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  Subjects -> ENVIRONMENTAL STUDIES (Total: 804 journals)
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ENVIRONMENTAL STUDIES (733 journals)            First | 1 2 3 4 5 6 7 8     

Ideas in Ecology and Evolution     Open Access   (Followers: 11)
IEEE Transactions on Network and Service Management     Hybrid Journal   (Followers: 10)
IMA Journal of Management Mathematics     Hybrid Journal   (Followers: 1)
Indiana Journal of Global Legal Studies     Full-text available via subscription   (Followers: 2)
Indoor Air     Hybrid Journal   (Followers: 1)
Information Systems Management     Hybrid Journal   (Followers: 18)
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Inhalation Toxicology     Hybrid Journal   (Followers: 7)
Integrated Environmental Assessment and Management     Hybrid Journal   (Followers: 5)
Interdisciplinary Environmental Review     Hybrid Journal   (Followers: 4)
Interfaces     Full-text available via subscription   (Followers: 6)
International Aquatic Research     Open Access   (Followers: 3)
International Archives of Occupational and Environmental Health     Hybrid Journal   (Followers: 4)
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International Gambling Studies     Hybrid Journal   (Followers: 5)
International Innovation - climate     Open Access  
International innovation. Environment     Open Access  
International Journal of Acarology     Hybrid Journal   (Followers: 1)
International Journal of Advancement in Earth and Enviromental Sciences     Open Access   (Followers: 1)
International Journal of African Renaissance Studies - Multi-, Inter- and Transdisciplinarity     Hybrid Journal   (Followers: 2)
International Journal of Agricultural and Environmental Information Systems     Full-text available via subscription   (Followers: 1)
International Journal of Alternative Propulsion     Hybrid Journal   (Followers: 1)
International Journal of Applied Psychoanalytic Studies     Hybrid Journal   (Followers: 2)
International Journal of Chinese Culture and Management     Hybrid Journal   (Followers: 2)
International Journal of Corrosion     Open Access   (Followers: 11)
International Journal of Critical Infrastructures     Hybrid Journal   (Followers: 3)
International Journal of Disaster Risk Reduction     Hybrid Journal   (Followers: 6)
International Journal of Disaster Risk Science     Open Access   (Followers: 9)
International Journal of Ecological Economics and Statistics     Full-text available via subscription  
International Journal of Ecology     Open Access   (Followers: 8)
International Journal of Ecology & Development     Full-text available via subscription   (Followers: 2)
International Journal of Energy and Environmental Engineering     Open Access   (Followers: 2)
International Journal of Environment     Open Access   (Followers: 3)
International Journal of Environment and Health     Hybrid Journal   (Followers: 7)
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International Journal of Environment and Waste Management     Hybrid Journal   (Followers: 6)
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International Journal of Environmental Engineering     Hybrid Journal   (Followers: 5)
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International Journal of Forest, Soil and Erosion     Open Access   (Followers: 4)
International Journal of Global Environmental Issues     Hybrid Journal   (Followers: 4)
International Journal of Global Warming     Hybrid Journal   (Followers: 5)
International Journal of Greenhouse Gas Control     Partially Free   (Followers: 6)
International Journal of Health Planning and Management     Hybrid Journal   (Followers: 6)
International Journal of Hygiene and Environmental Health     Hybrid Journal   (Followers: 6)
International Journal of Logistics Research and Applications : A Leading Journal of Supply Chain Management     Hybrid Journal   (Followers: 11)
International Journal of Philosophical Studies     Hybrid Journal   (Followers: 2)
International Journal of Phytoremediation     Hybrid Journal   (Followers: 2)
International Journal of Process Systems Engineering     Hybrid Journal   (Followers: 1)
International Journal of Recycling of Organic Waste in Agriculture     Open Access   (Followers: 2)
International Journal of Reliability and Safety     Hybrid Journal   (Followers: 7)
International Journal of Renewable Energy Development     Open Access   (Followers: 5)
International Journal of Social Sciences and Management     Open Access   (Followers: 1)
International Journal of Soil, Sediment and Water     Open Access   (Followers: 8)
International Journal of Stress Management     Full-text available via subscription   (Followers: 10)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 10)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Materials and Structural Systems     Hybrid Journal   (Followers: 5)
International Journal of Sustainable Society     Hybrid Journal   (Followers: 7)
International Journal of Testing     Hybrid Journal   (Followers: 1)
International Journal of the Commons     Open Access   (Followers: 3)
International Journal of Toxicology     Hybrid Journal   (Followers: 6)
International Journal of Water Resources and Environmental Engineering     Open Access   (Followers: 1)
International Studies in the Philosophy of Science     Hybrid Journal   (Followers: 12)
Interventions : International Journal of Postcolonial Studies     Hybrid Journal   (Followers: 11)
IOP Conference Series: Earth and Environmental Science     Open Access   (Followers: 7)
Iranian Studies     Hybrid Journal   (Followers: 10)
Irish Educational Studies     Hybrid Journal   (Followers: 2)
Irish Journal of Earth Sciences     Full-text available via subscription  
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Isotopes in Environmental and Health Studies     Hybrid Journal   (Followers: 1)
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Italian Studies     Hybrid Journal   (Followers: 6)
Jahangirnagar University Environmental Bulletin     Open Access  
Journal of Bioremediation & Biodegradation     Open Access   (Followers: 2)
Journal of Earth Science & Climatic Change     Open Access   (Followers: 7)
Journal of Petroleum & Environmental Biotechnology     Open Access   (Followers: 2)
Journal of Advanced Research in Civil and Environmental Engineering     Open Access   (Followers: 1)
Journal of Advances in Environmental Health Research     Open Access   (Followers: 2)
Journal of Agricultural and Environmental Ethics     Hybrid Journal   (Followers: 9)
Journal of Agricultural Biotechnology and Sustainable Development     Open Access  
Journal of Agricultural Chemistry and Environment     Open Access  
Journal of Agriculture and Environment     Open Access   (Followers: 1)
Journal of Agriculture and Environment for International Development     Open Access   (Followers: 6)
Journal of Agrobiology     Open Access   (Followers: 2)
Journal of Applied Ecology     Hybrid Journal   (Followers: 131)
Journal of Applied Meteorology and Climatology     Full-text available via subscription   (Followers: 9)
Journal of Applied Psychoanalytic Studies     Hybrid Journal   (Followers: 1)
Journal of Applied Sciences and Environmental Management     Open Access   (Followers: 1)
Journal of Applied Sciences in Environmental Sanitation     Open Access   (Followers: 6)
Journal of Applied Toxicology     Hybrid Journal   (Followers: 10)

  First | 1 2 3 4 5 6 7 8     

Journal Cover   Journal of Iron and Steel Research, International
  [SJR: 0.784]   [H-I: 16]   [8 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 1006-706X
   Published by Elsevier Homepage  [2812 journals]
  • Verification of Interpretation of Dynamic Strain Aging for Intermediate
           Temperature Embrittlement in Ni-Bi Alloy
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Wu-qiang YANG , Min XU , Ye MENG , Lei ZHENG , Xiao-dong MENG
      Intermediate temperature embrittlement (ITE) is a general phenomenon in Ni alloys and recently was interpreted by dynamic strain aging (DSA). The relationship between ITE and DSA was studied by a binary Ni-Bi alloy. The experimental alloy of well-controlled purity was produced by vacuum induction melting and then heat-treated properly. Tensile tests were performed at various tensile temperatures, and the elongation at fracture was used to indicate the ductility. In order to identify the mechanisms of fracture and ITE, fracture morphologies of the samples of low ductility were observed by scanning electron microscopy. According to the tensile ductility, Ni-Bi alloy shows an obvious embrittlement behavior in the intermediate temperature range (700 – 750 °C). However, the stress-strain curves of Ni-Bi alloy and the fracture morphologies indicate that DSA does not exist over the whole temperature range. Based on the experimental results and literatures, the interpretation of DSA was then discussed and proved to be invalid for elucidating the general feature of ITE in Ni-Bi alloy and Ni-based superalloys.


