2020年, 第27卷, 第2期　刊出日期：2020-02-25

  

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  Review on improving gas permeability of blast furnace

  Yu-zhu Pan, Hai-bin Zuo, Jing-song Wang, Qing-guo Xue, Guang Wang, Xue-feng She

  钢铁研究学报(英文版). 2020, 27(2): 121-131.
  https://doi.org/10.1007/s42243-019-00321-y

  摘要 ( )   可视化   收藏

  Blast furnace ironmaking process is the most mature and highly effective process for producing liquid iron. Blast furnace is a gas–solid and gas–solid–liquid countercurrent reactor, and maintaining gas permeability is the precondition of smooth production. Therefore, improving the gas permeability throughout the blast furnace remains a hot issue which is concerned by many metallurgical scholars. According to the research results of many scholars, the dominant factors influencing the gas permeability of different locations in the blast furnace (locations are distinguished according to the morphology change of the burdens) were reviewed. And the strategies for improving the gas permeability of different locations in the blast furnace were summarized based on these dominant influencing factors, such as suppressing the low-temperature reduction degradation of sinter in the lump zone, improving the indirect reduction degree and suppressing the interaction between different burdens. It is hoped to provide both theoretical and practical values for guiding the blast furnace so as to improve smooth operation and smelting efficiency.
论著
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  Effect of H2 addition on process of primary slag formation in cohesive zone

  Ya-na Qie, Qing Lyu, Chen-chen Lan, Shu-hui Zhang, Ran Liu

  钢铁研究学报(英文版). 2020, 27(2): 132-140.
  https://doi.org/10.1007/s42243-019-00303-0

  摘要 ( )   可视化   收藏

  Based on the technology of gas-injection blast furnace (BF), the characteristics of primary slag formation with H2 addition were researched. The results indicate that, compared with traditional BF, the primary melt is formed at a lower temper- ature, which promotes the deformation of the solid burden particles. With the increase in temperature and H2 content, the quantity of formed melt containing FeO decreases sharply, corresponding to the crystallization of solid 2CaO·SiO2 during reduction. A wider softening range and narrower melting zone could be found in the gas-injection BF with a higher reduction potential. The permeability of burden layer is ameliorated as a result of decreased melt quantity. The influence of H2 on the high-temperature properties of burden is not so conspicuous when the H2 addition is from 10 to 15 vol.% against 5 to 10 vol.%. What is more, the slag shows a better liquidity with the decrease in basicity, owing to the transformation of melt composition from a primary phase field with high melting point to that with low melting point. The process of slag forming in gas-injection BF is characterized by earlier melt formation, less primary slag, higher melting temperature, better permeability and better liquidity, and the phase compositions of primary slag are close to those of final slag.
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  Effect of final electromagnetic stirring on solidification microstructure of GCr15 bearing steel in simulated continuous casting

  Dan-qing Jiang, Rui Wang, Qiong Zhang, Zhen-qiang Zhang, Ting-sheng Tu, Jiang Wang, Zhong-ming Ren

  钢铁研究学报(英文版). 2020, 27(2): 141-147.
  https://doi.org/10.1007/s42243-019-00257-3

  摘要 ( )   可视化   收藏

  The effect of final electromagnetic stirring on the solidification structure, element segregation, and carbides of GCr15 bearing steel was investigated. The experiment of continuous casting of the steel was carried out by using a continuous casting physical simulation apparatus with the final electromagnetic stirring. The liquid core profile was revealed by the pour-out method during the solidification process. Eight ingots were produced under different electromagnetic stirring parameters for comparison. The results show that, at the final stage of solidification, intense electromagnetic stirring exacerbates the central carbon segregation, resulting in more serious precipitation of the primary carbides. It is also found that the carbides in the segregation area are dominantly M3C type, together with a small amount of M7C3-type and M3C2- type carbides. In this physical simulation model, the optimal stirring parameters to obtain a fine and homogeneous structure are the liquid pool width of 15 mm, current intensity of 150 A, and stirring frequency of 5 Hz.
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  Effect of direct charging of hot recycled slag on hot metal pretreatment dephosphorization in a dephosphorization furnace

