7 mass% MgO to the 80mass%A‐20mass%B flux. (A: 12CaO‐7Al₂O₃, B: BaCeO₃+12mass%Al₂O₃). The distribution ratios of sulphur and sulphide capacities of the fluxes in this study were higher than those of the commercial product of calcium aluminate flux. This means that the CaO‐Al₂O₃‐BaO‐CeO₂‐MgO fluxes developed in this study have higher desulphurization and melting abilities compared with the commercial product of calcium aluminate flux.     

Precipitation Behavior of Modified as Cast High Nitrogen Super Hard High‐Speed Tool Steel

The properties of high‐speed tool steels can be improved by modifying their chemical composition or the technology of production. Nitrogen alloying is an attractive technology to enhance the mechanical and physical properties of tool steels. In this work, modified super hard high‐speed tool steel was produced through nitrogen alloying and decreasing the level of cobalt content in investigated steels. This work aims to study the effect of nitrogen as alloying element on carbides and carbo‐nitrides precipitates type, shape, and size for investigated steels. From the results obtained from Thermo‐Calc, it was concluded that nitrogen alloying produced large amount of stable austenite, also eutectic carbides precipitates (M₆C and M₇C₃) were stable at room temperature. Transmission electron microscope (TEM) images for traditional grade showed that the as cast structure contains beside the carbides network other single carbides precipitates. While on the other hand the selected area diffraction pattern (SADP) images of nitrogen alloyed grade shows fine carbides and carbo‐nitrides precipitates with more amount of retained austenite in the ferrite matrix, they showed also the presence of the eutectic precipitates as well as the dislocations.     

Crystallisation behaviour of the iron oxide-devoid BOF slag with adding SiO2

The current research attempted to investigate the crystallisation mechanism of iron oxide-devoid basic oxygen furnace (BOF) slag with adding SiO₂. First, the glass sample was prepared by adding 29?wt-% of SiO₂ to BOF slag, followed by eliminating iron oxide by reduction process. Non-isothermal DSC analysis together with confocal laser microscopy, XRD and EPMA mappings were carried out to observe the crystallisation process. The glass sample showed that the crystallisation process started from the surface where the main phases were identified to be akermanite, merwinite and wollastonite. In addition, the crystallisation process was affected by the nucleation temperature which was decided by the heating rate because of the difference in the nucleation rate between wollastonite and Mg-rich phases. The current results could be used to propose the feasibility of utilising BOF slag as glass-ceramics by chemical modification with heat treatment, which controls the crystallisation behaviour.     

Nitrogen in SL/RN direct reduced iron: origin and effect on nitrogen control in EAF steelmaking

Abstract

In the steel plant considered here, direct reduced iron (DRI), produced by the coal based Stelco–Lurgi/Republic–National (SL/RN) process, makes up 50% or more of the total iron charge. The SL/RN DRI samples from a kiln cooler had high nitrogen contents (50–250 ppm, depending on particle size), contributing to elevated nitrogen levels in liquid steel produced in the electric arc furnaces. The proposed mechanism of nitriding of SL/RN DRI involves gaseous nitrogen (present within the rotary cooler) diffusing into the solid bed and is supported by a simple diffusion model. A strong correlation was found between the melt-in carbon content of the liquid steel and the final tap nitrogen content, with melt-in carbon of 0·3%C or higher resulting in nitrogen levels below 50 ppm at tap, even when charging DRI material that is high in nitrogen.