2020年, 第27卷, 第12期　刊出日期：2020-12-25

  

• 全选
  |

论著
• Select
  Preparation of blast furnace burdens by composite agglomeration process: effect of distribution of magnetite and hematite concentrates in pelletized and matrix feed

  Fo‑quan Gu, Yuan‑bo Zhang, Guang‑hui Li, Qiang Zhong, Jun Luo, Zi‑jian Su, Ming‑jun Rao, Zhi‑wei Peng, Tao Jiang

  钢铁研究学报(英文版). 2020, 27(12): 1363-1371.
  https://doi.org/10.1007/s42243-020-00376-2

  摘要 ( )   可视化   收藏

  Effect of distribution of iron concentrates between pelletized and matrix feed on the preparation of blast furnace burdens from two different kinds of fine iron concentrates (magnetite and hematite) by composite agglomeration process (CAP) was explored. It was found that when the mass ratio of iron concentrate A (magnetite) to iron concentrate B (hematite) in the mixed feed was constant, the proportion of iron concentrate A in the pelletized and matrix feed significantly affected the quality of CAP products. Particularly, as the proportion of iron concentrate A in the pelletized feed increased from 0 to 100%, the yield decreased from 82.11% to 79.19% and the tumbler index decreased from 71.33% to 68.27%. The mineralization characterization results indicated that when 100% iron concentrate A was used as the pelletized feed, the crystallization styles of the outer layer and the inner layer of the pellet were different, and a lot of pores exist around hematite and magnetite phases in the pelletized part, with the weak connection of pelletized and matrix part, resulting in poor strength of agglomeration product.
• Select
  Transformation and separation of metallic iron in reduced ilmenite during corrosion process

  Fu‑qiang Zheng, Xia Liu, Yu‑feng Guo, Shuai Wang, Feng Chen, Ling‑zhi Yang, Tao Jiang1 · Guan‑zhou Qiu1

  钢铁研究学报(英文版). 2020, 27(12): 1372-1381.
  https://doi.org/10.1007/s42243-020-00476-z

  摘要 ( )   可视化   收藏

  The effects of corrosion temperature, oxygen flow rate and corrosion time on the transformation of metallic iron were systematically studied, and the effects of mineral phases of Fe-bearing products on Ti–Fe separation were investigated. The reaction mechanism of metallic iron in corrosion process was proposed. The results showed that corrosion temperature played a key role in determining the transformation of metallic iron in reduced ilmenite during corrosion process. Under suitable corrosion conditions, Fe-bearing mineral in reduced ilmenite could be converted to amorphous ferric hydroxide, lepidocrocite, hematite and magnetite, respectively, and lepidocrocite was the most easily separated Fe-bearing mineral from corrosion products owing to the significant density difference between lepidocrocite and Ti-rich materials. The Ti-rich material with 77.81 wt.% TiO2 and Fe-bearing product with 52.69 wt.% total Fe were obtained by gravity separation. The Ti recovery ratio and Fe recovery ratio were 91.16% and 86.27%, respectively.
• Select
  Distribution of reformed coke oven gas in a shaft furnace

  Xin Jiang, Jia-xin Yu, Lin Wang, Dong-wen Xiang, Qiang-jian Gao, Hai-yan Zheng, Feng-man Shen

  钢铁研究学报(英文版). 2020, 27(12): 1382-1390.
  https://doi.org/10.1007/s42243-020-00508-8

  摘要 ( )   可视化   收藏

  In recent years, the reformed coke oven gas (COG) was proposed to be used as reducing gas in a shaft furnace. A mathematical model of gas flow based on the reformed COG was built. The effects of the pressure ratio of reducing gas to cooling gas (k) on the gas distribution in the shaft furnace were investigated. The calculation results show that k is an important operation parameter, which can obviously affect the gas distribution in the shaft furnace. The value of k should be compromised. Both too big and too small k values are not appropriate, and the most reasonable value for k is 1:1.33. Under this condition, the utilization coefficient of reducing gas, the utilization coefficient of cooling gas and the coefficient of upward gas are 0.94, 0.92 and 1.03, respectively. Based on the validation of physical experiments, the calculated values of the model agreed well with the physical experimental data. Thus, the established model can properly describe the reformed COG distribution in an actual shaft furnace.
• Select
  Effect of magnesium injection process on hot metal desulfurization

  Jian-ming Su, Zhi-he Dou, Ting-an Zhang, Yan Liu

  钢铁研究学报(英文版). 2020, 27(12): 1391-1399.
  https://doi.org/10.1007/s42243-020-00507-9

