2003年, 第10卷, 第1期　刊出日期：2003-02-25

  

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  Coexistence Theory of Slag Structure and Its Application to Calculation of Oxidizing Capability of Slag Melts

  ZHANG Jian

  钢铁研究学报（英文版）. 2003, 10(1): 1-10.

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  The coexistence theory of slag structure and it's application to calculation of the oxidizing capabilities of slag melts is described. It is shown that the law of mass action can be widely applied to the calculation of oxidizing capabilities of slag melts in combination with the coexistence theory of slag structure. For slag melts containing basic oxides FeO and MnO, their oxidizing capabilities can be expressed by N_Feto=N_Feo+6N_Fe₂O_₃, while for slag melts containing basic oxides CaO, MgO, etc., in addition to FeO and MnO, their oxidizing capabilities can be given as N_Feto=N_Feo+6N_Fe2O3+8N_Fe3O4.
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  Experimental Research on Refining Slag Systems Containing BaO forUltra-Low Sulphur Steel

  LI Su-qin, ZHU Rong, GUO Han-jie, WANG Ya-na, LI Shi-qi, WANG Xin-hua

  钢铁研究学报（英文版）. 2003, 10(1): 11-14.

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  The experimental research on refining slag systems for ultra-low sulphur steel was carried out in a 10 kg induction furnace. It was proved that sulphur element in molten steel can be removed to less than 5×10^-6 by adding CaO-Al₂O₃-SiO₂-MgO-CaF₂ slag on the surface of molten steel and feeding CaO-BaO-CaF₂ wire into molten steel. And Ls, which is the coefficient of sulphur between slag and molten steel, that isω_(s)/ω_[s], increases by increasing I(I=ω_Bao/ω_Cao).When I=5/3, L_s can be up to its maximum of 633.The CaSi is effective for deep desulphurization, especially when it is added to the slag of wire feeding.
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  Solidification in Soft-Contact Continuous Casting Mold withAlternating Electromagnetic Field

  DENG An-yuan, HE Ji-cheng

  钢铁研究学报（英文版）. 2003, 10(1): 15-19.

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  A three-dimensional coupled mathematical model for steel flow and solidification in a soft-contact EMC (Electro-Magnetic Casting) mold was developed. Non-staggered grid system with BFC (Body Fitted Coordinate) for the steel flow and solidification considering the complex geometry of the electromagnetic mold and the irregular meniscus shape of the melt were used. This mathematical model was applied to investigate the steel flow and solidification, and the effect of electromagnetic parameters on steel solidification in a 100 mm×100mm square billet soft-contact mold. Numerical results showed that the electromagnetic induction heat mainly affects the distribution of steel temperature at upper part of EMC mold especially in the vicinity of meniscus. Consequently the steel temperature near the free surface is increased distinctly, and the hot-top condition is formed at the top of mold. It was clearly seen that the solidification start point shifts downward under the three-phase point by applying alternative electromagnetic field. As a result, the initial shell thickness gets thinner and the shell length shorter.
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  Research on Mechanical Model of Material during Twin Roll Strip Casting Process

  MIAO Yu-chuan, ZHANG Xiao-ming, DI Hong-shuang, WANG Guo-dong, LIU Xiang-hua

  钢铁研究学报（英文版）. 2003, 10(1): 20-23.

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  The mechanical behavior of the mushy zone was studied in detail. Based on the analysis of conventional high temperature mechanical model, considering the physical phenomenon in casting process, a mechanical model suitable for describing the mechanical behavior of the casting material in twin roll casting process was built. Comparing experimental results to the numerical simulated ones, the mechanical model was proved to be correct.
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  Research on Computer Simulation System of Stretch Reducing Mill for Tube

  XUE Zhong-ming, QU Wen-qing, ZHANG Yan-hua, LI Shu-chun

  钢铁研究学报（英文版）. 2003, 10(1): 24-27.

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  The prototype, basic parameters, composition and structure of computer simulation system of stretch reducing mill for tubes were introduced. The software has an obvious style of object-oriented programming, and the modules were integrated in the simulation system. The system can optimize pass design, and it can automatically classify pass series according to the product syllabus, formulate the rolling table and simulate the rolling parameters in stretch reducing process. The simulation results were compared with the detailed technical data(used as experimental data)provided by Baotou Iron and Steel Company, and the comparison gave aclear proof of the precision of the models.
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  Effect of Carbon on Grain Boundary Segregation of Phosphorus and Phosphorus-Induced Intergranular Fracture in High Purity Iron with Phosphorus

  WANG Ya-nan, LIU Chun-ming

  钢铁研究学报（英文版）. 2003, 10(1): 28-32.

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  The segregation of carbon at grain boundaries and its effect on phosphorus segregation and phosphorus-induced intergranular fracture in the alloy of high purity iron with phosphorus were investigated by scanning Auger electron spectroscopy, impact test and SEM observation of fractured surface. The experimental results showed that the carbon segregation at grain boundaries decreases the phosphorus segregation, and a change of fracture mode from intergranular fracture to transgranular one, hence a decrease of ductile-brittle transition temperature is observed. The mechanism of these effects was discussed.
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  Model of Primary Austenite Dendrite Structure in Hypoeutectic Cast Iron

  WU Xu-min, YU Xiao-hua, XU Jun, ZHANG You-ling

  钢铁研究学报（英文版）. 2003, 10(1): 33-35.

