2011年, 第18卷, 第1期　刊出日期：2011-01-15

  

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  Prospects for Variable Gauge Rolling: Technology, Theory and Application

  LIU Xianghua

  中国钢铁期刊网. 2011, 18(1): 1-0.

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  Rolling of gauge changeable (RGC) is a new technology to produce flat with different thickness (FDT), which could be used to replace conventional flat products in order to save metals and reduce structure weight. This paper introduced the method of RGC, investigated new problems in rolling theory of RGC, proposed the new formulas for caluclating parameters of RGC, and described some results of numerical simulation by FEM. As example, the products applications of FDT in bridge construction, ship building and auto manufacturing were presented. Finally the prospect for RGC and FDT was discussed.
工艺
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  Quantitative Analysis of Non-Crystalline and Crystalline Solids in Blast Furnace Slag

  WANG Haifeng;ZHANG Chunxia;QI Yuanhong

  中国钢铁期刊网. 2011, 18(1): 8-10.

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  China is short of water seriously. But granulation of blast furnace slag (BFS) with water has many disadvantages, such as high water consumption and difficulty in heat recycling. So developing a new dry granulation technique to treat BFS is very important. The applicability of BFS directly depends on the content of non-crystalline solids in the slag after treatment. So it is of theoretical and practical significance to analyze the content of non-crystalline solids in the slag quantitatively and simply. Metallographical test is mainly adopted to quantify the non-crystalline in BFS now with the shortages such as making sample complexly, determining difficultly and personally. For the diffraction intensity of non-crystalline is proportionate to the content of non-crystalline in BFS, X-ray diffraction method was adopted to quantify the non-crystalline and the crystalline solids in BFS. The quantificational coefficient between the crystalline and the non-crystalline solids of BFS is 0.70 whose main composition is: w（CaO）38.2%，w（SiO2）35.7%，w（Al2O3）16.3%，w（MgO）8.3%. The relatively error of using X-ray diffraction instrument to quantitative analyse non-crystalline content of BFS is less than 1%.
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  Performance of Low Fluoride Dephosphorization Slag of Hot Metal

  LIU Lixia;WANG Shijun;DONG Yuanchi;JIA Xiaohui

  中国钢铁期刊网. 2011, 18(1): 11-11.

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  The purpose of this study is decreasing content of CaF2 in dephosphorization slag. The dephosphorization effects with CaF2 replaced by B2O3 were investigated. The dephosphorization experiments were carried at 1450℃ in air atmosphere. The results show that the melting points and dephosphorization ratios change little when B2O3 replaced CaF2. The dephosphorization ratios which are all greater than 80% and melting points can meet the requirement of hot metal pretreatment. Because of the change of alkalinity caused by B2O3, the oxidation of slag increases with increasing of B2O3 contents. It is beneficial to pre-dephosphorization. As a result, for decreasing its pollution, CaF2 can be replaced by B2O3 to dispose fluoride-free pre-dephosphorization slag.
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  Characteristic Analysis of Solidified Crust for Basic Tundish Flux With AlKilled Steel Casting

  WANG Deyong;ZHANG Zhixiang;WANG Huihua;JIANG Maofa

  中国钢铁期刊网. 2011, 18(1): 16-16.

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  This present paper focused on the formation reasons of solidified crust when a basic tundish flux was used to cast the Al-killed steel. Crust samples were taken in an actual tundish, and analyzed by the methods of XRD, SEM and EDX. It was found that the main compositions of crystallization phases existing in tundish crust are Ca12Al4O33, Ca2SiO4 and a little spinel. Spinel and Ca2SiO4 distributed at grain boundaries of Ca12Al4O33, which increased the connection strength of crystallization phases by pinning the grain boundary, density or hardness of tundish crust will also significantly increased. When an initial composition of tundish flux was in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to form spinel in crust. Three approaches for spinel formation in crust were summarized. When flux is nearly saturated with magnesia, on the metal/flux interface, MgO in flux reduced by dissolved Al and formed the spinel. Inside molten steel and on the interface of steel/refractory, with a feasible Al content it is also easy to form spinel and spinel inclusions will float and captured by flux.
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  Behavior of Mold Slag Used for 20Mn23Al Nonmagnetic Steel During Casting

  YU Xiong;WEN Guanghua;TANG Ping;MA Fanjun;WANG Huan

  中国钢铁期刊网. 2011, 18(1): 20-25.