  摘要 ( )   可视化   收藏

  To solve the technical problems of hot metal desulfurization by injecting magnesium particulate, a new method of hot metal desulfurization by bottom-blowing magnesium vapor combined with mechanical agitation was put forward. The effects of three different desulfurization processes on the desulfurization efficiency were studied in view of thermodynamics and kinetics. It was found that the utilization efficiency of magnesium can reach 82.6% and desulfurization efficiency can reach 86.2% during the first 4 min using the method of magnesium vapor injection combined with mechanical agitation. The gasification of magnesium powder leads to significant splashing and magnesium losses in the process of magnesium powder injection, resulting in a low utilization efficiency of magnesium of 51.8% and a low desulfurization efficiency of 55.76%. Activation energy for a first-order kinetic relationship between magnesium powder and sulfur was measured from the experiments, which was 142.82 kJ/mol in the temperature range of 1573–1723 K. The activation energy of the reaction between magnesium vapor and sulfur was around 54.8–65.0 kJ/mol in the temperature range of 1573–1723 K, which indicates that the desulfurization with magnesium vapor proceeds relatively easier than the desulfurization with magnesium powder.
• Select
  Effect of basicity and Al₂O₃ on viscosity of ferronickel smelting slag

  Yong-feng Chen, Xue-ming Lv, Zheng-de Pang, Xue-wei Lv

  钢铁研究学报(英文版). 2020, 27(12): 1400-1406.
  https://doi.org/10.1007/s42243-020-00504-y

  摘要 ( )   可视化   收藏

  The effect of the Al₂O₃ content and basicity (the molar ratio of MgO to SiO₂) on the viscosity of a SiO₂–MgO–FeO– Al₂O₃–CaO slag was studied to fully understand the smelting process of the ferronickel alloy. Experimental results show that the slag is a mixture of liquid and solid phases at the experimental temperature. The viscosity decreased as the basicity increased and increased as the Al₂O₃ content increased. To determine the effect of the Al₂O₃ content and basicity on the structure of the molten slag, Raman spectroscopy was performed on the slag sample, which was quenched from the high temperature with water. The Raman spectra showed that the fractions of the polymerization structural units decreased significantly as the basicity of the slag increased, resulting in a decrease in the apparent viscosity. However, Al₂O₃ acts as a network former in the slag system, thereby making the slag structure further polymerized and increasing the viscosity.
• Select
  Unbalanced classification method using least squares support vector machine with sparse strategy for steel surface defects with label noise

  Li-ming Liu, Mao-xiang Chu, Rong-fen Gong, Xin-yu Qi

  钢铁研究学报(英文版). 2020, 27(12): 1407-1419.
  https://doi.org/10.1007/s42243-020-00499-6

  摘要 ( )   可视化   收藏

  Least squares support vector machine (LS-SVM) plays an important role in steel surface defects classification because of its high speed. However, the defect samples obtained from the real production line may be noise. LS-SVM suffers from the poor classification performance in the classification stage when there are noise samples. Thus, in the classification stage, it is necessary to design an effective algorithm to process the defects dataset obtained from the real production line. To this end, an adaptive weight function was employed to reduce the adverse effect of noise samples. Moreover, although LSSVM offers fast speed, it still suffers from a high computational complexity if the number of training samples is large. The time for steel surface defects classification should be as short as possible. Therefore, a sparse strategy was adopted to prune the training samples. Finally, since the steel surface defects classification belongs to unbalanced data classification, LSSVM algorithm is not applicable. Hence, the unbalanced data information was introduced to improve the classification performance. Comprehensively considering above-mentioned factors, an improved LS-SVM classification model was proposed, termed as ILS-SVM. Experimental results show that the new algorithm has the advantages of high speed and great anti-noise ability.
• Select
  Effect of cold rolling and annealing on microstructure and properties of a new resource-saving duplex stainless steel Fe–19Cr–0.6Al–12Mn

  Ming‑ming Pan, Xiao‑ming Zhang, Yong Chen, Xiang‑bin Su, Peng Chen

  钢铁研究学报(英文版). 2020, 27(12): 1420-1432.
  https://doi.org/10.1007/s42243-020-00438-5

