2015年, 第22卷, 第5期　刊出日期：2015-05-15

  

• 全选
  |

Metallurgy and Metal Working
• Select
  Effect of Biochar as Reductant on Magnetizing-roasting Behavior of Pyrite Cinder

  Xiao-hui FAN,Qiong DENG,Min GAN,Hai-bo WANG

  中国钢铁期刊网. 2015, 22(5): 371-376.

  摘要 ( )   可视化   收藏

  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 φCO/(φCO+φCO2) about 10%-20% between 700-800 ℃, 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 ℃ 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 64% 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 0.124-0.194 T.
• Select
  Phosphorus Capacity of CaO-SiO2-Al2O3-MgO-FexO Slag

  Jian-chao LI,Qing L,Xiao-jie LIU,Shu-hui ZHANG,Dong-hui LIU

  中国钢铁期刊网. 2015, 22(5): 377-381.

  摘要 ( )   可视化   收藏

  The CaO-SiO2-Al2O3-MgO-FexO 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-FexO 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-FexO slag, and a constant flow of CO-CO2-N2 gas was used to provide oxygen partial pressure in the experiment. The effects of MgO, FexO 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, FexO 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 FexO content. The phosphorus capacity rises linearly when the basicity is increased from 1.1 to 1.5.
• Select
  Critical Heat Flux of Blast Furnace Hearth in China

  Yang-long LI,,Shu-sen CHENG,,Chuan CHEN,

  中国钢铁期刊网. 2015, 22(5): 382-390.

  摘要 ( )   可视化   收藏

  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.
• Select
  Reduction Kinetics of Fine Iron Ore Powder in Mixtures of H2-N2 and H2-H2O-N2 of Fluidized Bed

  Jian-ming PANG,Pei-min GUO,Pei ZHAO

  中国钢铁期刊网. 2015, 22(5): 391-395.

  摘要 ( )   可视化   收藏

  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 ℃; when the average size of iron ore fines was more than 1 mm, a high reaction temperature of 800 ℃ was required. In addition, it was also found that the content of H2O should be less than 10% for efficient reduction.
• Select
  A New Technology for Copper Slag Reduction to Get Molten Iron and Copper Matte

  Jun ZHANG,Yuan-hong QI,Ding-liu YAN,Hai-chuan XU

  中国钢铁期刊网. 2015, 22(5): 396-401.

  摘要 ( )   可视化   收藏

  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.
• Select
  Self-reduction of Manganese-rich Slag Briquette Containing Carbon

  Bo ZHANG,Zheng-liang XUE,Ting-ting ZHU,Jiang DONG

  中国钢铁期刊网. 2015, 22(5): 402-407.

  摘要 ( )   可视化   收藏

  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.
• Select
  Optimization and Scheduling of Byproduct Gas System in Steel Plant

  Jing-hui YANG,Jiu-ju CAI,Wen-qiang SUN,Jing-yu LIU

  中国钢铁期刊网. 2015, 22(5): 408-413.

  摘要 ( )   可视化   收藏

  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.
• Select
  Numerical Simulation of Electromagnetic Field and Flow Pattern in a Continuous Slab Caster with In-roll Type Strand Electromagnetic Stirring

  Jian GONG,,He-ping LIU,Xian-hui WANG,Yan-ping BAO

  中国钢铁期刊网. 2015, 22(5): 414-422.

  摘要 ( )   可视化   收藏

  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 (S-EMS) 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.
Material
• Select
  Preparation and Oxidation Resistance of BN-MgAlON Composites by Hot-pressing Sintering

  Ran LIU,,Xin-yuan ZHANG,,Xing-juan WANG,,Ya-na QIE,,Qing L,,Fu GAO,

  中国钢铁期刊网. 2015, 22(5): 423-430.

  摘要 ( )   可视化   收藏

  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 ℃, and the content of CaYAl3O7 decreases as the sintering temperature increases. The BN-MgAlON composites prepared at 1750 ℃ 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 ℃ 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 2.13×105 J/mol and the frequency factor is 4.66×106.
• Select
  Influence of Ti on Weld Microstructure and Mechanical Properties in Large Heat Input Welding of High Strength Low Alloy Steels

  A-rong,Lin ZHAO,Chuan PAN,Zhi-ling TIAN

  中国钢铁期刊网. 2015, 22(5): 431-437.

  摘要 ( )   可视化   收藏

  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-Mn-Al-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%.
• Select
  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

  Zheng-yi JIANG,,Xing-jian GAO,,Sheng-li LI,Hong-mei ZHANG,Deng-fu CHEN,Jian-zhong XU

  中国钢铁期刊网. 2015, 22(5): 438-445.

  摘要 ( )   可视化   收藏

  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 ℃ 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.
• Select
  Artificial Neural Networks for Hardness Prediction of HAZ with Chemical Composition and Tensile Test of X70 Pipeline Steels

  Hesam POURALIAKBAR,,Mohammad-javad KHALAJ,Mohsen NAZERFAKHARI,Gholamreza KHALAJ

  中国钢铁期刊网. 2015, 22(5): 446-450.

  摘要 ( )   可视化   收藏

  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 (CEIIW), the carbon equivalent based upon the chemical portion of the Ito-Bessyo carbon equivalent equation (CEPcm), the sum of the niobium, vanadium and titanium concentrations (CVTiNb), the sum of the niobium and vanadium concentrations (CNbV), the sum of the chromium, molybdenum, nickel and copper concentrations (CCrMoNiCu)), 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 (R2) 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.
• Select
  Effect of Deep Cryogenic Treatment on Formation of Reversed Austenite in Super Martensitic Stainless Steel

  Shi-qi ZHENG,Wen JIANG,Xuan BAI,Shao-hong LI,Kun-yu ZHAO,Xin-kun ZHU

  中国钢铁期刊网. 2015, 22(5): 451-456.

  摘要 ( )   可视化   收藏

  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 ℃ for the two steels, which were quenched at 1050 ℃. In addition, for both with and without deep cryogenic treatment, the RA content reached a maximum value at 650 ℃ 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 ℃. 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 ℃, 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.