2010年, 第17卷, 第3期　刊出日期：2010-03-15

  

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  A Brief Overview of Low CO2 Emission Technologies for Iron & Steel Making

  Chunbao (Charles) Xu

  中国钢铁期刊网. 2010, 17(3): 1-7.

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  The global steel production has been growing for the last 50 years, from 200 million metric tons in 1950s to 1,240 million metric tons in 2006. Iron and steelmaking industry is one of the most energy-intensive industries, with an annual energy consumption of about 24 EJ, 5% of the world's total energy consumption. The steel industry accounts for 3-4% of total world greenhouse gas emissions. While enhancing energy efficiency could be a short-term approach for the steel industry to reduce greenhouse gas emission, the long-term approaches to achieve a significant reduction in CO2 emissions from the steel industry would be through (1) developing and applying CO2 breakthrough technologies for iron and steelmaking, and (2) increasing use of renewable energy (in particular, bio-energy) for iron and steelmaking. This paper presents an overview of new CO2 breakthrough technologies for iron and steelmaking, and the current research and development for the use of biomass and bio-fuels as substitutes for coke, coal and natural gas in various iron and steelmaking processes including iron-ore sintering, blast furnace operations, and new iron and steelmaking processes. The key challenges for utilization of bio-energy on a large scale for iron and steelmaking are also discussed in this paper.
工艺
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  Evaluation of four coals for blast furnace pulverized coal injection

  Sh. Raygan

  中国钢铁期刊网. 2010, 17(3): 8-12.

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  One of the effective methods to reduce coke consumption is Pulverized Coal Injection (PCI). The most important problems encountered in this method are reduced permeability, unburned and high ash content. In order to select the best coal for injection suitable tests can be used. In this investigation, experiments such as proximate and ultimate analysis, Rock- Eval and combustion tests have been performed on four kinds of coals from different mines, Sarakhs, Sangrood, Karmozd and Tabas. The results of proximate and ultimate analysis indicate that although the sulfur and ash content of selected coals are a little high, but they are suitable for coal injection. The results of combustion experiments and Rock-Eval tests show that karmozd coal is the best one to inject into the blast furnace. It is shown that mixing of coals can improve the combustion properties of pulverized coals.
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  Microstructure of Solid Phase Reduction on Manganese Oxide Ore Fines Containing Coal by microwave heating

  CHEN Jin;TIAN Peng-fei

  中国钢铁期刊网. 2010, 17(3): 13-13.

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  Microstructure of solid-phase reduction on manganese oxide ore fines containing coal (MOOFCC) is one of important kinetics conditions of influencing microwave heating. In the condition that an atomic molar ratio of rO: rC in MOOFCC is 1:1.06 as well as a molecular molar ratio of rSiO2: rCaO is 1:1.28, 1 kg of MOOFCC is heated by microwave to reach 1000～1300℃ and hold different time respectively. Experiments show that the metal phase takes the iron-based metal compounds containing manganese as the main content. The manganese content of metal phase increases with the rise of temperature. The partical size of the metal phase is within the range from 0.01 to 0.05mm. MO2 phase in the stuff is entirely changed into MnO phase and the slag phase is mainly composed of wollastonite and manganese olivine. The stuff reduced is loose and massive as a whole with porosity of it from 30 to 45 %. The low softening-melting property and the low density of the stuff impact, to some degree, the solid-phase reduction of powder by microwave heating.
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  Development of Strip Flatness and Crown Control Model for Hot Strip Mills

  LI Hai-jun;XU Jian-zhong

  中国钢铁期刊网. 2010, 17(3): 21-21.

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  The strip flatness and crown control model is the foundation of automatic strip shape control. In this paper, considering the metal transverse flows and the inter stand second deformation, the trip flatness and crown control model has been developed , which can be applied to CVC mills and PC mills as well as normal four-high mills. The strip flatness and crown control model has a high precision, and has been successfully applied to the automatic strip shape control system reconstruction of Tangshan Ganglu 1250mm hot strip plant.
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  Linear Integral Analysis of Bar Rough Rolling by Strain Rate Vector

  DENG Wei;ZHAO De-wen

  中国钢铁期刊网. 2010, 17(3): 28-33.