  摘要 ( )   可视化   收藏

  An Fe–19Cr–0.6Al–12Mn duplex stainless steel with an optimized alloy composition of Ni replaced by Mn and Cr partially replaced by Al was developed to avoid the edge cracking, which is a common defect in the hot rolling of traditional two-phase stainless steels. The newly developed duplex stainless steel could be hot-rolled in the single-phase ferrite (α) region by controlling rolling temperature and the single-phase ferrite microstructure was retained on water cooling. To obtain the two-phase stainless steel product with ferrite and austenite (γ) microstructure, cold rolling and annealing were carried out, and appropriate cold rolling reduction and annealing process parameters were determined. The significant impact of annealing on microstructure, mechanical properties and pitting resistance of the experimental steel was studied. It was observed that with the increase in cold rolling reduction, the number of γ nucleation points was dramatically increased leading to the precipitation of more γ at α grain boundaries after annealing. During annealing at 800 °C and with the increase in annealing time, the austenite fraction was increased with a lower rate and remained almost constant when the annealing time was greater than 4 h. With the increase in annealing temperature, the austenite fraction decreased gradually in the temperature range of 750–860 °C. Good combination of strength, ductility and excellent pitting resistance was obtained by cold rolling to 80% reduction and annealing at 800 °C for 4 h. Grain refinement and the existence of Σ3 boundaries played a vital role in improving the pitting resistance of the experimental steel. With good combination of strength, ductility and corrosion resistance, the newly developed duplex stainless steel is expected to be a new resource-saving dual-phase stainless steel.
• Select
  Tensile behavior of ultrafine-grained low carbon medium manganese steel by intercritical annealing treatment

  Sohail Ahmad, Zheng Han, Li‑ming Fu, Huan‑rong Wang, Wei Wang, Ai‑dang Shan

  钢铁研究学报(英文版). 2020, 27(12): 1433-1445.
  https://doi.org/10.1007/s42243-020-00405-0

  摘要 ( )   可视化   收藏

  The intercritical annealing treatment at 650 and 700 °C results in two ultrafine-grained (UFG) dual-phase ferrite–austenite steels. The two steels exhibit different and special discontinuous yielding and pronounced Lüders-like strain phenomena with large yielding strain which are related to their retained γ-austenite (RA) volume fractions and RA stabilities. The steel annealed at 650 °C shows an absent or very small strain hardening, while the steel annealed at 700 °C shows an obvious strain hardening upward curvature with increasing strain. The results show that before and during straining, the steel annealed at 650 °C exhibits a mixture of equiaxed and elongated UFG α-ferrite and austenite phases; however, the steel annealed at 700 °C exhibits only elongated UFG α and γ phases. It was found that most of the γ-austenite to α′-martensite transformation occurred at the initial deformation stage and very small or almost no transformation occurred afterward. This demonstrates that the strain-induced martensite (SIM) transformation (γ–α′) or transformation-induced plasticity (TRIP) effect dominates only at the initial deformation stage. RA remained stable, and no TRIP effect was observed at the final deformation stage. The load–unload–reload test was performed to evaluate the back stress (σ_b) hardening effect. It is believed that the pronounced strain hardening behavior at the later deformation stage is mainly associated with σ_b enhancement induced by the strain partitioning between the soft and hard phases due to SIM transformation during tensile deformation.
• Select
  Comparison of microstructure, mechanical and wear behaviour of laser cladded stainless steel 410 substrate using stainless steel 420 and Colmonoy 5 particles

  N. Jeyaprakash, Che‑hua Yang, K.R. Ramkumar, Guang‑zhou Sui

  钢铁研究学报(英文版). 2020, 27(12): 1446-1455.
  https://doi.org/10.1007/s42243-020-00447-4

  摘要 ( )   可视化   收藏

  Stainless steel (SS) 410 is widely used in many components of nuclear reactors due to its good corrosion resistance and high strength. However, wear is a major issue of these components due to its continuous sliding. SS 420 and Colmonoy 5 particles were deposited over SS 410 substrate by laser cladding process. Then, X-ray diffraction was used to find the phases present after cladding process. Further, coating morphologies were analysed by scanning electron microscopy (SEM) twinned with energy-dispersive spectroscopy. The obtained morphology indicates the hard laves phase present in the Colmonoy 5 cladding surface and needle-like structure in SS 420 cladding surface. Then, Vickers microhardness test was carried out in order to study the hardness and load-carrying capacity of the cladding specimen. Among those, Colmonoy 5 cladding specimen provide higher hardness due to the presence of laves phase formation. Then, the dry sliding wear study was conducted to calculate the mass loss after 2500 m of sliding. The combined effect of hardness and laves phase formation were reflected in dry sliding wear study analysis of the specimens. Then, to study the wear mechanism and roughness, worn surface morphologies were captured using SEM and white light interferometer, respectively.
• Select
  Microstructure evolution and corrosion behavior of Nb-alloyed cast heat-resistant steel during different aging treatments