      PubDate: 2015-07-15T20:28:33Z
       
  • Preparation of Sintered (Ce1−x Ndx)30FebalCu0.1B1 Magnets by
           Blending Powder Method
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Shu-lin HUANG , Hai-bo FENG , Ming-gang ZHU , An-hua LI , Yue ZHANG , Wei LI
      Magnets with nominal compositions of (Nd1-x Ce x )30 Febal Cu0.1 B1 (x = 0, 0.15, 0.3 and 0.4, mass %) have been fabricated by blending powder method. The remanence (B r), intrinsic coercivity (H c) and maximum energy product (BH)max of the RE2Fe14B type magnets deteriorated when Nd was replaced by Ce. The chemical composition and crystal structure of magnet were investigated systemically. Backscattered electron (BSE) and energy dispersive spectroscopy (EDS) results revealed that Ce-rich and Ce-lean matrix grains coexisted in the magnets. The magnetic coupling mechanism among the double hard magnetic phases was discussed. Low melting point RE-Cu phase was in favor of the formation of uniform continuous grain boundary. Transmission electron microscopy (TEM) investigation showed the presence of fcc (Nd, Ce)O x phase in the grain boundary. When the Ce content was 15% of the total amounts of all the rare earth, the maximum energy product of the sintered magnet was 359.8 kJ/m3.


      PubDate: 2015-07-15T20:28:33Z
       
  • Optimization of Calcium Addition to High-strength Low-alloy Steels
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Gu-jun CHEN , Sheng-ping HE , Yin-tao GUO , Bo-yi SHEN , Shuo ZHAO , Qian WANG
      Nozzle blockage is a common problem during continuous casting of Al-killed steel, and calcium treatment is widely used to resolve it. In consideration of the production costs, the technology of nonmetallic inclusion control was studied to optimize the Ca consumption. The proposed process of slag washing was employed, and the refining slag composition, deoxidation conditions and alloying systems were optimized. Using these measures, the steel cleanliness before Ca addition was improved significantly, and the corresponding Ca consumption was reduced. Moreover, the continuous casting could be conducted smoothly.


      PubDate: 2015-07-15T20:28:33Z
       
  • Effect of Tempcore Processing on Mitigating Problems of Tramp Elements in
           Low C Steel Produced from Recycled Material
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Ahmed RAMADAN , A.Y. SHASH , I.S. EL-MAHALLAWI , D. SENK , Taha MATTAR
      The effect of tramp elements in the steel was intensively studied. It was found that the solubility of tramp elements decreased as the temperature decreased under normal cooling conditions. The tramp elements (Cu, Pb, and Sn) diffused toward the grain boundaries, and intermetallic compounds or rich phases which have low melting points were formed, causing reduction in ductility and failure during the bending test. Rebars with Cu content which were left to air cooling after the last step showed drop in elongation, up to 32%. On contrast, the samples with high percentage of tramp elements (Cu, Pb, and Sn) in the billet, which were rolled and subjected to Tempcore process, did not show drop in elongation or failure in bending test (especially for rebar with diameter less than 32 mm); however, copper must be less than 0. 35 mass % to prevent the precipitation of Cu-rich zones of critical size in 32 mm. When quenching was applied, the tramp elements remained in the interstitial supersaturated solid solution positions inside the grains and would not have the chance to diffuse and form precipitates, hindering the copper precipitates from reaching the critical size necessary for impairing the properties. This would hinder the occurrence of the harmful effect of the tramp elements on the elongation or the hot shortness after rolling.


      PubDate: 2015-07-15T20:28:33Z
       
  • Characteristics and Metallurgical Effects of Medium Basicity Refining Slag
           on Low Melting Temperature Inclusions
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Hui-xiang YU , Xin-hua WANG , Jing ZHANG , Wan-jun WANG
      Recently, large sized CaO-Al2 O3 inclusions with low melting temperature have been the main reason for lowering mechanical properties of high strength low alloy (HSLA) steel plates. New philosophy, i. e. refining by top slag with relatively low basicity and Al2 O3 content, was proposed to control such kind of inclusions. Firstly, the characteristics of refining slag, such as component activities and sulphide capacity (C s) of CaO-A12O3-SiO2-MgO slag, were studied through thermodynamic calculation. Then, slag-metal equilibrium experiments were carried out in laboratory to investigate the exact chemical composition of refining slag together with thermodynamic analysis. Finally, industrial trials were done to verify the desulphurization ability and inclusions control in steel refined by the new slag. Thermodynamic calculations indicated that the slags with basicity of 3. 5 and Al2 O3 content of 20% and basicity of 5.0 and A12O3 content of 20% or 25% have high values of CaO activity, sulphide capacity and ratio of MgO activity to Al2 O3 activity. Laboratory equilibrium experiments showed that the slag with basicity of about 4. 5 and Al2 O3 content of about 20% is helpful for increasing the melting temperature of inclusions in steel. After introducing such kind of refining slag in industrial trials, the sulphur content in eight heats of steel is below 20 × 10−6, which meets the requirement of HSLA steel, and most inclusions distribute in relatively high melting zone (±1773 K) of CaO-Al2O3-MgO(-SiO2) quasi-ternary diagram. New philosophy of top refining slag is feasible to control low melting point inclusions of CaO-Al2O3 system in HSLA steel.


      PubDate: 2015-07-15T20:28:33Z
       
  • Characterization and Thermodynamics of Al2O3-MnO-SiO2 (-MnS) Inclusion
           Formation in Carbon Steel Billet
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Guo-cheng WANG , Sheng-li LI , Xin-gang AI , Chong-min ZHANG , Chao-bin LAI
      A method to extract inclusion particles from solid steel by electrolysis with organic electrolyte solution was introduced; meanwhile, thermodynamics of inclusion formation was calculated using FactSage software. The results showed that there were two kinds of inclusions in the billet, i. e. Al2 O3-MnO-SiO2-MnS (AMS-MnS) and A12O3-MnO-SiO2 (AMS). Most of AMS-MnS inclusion particles, with diameter of 10 – 30 µm, showed three-layer structures: SiO2-rich core with a small quantity of Mn, intermediate AMS layer, and MnS outer layer containing small quantities of Al and O. Most AMS inclusion particles were 50 – 90 µm and exhibited homogeneous composition. Thermodynamic results indicated that SiO2-rich core could form firstly by Si reacting with O in molten steel at temperatures above 1923 K during Si-Fe alloy addition, and then, the SiO2-rich core could react with Mn and Al to form liquid AMS enveloping the SiO2-rich core at 1823 – 1873 K. MnS began to precipitate from AMS when temperature reached 1728 K. Liquid AMS could form by coupled reaction among Si, Mn, Al and O in molten steel.


      PubDate: 2015-07-15T20:28:33Z
       
  • An Estimation of Component Activity of Vanadium-bearing Liquid Iron and
           Transition Temperature of Vanadium Oxidization Using MIVM
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Ya-yu LI , Zhen-nan LIU , Dong-ping TAO
      The component activity of Mn in Fe-C-Mn system as well as the component activities of C and Si in Fe-C-Si system was predicted by applying the pseudo-multicomponent approach of the molecular interaction volume model (MIVM) and the Wagner interaction parameter formalism (WIPF) respectively. The average relative errors between the predicted values of MIVM and the experimental data for the three components were 4.5%, 17.0% and 13.0%, respectively, and those between the calculation results of the WIPF and the experimental data were 18.0% for Mn, 9.0% for C and 27.0% for Si. The results indicated that the MIVM method could better predict the component activity of carbonaceous iron-based solution. Based on the data in an actual blowing process, the MIVM method was applied to predict the component activities of C and V as well as the transition temperature of vanadium oxidization (TTVO) in Fe-C-V-Si quaternary iron-based solution, and a comparative analysis of the predictions against the experimental data was carried out, with their average relative errors being 24.0% for C, 7.3% for V and 1.0% for TTVO respectively. On that basis, the TTVO at Panzhihua Iron and Steel (Group) Co., Ltd. was estimated by the MIVM method and an expression that the TTVO changed with composition and temperature of iron solutions was obtained by multiple linear regression method. The research results showed that the estimated values were in good agreement with the practical data.


      PubDate: 2015-07-15T20:28:33Z
       
  • Effect of Aging on Hardening Behavior of 15-5 PH Stainless Steel
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Xin-yuan PENG , Xian-liang ZHOU , Xiao-zhen HUA , Zhen-wei WEI , Hua-ying LIU
      Microstructure transformation and aging hardening behavior of 15-5 PH stainless steel were studied by optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the 15-5 PH stainless steel consists of NbC precipitates and lath matensite with a high dislocation density after solution treatment. With increasing aging temperature and aging time, the martensitic laths were resolved gradually. Meanwhile, the nanometric-sized Cu precipitates gradually coarsened and lost their coherency with the martensite matrix, which exhibited an elliptical shape finally. Fine Cu precipitates can lead to significant dispersion hardening effect, while the coarsened Cu precipitates have no contribution to strengthening. The reversed austenite was observed in the specimens aged at 550 °C and above; moreover, the amount of reversed austenite increased as aging temperature increased. The precipitation hardening behavior of 15-5 PH stainless steel may depend on the balance between the softening caused by the formation of reversed austenite and the hardening caused by the precipitation of copper.


