2014年, 第21卷, 第11期　刊出日期：2014-11-15

  

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Metallurgy and Metal Working
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  Quantitative Evaluation Method of Shape Indicator for Cold-rolled Strip

  Li-po YANG,,Bing-qiang YU,,Hua-xin YU,Chang-zheng DU

  中国钢铁期刊网. 2014, 21(11): 983-989.

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  Quantitative level evaluation of cold-rolled strip was significant for the shape control and the product structure optimization. Based on the probability statistics method and the shape pattern recognition method, the shape evaluation model of cold-rolled strip was established to evaluate real-time shape of the online strip. The model was embedded in the shape control system, and the online strip shape state was real-time observed whether to meet the technical indicators, so the shape level could be identified and evaluated. Based on the shape evaluation indicators, the shape component could be well controlled to improve the shape hit rate and the control stability, so that the rolled strip shape could meet the technical requirements. At a 1050 cold strip mill, the shape data of the scene typical specifications strip were online collected and real-time evaluated, and the hit of macro shape in less than 8 I was 68.44%, indicating that the mill shape control had considerable room for improvement, as well as the evaluation method was feasible and practical for quantitative evaluation of the strip shape. So the new evaluation model has important guiding significance to increase value-added and reduce product quality objection.
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  Effect of Iron Oxides on Activity of Calcium Aluminate Clinker in CaO-Al2O3-SiO2 System

  Hai-yan YU,Xiao-lin PAN,Bao-wei LIU,Bo WANG,Shi-wen BI

  中国钢铁期刊网. 2014, 21(11): 990-994.

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  The sintering characteristics at 1350 ℃ and leaching property at 80 ℃ of calcium aluminate clinkers in the CaO-Al2O3-SiO2 (C-A-S) system with different additions of FeO and Fe2O3 were investigated. FeO inhibits the conversion of β-Ca2SiO4 to γ-Ca2SiO4 and makes the clinker not pulverizable. FeO and Fe2O3 inhibit the formation of CaAl2O4, but promote the formation of Ca12Al14O33. The interplanar spacing at (2 1 1) crystal face of Ca12Al14O33 in the clinker increases with the increase of FeO addition, which indicates that FeO forms solid solutions in Ca12Al14O33. The clinkers with Fe2O3 addition form a new phase Ca2Fe2O5, and the amount of Ca2Fe2O5 increases with the increase of Fe2O3 addition. Both FeO and Fe2O3 do not affect the Al2O3 leaching rate of calcium aluminate clinker in sodium carbonate solution, but they increase the molar ratio of caustic Na2O to Al2O3 in the leached liquor.
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  A Mathematical Model to Characterize RH Desulfurization Process

  Hong-bo YANG,Shu-feng YANG,Jing-she LI,Jiang-shan ZHANG

  中国钢铁期刊网. 2014, 21(11): 995-1001.

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  A physical model based on similarity principles was built to simulate RH desulfurization process. In order to quantitatively analyze RH desulfurization process, a mathematical model was proposed. By analyzing experimental results with the mathematical model, an empirical formula whose determination coefficient was 0.98 was given to express the relationship between transient desulfurization efficiency and time. All the determination coefficients of four fitted curves based on four repeated experiments with different gas flow rates were more than 0.94, which was the exact evidence of the rationality of the empirical formula. Meanwhile, it was found that transient desulfurization ability increased firstly and then decreased with increasing gas flow rate and reached the maximum value when the gas flow rate was 1.8 m3/h. A plenty of repeated trials showed the same rule, which validated the mathematical model and the conclusions obtained from physical experiments.
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  Combustion Property and Kinetic Modeling of Pulverized Coal Based on Non-isothermal Thermogravimetric Analysis

  Jiu-gang SHAO,Jian-liang ZHANG,Guang-wei WANG,Zhe WANG,Hong-wei GUO

  中国钢铁期刊网. 2014, 21(11): 1002-1008.

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  Non-isothermal combustion kinetics of two kinds of low volatile pulverized coals (HL coal and RU coal) were investigated by thermogravimetric analysis. The results show that the combustibility of HL coal was better than that of RU coal, and with increasing heating rate, ignition and burnout characteristics of pulverized coal were improved. The volume model (VM), the random pore model (RPM), and the new model (NEWM) in which the whole combustion process is considered to be the overlapping process of volatile combustion and coal char combustion, were used to fit with the experimental data. The comparison of these three fitted results indicated that the combustion process of coal could be simulated by the NEWM with highest precision. When calculated by the NEWM, the activation energies of volatile combustion and coal char combustion are 130.5 and 95.7 kJ·mol-1 for HL coal, respectively, while they are 114.5 and 147.6 kJ·mol-1 for RU coal, respectively.
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  Slag/metal Separation Process of Gas-reduced Oolitic High-phosphorus Iron Ore Fines

  Hui-qing TANG,Long MA,Jun-wei WANG,Zhan-cheng GUO

  中国钢铁期刊网. 2014, 21(11): 1009-1015.