  Lv‑dan Teng, Tian‑tian Zhao, Teng‑fei Cheng, Yi‑tao Yang

  钢铁研究学报(英文版). 2020, 27(12): 1456-1465.
  https://doi.org/10.1007/s42243-020-00433-w

  摘要 ( )   可视化   收藏

  The microstructure evolution of heat-resistant cast stainless steels aged at 600, 700, 800 and 900 °C for 2 h was investigated by scanning electron microscopy and X-ray diffraction. Potentiodynamic polarization curves were applied to study the effects of Nb addition and aging temperature on corrosion resistance. The results demonstrated that eutectoid decomposition of the ferritic phase (δ→σ+γ2) was observed at 700–900 °C. The content of σ-phase first increased and then decreased in the steels, where the maximum content was obtained at 800 °C, indicating that the highest hardness occurred at 800 °C accordingly. The hardness of Nb-containing steels was significantly higher than that of Nb-free steels. The corrosion resistance of heat-resistant cast steels in various aging temperatures was different due to the formation of σ-phase. Both Cr-rich carbides and σ-phase were harmful to the corrosion resistance, while Cr-rich carbides were the main factor. Nb-containing heat-resistant cast steels exhibited superior corrosion resistance, as Cr-rich carbides were reduced and the corrosion products of Nb-rich slowed down the formation of steady-state pits.
• Select
  Effects of nitrogen content on pitting corrosion resistance of non-magnetic drill collar steel

  Li‑wei Xu, Hua‑bing Li, Huai‑bei Zheng, Peng‑chong Lu, Hao Feng, Shu‑cai Zhang, Wei‑chao Jiao, Zhou‑hua Jiang ¹

  钢铁研究学报(英文版). 2020, 27(12): 1466-1475.
  https://doi.org/10.1007/s42243-020-00428-7

  摘要 ( )   可视化   收藏

  High-nitrogen (N) austenitic stainless steel (Cr–Mn–N series) is commonly used for non-magnetic drill collars, which exhibits excellent mechanical properties and corrosion resistance. The effects of N content (0.63 to 0.86 wt.%) on the pitting corrosion behavior of the experimental non-magnetic drill collar steel were investigated using the electrochemical tests and immersion tests. Besides, X-ray photoelectron spectroscopy was used to analyze the constitution of the passive film. The results show that with the enhancement of N content from 0.63 to 0.86 wt.%, the metastable pitting corrosion sensitivity of the tested materials in 3.5 wt.% NaCl solution decreased and the pitting corrosion resistance increased. Meanwhile, the corrosion rate in 6 wt.% FeCl3 solution at 30 °C decreased from 10.40 to 4.93 mm/a. On the other hand, nitrogen was concentrated in the form of ammonia (NH4+ and NH3) on the outermost surface of the passive films. The contents of Cr2O3 and Fe2O3 raised in the passive films, together with the content of CrN, at metal/film interface increased as N content increased from 0.63 to 0.86 wt.%, which facilitated protective ability of the passive films, thus contributing to higher pitting corrosion resistance.
• Select
  Effect of thermal deformation on microstructure and properties of TC18 titanium alloy produced by laser additive manufacturing

  Xiao‑dong Li, Chang‑yue Qiu, Yu‑ting Liu, Hong‑fang Wang, Dong‑dong Zheng, Yan‑yan Zhu, Shu‑quan Zhang

  钢铁研究学报(英文版). 2020, 27(12): 1476-1484.
  https://doi.org/10.1007/s42243-020-00456-3

  摘要 ( )   可视化   收藏

  Grain boundary of α phase damaged ductility of laser melting-deposited TC18 titanium alloy and grain boundary of α phases were difficult to break by nominal heat treatment. An extra thermal deformation was introduced to break the grain boundary of α phase with the improved mechanical property of TC18 titanium alloy fabricated by laser melting deposition technique. Results indicated that after thermal deformation, β grains in alloy seriously elongated. When sample was deformed at temperatures from 750 to 850 °C, α phase exhibited both rod and irregular morphologies with discontinuous distribution at grain boundary, and the subsequent heat treatment would lead to spheroidization of the α phase. However, after deformation at 900 °C, α phase transferred into β phase and the subsequent heat treatment would make continuous grain boundary of α phase reappear. The suitable hot deformation can effectively break the continuous grain boundary in laser melting-deposited TC18 alloy with respected improved ductility.