2023年, 第30卷, 第12期　刊出日期：2023-12-25

  

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综述
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  A review of use of metallurgical slag for its carbonation products: processes, crystallization behavior, and application status

  Ya-jun Wang, Meng-jie Tao, Jun-guo Li, Jian-bao Zhang, Song Qin, Shao-hua Liu, Li-jie Peng, Xiao-pei Zhang, Xi Zhang, Ya-nan Zeng

  钢铁研究学报(英文版). 2023, 30(12): 2341-2365.
  https://doi.org/10.1007/s42243-023-01108-y

  摘要 ( )   可视化   收藏

  In response to the pressing global issue of reducing carbon emissions and the crucial technical challenges of fully utilizing steel slag, researchers have been studying an accelerated carbonation process that entails the carbonation of basic oxides in steel slag to store CO2. However, despite its promising potential, the process has yet to see widespread industrial application. The latest research progress in the area of mineral carbonation processes, both direct and indirect, that are used to capture, utilize, and store carbon in steel slag are summarized. Given the limited scale of steel slag carbonation and the underutilized products that can be derived from it, a new research focus is proposed for examining the regulation of calcium carbonate crystal forms during carbonation using the Ca source in steel slag. Precise control of synthesis variables will help to ensure accurate control of calcium carbonate precipitation in the carbonation process. A summary of the effects of synthesis variables on CaCO3 crystal form and the latest research findings on controlling aragonite morphology are provided. The review is concluded with a discussion of the potential applications and future development prospects of CaCO3 whiskers.
论著
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  Softening and melting behaviors of ferrous burden in hydrogen-rich blast furnace cohesive zone

  Bin-bin Lyu, Guang Wang, Fan Yang, Hai-bin Zuo, Qing-guo Xue, Jing-song Wang

  钢铁研究学报(英文版). 2023, 30(12): 2366-2377.
  https://doi.org/10.1007/s42243-023-00951-3

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  The changes in the softening and melting behaviors of ferrous burden in the cohesive zone and the characteristics of the slag–iron–coke interface in a blast furnace were investigated by simulating an actual blast furnace under hydrogen-rich conditions. According to the variation in the transient shrinkage of the burden under different atmospheres, the shrinkage start temperature of the sinter was higher than that of the pellets. The negative shrinkage rate of the pellets was greater than that of the sinter. Additionally, the softening start temperature in the blast furnace decreased under hydrogen-rich conditions, giving the blast furnace a broader range of softening zones. The softening start temperatures of the pellets and sinter decreased from 1102 to 949 C and 1152 to 1080 C, respectively. The hydrogen-rich traditional blast furnace conditions narrowed the melting zone temperature range and shifted it toward the high-temperature zone, significantly improving the burden layer permeability. However, under the hydrogen-rich oxygen blast furnace conditions, there were a decrease in the melting start temperature, a shift of the melting zone location to the low-temperature zone, and an increase in the burden layer permeability and pressure difference. A comparison of the slag–iron–coke interface characteristics under different atmospheric conditions showed that the carbon content in metallic iron decreased under hydrogen-rich traditional blast furnace conditions compared with traditional blast furnace conditions. Contrastingly, under hydrogen-rich oxygen blast furnace conditions, the carbon content in metallic iron increased compared with oxygen blast furnace conditions. These findings provide guidance for the development of low-carbon ironmaking processes in blast furnaces.
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  Effect of flue gas outlet temperature in evaporator on thermal economic performance of organic Rankine cycle system for sinter waste heat recovery

  Jun-sheng Feng, Xin-ni Cheng, Huan-huan Wang, Liang Zhao, Hui Dong

  钢铁研究学报(英文版). 2023, 30(12): 2378-2390.
  https://doi.org/10.1007/s42243-023-01025-0

