2011年, 第18卷, 第4期　刊出日期：2011-04-15

  

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工艺
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  Development of Test Method for Measuring Sintering Temperature of Mould Fluxes

  WANG Qian,LU Yongjian,HE Shengping,WANG Lijuan,K C Mills

  中国钢铁期刊网. 2011, 18(4): 1-6.

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  Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.
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  Development of Intensified Technologies of VanadiumBearing anomagnetite Smelting

  FU Wei-guo,WEN Yongcai,XIE Hongen

  中国钢铁期刊网. 2011, 18(4): 7-10.

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  It was very difficult for the smelting of vanadiumbearing titanomagnetite by blast furnace because the content of TiO2 of blast furnace slag could amount to 20%-25%. After long term development and continuous improvement, special intensified smelting technologies for vanadiumbearing titanomagnetite by blast furnace were obtained and improved gradually. With the improvement of beneficiated material level and equipment level, smelting intensity has been increased gradually and the highest comprehensive smelting intensity reached 145 t/(m3·d). Technicaleconomic indexes of blast furnace have also been increased remarkably. The highest utilization coefficient exceeded 27 t/(m3·d) on the condition that the burden grade was only about 50%.
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  Simulation of Flow Field of Oxygen Lance Gas Jet Utilized for 50 t Converter

  LI Junguo,ZENG Yanan,WANG Jianqiang,HAN Zhijie

  中国钢铁期刊网. 2011, 18(4): 11-18.

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  Based on the operating conditions of oxygen lance utilized for a 50 t converter in Tangsteel, gas jet flow fields of three types of oxygen lances were simulated by FLUENT software. The influence of lance configuration and lance level on penetrating area was studied through cold model experiment. The results showed that the gas flow velocities of fourhole, variable angle fourhole and fivehole oxygen lances declined rapidly with an increase in gas jet length within 1 m, 1 m and 08 m, respectively. Besides, the multi gas streams sprayed from these three lances should be syncretized at 16 m, 17 m and 14 m, respectively. At the highest lance level, the effective penetrating area of these three lances could be 0255 m2, 0385 m2 and 00907 m2, respectively. It was suggested that the effective penetrating area of variable angle fourhole oxygen lance was the biggest, while that of fivehole oxygen lance was the least. The validity of numerical simulation results was proved through cold model experiment. The lance level was suggested to be controlled in the range of 1-16 m, 1-17 m and 08-14 m for the fourhole, variable angle fourhole and fivehole oxygen lances, respectively.
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  Hydrogen PickUp During Electroslag Remelting Process

  JIANG Zhouhua,DONG Yanwu,LIANG Lianke,LI Zhengbang

  中国钢铁期刊网. 2011, 18(4): 19-23.

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  The pickup of hydrogen during electroslag remelting process for several slags consisting of CaF2Al2O3CaOSiO2MgO had been investigated. The laboratoryscale remelting experiments had been carried out in open air and waterfree argon atmosphere, and then the influencing factors were analyzed. It had been found that the hydrogen content in steel varied with different slag compositions. The compositions and state of slag had significant effect on the hydrogen level in steel. Partial return slag and premelted slag could avoid the hydrogen pickup especially in the early stages of the process. However, premelted slag was the optimum state to control the hydrogen pickup in steel. Experimental results indicated that waterfree argon atmosphere was very favorable to the control of hydrogen in steel in the normal remelting period.
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  Research on Predicting Molten Steel Breakouts by the friction

  秦旭 朱超甫 郑立文

  中国钢铁期刊网. 2011, 18(4): 24-29.

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  通过对板坯连铸机结晶器液压伺服振动系统液压伺服油缸压力及活塞行程的检测，并应用结晶器伺服液压振动系统的运动方程，确定结晶器与连铸坯坯壳之间的摩擦力,找出该摩擦力在漏钢前的变化特征，用来预报粘结、裂纹及异物卷入漏钢，有效减少漏钢事故的发生。
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  Research and Application of Flat Roll Technology in the Downstream Stands for CSP

  GUO Defu,HE Anrui,SHAO Jian,YANG Quan,WANG Zhongming,WANG bo

  中国钢铁期刊网. 2011, 18(4): 30-35.

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  CVC mills are generally used in the whole stands of CSP (Compact Strip Product). Their special “s” curve of work roll contour and shifting strategy aimed at controlling strip shape, and the characteristics of continuous casting and rolling production, which make the work roll wear in downstream stands seriously uneven, and easily form abnormal transverse profile at the rolling end. As a result, CVC mill configuration in the downstream stands can not meet the profile and flatness control requirement for schedule free rolling, and bring some difficulties in profile and flatness control for the subsequent cold rolling. Based on the characteristics of the shape control system of CSP production line, and combined with the theory of flat roll technology, a kind of technology solution of using flat roll in the downsteam stands for CSP hot strip mills was proposed. At last, industrial test was carried out in the last stand of Masteel CSP, and good results were obtained.
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  Adaptive Coordinated Control for Hot Strip Finishing Mills

  JIAO Xiaohong,SHAO Liping,PENG Yan

  中国钢铁期刊网. 2011, 18(4): 36-43.