      PubDate: 2015-07-15T20:28:33Z
       
  • Hot Deformation Behavior of Vanadium-microalloyed Medium-carbon Steel for
           Fracture Splitting Connecting Rod
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Wei-jun HUI , Si-lian CHEN , Cheng-wei SHAO , Yong-jian ZHANG , Han DONG
      Single compression tests were carried out with a Gleeble-3800 thermal simulator to investigate hot deformation behavior of two vanadium-microalloyed medium-carbon steels for fracture splitting connecting rod. The tests were performed to a total true strain of 0.92 at true strain rates ranging from 10−2 to 10 s−1 and deformation temperature of 900 – 1150 °C. The results show that hot deformation behavior of the tested steels is similar to that of conventional medium-carbon microalloyed steels and dynamic recrystallization is easier to occur at higher deformation temperature and lower strain rate. The austenite deformation resistance and activation energy of deformation increase with increasing vanadium content from 0. 15% to 0. 28% and thus the starting time of dynamic recrystallization was delayed. Finer recrystallized austenite grain could be obtained at higher strain rate, lower deformation temperature and higher vanadium content. TEM observation of the specimens quenched just before and after deformation reveals that vanadium is mainly in dissolved solute condition in austenite and thus affects the dynamic recrystallization behavior of the tested steels mainly through solute-drag effect.


      PubDate: 2015-07-15T20:28:33Z
       
  • Effect of Annealing Process on Microstructure and Mechanical Property of
           1100 MPa Grade TRIP Steel
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Hong-xiang YIN , Zheng-zhi ZHAO , Ai-min ZHAO , Xiao LI , Han-jiang HU , Jiang-tao LIANG
      To develop super-high strength TRIP steel for automobile application with good combination of strength and plasticity, an ultra-high-strength TRIP steel 0. 2%C-2. 0% Si-1. 8% Mn was investigated at different intercritical annealing temperatures and bainitic isothermal temperatures. Microstructures were observed by scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and X-ray diffraction, and mechanical properties were tested under a uniaxial tensile testing machine. It shows that the best comprehensive mechanical properties were obtained for the experimental steel particularly annealed at 820 °C and austempered at 410 °C. Yield strength of the tested steel mainly depends on ferrite, while the high strength of the tested steel is related to martensite which forms through blocky austenite transformation during cooling and subsequent tensile test attributed to the TRIP effect. Hence, it could be concluded that the grain size of the retained austenite and carbon content in retained austenite are the main reasons for high elongation of the tested steel.


      PubDate: 2015-07-15T20:28:33Z
       
  • Influence of Chromium on Corrosion Behavior of Low-alloy Steel in Cargo
           Oil Tank O2-CO2-SO2-H2S Wet Gas Environment
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Peng ZHOU , Jin-ming LIANG , Fei ZHANG , Hui-bin WU , Di TANG
      As international maritime organization (IMO) draft 289 was adopted to develop a low-alloy anti-corrosion steel for the deck of cargo oil tank and to understand corrosion mechanism, corrosion behavior of a low-alloy steel with chromium contents was studied in O2-CO2-SO2-H2S wet gas environment. Corrosion rate was measured, and the microstructure and morphology of corrosion product film were characterized by scanning electron microscopy (SEM). The phase and chemical composition of the corrosion product film were investigated by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The effect of misorientation distribution on corrosion resistance of steel was evaluated by electron backscattered diffraction (EBSD). The results showed that corrosion rate decreased with increasing chromium content in the low-alloy steel, and the corrosion type was general corrosion. The phenomenon of chromium enrichment was found in corrosion product film consisting of α-FeOOH, γ-FeOOH, sulphur, FeS2 and Fe1–x S. The increase of chromium content decreases the amount of high-angle grain boundaries, thus resulting in the improvement of corrosion resistance.


      PubDate: 2015-07-15T20:28:33Z
       
  • Ultrasonic Fatigue Damage Behavior of 304L Austenitic Stainless Steel
           Based on Micro-plasticity and Heat Dissipation
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Chao HE , Ren-hui TIAN , Yong-jie LIU , Jiu-kai LI , Qing-yuan WANG
      Very high cycle fatigue behavior (107 – 109 cycles) of 304L austenitic stainless steel was studied with ultrasonic fatigue testing system (20 kHz). The characteristics of fatigue crack initiation and propagation were discussed based on the observation of surface plastic deformation and heat dissipation. It was found that micro-plasticity (slip markings) could be observed on the specimen surface even at very low stress amplitudes. The persistent slip markings increased clearly along with a remarkable process of heat dissipation just before the fatigue failure. By detailed investigation using a scanning electron microscope and an infrared camera, slip markings appeared at the large grains where the fatigue crack initiation site was located. The surface temperature around the fatigue crack tip and the slip markings close to the fracture surface increased prominently with the propagation of fatigue crack. Finally, the coupling relationship among the fatigue crack propagation, appearance of surface slip markings and heat dissipation was analyzed for a better understanding of ultrasonic fatigue damage behavior.


      PubDate: 2015-07-15T20:28:33Z
       
  • Effect of Martensite Fine Structure on Mechanical Properties of an 1100
           MPa Grade Ultra-high Strength Steel
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Fan ZHEN , Kuan ZHANG , Zhi-long GUO , Jin-bo QU
      An 1100 MPa grade ultra-high strength steel with different martensite fine structures, characterized by prior austenite grain size, martensite packet size, block width and lath width, was studied by various heat treatment processes. The result shows that with decreasing prior austenite grain size, both the packet size and block width decrease, while the lath width has virtually no change. Accordingly, both strength and toughness increase, while total elongation decreases. The yield strength has a Hall-Petch type relationship with the prior austenite grain size, packet size and block width, and the block width may be regarded as a key factor influencing strength. On the other hand, the ductile to brittle transition temperature (DBTT) is found to be more related to the packet size, which may be considered as a dominant factor influencing toughness.


      PubDate: 2015-07-15T20:28:33Z
       
  • Structure and Performance Changes of Ni-Co-Al Shape Memory Alloys in
           Relation to Co/Al Atomic Ratio
    • Abstract: Publication date: July 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 7
      Author(s): Jia JU , Feng XUE , Liu-xia SUN
      As a potential ferromagnetic shape memory alloy, Ni-Co-Al has excellent mechanical properties, large magentic-field-induced strain and high martensitic transformation temperature. The relationship between microstructure and performance (mechanical and magnetic properties) of Ni-Co-Al with different Co/Al atomic ratios (R Co/A1) was investigated. Samples exhibit β and γ dual-phase structure. The γ phase grows coarse and the volume fraction of γ phase increases with the rise of R Co/A1. Besides, sample with high amount of γ phase content has smaller β grains owing to the pinning effect of γ phase. The martensite, transformed from β phase, is tetragonal L10 structure with a (1 1) twinning plane. The martensitic transformation temperature of samples ascends with increasing R Co/A1 owing to more Co embedded into the cell, which makes the valence electron concentration (e/a) of system rise. The saturation magnetization (M s) of samples increases as R Co/A1 rises because Co-rich γ phase has excellent magnetic property. Meanwhile, both compressive and micro-hardness tests reveal that the samples containing more γ phase have excellent ductility due to the intrinsic good ductility nature of γ phase.


      PubDate: 2015-07-15T20:28:33Z
       
  • Life Cycle Assessment of Iron Ore Sintering Process
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Zong-ping LI , Xiao-hui FAN , Gui-ming YANG , Jin-chao WEI , Ying SUN , Min WANG
      Iron ore sintering is an energy-intensive process associated with emission of pollutants in iron and steel industry. In order to comprehensively evaluate the environmental impacts of sintering, a detailed life cycle assessment of a sintering plant was conducted. Life cycle inventory showed that, in the production of 1 t sinter ore, 241. 53 kg CO2, 22. 68 kg CO, 0. 294 kg SO2, 0.63 kg NO x , 1.18 μg dioxin and 0. 48 kg dust were discharged. Global warming potentials, acidification potentials, photochemical ozone creation potentials and human toxicity potentials were selected as four impact categories, and the evaluation index for the sintering plant was calculated as 3. 45 × 10−12. Finally, based on the environmental impact analysis, several measures of reducing environmental loadings of the sintering plant were provided, which included the utilization of denitrification equipment, recirculation of the hot waste gas and process improvement to reduce fuel consumption.