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  In order to improve the recovery and utilization rates of sinter waste heat effectively, the organic Rankine cycle (ORC) system with subcritical cycle was designed to recover the low-temperature sinter cooling flue gas waste heat in an annular cooler for power generation. The thermodynamic, economic and multi-objective optimization models of ORC system were established, and R600a was selected as the ORC working medium. Subsequently, the variations in system thermodynamic performance and economic performance with the ORC thermal parameters were discussed in detail, and the optimal ORC thermal parameters were determined. The results show that the system net output power increases with increasing the evaporation temperature and decreasing the condensation temperature and increases first and then, decreases with the increase in superheat degree for a given flue gas outlet temperature in the evaporator, while the heat transfer area per unit net output power appears different variation trends in various ranges of flue gas outlet temperature. Taking the sinter cooling flue gas waste heat of 160 C as the ORC heat source, the optimal thermal parameters of ORC system were the flue gas outlet temperature of 90 C, the evaporation temperature of 95 C, the superheat degree of 10 C, and the condensation temperature of 28 C.
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  Optimization of preparation process of high-strength pellets from Panzhihua ilmenite concentrate

  Gang-wei Zhou, Wei Lv, Fu-rong Chen, Zheng-gen Liu, Man-sheng Chu, Xue-wei Lv

  钢铁研究学报(英文版). 2023, 30(12): 2391-2402.
  https://doi.org/10.1007/s42243-023-00981-x

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  The preparation of high-strength pellets from Panzhihua ilmenite concentrate is important for the hydrogen-rich smelting of titania slag and was investigated. The effects of the magnetite concentrate and heating procedure including the preheating temperature and period as well as roasting temperature and period on the compressive strength of the roasted pellets were investigated. High-strength ilmenite concentrate pellets ([2000 N) were prepared by optimizing the roasting process. The addition of magnetite concentrate is beneficial for increasing the compressive strength of the Panzhihua ilmenite concentrate pellet by oxidizing hematite which filled the pseudobrookite particles, functioned as a bridge bond, and improved the interconnection between the grains. The compressive strength can reach up to 2900 N when the ilmenite concentrate pellet with 15% magnetite concentrate is pre-heated above 800 C for 20 min and then roasted at 1250 C for 20 min. In addition, there is an overall upward trend in the compressive strength with an increase in the pre-heating temperature and period as well as the roasting temperature and period. The micromorphology and strengthening consolidation mechanism of Panzhihua ilmenite concentrate pellets were also discussed.
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  Simulation study on fluid flow performance of injection stirring composite process in molten iron desulfurization process

  Chao Lv, Xu-xin Chen, Hai-wei Zhang, Hong-liang Zhao, Lin-hui Yu, Wen-ming Guo

  钢铁研究学报(英文版). 2023, 30(12): 2403-2415.
  https://doi.org/10.1007/s42243-023-00948-y

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  The blowing and stirring composite process of molten iron desulfurization process affects the desulfurization efficiency and has obvious advantages in improving steel properties and expanding the scale of converter steelmaking. At present, the injection position of the injection stirring research is fixed, and the desulfurization efficiency needs to be improved. The gas–liquid flow behavior of single-scale bubble model and the size and distribution of bubbles in multi-scale bubble model were studied by computational fluid dynamics numerical simulation method for the injection mixing composite process of jet inlet and stirring paddle rotating at the same speed. The pressure distribution and velocity distribution inside the fluid indicate that the velocity difference between the gas–liquid phases and the turbulence of the liquid are due to the collisions of bubbles, which are due to essential conditions for bubble breaking. Different injection air volumes have essential influence on the formation of single bubbles. When the injection volume reaches 2.8 m3/h, the turbulent kinetic energy is maximum, the bubble formation is rapid, and the desulfurization efficiency can be improved. The multi-bubble results show that the bubble diameter is mainly distributed in the range of 2–5 mm. The higher gas flow rate will increase the number of bubbles in the fluid and promote the bubble refinement process.
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  Strip width spread prediction in rough rolling process based on mechanism modeling and optimization

  Yan-jiu Zhong, Jing-cheng Wang, Jia-hui Xu, Jun Rao

  钢铁研究学报(英文版). 2023, 30(12): 2416-2424.
  https://doi.org/10.1007/s42243-023-01085-2