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  Slag/metal separation process of the highly reduced oolitic high-phosphorus iron ore fines was investigated. Samples were prepared using the reduced ore fines (metallization rate: 88%) and powder additives of CaO and Na2CO3. Slag/metal separation behavior tests were conducted using a quenching method and the obtained metal parts were subjected to direct observation as well as microstructure examination with SEM and EDS; iron recovery and phosphorus distribution tests were conducted using a Si-Mo high temperature furnace and the obtained metal parts were examined by ICP-AES analysis and mass measurement. Thermodynamic calculation using coexistence theory of slag structure was also performed. Results show that temperature for slag/metal separation must be higher than 1823 K and a satisfying slag/metal separation of the highly reduced ore fines needs at least 4 min; phosphorus content of hot metal is mainly determined by thermodynamics; temperature of 1823-1873 K and Na2CO3 mixing ratio of about 3% are adequate for controlling phosphorus content to be less than 0.3 mass% in hot metal; temperature, time and Na2CO3 mixing ratio do not have significant effect on iron recovery, and iron recovery rate could be higher than 80% as long as a good slag/metal separation result is obtained.
Material
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  Influence of Inclusion on Corrosion Behavior of E36 Grade Low-alloy Steel in Cargo Oil Tank Bottom Plate Environment

  Hui-bin WU,Jin-ming LIANG,Di TANG,Xiao-tong LIU,Peng-cheng ZHANG,Yuan-jie YUE

  中国钢铁期刊网. 2014, 21(11): 1016-1021.

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  Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank (COT) bottom plate service environment (10% NaCl solution, pH=0.85). The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10-20 μm in diameter was formed as a circinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low-alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.
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  Numerical Simulation of Microstructure Evolution for SA508-3 Steel during Inhomogeneous Hot Deformation Process

  Da-shan SUI,Fei CHEN,Pei-pei ZHANG,Zhen-shan CUI

  中国钢铁期刊网. 2014, 21(11): 1022-1029.

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  Based on hot compression tests by a Gleeble-1500D thermo-mechanical simulator, the flow stress model and microstructure evolution model for SA508-3 steel were established through the classical theories on work hardening and softening. The developed models were integrated into 3D thermal-mechanical coupled rigid-plastic finite element software DEFORM3D. The inhomogeneous hot deformation (IHD) experiments of SA508-3 steel were designed and carried out. Meanwhile, numerical simulation was implemented to investigate the effect of temperature, strain and strain rate on microstructure during IHD process through measuring grain sizes at given positions. The simulated grain sizes were basically in agreement with the experimental ones. The results of experiment and simulation demonstrated that temperature is the main factor for the initiation of dynamic recrystallization (DRX), and higher temperature means lower critical strain so that DRX can be facilitated to obtain uniform fine microstructure.
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  Effect of Heat Treatment on Corrosion Behaviour of Amorphous Metal Fibers

  Zhong-wang WU,,Zhi-chao LU,Xiao-jun NI,De-ren LI,Shuo FENG,Yuan-hong QI

  中国钢铁期刊网. 2014, 21(11): 1030-1034.

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  Amorphous metal fiber has high corrosion resistance and excellent mechanical properties, making it a kind of good material for reinforcing concrete matrix. The effect of heat treatment on the corrosion behaviour of Fe73-Cr6C9Si1P11 amorphous metal fibers in 0.5 mol/L H2SO4 solution was investigated by electrochemical polarization analysis. Differential scanning calorimetry (DSC) was used to measure the thermal properties. The evolution of the crystallization process after heat treatment was identified by X-ray diffraction (XRD). The results show that the α-Fe, Fe2P and Fe3P crystalline phases individually precipitate in the amorphous matrix with increasing annealing temperature. The as prepared amorphous sample shows high corrosion resistance with a lower passivation current density and a wider passive region. The corrosion resistance dramatically decreases after the annealing temperature is higher than 400 ℃.
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  Hot Deformation Behavior of F6NM Stainless Steel

  Long-teng MA,Li-min WANG,Zheng-dong LIU,Gang YANG,Lun LU,Meng-du PENG,

  中国钢铁期刊网. 2014, 21(11): 1035-1041.