      PubDate: 2015-06-27T10:28:57Z
       
  • Influence of Coating MgO on Sticking and Functional Mechanism during
           Fluidized Bed Reduction of Vanadium Titano-magnetite
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Lei GUO , Jin-tao YU , Jing-kun TANG , Yin-he LIN , Zhan-cheng GUO , Hui-qing TANG
      The vanadium titano-magnetite (VTM) iron ore fines of 110–150 μm in diameter were reduced in a transparent quartz fluidized bed by 70%CO-30%H2 (volume fraction) mixtures. MgO powders served as coating agent to solve sticking problem. Two coating methods were introduced in this experiment: high temperature injection method and briquetting→oxidizing roast→crushing method. According to the experimental results, the minimum effective coating amount of MgO was 0.1 mass%. The metallization ratio (MR) of the product rose from around 58% to above 90% with the above treatments. To investigate the sticking mechanism of fine ore, the morphology evolution was investigated. Instead of iron whiskers, an interlaced fibrous porous surface formed. The ulvospinel (2FeO · TiO2) in VTM is more difficult to be reduced than FeO according to thermodynamic calculation. XRD results showed that MgO diffused into Fe2O3 lattice before forming pleonaste (MgO · Fe2O3) during oxidizing roast at 1273 K. The melting point of the pleonaste is 1986 K and that made contribution to prevent the sticking problem.


      PubDate: 2015-06-27T10:28:57Z
       
  • Corrosion Behavior of High Performance Offshore Platform Steel with
           Chromium and Nickel Addition in the Environment Containing Chloride Ions
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Yan-lei ZHOU , Xiang-jun ZHANG , Tao JIA , Zhen-yu LIU
      The characterization of corrosion products formed on a high performance offshore platform steel in the environment containing chloride ions has been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and electrochemical impedance spectroscopy (EIS). The results reveal that the corrosion process can be divided into the initial stage and the later stage. The main constituents of rust layers are α-FeOOH, β-FeOOH, γ-FeOOH, Fe3O4 and large amounts of amorphous compounds. With increasing corrosion time, the mass fraction of α-FeOOH and Fe3O4 increased, while that of γ-FeOOH and β-FeOOH changed slightly. The enrichment of Cr and Ni at the inner/outer interface, especially the side of inner rust, can be observed in the later corrosion stage of Cr-Ni steel, which can promote the formation of compact inner rust layer, impeding the transmission of corrosion mediums and slowing down the electrochemical reaction process.


      PubDate: 2015-06-27T10:28:57Z
       
  • Intelligent Multivariable Modeling of Blast Furnace Molten Iron Quality
           Based on Dynamic AGA-ANN and PCA
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Meng YUAN , Ping ZHOU , Ming-liang LI , Rui-feng LI , Hong WANG , Tian-you CHAI
      Blast furnace (BF) ironmaking process has complex and nonlinear dynamic characteristics. The molten iron temperature (MIT) as well as Si, P and S contents of molten iron is difficult to be directly measured online, and large-time delay exists in offline analysis through laboratory sampling. A nonlinear multivariate intelligent modeling method was proposed for molten iron quality (MIQ) based on principal component analysis (PCA) and dynamic genetic neural network. The modeling method used the practical data processed by PCA dimension reduction as inputs of the dynamic artificial neural network (ANN). A dynamic feedback link was introduced to produce a dynamic neural network on the basis of traditional back propagation ANN. The proposed model improved the dynamic adaptability of networks and solved the strong fluctuation and resistance problem in a nonlinear dynamic system. Moreover, a new hybrid training method was presented where adaptive genetic algorithms (AGA) and ANN were integrated, which could improve network convergence speed and avoid network into local minima. The proposed method made it easier for operators to understand the inside status of blast furnace and offered real-time and reliable feedback information for realizing close-loop control for MIQ. Industrial experiments were made through the proposed model based on data collected from a practical steel company. The accuracy could meet the requirements of actual operation.


      PubDate: 2015-06-27T10:28:57Z
       
  • Effect of Nickel on Formation Mechanisms of Silico-ferrite of Calcium and
           Aluminum (SFCA)
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Xin-yu LI , Bu-xin SU , Lei-ge XIA , Jian-liang ZHANG , Hong-wei GUO
      Under the pressures of both the decrease of high-grade high-quality iron ore resources and the increase of raw material costs, the iron and steel enterprises in China turn to adopt iron ores which contain special elements such as nickel, manganese, etc. in the sintering blend. Analytical reagents were used for sintering experiments, and the sinters were analyzed with X-ray diffraction, scanning electron microscopy and mineralogical microscopy to study the effect of nickel on the silico-ferrite of calcium and aluminum (SFCA) bonding phase formation during sintering. The results indicated that SFCA was divided into nickel-containing and nickel-free areas due to the presence of nickel. The increasing content of nickel would greatly reduce the content of SFCA and promote the formation of calcium aluminum silicate. A great deal of Fe2O3 participated in the crystal transition to Fe3O4, reducing the amount of Fe2O3 involved in the formation of calcium ferrite. When the blending ratio of NiO, which is used to provide the nickel in the sintering process, is less than 3%, the calcium ferrite is in substantially interleaving corrosion with hematite and magnetite. Both the porosity and silicate glass phase content are low, which contributes to the sintering production.


      PubDate: 2015-06-27T10:28:57Z
       
  • A Coupled Thermodynamic Model for Prediction of Inclusions Precipitation
           during Solidification of Heat-resistant Steel Containing Cerium
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Yan-dong LI , Cheng-jun LIU , Chun-long LI , Mao-fa JIANG
      A coupled thermodynamic model of inclusions precipitation both in liquid and solid phase and microsegregation of solute elements during solidification of heat-resistant steel containing cerium was established. Then the model was validated by the SEM analysis of the industrial products. The type and amount of inclusions in solidification structure of 253MA heat-resistant steel were predicted by the model, and the valuable results for the inclusions controlling in 253MA steel were obtained. When the cerium addition increases, the types of inclusions transform from SiO2 and MnS to Ce2O3 and Ce2O2S in 253MA steel and the precipitation temperature of SiO2 and MnS decreases. The inclusions CeS and CeN convert to Ce2O3 and Ce2O2S as the oxygen content increases and Ce2O3 and CeN convert to Ce2O2S, Ce3S4, and MnS as the sulfur content increases. The formation temperature of SiO2 increases when the oxygen content increases and the MnS precipitation temperature increases when the sulfur content increases. There is only a small quantity of inclusions containing cerium in 253MA steel with high cleanliness, i.e., low oxygen and sulfur contents. By contrast, a mass of SiO2, MnS and Ce2O2S are formed in steel when the oxygen and sulfur contents are high enough. The condition that MnS precipitates in 253MA steel is 1.2w [O] + w [s]>). 01% and SiO2 precipitates when 2w [O]+w [s]>0.017% (w [S]<0.005%) and w [O]>0. 006% (w [S]>0. 005%).


      PubDate: 2015-06-27T10:28:57Z
       
  • High Temperature Low Cycle Fatigue Behavior of GH4742 Alloy
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): He-yong QIN , Gang CHEN , Qiang ZHU , Chuan-jie WANG , Peng ZHANG
      High temperature low cycle fatigue tests on GH4742 superalloy were studied under the total strain-controlled conditions at 650 °C. Combined with fatigue test data, fatigue properties of the alloy were analyzed. Fracture morphology and dislocation structure were observed by scanning electron microscopy and transmission electron microscopy. The results showed that fatigue life and fatigue resistance of GH4742 alloy decreased significantly with increasing total strain amplitude. The cyclic hardening, cyclic softening and cyclic stability phenomena of the alloy occurred during the low cycle fatigue process. The increasing total strain amplitude is conducive to the formation of γ′ phase. Fatigue crack propagation is controlled jointly by ductile and brittle fracture. Inhomogeneous deformation and deformation restricted in slip bands are the main reasons for the reduction of fatigue life of GH4742 alloy.


      PubDate: 2015-06-27T10:28:57Z
       
  • Effects of Particle Size on Nitridation Kinetics of Manganese Powder
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Ting LUO , Jian-hua LIU , Hong-bo LIU , Jian LIU
      Isothermal thermo-gravimetric analysis was applied to investigate the nitridation kinetics of manganese powder with different particle sizes at 800, 900 and 1000 °C. The apparent activation energy and nitridation kinetics equations of manganese powder with different particle sizes were obtained from unreacted shrinking core model and Arrhenius formula. It was found that the nitridation mechanism was controlled by interfacial chemical reaction. The apparent activation energy and the apparent rate constant of nitridation reaction were affected by particle sizes. With the decrease of particle size, the apparent activation energy decreased whilst the apparent rate constant increased. It was suggested that the refinement of the manganese powder contributed to the increase of molar surface energy, which accounted for the lower apparent activation energy.