  Xue-feng Bai, Yan-hui Sun, Lei Luo, Chang-liang Zhao

  钢铁研究学报(英文版). 2020, 27(2): 148-159.
  https://doi.org/10.1007/s42243-019-00296-w

  摘要 ( )   可视化   收藏

  Industrial experiments were carried out to investigate the effect of the direct charging of hot recycled slag (DCHRS) on hot metal pretreatment dephosphorization in a dephosphorization furnace. The bulk compositions of semi-steel and slag show that a better dephosphorization effect could be achieved by applying the DCHRS process in the dephosphorization furnace. Compared with the bulk compositions in normal heats, the mean contents of phosphorus in the semi-steel and total Fe in the final slag were decreased by 0.006 and 1.93 wt.%, respectively, with an increase of approximately 6 °C in the semi- steel temperature. According to mineralogical observations, the dephosphorization slags in normal heats and test heats were similar in petrographic constituents, but the metal loss was markedly decreased in the DCHRS process. Thermo- dynamic calculations show that even though the dephosphorization slag in the DCHRS process had the same dephos- phorization capacity as that in the normal refining process, the phosphorus distribution between slag and hot metal in the new process was slightly higher and closer to the reaction equilibrium. Meanwhile, proper operating conditions, including slag basicity, total Fe content in the final slag, bath temperature, slag formation and slag volume, were optimized to improve the dephosphorization efficiency under the condition of the DCHRS process. The consumption of lime, light-burnt dolomite and oxygen during blowing was significantly decreased by the DCHRS process.
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  Abnormal mold level fluctuation during slab casting of peritectic steels

  Zhong-kuai Jiang, Zhi-jian Su, Cheng-qian Xu, Jin Chen, Ji-cheng He

  钢铁研究学报(英文版). 2020, 27(2): 160-168.
  https://doi.org/10.1007/s42243-019-00299-7

  摘要 ( )   可视化   收藏

  Abnormal mold level fluctuation is frequently observed in high-speed casting, especially for peritectic steels, which has been shown to severely deteriorate product quality. Both an online electromagnetic sensor and an ibaAnalyzer are used to analyze the frequency and amplitude of massive mold level fluctuation data from the slab casting process of different steel grades using different casting speeds, slab widths and physical parameters of mold flux. The results show that in the slab continuous casting process of peritectic steels, the main frequency and equivalent amplitude of abnormal mold level fluctuations first increase and then decrease with increasing the carbon content. In the production of various grades of steel, the main frequency of abnormal mold level fluctuation and the equivalent amplitude increase with increasing the casting speed, while the main frequency of abnormal mold level fluctuation changes little with increasing the casting width. The main frequency of abnormal mold level fluctuation is positively related to the surface tension of the mold flux. Based on these results, a new mechanism has been presented. It is shown that the abnormal mold level fluctuation is mainly induced by shell bulging while moving through the rollers, and resonance occurs when the frequency approaches the natural frequency of the molten steel in mold, which results in a large amplitude of the abnormal mold level fluctuation. Based on this mechanism, a new equation for the resonance frequency of molten steel is proposed. The improved method based on this mechanism has proved to be effective in controlling abnormal mold fluctuations.
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  High-performance chromite by structure stabilization treatment

  En-hui Wang, Chang Luo, Jun-hong Chen, Xin-mei Hou

  钢铁研究学报(英文版). 2020, 27(2): 169-179.
  https://doi.org/10.1007/s42243-019-00354-3

  摘要 ( )   可视化   收藏

  Chromite is an important raw material applied in refractories. Efforts have been made to obtain high-performance chromite by adding MgO and Al2O3 from the viewpoint of structure optimization. In order to explore the effect of Al2O3 and MgO on the structure, two formulas, i.e., Mg-rich and Al-rich ones, were selected. The phase and microstructure development of samples heated in the temperature range of 1200–1600 °C were studied by X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry. MgO and Al2O3 added have diffused into chromite successfully by heat treatment. MgO diffuses into chromite, occupying the tetrahedral vacancies caused by the diffusion and oxidation of Fe2+ ions to stabilize the structure. Al2O3 diffuses into the surface layer of chromite, forming spinel-sesquioxide structure. Al-rich sample which has spinel-sesquioxide structure shows better corrosion resistance toward fayalite slag than Mg-rich sample which has single spinel structure by blocking the interdiffusion between Fe2+ ions in fayalite slag and Mg2+ ions in chromite.
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  Comprehensive impact of as-cast microstructure and ordered structures on formability of large-scale Fe-6.5 wt.%Si alloy ingots

  Xiang-ju Shi, Yong-feng Liang, Shi-bo Wen, Zhi-yi Ding, Bao Zhang, Wei Song, Feng Ye