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  Aiming at the problems of low accuracy and poor robustness that existed in the current hot rolling strip width spread model, an improved strip spread prediction model based on a material forming mechanism and Bayesian optimized adaptive differential evolution algorithm (BADE) was proposed. At first, we improved the original spread mechanism model by adding the weight and bias term to enhance the model robustness based on rolling temperature. Then, the BADE algorithm was proposed to optimize the improved spread mechanism model. The optimization algorithm is based on a novel adaptive differential evolution algorithm, which can effectively achieve the global optimal solution. Finally, the prediction performances of five machine learning algorithms were compared in experiments. The results show that the prediction accuracy of the improved spread model is obviously better than that of the machine learning algorithms, which proves the effectiveness of the proposed method.
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  Analysis of coupling mechanism between roll system crossing and liner wear of hot strip mill

  Jia-li Zheng, Hua-gui Huang, Guang-lu Song, Zhen-yao Lei, Jing-na Sun, Shi-min Xu

  钢铁研究学报(英文版). 2023, 30(12): 2425-2435.
  https://doi.org/10.1007/s42243-023-01041-0

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  Non-design roll system crossing seriously affects the plate shape and rolling mill performance. The problem of roll system crossing caused by liner wear was studied. The finite element model of rolling mill was established to analyze the relationship between roll system crossing and liner wear. The wear of liner was measured by laser tracker. The range of roll system crossing angle was calculated by considering the amount of stand clearance obtained by numerical simulation. The wear surface morphology of liner was observed and the wear mechanism was analyzed. The liner wear experiment was carried out to analyze the wear amount of the liner. Finally, based on the Archard wear theory, the prediction model of the cross angle of the roll system and the wear amount of the liner was established. Because there are more uncertain factors in the field production, the prediction model cannot be considered one by one. Therefore, the predicted value is smaller than the actual wear value, but it still has great reference.
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  A defect recognition model for cross-section profile of hot-rolled strip based on deep learning

  Tian-lun Li, Wen-quan Sun, An-rui He, Jian Shao, Chao Liu, Ai-bin Zhang, Yi Qiang, Xiang-hong Ma

  钢铁研究学报(英文版). 2023, 30(12): 2436-2447.
  https://doi.org/10.1007/s42243-023-01104-2

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  The cross-section profile is a key signal for evaluating hot-rolled strip quality, and ignoring its defects can easily lead to a final failure. The characteristics of complex curve, significant irregular fluctuation and imperfect sample data make it a challenge of recognizing cross-section defects, and current industrial judgment methods rely excessively on human decision making. A novel stacked denoising autoencoders (SDAE) model optimized with support vector machine (SVM) theory was proposed for the recognition of cross-section defects. Firstly, interpolation filtering and principal component analysis were employed to linearly reduce the data dimensionality of the profile curve. Secondly, the deep learning algorithm SDAE was used layer by layer for greedy unsupervised feature learning, and its final layer of back-propagation neural network was replaced by SVM for supervised learning of the final features, and the final model SDAE_SVM was obtained by further optimizing the entire network parameters via error back-propagation. Finally, the curve mirroring and combination stitching methods were used as data augmentation for the training set, which dealt with the problem of sample imbalance in the original data set, and the accuracy of cross-section defect prediction was further improved. The approach was applied in a 1780-mm hot rolling line of a steel mill to achieve the automatic diagnosis and classification of defects in cross-section profile of hot-rolled strip, which helps to reduce flatness quality concerns in downstream processes.
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  Whole process prediction model of silicon steel strip on transverse thickness difference based on Takagi-Sugeno fuzzy network

  Hai-nan He, Zhuo-hao Dai, Xiao-chen Wang, Quan Yang, Jian Shao, Jing-dong Li, Zhi-hong Zhang, Liang Zhang

  钢铁研究学报(英文版). 2023, 30(12): 2448-2458.
  https://doi.org/10.1007/s42243-023-01094-1

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  The hot rolling and cold rolling control models of silicon steel strip were examined. Shape control of silicon steel strip of hot rolling was a theoretical analysis model, and the shape control of cold rolling was a data-based prediction model. The mathematical model of the hot-rolled silicon steel section, including the crown genetic model, inter-stand crown recovery model, and hot-rolled strip section prediction model, is used to control the shape of hot-rolled strip. The cold rolling shape control is mainly based on Takagi-Sugeno fuzzy network, which is used to simulate and predict the transverse thickness difference of cold-rolled silicon steel strip. Finally, a predictive model for the transverse thickness difference of silicon steel strips is developed to provide a new quality control method of transverse thickness of combined hot and cold rolling to improve the strip profile quality and increase economic efficiency. The qualified rate of the non-oriented silicon steel strip is finally obtained by applying this model, and it has been steadily upgraded to meet the needs of product quality and flexible production.
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  Predicting buckling of carbon fiber composite cylindrical shells based on backpropagation neural network improved by sparrow search algorithm