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  Because of the addition of significant quantities of Al and Mn, the great challenge of casting 20Mn23Al non-magnetic steel is to design a mold slag that is chemically compatible with this steel chemistry. In this paper, a new mold slag with low melting point, low basicity was proposed. The initial slag (the base mold slag) and two corresponding spent mold slag (8min slag and 15min slag), which was sampled from the caster after 8 minutes and 15minutes of casting, were investigated, the changes of mold slag composition and properties of molten slag were discussed. The results showed that:(i) The slag quickly changed in chemistry to a slag that contained a low quantity of silica and a higher quantity of alumina, and the basicity increased obviously; (ii) Heat flux density through the slag film decreased appreciably with the time increase; (iii) Mold slag used for non-magnetic steel precipitated CaF2 crystals; (iv) The slab has good surface quality with not occurrences of longitudinal face cracks and slag inclusions; (v) The Al2O3 content in the molten slag pool increased with time, and Al2O3 concentration of the pool can be regarded as being in a practically equilibrium state after about 600sec.
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  Design and Simulation Test of Advanced Secondary Cooling Control System of Continuous Casting Based on Fuzzy SelfAdaptive PID

  LIU Wenhong;XIE Zhi

  中国钢铁期刊网. 2011, 18(1): 26-26.

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  To improve billet quality and the trackability and stability of secondary cooling water during continuous casting, the superheat is introduced into the water distribution for secondary cooling to design the relevant control system, based on the water distribution model, superheat, surface temperature and fuzzy self-adaptive PID. A spray cooling system is thus set up for simulation test in laboratory to test the step signal from the conventional, integral separated and fuzzy self-adaptive PID controllers and the simulation casting. The simulation test results show that the fuzzy self-adaptive PID controller’s performance is better than the other two controllers, which provides a foundation for further study and application.
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  A Wavelet and Neural Networks Based on Fault Diagnosis for HAGC System of Strip Rolling Mill

  LI Guoyou;DONG Min

  中国钢铁期刊网. 2011, 18(1): 31-31.

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  The research is aiming at the fault diagnosis of HAGC system of strip rolling mill. Taking the advantage of the accompany characteristics of the closed-loop control system, rolling force forecasting model is established based on neural networks. The comparison results between the forecasting results and the actual signal are taken as residual signals, which have eliminated the effects of abrupt input. Wavelet transform is used to acquire the components of high and low frequency, and fault numerical criterion is established through Lipschitz exponent. Wavelet decomposition results make fault feature clear and time-domain positioning accurately. By analyzing the varied fault features which correspond to varied fault reasons, the fault diagnosis of HAGC system is implemented successfully.
材料
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  Formability of TRIP/TWIP Steel Containing Manganese of 18.8%

  DING Hao;DING Hua;QIU Chunlin;TANG Zhengyou;ZENG Jianmin;YANG Ping

  中国钢铁期刊网. 2011, 18(1): 36-40.

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  The mechanical property and forming limit experiments were carried out on a high manganese TRIP/TWIP steels with 18.8% manganese. And the forming limit diagram was obtained. This high manganese steel shows outstanding mechanical properties combining high strength and good formability. Its FLD0 is about 38%. The effects of conventional mechanical property on the FLD0 were analyzed. With the contents of Mn increasing, FLD0 increases, which indicates TWIP effect is advantageous to enhance formability. Combining with three classical models and volume invariable principle, a FLD model was established, which fits high manganese steels very well.
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  Breakdown Behavior of Eutectic Carbide in High speed Steel during Hot Compression

  ZHOU Bin;SHEN Yu;CHEN Jun;CUI Zhenshan

  中国钢铁期刊网. 2011, 18(1): 41-48.

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  The evolution of eutectic carbide in as-cast M2 high-speed steel on different deforming conditions was investigated. Initially, specimens were deformed by hot compression in the range of 1223 to 1398K at strain rates of 0.01 to 1.0s-1. In a series of continuous deformation tests the flow stress curves were determined for the downstream process simulation. Subsequently, metallographic examination was carried out before and after deformed specimens for carbides analysis. As-cast microstructure is characterized as a spherical matrix of austenite and a continuous network of rodlike or irregular eutectic carbide, whereas deformed microstructure has broken carbide network and smaller granular products on all experimental conditions. It suggests that eutectic carbides fracture to particles during hot deformation by thermomechanical disintegration, while diffusion-controlled phase transformation was not remarkable. Combination with numerical simulation, the relationship between breakdown ratio of carbide network and deforming parameters were concluded. Strain was the most important one to shatter eutectic carbides and disperse products. Furthermore, critical strain values were obtained, beyond which carbide network disappeared, and fractured carbides kept a stable profile and deformed with matrix coordinately. A higher temperature or lower strain rate resulted in a lower critical strain.
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  Influence of Inclusion on Crack Initiation in Wheel Rim

  MI Guofa;NAN Hongyan;LIU Yanlei;ZHANG Bin;ZHANG Hong;SONG Guoxiang

  中国钢铁期刊网. 2011, 18(1): 49-54.