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  A new linear integral method for bar hot rolling on roughing train was obtained. Above all, for inner deformation power, equivalent strain rate about Kobayashi’s three-dimensional velocity field was expressed by two-dimensional strain rate vector then inverted it into inner product and integrated term by term. During those processes, boundary equations and mean value theorem were introduced; but solution by definite integral was applied to integral procedure for friction and shear power. Then minimized the total upper bound power, and sequentially, analytical expressions of roll torque and separating force, and stress state factor were obtained. The calculated results by the expressions were compared with those of experimental values. The results show that this new linear integral method is available for analysis of bar rough rolling and the calculated results by the method are higher than those of experimental ones. However, the maximum error percentage between them is less than 10%.
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  Influence of Specimen Geometry of Hot Torsion Test on Temperature Distribution During Reheating Treatment of APIX70

  Bahman Mirzakhani

  中国钢铁期刊网. 2010, 17(3): 34-34.

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  The commercial finite element package ANSYSTM was utilized for prediction of temperature distribution during reheating treatment of hot torsion test (HTT) samples with different geometries for APIX70 microalloyed steel. Simulation results show that an inappropriate choice of test specimen geometry and reheating conditions before deformation could lead to nonuniform temperature distribution within the gauge section of specimen. Therefore, assumptions of isothermal experimental conditions and zero temperature gradient within the specimen cross section appear unjustified and led to uncertainties of flow curve obtained. Recommendations on finding proper specimen geometry for reducing temperature gradient along the gauge part of specimen will be given to create homogeneous initial microstructure as much as possible before deformation in order to avoid uncertainty in consequent results of HTT.
材料
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  Construction and Application of Quenching Critical Cooling Rate Model

  付天亮 王日清 王昭东 王国栋 王明涛

  中国钢铁期刊网. 2010, 17(3): 40-45.

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  Based on exploring quenching mechanism, three types of medium-low carbon steel and low-alloy construction steel’s quenching critical cooling rate models were established, respectively speaking, modified Maynier model, Eldis model and isothermal curve model. During construction process, regression analysis and Newton interpolation method were used for higher calculated precision. Through comparing and analyzing, the superior one was singled out to evaluate the full hardening thickness after quenching. According to hardness analyzing, the deviation between predicted hardness distribution and the experimental value is within 6%.
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  CCT Curves of low carbon Mn-Si steels and development of water cooled bainitic steels

  XU Feng-yun;WANG Yong-wei

  中国钢铁期刊网. 2010, 17(3): 46-50.

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  CCT curves of Mn-Si steels with different Mn content or carbon content were tested and on this basis, water cooled baintic steels with non-expensive alloy element were developed. The results show that transformation of bainite can be separated from that of ferrite when Mn content approach certain content; relative length of incubation time of ferrite and bainite transformation can be controlled by changing carbon content in Mn-Si; granular bainite was obtained when Ф300mm bar cooled by water, mix structure of fine widmanstatten ferrite, granular bainite and martensite was obtained as plate of 40mm thickness cooled by water; water cooled baintic steels developed with non-expensive alloy shows good combination of strength and toughness and tensile strength, yield strength and toughness (AKU -20 oC ) of Ф300m bar after water cooled is higher than 850MPa, 620MPa, 65 J respectively, and tensile strength, yield strength and toughness (AKU -20 oC ) of plate of 40mm thickness after water cooled is higher than 1000 MPa, 800MPa, 50 J respectively
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  Influence of PreTransformed Martensite on WorkHardening Behavior of SUS 304 Metastable Austenitic Stainless Steel

  XUE Zong-yu;ZHOU Sheng

  中国钢铁期刊网. 2010, 17(3): 51-55.