  钢铁研究学报(英文版). 2020, 27(2): 180-187.
  https://doi.org/10.1007/s42243-019-00281-3

  摘要 ( )   可视化   收藏

  Large-scale Fe–6.5 wt.%Si ingot with excellent formability is required for a pilot line producing sheets through hot/cold rolling. The variation of the as-cast microstructure, ordered structures and the formability of the Fe–6.5 wt.%Si alloy ingots with the cooling rate during casting was investigated. Under air-cooling condition, inhomogeneous microstructures with a low proportion of equiaxed grains were formed, but the formation of ordered structures was partially inhibited, especially D03. Homogeneous microstructures with a high proportion of equiaxed grains were observed under the condition of furnace cooling, but the ordered structures were fully generated, and the degree of order is high. It is generally believed that high degree of order is the main factor of brittleness, but the homogeneous microstructure (including grain morphology and size) of the furnace-cooled sample helps to improve the formability. The influence of these two aspects on formability is contradictory. Therefore, the formability is tested through the flow stress during the compression and the microstructure after the compression. The results show that the furnace-cooled sample has better formability. For large-scale ingots, the control of as-cast microstructure becomes more significant than the control of degree of order. Slow cooling during casting is important for the large-scale ingots to have good formability meeting the requirements of direct hot rolling.
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  Effect of grain recrystallization on stir zone and mechanical property behavior of TRIP 780 steel

  Gladys Pe′rez-Medina, Hugo Lopez, Argelia Miranda-Pe′rez, Eduardo Hurtado-Delgado

  钢铁研究学报(英文版). 2020, 27(2): 188-196.
  https://doi.org/10.1007/s42243-019-00309-8

  摘要 ( )   可视化   收藏

  Electron backscatter diffraction (EBSD) and transmission electron microscopy were used to determine the presence of retained austenite and displacive-type phase transformation in the stir zone of friction stir welding (FSW). Severe plastic deformations occurred in the stir zone where there was an increase in the temperature attributed to the FSW process and subsequently a grain recrystallization. Besides the recrystallization phenomena, the formation of grain evolution devel- opment in steels was resolved using EBSD. In addition, a tensile test was carried out in order to reveal the results of mechanical strength. It was found that the fracture zone occurred in the stir zone with an ultimate tensile strength of 587 MPa, a decrease of 267 MPa compared with that of the base metal. From this result, it is evident that the fracture exhibits numerous elongated dimples, distributed homogeneously, and certain locations contain cleavage fractures due to differences in the microstructure of the base metal. Microhardness profile tests of the welding regions were conducted, and the results showed that the stir zone was present with elevated hardness (near 350 HV). Characterization techniques revealed that the austenite-to-martensite transformation occurred in the stir zone, resulting in a loss of mechanical prop- erties in the joint.
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  Effects of yttrium and zirconium additions on inclusionsand mechanical properties of a reduced activation ferritic/martensitic steel

  Dong-ping Zhan, Guo-xing Qiu, Chang-sheng Li, Min Qi, Zhou-hua Jiang, Hui-shu Zhang

  钢铁研究学报(英文版). 2020, 27(2): 197-207.
  https://doi.org/10.1007/s42243-019-00332-9

  摘要 ( )   可视化   收藏

  The effects of two alloying elements, i.e., yttrium (Y) and zirconium (Zr), on the inclusion, microstructure, tensile property and impact toughness of reduced activation ferritic/martensitic (RAFM) steel are analyzed. The size and number of particles were determined by optical microscopy, and the particle types were examined by scanning electron microscopy. The size of ~ 20% and ~ 85% of the inclusions lied in the range of 0.5–1.0 μm and 0.5–3.0 μm, respectively. In Y- and Y–Zr-containing specimens, the density of the fine inclusions, with a size less than 0.5 μm, was found to be 1.06 × 1017 and 9.82 × 1016 m?3, respectively. All specimens were normalized at 1323 K for 30 min and tempered at 923 and 1023 K for 90 min, resulting in the formation of tempered martensite with M23C6 carbides and MX precipitates. Zr-containing RAFM steel tempered at 923 K formed M23C6 carbides and nano-sized carbides with Zr, conferring superior strength balance and impact toughness. The yield strength of alloy reached 695 MPa, and a low ductile–brittle transition temperature of 238 K was maintained.
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  Effect of intercritical deformation on tensile performanceof a low?carbon Si–Mn steel processed by quenching and bainitic partitioning

  Ya-qiang Tian, Zhong-qian Cao, Wang Li, Hong-bo Pan, Xiao-ping Zheng, Jin-ying Song, Ying-li Wei, Lian-sheng Chen