  Wei Guan, Yong-mei Zhu, Jun-jie Bao, Jian Zhang

  钢铁研究学报(英文版). 2023, 30(12): 2459-2470.
  https://doi.org/10.1007/s42243-023-00966-w

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  The buckling load of carbon fiber composite cylindrical shells (CF-CCSs) was predicted using a backpropagation neural network improved by the sparrow search algorithm (SSA-BPNN). Firstly, two CF-CCSs, each with an inner diameter of 100 mm, were manufactured and tested. The buckling behavior of CF-CCSs was analyzed by finite element and experiment. Subsequently, the effects of ply angle and length–diameter ratio on buckling load of CF-CCSs were analyzed, and the dataset of the neural network was generated using the finite element method. On this basis, the SSA-BPNN model for predicting buckling load of CF-CCS was established. The results show that the maximum and average errors of the SSABPNN to the test data are 6.88% and 2.24%, respectively. The buckling load prediction for CF-CCSs based on SSA-BPNN has satisfactory generalizability and can be used to analyze buckling loads on cylindrical shells of carbon fiber composites.
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  Influence of lanthanum on inclusions and as-cast microstructures in a low-alloy high-strength steel

  Can Liu, Ji Zhang, Qiang Ren, Li-feng Zhang

  钢铁研究学报(英文版). 2023, 30(12): 2471-2481.
  https://doi.org/10.1007/s42243-023-01022-3

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  Advanced high-strength steel ingots with total lanthanum (TLa) contents of 0, 15 9 10–6, 86 9 10–6 and 360 9 10–6 were prepared through laboratory experiments. The modification of inclusions and the variation of the as-cast microstructure with the content of lanthanum in the high-strength steel were analyzed. The result showed that with the increase in the TLa content in the steel from 0 to 360 9 10–6, the modification path of inclusions in the as-cast steel was Al2O3 and calcium aluminate ? LaAlO3 ? La2O2S ? La2O2S–La2O3. The addition of La in the high-strength steel significantly refined the solidification structures. With the increase in the TLa content in the steel from 0 to 360 9 10–6, the ratio of the equiaxed crystal region in the macrostructure increased from 30.1% to 50.7%, the proportion of the high-angle grain boundary in the microstructure increased from 36.9% to 69.8%, and the area fraction of the acicular ferrite and the bainite increased from 0 to 93.3%. Inclusions of LaAlO3, La2O2S and La2O3 in the La-containing steel could act as heterogeneous nucleation cores of a-Fe during the solidification. With the increase in the TLa content in the steel, the number density of inclusions that could act as effective heterogeneous nucleation cores in the steel gradually increased, which enlarged the ratio of the equiaxed crystal region and the proportion of intragranular acicular ferrite, and refined the as-cast microstructure of the high-strength steel.
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  Influence of notch volume on mechanical properties of a novel highstrength and high-toughness steel

  Zhi-gang Tao, Ke Qin, Shu-lin Ren, Hao-tian Xu, Man-chao He

  钢铁研究学报(英文版). 2023, 30(12): 2482-2493.
  https://doi.org/10.1007/s42243-023-00953-1

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  The effect of notch volume on the mechanical behavior of a novel high-strength and high-toughness steel with negative Poisson’s ratio effect (called NPR steel) was studied. First, the quasi-static tensile test of NPR steel with different notch volumes was carried out, and its failure characteristics and mechanical properties parameters were studied. Then, the modified Johnson-Cook (J-C) constitutive model with coupled notch volume ratio was proposed. The model was validated based on three-dimensional finite element numerical simulations. The results show that the engineering stress–strain curve of NPR steel has no yield platform, and has the mechanical properties of high strength, high elongation, and high energy absorption. Notch volume significantly affects the mechanical properties of NPR steel. The elongation, yield strength, tensile strength, and energy absorption characteristics of steel bar gradually decrease with the increase in notch volume. The notch volume ratio V , a characteristic parameter describing the notch volume of reinforcement, is defined, and the quantitative relationship between this parameter and mechanical parameters is established, which can accurately characterize the mechanical properties of specimens with different notch volume ratios. Based on the true stress–strain curves with different notch volume ratios, a constitutive model with modified Johnson-Cook model parameters is proposed. The finite element results show that the modified J-C model can accurately fit the quasi-static tensile mechanical behavior of NPR steel.
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  Enhancing strength of an ultra-low-carbon weathering steel to 700 MPa by adjusting Ti content