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  Speed increase and heavy-haul of the railway freight car are the effective measures to raise the transport ability of railway, and they have been the new trend for railway freight car development. The increase of speed and axle load will lead to the increase of wheel-rail contact stress, which will make a great change of stress distribution in the whole wheel rim. Goodier equation was employed to analyze the stress state around inclusion and cavity. In the operation of wheel-rail contact stress, stress concentration occurred in the pole of Al2O3 spherical inclusion, while it appeared on the equator of cavity. The critical inclusion sizes of 25t axle load freight car wheel at different velocities, a certain distance away from the tread, were calculated by Murakami equation. By contrast the inclusion state in cast-steel wheel and rolled-steel wheel, the inclusion character in cast-steel wheel determined that it has much more excellent crack resistance than that of rolled-steel wheel. In the meantime, in order to reduce the probability of rim crack, some suggestions were put forward.
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  Dynamic and Static Recrystallization Behavior of Low Carbon High Niobium Microalloyed Steel

  LAN Liangyun;QIU Chunlin;ZHAO Dewen;GAO Xiuhua;DU Linxiu

  中国钢铁期刊网. 2011, 18(1): 55-60.

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  The recrystallization behavior of a low carbon high Nb microalloyed steel was investigated using Continuous and interrupted hot compression tests. The results showed that the onset of dynamic recrystallization (DRX) could be detected from inflection in the plot of the strain hardening rate θ against stress σ regardless of whether the stress peak appears or not. According to Zener-Hollomon parameter the activity energy of DRX (Qdef) was obtained, and a new modified expression calculating Qdef was proposed in consideration of the chemical composition of experimental steel. Applying the 2% offset method the static softening fraction was determined. The graphic representation of the softening fraction vs. interrupt time gave the information of the non-static recrystallization temperature (about 1000℃)and the relationship of precipitation-time-temperature. Static recrystallization kinetics follow Avrami’s law in high deformation temperature, and different values of the exponent n were given to illustrate the different effects of Nb element on static recrystallization at different deformation temperature.
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  Nonequilibrium Grain Boundary Segregation of Phosphorus in Ni-Cr-Fe Superalloy

  WANG Kai;SI Hong;YANG Chun;XU Tingdong

  中国钢铁期刊网. 2011, 18(1): 61-65.

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  In virtue of Auger electron spectroscopy, the grain-boundary concentrations of phosphorus in Ni-Cr-Fe superalloy after solution-treated at 1180℃ for 45 min are measured, the results show that a peak of phosphorus concentration occurs at about 180 min during isothermal ageing at 500℃, and a maximum concentration of phosphorus appears also at about 500℃ for all specimens aged for 20 min at temperatures of 200,400,500,700 and 800℃. The results are analysed with the laws of non-equilibrium grain-boundary segregation. It is found from the analysis that peaks are relative to critical time for non-equilibrium grain-boundary segregation of phosphorus.
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  Relationship Between Grain Boundary Segregation of Antimony and Temper Embrittlement in TitaniumDoped Nickel-Chromium Steel

  ZHENG Lei;ZHANG Maicang;DONG Jianxin;MENG Ye

  中国钢铁期刊网. 2011, 18(1): 68-72.

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  The observations given by Ohtani et al are analyzed in the present paper and it is concluded that the kinetics of temper embrittlement in titanium-doped low carbon NiCr steel agree well with those of non-equilibrium grain-boundary segregation of Sb. Besides, the mechanism of non-equilibrium grain-boundary segregation of Sb is determined to be the most satisfactory one among the existed mechanisms in the literature to interpret the Sb-induced embrittlement kinetics in the NiCr steel. Based on the conclusion and the determination, the activation energy and frequency factor of diffusion of Sb-vacancy complexes are obtained for the first time according to the concept of critical time in non-equilibrium grain-boundary segregation theory. The calculated results can give theoretical basis for predicting and controlling over the Sb-induced embrittlement in steels.
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  Effect of Laser Power on the Cladding Temperature Field and the Heat Affected Zone

  LUO Fang;YAO Jianhua;HU Xiaxia;CHAI Guozhong

  中国钢铁期刊网. 2011, 18(1): 73-78.

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  Abstract: In this paper, H13 powder is cladded on P20 base during continuous CO2 laser, the influence of processing technologies such as the laser power is analyzed. The 3-D model of synchronous powder feeding is established under Gauss heat source, the simulation results are compared with the experimental data. The results show that the temperature field and the size of heat affected zone are affected by laser power. In the heat affected zone, experimental sizes are compared with simulative sizes, the average errors in width and in depth are 15% and 4.5%, respectively.