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2020年, 第27卷, 第9期 刊出日期:2020-09-25
  

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  • Yong Deng, Jian‑liang Zhang, Ran Liu, Ke‑xin Jiao, Bing‑ji Yan
    钢铁研究学报(英文版). 2020, 27(9): 1005-1010.
    https://doi.org/10.1007/s42243-020-00477-y
    摘要 ( )   可视化   收藏
    The recycling of scrap has attracted more attention in recent years, and scrap can be used as iron-bearing material to smelt hot metal. The smelting practice of blast furnace (BF) with scrap addition in China was investigated, with the types of scrap being small pieces of scrap, such as crushed materials, light and thin materials, and small compacts which were easy to be added into BFs. The higher productivity of BFs with scrap addition was observed compared with that of BFs without scrap addition at the same volume, and the positive correlation between production increase rate and addition amount of scrap was found. The reducing agent rate of most BFs with scrap addition was lower than the average reducing agent rate at the same volume, while the gas utilization of BFs with scrap addition would not be reduced significantly. The theoretical analysis of cost saving was carried out as well, and the results indicated that the cost could be saved by scrap addition. The melting and carburizing were the two main processes of scrap in BF, in which three steps were involved in the melting process of scrap. The amount of carburization depended on the carbon content of hot metal in hearth and the original carbon content in scrap. The calculation showed that the coke rate could be reduced by 27 kg with 100 kg scrap addition per ton of hot metal, and the saving cost was decided by the amount of scrap and the actual situation of BF.
  • Jian‑fei Xu, Kun‑peng Wang, Ying Wang, Zhi‑dong Qu, Xing‑kuang Tu
    钢铁研究学报(英文版). 2020, 27(9): 1011-1017.
    https://doi.org/10.1007/s42243-020-00384-2
    摘要 ( )   可视化   收藏
    To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace (LF) refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing, the effects of ferrosilicon alloy, Si content of steel, and slag basicity on the compositions of inclusions during LF refining were investigated in Al-killed steel. Al2O3 inclusions could be transformed into CaO–Al2O3–MgO–CaS inclusions after adding ferrosilicon alloy in the LF refining process as this alloy contains some CaSi alloy impurities. The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions. Si in liquid steel had a significant influence on the compositions of inclusions during LF refining when CaO–Al2O3–SiO2–MgO slag with high basicity of 7.0 was used. This was because [Ca] produced by the reaction of CaO and [Al] could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel, which was confirmed by the difference of total calcium content between Si-free and Si-containing steels. As a result, Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. For CaO–Al2O3–SiO2–MgO slag with low basicity of 2.8, Al2O3 and MgO·Al2O3 inclusions were obtained after LF refining in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process. This was because the reaction of CaO and [Al] was weak, and residual [Ca] in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2, leading to a low total calcium content of 0.0003% in Si-containing steel.
  • Jin‑yin Xie, Bo Wang, Jie‑yu Zhang
    钢铁研究学报(英文版). 2020, 27(9): 1018-1034.
    https://doi.org/10.1007/s42243-020-00436-7
    摘要 ( )   可视化   收藏
    With the growing demand for energy saving, emission reduction, and green metallurgy, we had designed a new C–H2 smelting reduction reactor. In order to solve the key problem that the heat transfer efficiency from high temperature oxidation zone in upper region to low temperature reduction zone in lower region is low in traditional metallurgical reduction reactor, a water simulation was adopted to optimize the mean residence time and to improve the transmission efficiency within the reactor. According to the modified Froude similarity, a water model experimental reactor with a ratio of 1:1 to the prototype was constructed. In the prototype, the feed port was used to feed preheated ore and flux. In order to simulate the effect of different feeding positions of the tracer on the mixing behavior in the molten pool, four points of tracer feeding position were arranged for a systematic study. At the same time, based on double-row side nozzle with thick slag layer in a C–H2 smelting reduction reactor, nine influencing factors, including relative angle between upper and lower side nozzles, were studied. The experimental results showed that the tracer feeding position had a great influence on the mean residence time, and the relative angle also had a great influence on tracer feeding position. Finally, through comprehensive analysis, the optimal condition parameters were obtained under different tracer feeding positions. These results provide valuable help for the design and optimization of the C-H2 smelting reduction reactor.
  • Xin‑gang Ai, Dong Han, Sheng‑li Li, Hong‑bo Zeng, Hui‑ya Li
    钢铁研究学报(英文版). 2020, 27(9): 1035-1044.
    https://doi.org/10.1007/s42243-020-00418-9
    摘要 ( )   可视化   收藏
    For a multistream tundish, the uniformity among the streams plays a significant role in the quality of molten steel. How to analyze the uniformity quantitatively and optimize structures of a multistream tundish is an important research content for a multistream tundish. A new approach was proposed to quantify the uniformity among the streams. And a physical study and a numerical study were carried out to optimize the structure of the diversion hole based on the prototype of a six-stream tundish in a steel plant. On the basis of average residence time, the uniformity of each flow was considered fully and then the optimal structure of the diversion hole was obtained by means of the comprehensive analysis of temperature field and velocity field. The results show that the optimum structural parameters adopted for diversion holes are height of 20 mm, angle of 15° and diameter of 80 mm.