  Tian-en Peng, Zhi-wei Lian, Yuan-yang Zhang, Bo He, Xue-wen Hu, Tao Zhu, Bo Jiang

  钢铁研究学报(英文版). 2023, 30(12): 2494-2504.
  https://doi.org/10.1007/s42243-022-00871-8

  摘要 ( )   可视化   收藏

  The microstructure and mechanical properties of a traditional Ti-microalloyed weathering steel were analyzed, and the strength was improved by proposing an optimized Ti content. The yield strength and elongation of the steel were 640 MPa and 25.5%, respectively. The microstructure was ferrite and pearlite, and the average grain size was 5.4 lm. The precipitates were mainly TiC with the size below 20 nm, and the average diameter was 18.2 nm. The yield strength of the newly proposed weathering steel with Ti content of 0.018% higher than that of the traditional steel reached up to 709 MPa, and the elongation was 23.5%. The ferrite grain was refined to 3.8 lm, the fraction of TiC under 10 nm was obviously increased, and the average diameter of particles was 9.8 nm. The increase in Ti also promoted the recrystallization process, thus leading to the reduction in dislocation density. The yield strength of the newly proposed weathering steel was increased to higher than 700 MPa by adjusting the Ti content mainly resulting from three aspects: grain refinement, precipitation and dislocation strengthening. The contributed values were 45, 64 and –40 MPa, respectively.
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  Effect of heat treatment on corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3Mo carbon steel

  Yun-sheng Xue, Jia-ji Wang, Ying-xue Teng, Kui-jun Fu, Yin Lei, Jin Liu, Da-zheng Zhang, Shu-wen Chen

  钢铁研究学报(英文版). 2023, 30(12): 2505-2516.
  https://doi.org/10.1007/s42243-023-00946-0

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  Before and after heat treatment, 0Cr15Ni5Cu3MoN stainless steel (SS) samples were immersed in sulfate-reducing bacteria (SRB) environment to study the effect of heat treatment on the antimicrobial properties of Cu-containing stainless steel. The effect of heat treatment on the corrosion resistance and antibacterial ability of 0Cr15Ni5Cu3MoN SS was studied by scanning electron microscopy, transmission electron microscopy, laser scanning confocal microscopy, and electrochemistry. The results show that 0Cr15Cu3 SS has better antibacterial properties with fewer bacteria adsorbed on the surface after heat treatment, and its corrosion resistance is significantly improved. Interestingly, on the 7th day of immersion, the corrosion resistance of the heat-treated stainless steel was lower than that of the rolled stainless steel. This was due to the fact that the rolled samples were protected by biofilm at this time, while the surface bacteria on the heattreated samples died, resulting in the exposure of the substrate surface and thus reducing the corrosion resistance of the heat-treated samples. Thus, because of the strong bactericidal properties of the heat-treated Cu-containing stainless steel, the corrosion resistance of the samples suddenly decreases in the middle stage of corrosion, and this discovery provides a new view to study the corrosion process of Cu-containing stainless steel in the SRB environment.
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  Microstructure and corrosion behaviors of friction stir-welded Q235 low-carbon steel joint

  Hong-duo Wang, Zhi-yong Zhou, Kuai-she Wang, Wen Wang, Peng Han, Cheng-wen Zhang, Yong-xin Lu, Guang Li, Yi-di Lu, Xiao Li, Yan-ming Liu, Xiao-yong Zhang

  钢铁研究学报(英文版). 2023, 30(12): 2517-2530.
  https://doi.org/10.1007/s42243-023-00931-7