      PubDate: 2015-06-27T10:28:57Z
       
  • Low Cycle Fatigue Behavior and Cyclic Softening of P92
           Ferritic-martensitic Steel
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Zhen ZHANG , Zheng-fei HU , Li-kun FAN , Bin WANG
      The low cycle fatigue (LCF) behavior of P92 martensitic steel was investigated under different controlled strain amplitudes at room and high temperatures (873 K). The cyclic stress responses at all temperatures and strain amplitudes exhibited obviously rapid softening behavior at the early stage of fatigue life, and there was no saturated stage at high temperature. The fracture surfaces of the fatigue samples were observed by scanning electron microscopy (SEM) and optical microscopy. It was shown that crack initiation and propagation occurred transgranularly at both testing temperatures. A typical character was the high density crack branches or secondary cracks along fatigue striations at high temperature, which initiated from the oxidized inclusions and grain boundaries. Further investigation by transmission electron microscopy (TEM) showed that the softening behavior was attributed to the microstructure evolution during fatigue life, such as annihilation of dislocations and migration of martensite laths as well as carbide coarsening, especially for samples tested at high temperature.


      PubDate: 2015-06-27T10:28:57Z
       
  • Phase Transformation and Its Effect on Mechanical Properties of C300 Weld
           Metal after Aging Treatment at Different Temperatures
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Shuai YANG , Yun PENG , Xiao-mu ZHANG , Zhi-ling TIAN
      The influence of aging temperature on phase transformation and mechanical properties of weld metal of maraging steel (grade C300) was studied. Microstructure was analyzed by means of optical microscopy, transmission electron microscopy, scanning electron microscopy and energy dispersive spectrum analysis. Gibbs free energy of Ni3Ti and Fe2Mo at different temperature was calculated by Thermal-calc software. The microstructure of weld metal in as-welded state is martensite. The yield strength of weld metal after 430 °C aging process may increase to 1561 MPa from 890 MPa in as-welded state, which is ascribed to the formation of spinodal constitute and GP zones. After 480 °C aging process, there are great deal of Ni3Ti precipitates in the martensite matrix and 10% reverted austenite phase in the cellular grain boundary, and the yield strength increases to 1801 MPa. After aging process at 580 °C, there are many Fe2Mo precipitates in the martensite matrix and 30% reverted austenite phase in the cellular grain boundary, and the yield strength is 1329 MPa, which is the lowest among the three cases. The phase transformation may also influence the toughness. It is found that precipitates make the toughness decrease and reverted austenite increases it. The mechanism of phase transformation on strength and toughness is discussed.


      PubDate: 2015-06-27T10:28:57Z
       
  • Hot Stamping Parameters Optimization of Boron Steel Using a Response
           Surface Methodology Based on Central Composite Design
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Ming-dong HUANG , Bao-yu WANG , Jing ZHOU
      The effect of hot stamping parameters on the mechanical properties of 22MnB5 steel sheet with thickness of 1.1 mm is studied. The considered parameters are austenization temperature (800–1000 °C), austenitizing soaking time (60–540 s), initial deformation temperature (560–800 °C) and tool temperature (20–220 °C). In order to obtain hot stamped parts with optimal mechanical properties, response surface methodology based on the central composite design has been employed to design the experiment matrix. Tensile strength of hot stamped parts is determined as the relation in the mathematical model. The optimal condition and objective effects of parameters are determined via this relation. The statistical analysis showed that all four factors significantly affect the tensile strength of the hot stamped parts. The optimum austenization temperature is found to be 918.89 °C with the austenitizing soaking time, initial deformation temperature and tool temperature of 279. 45 s, 684. 69 °C and 21. 85 °C, respectively. These optimal hot stamping parameters prove to have high tensile strength (1631. 84 MPa) where deviation between predicted and actual response falls within 2%.


      PubDate: 2015-06-27T10:28:57Z
       
  • Determination of Flow Curve and Plastic Anisotropy of Medium-thick Metal
           Plate: Experiments and Inverse Analysis
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Xin-cun ZHUANG , Hua XIANG , Tao WANG , Zhen ZHAO , Tan LI
      Sheet bulk metal forming is widely used for medium-thick metal plate due to its convenience in the manufacture of accurately finished 3D functional components. To obtain precise anisotropy and flow curve of metal plate is a prerequisite for correct simulation of sheet bulk metal forming processes. Inverse analysis of compression test was introduced here to evaluate the sensitivity of different flow curve models and geometric influence of compression test specimen. Besides, a methodology was proposed to compute plastic anisotropic coefficients of Hill quadratic yield criterion, which is based on the ratios of flow curves obtained by inverse analysis of compression tests using specimens cut in six directions on the medium-thick metal plate. The obtained flow curves and anisotropic coefficients were compared with those calculated from tensile tests. Flow curves based on inverse analysis of compression tests cover the curves of the tensile tests well, while the anisotropic coefficients are different, especially for the coefficient related to the RT45 direction. To estimate the effectiveness of the proposed method, the calculated material properties and those based on the traditional tensile tests were applied in a rim-hole process simulation. The simulation results based on the material properties from inverse analysis of compression tests accorded with the tested properties better.


      PubDate: 2015-06-27T10:28:57Z
       
  • Surface Carbon Chemical States of Ion Implanted AISI 440C Martensitic
           Stainless Steel
    • Abstract: Publication date: June 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 6
      Author(s): Jie JIN , Feng-bin LIU , Yun-bo CHEN , Ke-wei GAO
      Carbon atoms segregate in the surface region for polished AISI 440C stainless steel. After ion implantation, the surface carbon atoms exist in different forms. To elucidate their existence, surface structures and carbon chemical states of unimplanted, N+ implanted, Ti+ implanted and N+/Ti+ co-implanted samples were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that various phases form in the surface or subsurface region after ion implantation, while the surface topography of the samples remains intact. For polished unimplanted sample, besides some Fe3C phase and C-C phase, Cr x Cy phase dominates its surface region. Little change of carbon chemical states occurs after N+ ion implantation. For Ti+ implanted sample, besides some metal oxycarbide phases, most carbon amorphous phases form in surface region. Concerning N+/Ti+ co-implantation, Cr x C y , compound as well as Fe3C phase dominates the surface region while no C-C phase is found. In addition, compared with single-ion implantation, N+/Ti+ co-implantation would increase the ion implantation depth significantly. The formed phases of the carbon atoms play an important role in affecting the surface properties of AISI 440C stainless steel.


      PubDate: 2015-06-27T10:28:57Z
       
  • Interface Analysis and Hot Deformation Behaviour of a Novel Laminated
           Composite with High-Cr Cast Iron and Low Carbon Steel Prepared by Hot
           Compression Bonding
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Zheng-yi JIANG , Xing-jian GAO , Sheng-li LI , Hong-mei ZHANG , Deng-fu CHEN , Jian-zhong XU
      A hot compression bonding process was developed to prepare a novel laminated composite consisting of high-Cr cast iron (HCCI) as the inner layer and low carbon steel (LCS) as the outer layers on a Gleeble 3500 thermomechanical simulator at a temperature of 950 °C and a strain rate of 0.001 S-1. Interfacial bond quality and hot deformation behaviour of the laminate were studied by microstructural characterisation and mechanical tests. Experimental results show that the metallurgical bond between the constituent metals was achieved under the proposed bonding conditions without discernible defects and the formation of interlayer or intermetallic layer along the interface. The interfacial bond quality is excellent since no deterioration occurred around the interface which was deformed by Vickers indentation and compression test at room temperature with parallel loading to the interface. After well cladding by the LCS, the brittle HCCI can be severely deformed (about 57 % of reduction) at high temperature with crack-free. This significant improvement should be attributed to the decrease of crack sensitivity due to stress relief by soft claddings and enhanced flow property of the HCCI by simultaneous deformation with the LCS.