  • Wei‑gang Li, Lu Xie, Yun‑tao Zhao, Zi‑xiang Li, Wen‑bo Wang
    钢铁研究学报(英文版). 2020, 27(9): 1045-1053.
    https://doi.org/10.1007/s42243-020-00450-9
    摘要 ( )   可视化   收藏
    The prediction of the mechanical properties of hot-rolled strips is a very complex, highly dimensional and nonlinear problem, and the published models might lack reliability, practicability and generalization. Thus, a new model was proposed for predicting the mechanical properties of hot-rolled strips by deep learning. First, the one-dimensional numerical data were transformed into two-dimensional data for expressing the complex interaction between the influencing factors. Subsequently, a new convolutional network was proposed to establish the prediction model of tensile strength of hot-rolled strips, and an improved inception module was introduced into this network to abstract features from different scales. Many comparative experiments were carried out to find the optimal network structure and its hyperparameters. Finally, the prediction experiments were carried out on different models to evaluate the performance of the new convolutional network, which includes the stepwise regression, ridge regression, support vector machine, random forest, shallow neural network, Bayesian neural network, deep feed-forward network and improved LeNet-5 convolutional neural network. The results show that the proposed convolutional network has better prediction accuracy of the mechanical properties of hot-rolled strips compared with other models.
  • Xue‑dao Shu, Song Zhang, Kornel F. Ehmann, Zi‑xuan Li, Yi‑lun Wei
    钢铁研究学报(英文版). 2020, 27(9): 1054-1063.
    https://doi.org/10.1007/s42243-020-00459-0
    摘要 ( )   可视化   收藏
    To realize cross-wedge rolling of shaft parts without a stub bar in a short process, an axial closed–open-type cross-wedge rolling technique was proposed. Based on the strain characteristics in the rolling, evaluation indices of deformation uniformity were provided, and the DEFORM-3D software was adopted to conduct numerical simulations of the rolling process. The metal flow and strain distribution in all stages of the rolling process were analyzed. It is shown that the strain value of the rolled piece close to the end is relatively high while the overall strain distribution is uniform in the rolling process. When the percentage reduction in area is smaller, the fluctuation range of the equivalent strain will be lower and the overall uniformity of the rolled piece will be better. A variable angle wedge was implemented to make metal flow inward and eliminate concavity. Finally, rolling experiment was performed, which indicate that the shape of the rolled piece obtained is consistent with the simulation results. Concavity value in the rolling is decreased by 92% as compared to conventional open rolling. The research results lay a theoretical basis for realizing closed–open-type cross-wedge rolling without a stub bar.
  • J. Chen, Y. Zhang, J.J. Wang, C.M. Liu, S.X. Zhao
    钢铁研究学报(英文版). 2020, 27(9): 1064-1072.
    https://doi.org/10.1007/s42243-019-00343-6
    摘要 ( )   可视化   收藏
    The deformation mechanisms and the flow stress behavior of a medium-manganese high-carbon steel during cold deformation at a strain rate of 10×5 s-1 were explored using a universal testing machine, an X-ray diffractometer, a field emission scanning electron microscope and a high-resolution transmission electron microscope. The results show that continuous step-up serrated flow behavior appears after the yielding point, and the true stress–strain curve is roughly divided into five stages based on distinctive densities and amplitudes of serration. The strengthening mechanisms of the experimental steel involve Cottrell atmosphere, twinning-induced plasticity (TWIP) efect and transformation-induced plasticity (TRIP) effect. TWIP effect is the dominant deformation mechanism, and deformation twins formed by TWIP effect comprise primary, secondary and nanotwins. Furthermore, TRIP effect arises in the local high-strain region. Carbon element plays a key role in the transformation of the deformation mechanism. A small amount of carbide precipitates around twin boundaries lead to the formation of local carbon-poor regions, and Md temperature and stacking fault energy of medium-manganese high-carbon steel are propitious to the occurrence of TRIP effect. In addition, the contributions of various deformation mechanisms to plasticity are calculated, and that of TWIP effect is the greatest.
  • Chang‑min Li, Yuan‑biao Tan, Fei Zhao
    钢铁研究学报(英文版). 2020, 27(9): 1073-1086.
    https://doi.org/10.1007/s42243-020-00462-5
    摘要 ( )   可视化   收藏
    H13-mod steel developed after optimizing the composition and heat treatment process exhibits good hardness and impact toughness and can be used as a shield machine hob. Based on the Avrami equation, the dynamic recrystallization (DRX) behaviour of H13-mod steel during hot compression was studied in the temperature of 900–1150 °C and strain rate ranges of 0.01–10 s-1. A DRX model and finite element software were used to study DRX behaviour of H13-mod steel. Significant DRX was found at both low and high strain rates. Electron backscatter diffraction and optical microscopy analyses found different DRX nucleation mechanisms at low and high strain rates under different deformations. At a low strain rate, the nucleation was dominated by the strain-induced grain boundary migration, whereas the subgrain coalescence mechanism was dominant at a high strain rate. Moreover, dynamic recovery occurred in both processes. In addition, it was easier to obtain small and uniform equiaxed grains at high strain rates than at low strain rates.