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  Friction stir welding (FSW) was used to prepare Q235 low-carbon steel joint, and the microstructure of different zones of the joint was characterized. The electrochemical corrosion behavior of different macroscopic zones of the joint was evaluated in 3.5 wt.% NaCl solution. The results showed that the retreated-side heat-affected zone (HAZRS) and the advanced-side heat-affected zone (HAZAS) did not undergo phase transformation during FSW, and their microstructures were similar to those of the base material (BM), which was mainly composed of blocky ferrite and pearlite. The retreatedside thermo-mechanical affected zone (TMAZRS), the stirring zone (SZ), and the advanced-side thermo-mechanical affected zone (TMAZAS) underwent phase transformation, and the microstructure was mainly composed of proeutectoid ferrite and pearlite. The order of the corrosion resistance of different micro-zones from high to low was: HAZRS[ BM[HAZAS[TMAZRS[SZ[TMAZAS. The corrosion mechanism for BM, HAZRS, and HAZAS was mainly the dissolution of ferrite. By contrast, the corrosion mechanism for TMAZRS, SZ, and TMAZAS was mainly galvanic corrosion between proeutectoid ferrite and pearlite.
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  Effect of pH and applied stress on hydrogen sulfide stress corrosion behavior of HSLA steel based on electrochemical noise analysis

  Xiao-hua Li, Chen-xi Liu, Teng Zhang, Chuan-tao Lv, Jiang-cheng Liu, Ran Ding, Zhi-ming Gao, Rui Wang, Yong-chang Liu

  钢铁研究学报(英文版). 2023, 30(12): 2531-2540.
  https://doi.org/10.1007/s42243-023-00998-2

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  The influence mechanism of pH and the externally applied stress on sulfide stress corrosion cracking behavior based on the joint analysis of the in situ electrochemical noise and microstructure was studied. The results showed that Hþ in solution changes the composition and structure of corrosion product film by affecting the concentration of S2 and Fe2þ near the anode surface. When the pH increased from 2.6 to 3.6 and 4.6, the corrosion product film changed from porous Mackinawite to dense and stable FeS. The change in corrosion product type delayed the crack initiation time by 10.5 and 45.5 h, while the uniform corrosion time was prolonged by 6.1 and 46 h, respectively, delaying SSC behavior. After increasing the applied stress, the local plastic deformation on the material surface increases the porosity and crack rate of the corrosion product film and becomes a fast propagation channel for SSC cracks. When the applied stress is 110% of the actual yield strength of the material, the initiation time of stress corrosion cracking is 6 and 18.1 h earlier than that of 90% and 100%, respectively. The local corrosion time was extended by 23.5 and 8.2 h, respectively, accelerating SSC behavior.
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  Effect of friction on corrosion behaviors of AISI 304 and Cr26Mo1 stainless steels in different solutions

  Z.X. Dai, S.L. Jiang, L.K. Ning, X.D. Xu, S. Li, D.L. Duan

  钢铁研究学报(英文版). 2023, 30(12): 2541-2556.
  https://doi.org/10.1007/s42243-023-00967-9

  摘要 ( )   可视化   收藏

  The corrosion and tribocorrosion behaviors of AISI 304 austenitic stainless steel and Cr26Mo1 ultrapure high chromium ferrite stainless steel in 3.5 wt.% NaCl and 0.5 mol/L H2SO4 solutions were investigated. Microelectrode electrochemical measurement technology was applied to identify electrochemistry behaviors during tribocorrosion tests in situ. The surface morphologies and compositions of the wear tracks were analyzed by scanning electron microscopy and Raman spectrum. The results showed that compositions of stainless steels, corrosive mediums and applied loads have great influence on tribocorrosion behaviors of stainless steels. Firstly, the corrosion resistance in static state of stainless steels primarily dominates its tribocorrosion behavior; meanwhile, better mechanical properties are in favor of tribocorrosion resistance. Secondly, the corrosion rate is promoted significantly in 3.5% NaCl solution by friction, while the tendency is inconspicuous in 0.5 mol/L H2SO4 solution. Last but not least, passive films on stainless steels can be wiped off by small friction force. With the increase in applied load, the effect of friction converts to forming friction oxide film from removing passivation film, so that a critical load exists below which the friction force can promote the corrosion process extremely.
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  Effect of phosphate conversion film on fatigue and corrosion fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al (in wt.%) alloy