      PubDate: 2015-05-07T17:41:35Z
       
  • Influence of Ti on Weld Microstructure and Mechanical Properties in Large
           Heat Input Welding of High Strength Low Alloy Steels
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): A-rong , Lin ZHAO , Chuan PAN , Zhi-ling TIAN
      The influence of Ti on weld microstructure and mechanical properties in large heat input welding of high strength low alloy steels is investigated. The results indicate that a moderate amount of Ti is still effective for grain refinement even under larger heat input and a large amount of acicular ferrite (AF) is formed in the weld metal when Ti content is within 0.028% – 0.038%. With increasing Ti content, proeutectoid ferrite in the weld metal decreases, whereas bainite and M-A constituent increase. The type of inclusion in the welds varies from Mn-Si-Al-O to Ti-MnAl-O and finally to Ti-Al-O as Ti content increases from 0 up to 0.064%. As for adding 0.028%–0.038% Ti, high weld toughness could be attained since most inclusions less than 2 μm which contain Ti2O3 provide the effective nuclei for acicular ferrite formation. However, the toughness of the weld metals severely reduces when Ti content is over the optimum range of 0.028%–0.038%.


      PubDate: 2015-05-07T17:41:35Z
       
  • Preparation and Oxidation Resistance of BN-MgAlON Composites by
           Hot-pressing Sintering
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Ran LIU , Xin-yuan ZHANG , Xing-juan WANG , Ya-na QIE , Qing LÜ , Fu GAO
      BN-MgAlON composites were prepared by hot-pressing sintering under nitrogen atmosphere with BN-MgAlON composite powders as raw material and Y2O3, as sintering additive. Based on thermodynamic analysis, the oxidation resistance of BN-MgAlON composites was investigated and the dynamics of oxidation process was also analyzed. The oxidation process and the micro-morphology of the samples before and after oxidation were characterized by X-ray diffraction and scanning electron microscopy. The dynamics of oxidation resistance of the BN-MgAlON composites was investigated via the analysis of the constant temperature oxidation mass gain curves. The results show that the main components of the material are MgAlON, Sialon. BN and CaYAl3O7 at 1650-1750 °C, and the content of CaYAl3O7 decreases as the sintering temperature increases. The BN-MgAlON composites prepared at 1750 °C is uniform and compact with the balanced distributions of Al, Mg. O. and N. The oxidation process of BN-MgAlON composites in air mainly consists of MgAlON, Sialon and BN oxidation. The section after being oxidized at 1000–1300 °C involves three layers, namely, the outer layer, the middle layer and the inner layer. The oxidation process follows the parabola model. The apparent activation energy of the oxidation process is 2. 13×103 J/mol and the frequency factor is 4.66 × 106.


      PubDate: 2015-05-07T17:41:35Z
       
  • Numerical Simulation of Electromagnetic Field and Flow Pattern in a
           Continuous Slab Caster with In-roll Type Strand Electromagnetic Stirring
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Jian GONG , He-ping LIU , Xian-hui WANG , Yan-ping BAO
      The electromagnetic field and flow analysis model were developed to simulate the electromagnetic field and the flow pattern in a vertical curved continuous slab caster with the in-roll type strand electromagnetic stirring. The transient electromagnetic field distribution and the induced electromagnetic force were numerically described. The effects of stirring current, stirring frequency, and different stirrer configurations on the electromagnetically driven flow field in the strand were investigated and the optimization of the stirring parameters was discussed by performing a relative comparison of numerical results. Results show that the in-roller type strand electromagnetic stirrer (SEMS) pair generates the fluctuating magnetic fields, penetrating through the cast slab and periodically parallel shifting along the slab wide face with time evolution. The transient induced electromagnetic forces travels toward the magnetic flux shifting direction. Different stirring parameters (i. e. current and frequency) and stirrer configurations affect the stirring strength and the flow recirculation pattern in the strand, which are closely related to metallurgical performances of the stirrers. There is an optimum frequency to obtain the maximum stirring. The present model provides a relatively theoretical insight into the in-roll type strand electromagnetic stirring system for best operating.


      PubDate: 2015-05-07T17:41:35Z
       
  • Optimization and Scheduling of Byproduct Gas System in Steel Plant
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Jing-hui YANG , Jiu-ju CAI , Wen-qiang SUN , Jing-yu LIU
      A mathematical model was proposed to optimize byproduct gas system and reduce the total cost. The scope and boundaries of the system were also discussed at the same time. Boilers and gasholders were buffer users to solve the fluctuation of byproduct gases. The priority of gasholders should be ranked the last. The allocation of surplus gases among gasholders and boilers was also discussed to make full use of gases and realize zero emission targets. Case study shows that the proposed model made good use of byproduct gases and at least 7.8% operation cost was reduced, compared with real data in iron and steel industry.


      PubDate: 2015-05-07T17:41:35Z
       
  • Self-reduction of Manganese-rich Slag Briquette Containing Carbon
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Bo ZHANG , Zheng-liang XUE , Ting-ting ZHU , Jiang DONG
      The self-reduction experiment of manganese-rich slag briquette containing carbon was carried out in a high-temperature carbon tube furnace. The main factors affecting the reduction rate were analyzed, and the kinetic model of reduction was established. The results show that the increase of basicity of briquette has an obvious effect on improving reduction rate. When the carbon ratio of briquettes is 1. 2 and its basicity is 1. 0, the reduction rate can reach 90%. It can accelerate reduction process and decrease reduction time when the appropriate flux CaF2 is added to the briquette. The apparent activation energy of chemical reaction is 24. 07 kJ/mol, and the apparent activation energy of internal diffusion is 107.55 kJ/mol by calculation. Therefore, the reduction rate of briquette is determined by the mass transfer of CO in the product layer.


      PubDate: 2015-05-07T17:41:35Z
       
  • A New Technology for Copper Slag Reduction to Get Molten Iron and Copper
           Matte
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Jun ZHANG , Yuan-hong QI , Ding-liu YAN , Hai-chuan XU
      The change of iron composition as well as the removal of copper from iron was investigated in the reduction process, and a new way to deal with copper slag was proposed. The iron in copper slag exists mainly in the form of fayalite, and the copper sulfide content accounts for just about 50%. Therefore, the magnetic separation as well as grinding floatation method is not suitable, and a pyrogenic treatment on copper slag is necessary. The carburization and desulfurization process is restricted to a degree within the carbon composite pellets, and copper matte phase precipitates from copper slag in the reduction process, which is immiscible with molten iron and slag. The copper content decreases to 0.4 % as the carbon content in molten iron reaches 3. 84 %, and the removal ratio of copper from molten iron approaches to 80%. The reduction and sulfurization process can be completed in one step, and the copper is separated from iron based on the ternary system of iron-matte-slag.


      PubDate: 2015-05-07T17:41:35Z
       
  • Reduction Kinetics of Fine Iron Ore Powder in Mixtures of H2-N2 and
           H2-H2O-N2 of Fluidized Bed
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Jian-ming PANG , Pei-min GUO , Pei ZHAO
      Reduction kinetics of fine iron ore powder in different gas mixtures were investigated in high-temperature fluidized bed at a scale of kilograms. Influence of processing parameters, such as particle size, gas flow velocity, height of charge, temperature, compositions of gas mixture, and percentage of inert components, on reduction kinetics was experimentally determined under the condition of fluidization. The equations for calculating instantaneous and average oxidation rates were deduced. It was found that an increasing H2O percentage in the gas mixture could obviously decrease the reduction rate because the equilibrium partial pressure of H2 decreased with increasing content of H2O in the gas mixture and then the driving force of reduction reaction was reduced. When the H2 content was high, the apparent reaction rate was so rapid when the average size of iron ore fines was less than 1 mm that the reaction temperature can be as low as 750 °C; when the average size of iron ore fines was more than 1 mm, a high reaction temperature of 800 °C was required. In addition, it was also found that the content of H2O should be less than 10% for efficient reduction.


      PubDate: 2015-05-07T17:41:35Z
       
  • Critical Heat Flux of Blast Furnace Hearth in China
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Yang-long LI , Shu-sen CHENG , Chuan CHEN
      The critical heat flux surveys of thirteen Chinese blast furnaces were carried out. The mathematical model of hearth bottom was established and the temperature field was simulated by utilizing the method of inverse problem based on the collected parameters and temperature data. The critical heat flux and dangerous critical heat flux of hearth were defined and analyzed as well as the initial and investigative critical heat flux of hearth, and the influences of thermal conductivity and residual thickness of carbon bricks on critical heat flux were discussed. The relationships between critical heat flux of stave and hearth bricks were also compared. It is found that the dangerous critical heat flux of these blast furnaces ranged from 9.38 to 57 kW/m2. Therefore, there was no uniform critical heat flux of hearth due to the structure design, refractory materials selection, construction quality of hearth and other factors. The heat flux should be lower than the critical heat flux with corresponding thickness of carbon bricks to control the erosion of hearth. The critical heat flux of stave would be much lower than that of hearth bricks with the air gap. However, the critical heat flux of stave should be higher than that of hearth bricks when gas existed between furnace shell and staves.