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  To further improve the control accuracy for strip dimension of hot strip mills, an adaptive control scheme is investigated for a hot strip finishing mill based on the decentralization and coordination among the controllers of gauge, tension and looper. Consequently, the adaptive controller designed can regulate simultaneously the strip exit thickness, the strip tension and the looper angle to ensure better performance of the strip quality of finishing mills. Moreover, the control scheme is proposed in consideration of the essential nonlinearity and the unavoidable friction phenomena in the mechanical system, so the controller can be efficient in a wider range of working situations. The simulation results of a model obtained from a real hot strip finishing mill show the effectiveness of the proposed control scheme in comparison with the conventional control method.
材料
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  Effect of Mold Hardness on Microstructure and Contraction Porosity in Ductile Cast Iron

  Jafar KhalilAllafi,Behnam AminAhmadi

  中国钢铁期刊网. 2011, 18(4): 44-47.

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  The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated. Molds with different hardnesses (041, 048, 055, 062 MPa) and a sand mold prepared by Co2 method were used. The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated. The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases; therefore, the possibility of achieving a sound product without using any riser increases.
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  Processing Maps for Use in Hot Working of Ductile Iron

  ZHAO Xin,YANG Xiaoling,JING Tianfu

  中国钢铁期刊网. 2011, 18(4): 48-51.

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  The hot deformation characteristics of ductile iron are studied in the temperature range of 973 to 1273K and strain rate range of 0001 to 1 s-1 by using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate. The results reveal that the flow stress of ductile iron is sensitive to strain rate. In the processing map under strain of 07, a domain is centered at 1273 K and 1 s-1, and the maximum efficiency is more than 36%. According to the maps, the zone with the temperature range of 1173 to 1273 K and strain rate range of 01 to 1 s-1 may be considered as the optimum region for hot working.
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  A New Economical Sigma-free Duplex Stainless Steel 19Cr-6Mn-1.0Mo-0.5Ni-0.5W-0.5Cu-0.2N

  陈宏 丁铁锁 肖学山 赵钧良 江来珠

  中国钢铁期刊网. 2011, 18(4): 52-56.

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  Crack Properties of Lean Duplex Stainless Steel 2101 in Hot-formming Processes

  方轶琉

  中国钢铁期刊网. 2011, 18(4): 58-62.

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  Effect of Microstructure on Corrosion Fatigue Behavior of 1500 MPa Level CarbideFree Bainite/Martensite DualPhase High Strength Steel

  XU Lei,WEI Dongyuan,YU Yang,ZHANG Han,BAI Bingzhe

  中国钢铁期刊网. 2011, 18(4): 63-67.

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  Influence of microstructure of the experimental steels on the corrosion fatigue behavior in 35% of NaCl aqueous solution was studied. Experimental results show that compared with the full martensite (FM) steel, the carbidefree bainite/martensite (CFB/M) steel has higher corrosion fatigue strength and corrosion fatigue crack threshold (ΔKthcf), and lower corrosion crack propagation rate [(da/dN)cf].
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  Hot Working Characteristics of CorrosionResistant Alloys G3 and 825

  YU Man,,LI Jingshe,TANG Haiyan,BAO Yaozong

  中国钢铁期刊网. 2011, 18(4): 68-72.

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  The G3 and 825 alloys, with excellent combination of mechanical properties and corrosion resistance, can be used in hot, and acid environments. Thermal simulation tests were conducted on the alloys G3 and 825 in the THERMECMASTORZ simulator, at temperature between 1030 and 1300 ℃, with strain rate from 1 to 50 s-1 and strain ε=08. The variations of flow stress with deformation temperature and strain rate were presented. Change of alloy structure with hot deformation and effect of strain rate on alloy dynamic recrystallization have been studied through microstructure observation by OM, SEM and TEM. Moreover, hot plasticity characteristics of alloy were analyzed by temperaturereduction of area curves. The results showed that available hot working temperature for G3, G3Z and 825 was 1100 to 1240 ℃, 1130 to 1220 ℃ and 1050 to 1240 ℃, respectively. The reliable information on hot working in the alloy pilot production in steelwork is given.
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  Laser Direct Metal Deposition Technology and Microstructure and Composition Segregation of Inconel 718 Superalloy

  ZHANG Qunli,,YAO Jianhua,,Jyoti Mazumder

  中国钢铁期刊网. 2011, 18(4): 73-78.

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  Multilayer of laser direct metal deposition (DMD) was prepared by depositing a gas atomized prealloyed powder with a composition close to Inconel 718 alloy on Inconel 718 high temperature alloy substrate. The effects of the DMD parameters on the buildup rate and the structure of the deposited layer were studied. The laser DMD sample was further processed by a solution treatment. The microstructure and property of the laser DMD zone before and after heat treatment were investigated as well. The results show that the laser parameters of actual laser power of 650 W, scanning speed of 58 mm/s, beam diameter of 1 mm, powder feed rate of 645 g/min, with a corresponding specific energy of 90-130 J/mm2, can be recommended as optimum parameters for high buildup rate of Inconel 718 alloy. Under the condition of optimized parameters, a directional solidification microstructure was obtained and the average distance between the columnar crystals was 5-10 μm. The microcomposition segregation was found between the columnar crystal trunk and columnar crystal. The elements of Nb, Mo, Ti concentrated in the columnar crystal trunk. After the heat treatment, the segregation was greatly minimized, and the segregation ratios were close to 1. The hardness of the laser deposited layer did not show obvious difference along the height of the layer either for the asdeposited layer or for the heat treated layer. However, the microhardness of the laser DMD zone after heat treatment was obviously higher than that after the asdeposited treatment. During the heat treatment process, some Nb and Morich phases precipitated and strengthened DMD layer.