  钢铁研究学报(英文版). 2020, 27(2): 208-216.
  https://doi.org/10.1007/s42243-019-00357-0

  摘要 ( )   可视化   收藏

  The effect of intercritical deformation on retained austenite and tensile performance of a low-carbon Si–Mn steel in modi- fied quenching and bainitic partitioning processes was evaluated. The results showed that the intercritical deformation can play a positive role in stabilizing and refining the retained austenite, and possessed promising potential in balancing tensile strength and ductility of multiphase high-strength steels. The experimental low-carbon Si–Mn steel exhibited multiphase configuration comprising polygonal ferrite, granular bainite and granular structure after two different modified quenching and bainitic partitioning processes, and the bainitic ferrite laths got refined by intercritical deformation. The volume fraction of retained austenite in film-like and blocky morphology was increased from 11.5% to 13.9% due to applied intercritical deformation, and the larger amount of retained austenite provided the sufficient transformation-induced plasticity effect and resulted in enhanced work hardening degree; in response, enhanced ultimate tensile strength 1260 MPa and fracture elongation 22.1% were obtained, leading to increased product of strength and elongation in value of 27.7 GPa% compared to 20.8 GPa% of undeformed structure.
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  Influence of annealing on microstructure and hydrogen storage properties of V48Fe12Ti15Cr25 alloy

  Long Luo, Xuan Bian, Wen-yuan Wu, Ze-ming Yuan, Yong-zhi Li, Ting-ting Zhai, Feng Hu

  钢铁研究学报(英文版). 2020, 27(2): 217-227.
  https://doi.org/10.1007/s42243-019-00337-4

  摘要 ( )   可视化   收藏

  V48Fe12Ti15Cr25 alloy was prepared using vacuum arc melting and was subsequently annealed for 10 h at 1273 K. The effects of annealing on the hydrogen storage properties and microstructure of the V48Fe12Ti15Cr25 alloys were investigated. The results indicated that the alloy consisted of main body-centered cubic, Ti-rich, and TiFe phases. After annealing, the kinetic properties of the alloy were improved but its hydrogen storage capacity was slightly reduced. The kinetic mechanisms of the hydrogen absorption and desorption of the alloys were studied. The dehydrogenation enthalpy of the alloy was decreased by2.57 kJ/mol after annealing. Differential scanning calorimetry indicated that the hydride decomposition temperature of the annealed alloy was decreased. The hydrogen desorption activation energies of the as-cast and annealed alloys were calculated to be 79.41 and 71.25 kJ/mol, respectively. The results illustrated that annealing was a beneficial method of improving the kinetic and thermodynamic properties of the hydrogen absorption/desorption of the alloy.
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  Microstructural evolution and abrasive resistance of WC7Co ceramic particle-reinforced Ti6Al4V composite coating prepared by pulse laser cladding

  Li-jing Yang, Shao-peng Wang, Pei Wang, Huan Li, Hai-yu Yang, Yuan-sheng Ye, Zheng-xian Li

  钢铁研究学报(英文版). 2020, 27(2): 228-237.
  https://doi.org/10.1007/s42243-019-00359-y

  摘要 ( )   可视化   收藏

  WC7Co/Ti6Al4V composite coatings are deposited on the pure Ti substrate by pulse laser cladding (LC). During the laser melting process, the decomposition of WC7Co particles will lead to the evolution of microstructure and phases, which is directly related to the wear resistance and mechanism of composite coating. The microstructural evolution, phase composi- tions and interface reaction of WC7Co/Ti6Al4V composite coating were examined by scanning electron microscopy, energy- dispersive spectrum and X-ray diffraction (XRD). The hardness of different structures and abrasive resistance of composite coating were measured. The results show that the typical microstructure of LC WC7Co/Ti6Al4V composite coating can be classified into dissolved WC7Co composite structure and un-dissolved WC7Co structure. According to XRD results, there are Ti solid solution, W, TiC, VC, Co3W3C and secondary W2C in composite coating. The eutectic structure formed by the dissolved WC7Co particles consisted of W, W2C, TiC and β-Ti solid solution. The mean hardness of different structures exhibits a significant gradient distribution in composite coating. A reaction layer composed of TiC, W and W2C is also generated onto the interface between un-dissolved WC7Co particles and Ti6Al4V alloy matrix. The abrasive mechanisms of WC7Co/Ti6Al4V composite coating are mainly adhesive wear and oxidation wear during the dry sliding process.