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  The metastable austenite was transformed to martensite by prestrain tension of SUS304 stainless steel to study the influence of transformed martensite on its subsequent workhardening behavior under the uniaxial tensile condition. The Xray diffractometer (XRD) was employed to detect the transformed martensite. Results showed that the volume fraction of transformed martensite increases with increasing prestrain. The pretransformed martensite in the microstructure remarkably affects the deformation behavior of the steel, and the strength increases and the elongation decreases. The workhardening curve of prestrained specimens observably changes with true strain. The workhardening exponent n of stainless steel decreases with the increase of pretransformed martensite. The achievement is a significant contribution to the process design during pressing.
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  Analysis on Microstructure Characteristics and Precipitation Behavior of Automobile Beam Steels Produced by Compact Strip Production

  ZHAO Zheng-zhi;LIU Jie

  中国钢铁期刊网. 2010, 17(3): 56-56.

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  The microstructure characteristics and precipitation behavior of automobile beam steels produced by Compact Strip Production (CSP) were investigated by use of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy. The result shows that the final microstructure is mainly of polygonal ferrite and small amount of pearlite, the average ferrite grain size is about 3～6μm. Small amount addition Ti to aluminium-killed steel can help to refine the microstructure and improve the mechanical properties. A large number of fine precipitates have been observed in automobile beam steels. The mean particle size is about 10～30nm. Remarkable strengthening and grain refinement can be obtained by these nano-particles.
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  Austenite Grain Growth Behavior of X80 Pipeline Steel in Heating Process

  DUAN Lin-na

  中国钢铁期刊网. 2010, 17(3): 62-66.

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  Through changing soaking temperature and soaking time, austenite grain growth behavior of X80 pipeline steel under different heating conditions was studied. Relationships of average grain size with soaking temperature and time were obtained respectively. The results show that the prior-austenite grains grow with the increase of soaking temperature and time. When soaking temperature is lower than 1180℃, austenite grain size and growth rate are small; when it higher than 1200℃, austenite grains grow rapidly and abnormal grain growth appears. Soaking at 1180℃, austenite grain growth rate is initially high and then decreases when soaking time exceeds 1h.
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  Influence of Solution Treatment on Microstructure of AEREX350 Alloy

  WAN Wen-juan;HAN Guang-wei

  中国钢铁期刊网. 2010, 17(3): 67-71.

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  The microstructure of hot-rolled AEREX350 alloy under various heat treatments was investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that with increasing temperature, η phase precipitated firstly at grain boundaries in parallel at 800℃ and then began precipitating within grains at about 980℃. The η phase precipitating at grain boundaries played a role on preventing the migration of grain boundaries, and that precipitating within grains would develop as Widmanstätten structure with further increasing temperature. Both η phase dissolved at the temperature between 1085℃ and 1095℃, resulting in grain growth promptly due to release of pinning effect on grain boundaries. γ′ phase precipitated during the process of air cooling after hot-roll, and dissolved at temperature between 1010℃ and 1020℃.
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  Chemistry and Process Optimization of V-Microalloyed N80-Class Seamless Casing Tube

  PAN Tao;YANG Cai-fu

  中国钢铁期刊网. 2010, 17(3): 72-78.

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  Chemistry and process optimization of N80 seamless tube was studied by thermo-mechanical simulation tester Gleeble 1500D. Several heats of V-microalloyed steel with different N contents were firstly made at lab in order to simulate N80 seamless tube steel. The results showed that N addition increased strength under condition that toughness was kept at a high level compared with low-N steel. In this study N content with 120-200 ppm enhanced combination performance of strength and toughness whether in-line normalizing process was adopted or not. In-line normalizing process was helpful to improve the toughness though it lowered strength by some degree. However, direct final rolling after tandem rolling (without in-line normalizing) helped increase strength while the toughness remained somehow poor. The above phenomena concerning N80 seamless tube was closely associated with dissolution and precipitation behavior of V(CN). V(CN) precipitation was optimized when N content was increased. When in-line normalizing process was adopted, V(CN) precipitation in austenite increased due to low temperature history during intermediate (in-line) normalizing process. V(CN) particles existing in austenite contributed to grain refinement for VN induced intergranular ferrite, while they weakened precipitation strengthening effect since V precipitating in ferrite wais reduced.