  • Tao Wang, Mei Zhang, Ren‑dong Liu, Liang Zhang, Lin Lu, Wen‑heng Wu
    钢铁研究学报(英文版). 2020, 27(9): 1087-1098.
    https://doi.org/10.1007/s42243-020-00397-x
    摘要 ( )   可视化   收藏
    The weldability of 0.28C–2.0Mn–0.93Al–0.97Si (wt.%) transformation induced plasticity (TRIP) steels was investigated using a 2.5 kW CO2 laser at the welding speeds of 2, 2.5 and 3 m/min. The welded joints were characterized in terms of hardness, tensile properties and microstructure. High-quality welded joints of TRIP steels with the carbon equivalent of 0.7 were obtained. Lower loss of ductility, nearly unvaried hardness of the fusion zone (FZ) and tensile strength equal to the base metal were observed with increasing welding speed. Lath martensite and lower bainite formed in FZ and the microstructure of FZ varied little with welding speed. Weld thermal simulations of heat-afected zone (HAZ) were carried out using a quenching dilatometer, and the microstructures of dilatometric samples revealed the carbon diffusion-controlled transformations in HAZ. The microstructure distribution of HAZ could be influenced by the welding speed due to the significant temperature gradient over the narrow HAZ.
  • Hong‑yang Wang, Yu‑qing Ma, Li‑ming Liu
    钢铁研究学报(英文版). 2020, 27(9): 1099-1107.
    https://doi.org/10.1007/s42243-020-00423-y
    摘要 ( )   可视化   收藏
    Aluminum alloy 6061 and high-strength steel Q460 were joined by laser-arc-adhesive hybrid welding technology successfully. A Cu alloy interlayer was added between Al alloy and high-strength steel. The effect of the adhesive on laser-arc-adhesive hybrid welding of Al alloy to high-strength steel was discussed. The optical microscope, scanning electron microscope and electron probe micro-analysis were applied to observe the microstructural evolution and phase transition at Al–Fe interface of laser-arc-adhesive hybrid welded joints. The results showed the maximum tensile shear strength of the joint without adhesive was 256 MPa. After adding adhesive, the maximum tensile shear strength reached 282 MPa. The combination of the mechanical bonding and the metallurgical effect could improve the mechanical performances. The shape of the joint in Al alloy changed into a canine-like morphology. There was no porosity in welds because the molten pool of Al alloy and the special keyhole phenomenon of laser welding provided a channel for the decomposed gas to escape from fusion zone.
  • Hong‑qiang Fan, Wen‑can Xu, Liang Wei, Zhi‑hong Zhang, Yu‑bao Liu, Qian Li
    钢铁研究学报(英文版). 2020, 27(9): 1108-1116.
    https://doi.org/10.1007/s42243-020-00482-1
    摘要 ( )   可视化   收藏
    Scanning electron microscopy, X-ray diffraction, a neutral salt spray test, and electrochemical methods were applied to observe the microstructure and test the corrosion resistance of hot-dip galvanized steel before and after the addition of La and Ce. La/Ce mixture existed in the form of (La, Ce)Zn13 on the coated surface, decreased the coating thickness and accelerated the zinc dendritic growth. The corrosion current density of Zn–0.1La–0.1Ce coating was 63% less than that of pure Zn coating. This phenomenon can be explained that La/Ce mixture inhibited the transformation of Zn5(OH)8Cl2·H2O into Zn5(CO3)2(OH)6 or ZnO, reduced the time for appearance of red rust, and thus enhanced the stability of corrosion products and delayed the oxidation and corrosion processes of galvanized coating. La/Ce mixture improved the corrosion resistance compared to a single La or a single Ce addition. A competitive relationship between La and Ce was observed in the corrosion resistance improvement of hot-dip galvanized steel.
  • Huang Xie, Yun‑xue Jin, Mu‑ye Niu, Ji‑heng Wang
    钢铁研究学报(英文版). 2020, 27(9): 1117-1126.
    https://doi.org/10.1007/s42243-020-00460-7
    摘要 ( )   可视化   收藏
    The wear tests of titanium matrix composites (TMCs) at the loads of 50, 100, 120, and 150 N were carried out with an MMW-1 vertical universal friction and wear tester to study the addition of multilayer graphene (MLG)/nano-Fe2O3 composites (0, 0.1, 0.2, 0.3, 0.4, and 0.5 g) on the dry sliding wear behavior of TMCs. TMCs presented a marked variation in wear loss as a function of the amount of MLG/Fe2O3 addition, and a significant decrease in the friction coefficient was obtained, reducing this parameter up to 50%. With the rise and fall of wear loss, TMCs underwent a transition from severe wear to mild wear. These phenomena were attributed to the existence of a protective lubricating film, which prevented the surface from coming in direct contact, and the lubricating film was 15–20 μm thick and made up of MLG/Fe2O3 (1:2) nanocomposites. Its structure was speculated to be similar to a rolling wood.