      PubDate: 2015-05-07T17:41:35Z
       
  • Effect of Biochar as Reductant on Magnetizing-roasting Behavior of Pyrite
           Cinder
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Xiao-hui FAN , Qiong DENG , Min GAN , Hai-bo WANG
      The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated. The key of magnetizing-roasting is the gasification reaction between reductants and CO2. Since biochar could react with CO2 more rapidly at lower temperature, the reactivity of biochar is better than that of anthracite. The gasification of biochar could produce reducing condition of φ CO / (φ CO + φ CO2) about 10% – 20% between 700–800 °C, which is in accord with the atmosphere and temperature of Fe2O3 reduction. So it is beneficial to the reduction of iron mineral of pyrite cinder. Compared with anthracite, biochar could decrease the roasting temperature from 825 to 750 °C and roasting time from 20 to 15 min, which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time. Using biochar as reductant, iron concentrate extracted from pyrite cinder as about 61% iron grade could be produced, and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.121–0.194 T.


      PubDate: 2015-05-07T17:41:35Z
       
  • Phosphorus Capacity of CaO-SiO2-Al2O3-MgO-FexO Slag
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Jian-chao LI , Qing LÜ , Xiao-jie LIU , Shu-hui ZHANG , Dong-hui LIU
      The CaO-SiO2-Al2O3-MgO-Fe x O slag occurs in the production process of Corex ironmaking technology. Most of its metallurgical properties, especially the phosphorus property, are different from the slag produced from blast furnace or converter. In order to explore the dephosphorization ability of CaO-SiO2-Al2O3-MgO-Fe x O slag, its phosphorus capacity was measured at 1673 K by gas-slag-metal equilibrium technique. An iron crucible was used as the reaction vessel, Ag alloy with 0.2% P was used as the metal phase which equilibrated with CaO-SiO2-Al2O3-MgO-Fe x O slag, and a constant flow of CO-CO2-N2 gas was used to provide oxygen partial pressure in the experiment. The effects of MgO, Fe x O and basicity on slag phosphorus capacity were investigated by single factor test. The results show that the phosphorus capacity rises firstly and then decreases with increasing MgO content under the condition of basicity 1. 3, Fe x O content of 2% and Al2O3 content of 12%. The phosphorus value reaches maximum as the MgO content is 8%. When the basicity of slag is 1. 1, MgO content is 10%, and Al2O3 is 12%, the phosphorus capacity increases with the increase of Fe x O content. The phosphorus capacity rises linearly when the basicity is increased from 1. 1 to 1. 5.


      PubDate: 2015-05-07T17:41:35Z
       
  • Artificial Neural Networks for Hardness Prediction of HAZ with Chemical
           Composition and Tensile Test of X70 Pipeline Steels
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Hesam POURALIAKBAR , Mohammad-javad KHALAJ , Mohsen NAZERFAKHARI , Gholamreza KHALAJ
      A neural network with feed-forward topology and back propagation algorithm was used to predict the effects of chemical composition and tensile test parameters on hardness of heat affected zone (HAZ) in X70 pipeline steels. The mass percent of chemical compositions (i. e. carbon equivalent based upon the International Institute of Welding equation (CE IIW), the carbon equivalent based upon the chemical portion of the Ito-Bessyo carbon equivalent equation (CE Pcm), the sum of the niobium, vanadium and titanium concentrations (C VTiNb), the sum of the niobium and vanadium concentrations (C NbV), the sum of the chromium, molybdenum, nickel and copper concentrations (C CrMoNiCu), yield strength (YS) at 0.005 offset, ultimate tensile strength (UTS) and percent elongation (El) were considered as input parameters to the network, while Vickers microhardness with 10 N load was considered as its output. For the purpose of constructing this model, 104 different data were gathered from the experimental results. Scatter diagrams and two statistical criteria, i. e. absolute fraction of variance (R 2) and mean relative error (MRE), were used to evaluate the prediction performance of the developed model. The developed model can be further used in practical applications of alloy and thermo-mechanical schedule design in manufacturing process of pipeline steels.


      PubDate: 2015-05-07T17:41:35Z
       
  • Effect of Deep Cryogenic Treatment on Formation of Reversed Austenite in
           Super Martensitic Stainless Steel
    • Abstract: Publication date: May 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 5
      Author(s): Shi-qi ZHENG , Wen JIANG , Xuan BAI , Shao-hong LI , Kun-yu ZHAO , Xin-kun ZHU
      The effect of deep cryogenic treatment on the formation of reversed austenite (RA) in super martensitic stainless steel was investigated. RA was found to form in steels without (A) and with (B) deep cryogenic treatment. The volume fraction of RA initially increased and then decreased with increasing tempering temperature over 550–750 °C for the two steels, which were quenched at 1050 °C. In addition, for both with and without deep cryogenic treatment, the RA content reached a maximum value at 650 °C although the RA content in steel B was greater than that in steel A over the entire range of tempering temperatures. Furthermore, the hardness (HRC) of steel B was greater than that of steel A at tempering temperatures of 550–750 °C. From these results, the basic mechanism for the formation of RA in steels A and B was determined to be Ni diffusion. However, there were more Ni-enriched points, a lower degree of enrichment, and a shorter diffusion path in steel B. It needed to be noted that the shapes of the RA consisted of blocks and stripes in both steels. These shapes resulted because the RA redissolved and transformed to martensite along the martensitic lath boundaries when the tempering temperature was 650-750 °C, and a portion of RA in the martensitic lath divided the originally wider martensitic laths into a number of thinner ones. Interestingly, the RA redissolved more rapidly in steel B and consequently resulted in a stronger refining effect.


      PubDate: 2015-05-07T17:41:35Z
       
  • Model of Iron Ore Sintering Based on Melt and Mineral Formation
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Jun ZHANG , Xing-min GUO , Yuan-hong QI , Ding-liu YAN
      A model of iron ore sintering was built with consideration of fuel combustion, catalysis of sinter mixture as well as formation of melt and mineral, which was verified via sintering pot tests and showed a good fit to the experimental results. The effect of bed depth on temperature was reflected by the residence time in high-temperature zone, rather than the top value of the temperature, which was weakened by melt formation as well as hematite decomposition. Moreover, the effect of bed depth, fuel content and distribution on sintering process was different, which was reflected by temperature profiles and the rule of calcium ferrite formation. The formation of melt as well as magnetite was a process which was decided by kinetic factors, while the formation of calcium ferrite was related to fuel blending conditions, which is determined by thermodynamics when the fuel ratio inside sinter granules is low or fuel content is high, otherwise, it is determined by kinetics.


      PubDate: 2015-04-13T01:01:09Z
       
  • Velocity Preset and Transitional Zone's Shape Optimization for Tailor
           Rolled Blank
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Dong-cheng WANG , Lian-chao DONG , Hong-min LIU , Yan WANG
      Tailor rolled blank (TRB) is a type of emerging material to produce lightweight vehicle parts. Transitional zone's shape is an important parameter for tailor rolled blank. It not only affects mold design and the local carrying capacity of the stamping parts, but also determines the maximum value and variation characteristics of rolling force. How to get the best transitional zone's shape is a key problem for production of tailor rolled blank. A double power function is put forward using for transitional curve, which is continuous and smooth at all connection points independent of its parameters, so the sudden change of mechanical parameters during rolling and forming process can be avoided. At the same time, the velocity formula and restriction for arbitrary transitional curve are derived to preset vertical velocity of the roller and judge whether the curve can be rolled successfully or not. Then, the finite element method (FEM) is used to verify the precision of velocity formula and study the mechanical characteristics of different curves. Finally, a method to obtain the optimal curve equation is put forward and verified.