  Bao-jie Wang, Dao-kui Xu, Shuo Wang, Xiang-bo Xu, En-hou Han

  钢铁研究学报(英文版). 2023, 30(12): 2557-2565.
  https://doi.org/10.1007/s42243-023-00922-8

  摘要 ( )   可视化   收藏

  Through investigating and comparing the fatigue behavior of an as-rolled Mg–3.08Zn–0.83Al (in wt.%) alloy performing surface phosphate conversion film treatment, it revealed that the determined fatigue strength of surface treated samples at 106 cycles in air was 65 MPa, whereas the fatigue strength was only 35 MPa when tested in 3.5 wt.% NaCl solution. Failure analysis demonstrated that in air, the fatigue crack initiation was mainly dominated by the interaction between the retarding effect of phosphate conversion film on cyclic slips occurring in the underneath substrate. When the matrix cannot endure the accumulated stress concentration due to the irreversibility of cyclic slips, the fatigue crack will preferentially initiate at sample subsurface. Since the phosphate conversion film cracked easily under the cyclic loading and lost its protectiveness on the substrate in 3.5 wt.% NaCl solution, fatigue cracks were preferentially nucleated at the localized corrosion pits.
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  Temperature dependence in tensile properties and deformation behavior of GH4169 alloy

  Qi Zheng, Tian Liu, Jia-bo Wei, Rui Luo, Yi-ming Zhou, Heng-nan Ding, Le-li Chen, Di Zhang, Xiao-nong Cheng

  钢铁研究学报(英文版). 2023, 30(12): 2566-2581.
  https://doi.org/10.1007/s42243-023-01050-z

  摘要 ( )   可视化   收藏

  The effect of temperature on the tensile properties and deformation mechanism of GH4169 alloy has been systematically studied over a wide range of room temperature (RT) to 1000 C. The results indicate that the stress–strain curve of the alloy shows serrations at 200–600 C, and the character of the serrations changes from type A to type B and then to type C at different temperatures. The ultimate tensile strength of the alloy decreases gradually from RT to 600 C. The yield strength decreases slowly from RT to 700 C but decreases rapidly above 800 C. Transmission electron microscopy analysis relieves that the primary deformation mechanism of the alloy below 500 C is Orowan bypass mechanism. At temperatures between 600 and 700 C, the coordinated deformation of twins and cross-slip of dislocations are activated. The transformation of c00 phase to d phase above 650 C will decrease the strength. The primary deformation mechanism above 800 C transforms into the repeated shearing of c00 by dislocations to form multiple stacking faults. Recrystallized grains were observed above 800 C, and continuous dynamic recrystallization and discontinuous dynamic recrystallization were observed. The stress concentration caused by Nb-rich carbides is the cause of intracrystalline crack nucleation. At 700 C, grain boundary crack sprouting is caused by the combined effect of slip band impact on grain boundaries and grain boundary dislocation plugging. The relationship between the serrated flow behavior and the deformation mechanism has been discussed based on the experimental results.
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  Oxidation damage zone formed in creep fatigue crack growth of GH4169 alloy at 650 C

  Lan-zhou Liu, Yi-fei Gao, Jin-hui Du, Teng An

  钢铁研究学报(英文版). 2023, 30(12): 2582-2592.
  https://doi.org/10.1007/s42243-023-01044-x

  摘要 ( )   可视化   收藏

  In the creep fatigue crack growth of GH4169 alloy, oxidation is a prominent damage source, which is mainly manifested as the oxidation damage zone in front of crack tip. In order to investigate the property of the oxidation damage zone formed in the creep fatigue crack growth, crack growth tests of directly aged GH4169 alloy were conducted at 650 C in air under various load conditions. Interrupted tests were performed to observe the damage characteristics at crack tip. Block tests were systematically executed to quantify the dependency of oxidation damage zone size on load and holding time. The crack propagation of the GH4169 alloy has a close relationship with grain boundary oxidation at 650 C. An oxidation damage zone in front of crack tip includes intergranular microcracks and oxidised but uncracked grain boundaries. Its size has been calculated from transient crack growth rate and described as a function of maximum stress intensity factor and holding time. Based on oxidation damage zone size, a novel model has been developed to predict the creep fatigue crack growth rate of the GH4169 alloy at 650 C.