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  The solidification of primary austenite in hypoeutectic gray cast iron was studied by stepped grinding and quantitative metallography. The dendrite structure of primary austenite can be described by three models: typical dendrite crystal model, metamorphic dendrite crystal model and network dendrite crystal model. The dendrite crystals formed according to 3rd model is much more than those formed according to other models in this experiment. The primary austenites are connected each other, and the primary stems of austenite could be regarded as secondary arms and vice versa.
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  Spheroidization and Ostwald Growth of Carbide in Isothermal Process of Hot-Deformed High Carbon Chromium Cast Steel

  CHANG Li-min, LIU Jian-hua, WANG Hai-yan, YU Sheng-xue

  钢铁研究学报（英文版）. 2003, 10(1): 36-39.

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  In isothermal spheroidizing process, the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were investigated. The results showed that the spheroidizing growth of carbide proceeds in such a way that the bigger carbide particles swallow the smaller ones, and the short rhabdoid carbides dissolve and are spheroidized by itself. When the samples were held at 720℃ for more than 3h, the spheroidization is not obvious. The feature of the process is the size increment and the amount decrement of carbide particles. The empirical equation for growth rate of carbides was obtained. The volume fraction of carbides keeps constant. The growth process agrees well with Ostwald Ripening Law.
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  Mechanism of Annealing Softening of Rolled or Forged Tool Steel

  LIU Zong-chang, GAO Zhan-yong, DONG Xue-dong, DAI Jian-ming

  钢铁研究学报（英文版）. 2003, 10(1): 40-43.

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  In order to reduce hardness of rolled or forged steels after annealing and improve processability, the diameter and dispersity of carbides were measured by SEM and quantitative metallography. The microstructure of annealed steel was analyzed by TEM. The effects of the factors such as solute atoms, carbides, grain boundary and interphase boundary were studied. The mechanism of annealing softening of steels was analyzed on the examples of steels H13, S5, S7, X45CrNiMo4, which are treated with new technology. The results showed that the softening of H13, S7, S5 is easier obtained by isothermal or slow cooling annealing from slightly below A1, but hardness of X45CrNiMo4 after annealing is reduced effectively by obtaining coarse lamellar pearlite. Economic results can be obtained from good processability.
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  Effect of Heat Treatment on Delayed Fracture Resistance of High Strength Steel 30CrMnSi2NiNb

  WANG Mao-qiu, DONG Han, HUI Wei-jun, CHEN Si-lian, WENG Yu-qing

  钢铁研究学报（英文版）. 2003, 10(1): 44-48.

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  The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni-0.04Nb were quenched and tempered or isothermally quenched from various temperatures. It is found that the steel quenched and tempered with a tensile strength of 1500-1600MPa has a K_ISCC (critical stress intensity factor)value below 15.0MPa·m^1/2.The steel isothermally quenched with a tensile strength of 1350-1750 MPa has a K_ISCC value about 20.0 MPa·m^1/2.In addition, with increase of isothermal quenching temperature, the tensile strength decreases greatly and K_ISCC value does not pronouncedly change. The microstructure of isothermally quenched specimens is composed of bainite and retained austenite. The delayed fracture resistance is dependent on the stability of austenite, which is in turn related to the retained austenite volume fraction and carbon content in austenite.
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  Effect of Microstructure in TRIP Steel on Its Tensile Behavior at High Strain Rate

  WEI Xi-cheng, LI Lin, FU Ren-yu, SHI Wen

  钢铁研究学报（英文版）. 2003, 10(1): 49-54.

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  The relationships between microstructure of 0.195C-1.6Si-1.58Mn TRIP steel and its dynamic mechanical properties at high strain rate were investigated. The effect of microstructures on dynamic properties was discussed and the comparison with its static mechanical properties was also presented. The specimens of TRIP steel via three heat treatment techniques exhibit different morphological structures, responsible for their dynamic mechanical performances. The dynamic tensile testing was performed on self-made pneumatic tensile im-pact tester. The results showed that the size, volume fraction, morphology and distribution of retained austenite all affect the final mechanical properties at high strain rate. Among them, the second phase (retained austenite+bainite) with net structure severely decreases the elongation of TRIP steel in spite of the fact that it enhances strength because it restrains fer-rite deformation. In order to obtain the excellent combination of strength and elongation, rational matching of morphology, size and volume fraction of several phases in TRIP steel can be obtained via proper heat treatment techniques.
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  Hot-Dip Galvanized Sheet Production and Application

  BIAN Jun, LIU Xiang-hua, WANG Guo-dong

  钢铁研究学报（英文版）. 2003, 10(1): 55-58.

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  Hot-dip galvanized sheet is wildly used in construction, household appliances, ship, vehicle and vessel building and machinery, etc. In last ten years, with the development of automobile industry, the anti-corrosion requirements for car body are increasingly strict, by which the rapid development in technology has been promoted. The application of hot-dip galvanized sheet, technological progress in production and some Chinese large units were introduced.
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  Investigation on Atmospheric Corrosiveness in Hainan Province

  WANG Zhen-yao, CHEN Hong-chuan, YU Guo-cai, HAN Wei

  钢铁研究学报（英文版）. 2003, 10(1): 59-62.

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  According to the results of four-year exposure tests for carbon steel samples in Hainan province, the influences of meteorological factors and Cl-on atmospheric corrosion were investigated. The feature of atmospheric corrosion in this area was summarized. A corrosive map for the area was drawn. The corrosion products on carbon steel at some typical places were analyzed by XRD and XPS.