      PubDate: 2015-04-13T01:01:09Z
       
  • Microstructural Evolution and Properties of a High Strength Steel with
           Different Direct Quenching Processes
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Feng LU , Chao WANG , Long LÜ , Zhao-dong WANG , Guo-dong WANG , Raja Devesh Kumar MISRA
      A high strength low alloy steel with low carbon equivalent was selected for simulating online direct quenching and coiling (DQ-C) process. The influence of stop quenching temperature on mechanical properties and microstructures was studied and compared with normal direct quenching and tempering (DQ-T) process. The study confirmed that required mechanical properties were obtained for both the processes. Properties of the experimental steel with DQ-C process could reach the same level as that of DQ-T process in general. In the DQ-C process, strength decreased with increase in stop quenching temperature. Martensite was obtained and experienced an aging process at stop quenching temperature below M f. On fast cooling below M s, martensite was partially transformed and carbon partitioning occurred during slow cooling. The reduction in solid solution carbon and increased amount of retained austenite led to lower strength compared with the DQ-T process. DQ-C process was more favorable for microalloy carbide precipitation. However, impact toughness under different cooling conditions was adequate because of low carbon equivalent and refined microstructure.


      PubDate: 2015-04-13T01:01:09Z
       
  • Microstructure and Mechanical Properties of Precipitation Strengthened
           Fire Resistant Steel Containing High Nb and Low Mo
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Zheng-yan ZHANG , Qi-long YONG , Xin-jun SUN , Zhao-dong LI , Jun-yu KANG , Guo-dong WANG
      Through the thermo-mechanical control process (TMCP), a high Nb low Mo fire resistant steel with the yield strength (YS) of 521 MPa at room temperature (RT) and 360 MPa at elevated temperature (ET) of 600 °C was developed based on MX (M=Nb, V, Mo; X=C, N) precipitation strengthening. A series of tensile and constant load tests were conducted to study the mechanical properties at ET. The dynamic continuous cooling transformation (CCT) as well as precipitation behavior of microalloy carbonitride was investigated by means of thermal simulator and electron microscopy approaches. Results showed that the failure temperature of tested steel was determined as 653 °C, and the granular bainite was obtained when the cooling rate was higher than 10 °C/s. In the rolled state, a certain amount of M/A islands was observed. During heating from RT to ET, M/A islands disappeared, and cementites and high dense compound precipitates (Nb, Mo, V)C with size of less than 10 nm precipitated in ferrite at ET (600 °C), which resulted in precipitation strengthening at ET.


      PubDate: 2015-04-13T01:01:09Z
       
  • Carbide Evolution in High Molybdenum Nb-microalloyed H13 Steel during
           Annealing Process
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Tian-sheng LI , Fu-ming WANG , Chang-rong LI , Guo-qing ZHANG , Qing-yong MENG
      Based on the Thermo-Calc thermodynamic software, the type of equilibrium precipitated carbides and their contents in high Mo Nb-microalloyed H13 steel (NMH13 steel) were calculated. The composition, morphology, and distribution of carbides after spheroidal annealing of two forged experimental steels were comparatively examined by means of optical microscopy (OM), scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). VC, M23C6 and M6C are identified in H13 steel after spheroidizing annealing, while (V, Nb)C, M23C6, M2C and M6C are observed in NMH13 steel. Moreover, it is found that the addition of Nb significantly enhances the stability of MC phase and the high Mo content accelerates the precipitation of small rod-shape M2C phase in NMH13 steel. The amount of the fine carbides in NMH13 steel obviously increased with M2C and M6C precipitated from the ferrite phase, which is in accordance with the results of thermodynamic calculations.


      PubDate: 2015-04-13T01:01:09Z
       
  • Effects of Different Substrates on Microstructures and Mechanical
           Properties of a Bulk Nanocrystalline Structure Pure Iron Prepared by
           Aluminothermic Reaction Casting
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Xiao-juan ZHEN , Pei-qing LA , Cui-ling LI , Su-lei HU
      A simple method was developed to produce the nanocrystalline pure iron by aluminothermic reaction casting. The microstructure of the iron was investigated by optical microscope (OM), transmission electron microscope (TEM), electron probe micro-analyzer (EPMA), scanning electron microscope (SEM) and X-ray diffraction (XRD). The mechanical performances of nanocrystalline pure iron were tested. It is found that the pure iron consists of nanocrystalline ferrite. For different substrates of copper and glass, the average grain size of the ferrite was 38 and 35 nm, respectively, which is larger on copper substrate than that on glass. The hardness, compressive strength, tensile strength, and total elongation are 167 and 137 HB, 400 and 500 MPa, 243 and 185 MPa, 16% and 10% on copper substrate and glass substrate, respectively. The hardness, tensile strength and total elongation are all larger on copper substrate than those on glass substrate, while the compressive strength is lower. The large supercooling in the product solidification provides the condition for high nucleation rate and thus leads to nano-grained austenite and final nano-grained ferrite transformed from those small austenite grains.


      PubDate: 2015-04-13T01:01:09Z
       
  • Solid-phase Decarburization Kinetics of High-carbon Ferromanganese Powders
           by Microwave Heating
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Li-na GUO , Jin CHEN , Jing ZHAO , Wan-ming LIN , Wen-li SHI , Min LIANG
      Solid-phase decarburization of high-carbon ferromanganese powders (HCFPs) was conducted using calcium carbonate powders (CCPs) as a decarburizer by microwave heating. Solid-phase decarburization kinetics was investigated by isothermal method. The results show that the HCFPs show excellent microwave absorption at a higher average heating rate of 80 °C/min, while CCPs exhibit poor microwave absorption at a lower heating rate of 5—20 °C/min; the heating characteristics are in-between when HCFPs and CCPs are mixed. The average heating rates of the mixture are 32. 14, 31. 25, 31. 43, and 30. 77 °C/min when the mixture is heated up to 900, 1000, 1100, and 1200 °C, respectively. The good microwave absorption property of the mixed material lays the foundation for the solid-phase decarburization of HCFPs containing CCPs. Solid-phase decarburization of HCFPs containing CCPs is a first-order reaction by microwave heating. Apparent activation energy of solid-phase decarburization is 55. 07 kJ/mol, which is far less than that of ordinary carbon gasification reaction and that of solid-phase decarburization under the same decarburization condition by conventional heating. It indicates that microwave heating not only produces thermal effect, but also has non-thermal effect.


      PubDate: 2015-04-13T01:01:09Z
       
  • Abrasive Wear Resistance of Dual Phase Steels DP980 and DP600
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Xiu-lin JI , Ju-yi WANG , Cui-cui JI , Jian-hua ZHAO
      The abrasive wear resistance of dual phase (DP) steels DP980 and DP600 was investigated by using an ASTM rubber wheel abrasion tester. At 2. 40 m • s−1 sliding speed under 19. 9 N load with 180—355 μm abrasive sands, the wear rates of DP980 and DP600 were 1. 01×10−11 and 0. 86×10−11 m3 • m−1, respectively, corresponding to about 1. 9 and 2. 3 times of the relative wear resistance of normal low-carbon steel ASTM A283C. Using directly water quenching from austenitic temperature, the abrasive wear resistance of DP980 samples under 19. 9 N load could be improved by 1. 65 times. The wear rates of DP980 and DP600 samples decreased respectively with increasing sliding speed and abrasive particle size and decreasing applied load. The experimental results reveal that the effect of martensite on the wear resistance not only depends on the volume fraction but also depends on the morphology, distribution and grain size.


      PubDate: 2015-04-13T01:01:09Z
       
  • Influence of Cohesive Zone Shape on Solid Flow in COREX Melter Gasifier by
           Discrete Element Method
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Li-hao HAN , Zhi-guo LUO , Heng ZHOU , Zong-shu ZOU , Yu-zhu ZHANG
      Based on the principle of discrete element method (DEM), a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the cohesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main regions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increases. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.


      PubDate: 2015-04-13T01:01:09Z
       
  • Softening and Melting Behavior of Ferrous Burden under Simulated Oxygen
           Blast Furnace Condition
    • Abstract: Publication date: April 2015
      Source:Journal of Iron and Steel Research, International, Volume 22, Issue 4
      Author(s): Hua-jie ZHANG , Xue-feng SHE , Yi-hua HAN , Jing-song WANG , Fan-bo ZENG , Qing-guo XUE
      The softening and melting behavior of sinter, pellet and mixed burden was researched through high temperature reaction tests under load simulating traditional blast furnace (T-BF) and oxygen blast furnace (OBF) conditions. The results indicated that compared with T-BF, the softening zone of sinter and pellet became wide, but the melting zone became narrow in OBF. The permeabilities of both sinter and pellet were improved in OBF. Under the condition of OBF, the temperature of softening zone of mixed burden was increased by 63 K, but the temperature of melting zone was decreased by 76 K. Therefore, the permeability of material layer was significantly improved. This was mainly caused by the change of the melting behavior of pellet. In addition, the quality of dripping iron in OBF was much better than that of T-BF.


      PubDate: 2015-04-13T01:01:09Z
       
 
 
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