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  The hot deformation behavior of F6NM stainless steel was investigated by hot compression test in a Gleeble-1500D thermal-mechanical simulator. The flow strain-stress curves were obtained and the corresponding metallographic observation of this steel under different deformation conditions was also carried out. This steel exhibited dynamic recrystallization (DRX) in the temperature range of 1273-1473 K and the strain rate range of 0.01-0.1 s-1. The activation energy for hot deformation was determined to be 457.91 kJ/mol, and the hot deformation equations were also established. The flow instability zone was determined and could be divided into two regions. The first one was located in the temperature range of 1173-1348 K and the strain rate range of 0.056-10 s-1, while the second one is in the temperature range of 1398-1448 K and the strain rate range of 1.25-10 s-1. In the end, the optimum conditions for hot working were provided.
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  Dynamic Recrystallization Behavior of GCr15SiMn Bearing Steel during Hot Deformation

  Dan ZHANG,Ya-zheng LIU,Le-yu ZHOU,Qiang HAN,Bo JIANG,Zhong-zhi LI

  中国钢铁期刊网. 2014, 21(11): 1042-1048.

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  The hot deformation behavior of GCr15SiMn steel was studied through high temperature compression tests on the Gleeble-1500 thermal-mechanical simulator. The initiation and evolution of dynamic recrystallization (DRX) were investigated with microstructural analysis and then the process variables were derived from flow curves. In the present deformation conditions, the curves of strain hardening exponent (n) and the true strain (ε) at the deformation temperature of 1423 K and strain rates of 0.1, 1 and 10 s-1 exhibit single peak and single valley. According to Zener-Hollomon and Ludwik equation, the experimental data have been regressed by using linear method. An expression of Z parameter and hot deformation equation of the tested steel were established. Moreover, the Q values of GCr15SiMn and GCr15 steels were compared. In order to determine the recrystallization fraction under different conditions, the volume fraction of DRX as a function of process variables, such as strain rate (), temperature (T), and strain (ε), was established. It was found that the calculated results agreed with the microstructure of the steel at any deformation conditions.
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  Microstructure and Mechanical Properties of Ductile Cast Iron in Lost Foam Casting with Vibration

  Bo-tao XIAO,,Zi-tian FAN,Wen-ming JIANG,,Xin-wang LIU,Wei LONG,Qiang HU,

  中国钢铁期刊网. 2014, 21(11): 1049-1054.

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  The microstructures and mechanical properties of the ductile cast iron (DI) specimens obtained by lost foam casting (LFC) with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm-2 of the specimens produced by LFC without vibration to 334 mm-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the “crystal shower” caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and pearlite colony, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.
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  Magnetic Properties of FeSiBC Amorphous Alloy Powder Cores Using Mechanical-crushed Powder

  Xiang-yue WANG,,Zhi-chao LU,,Cao-wei LU,,Guang-min LI,De-ren LI,

  中国钢铁期刊网. 2014, 21(11): 1055-1058.

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  The FeSiBC amorphous powder cores were fabricated using powders of the FeSiBC amorphous ribbons which were mechanically crushed for a short time, and the relationship between magnetic properties and powder particle sizes was evaluated. The saturation magnetization Bs of the amorphous Fe82Si2B15C1 alloy was 1.62 T, which provided a superior dc-bias property for the powder cores. Meanwhile, a stable permeability up to high frequency range over 10 MHz and the low core loss of 400 kW/m3 at f=50 kHz and Bm=0.1 T were obtained. These excellent high-frequency magnetic properties of the FeSiBC amorphous powder cores could be attributed to the effective electrical insulation between the FeSiBC amorphous powders made by mechanical crushing.
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  Influence of Oxide Morphologies on Galvanizability of Third Generation Automotive Steel

  She-ming JIANG,Shi-jie FENG,,Xun-hua YUAN,Yuan-peng LI,Zhen-hua LI,Qi-fu ZHANG

  中国钢铁期刊网. 2014, 21(11): 1059-1064.

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  Focusing on improving the galvanizability of the third generation automotive steel, the effect of surface oxide morphologies on the galvanizability was studied. The results show that the surface oxide types of sample steels by X-ray photoelectron spectroscopy (XPS) analysis after annealing in different conditions are the same. Only MnO, MnO2 and Cr2O3 were detected and no complex oxide exists on the surface. Morphologies of surface oxides can greatly influence the galvanizability of the third generation automotive steel. Nodule-like oxide surface can contribute to better wettability and inhibition layer than vitreous film-like oxide surface. Galvanized panels of nodule-like oxide surface steels only show pinhole-sized bare spots, while panels galvanized from vitreous film-like oxide surface steels reveal larger areas of bare spots and uncoated areas. Inhibition layer observed in galvanized panels of nodule-like oxide surface steels is compact but not homogeneous; some inhibition layer grains are fine, and others are coarse, while the inhibition layer grains of panels galvanized from vitreous film-like oxide surface steels have a non-compact morphology with some particularly fine equiaxed crystals which developed deficiently.