2019年, 第26卷, 第2期　刊出日期：2019-02-25

  

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  Phosphorus migration mechanism between iron and high phosphorus gangue phase at high temperatures

  Lei Guo, Jin-tao Gao, Sheng-ping Zhong, Zhan-cheng Guo

  钢铁研究学报(英文版). 2019, 26(2): 113-122.
  https://doi.org/https://doi.org/10.1007/s42243-018-0079-2

  摘要 ( ) PDF全文   可视化   收藏

  The phosphorus migration mechanism during melting separation of non-carbon-reduced high phosphorus iron ore was investigated. Firstly, the equilibrium compositions of hydrogen-reduced high phosphorus iron ore at different temperatures were simulated by the use of equilibrium composition module of HSC Chemistry software. Then, thermodynamic calculation was verified by the real heat treatment of simulated hydrogen-reduced high phosphorus iron ore with several pure reagents including self-made pure fluorapatite. The iron particles in the simulated samples gathered and grew up during heat treatment. Meanwhile, the hypoeutectic structure of Fe–P with grid shape of high phosphorus phase and circular shape of low phosphorus phase emerged within those iron particles. With the penetration of phosphorus from the periphery into the iron particles, the grid structure became denser and denser. It proves that the elemental phosphorus can be reduced from the gangue phase by metallic iron without solid carbon at high temperatures.
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  Wear-resistant coating spraying technique for wear-proofing cover of coke dry quenching furnace

  Zhang-fu Yuan, Shan-shan Xie, Xiang-tao Yu, Jian Liu, Ping Du, Zhi-hua Li

  钢铁研究学报(英文版). 2019, 26(2): 123-129.
  https://doi.org/https://doi.org/10.1007/s42243-018-0201-5

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  During the operation of a coke dry quenching system of coking plant, wear-proofing cover of the boiler was seriously eroded, and even the ceiling tube of the boiler was worn and torn. Thus, attentions were paid to the research, development and application of the wear-resistant coating spraying technique for wear-proofing cover of the coke dry quenching furnace. The Cr₃C₂–NiCr coatings for wear-proofing cover were fabricated via supersonic arc spraying process, and the residual coating of wear-proofing cover would be sampled for being analyzed after two years. The coating presents a dense microstructure with few pores and micro-cracks (the porosity is 4.65%). After thermal spraying of the wear-proofing cover, the hardness and the wear resistance of the surface are improved. The remaining coating is continuous and compact, with an average thickness of about 147 μm. Transverse micro-cracks parallel to the spreading direction of the coating surface are displayed on different areas of the coating, which demonstrates its serious erosion wear effect. The main chemical component of white zone is Fe–18Cr–Ni. The Cr level of light gray phase is about 77.57 wt.% and the O level is 22.43 wt.%. And the main chemical components of dark gray phase are C, O, Al, Si and Ca. X-ray diffraction patterns were adopted to implement phase analysis on the surface of coating sample, which indicated that the coating was composed of a large amount of Cr₃O₂ and a small amount of metal Cr.
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  Longitudinally profiled plate leveling theory based on linear decreasing leveling scheme

  Jian-liang Sun, Xing-ming Du, Kai Li, Yan Peng

  钢铁研究学报(英文版). 2019, 26(2): 130-136.
  https://doi.org/https://doi.org/10.1007/s42243-018-0191-3

  摘要 ( ) PDF全文   可视化   收藏

  An analytical model based on linear decreasing leveling scheme was proposed to investigate the longitudinally profiled plate leveling process. Considering the variable cross-sectional thickness of longitudinally profiled plate and the dynamic reductions in leveling rolls, the reduction models of upper and lower rolls, the leveling force model and the leveling moment model were established, respectively, based on linear decreasing leveling scheme. Moreover, the finite element model of longitudinally profiled plate leveling process was established based on ABAQUS. Then, the total displacements of upper and lower rolls, the leveling force and the stress distribution of longitudinally profiled plate in the leveling process were calculated. To verify the validity of the proposed models, calculated leveling forces were compared with the measured values, and very good agreements are found. Calculated results show that linear decreasing leveling scheme is suitable for leveling longitudinally profiled plate.
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  Solidification structure refinement of ferritic stainless steel based on heterogeneous nucleation technology

  Xiao-fang Shi, Li-zhong Chang, Li Zhou

  钢铁研究学报(英文版). 2019, 26(2): 137-147.
  https://doi.org/https://doi.org/10.1007/s42243-018-0141-0

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  The ridging defect on the surface of stainless steel products is related to the solidification structure of ferritic stainless steel. Refining the solidification structure and increasing the proportion of equiaxed grains are necessary to lessen the ridging defect. Therefore, a new idea of using a heterogeneous nucleating agent which was composed of the composite core containing Ti was proposed, that is, a large amount of dispersed fine particles were initially formed on the solidification front, and a great amount of δ iron was then nucleated using these fine particles as the heterogeneous cores. Through analyzing the crystallographic relationship between different crystals and inducing the calculation formulas of disregistry, the disregistry between the different oxides and TiN and δ iron was explored and the type of nucleation core was determined. The key parameters of forming the composite core containing Ti were obtained through a thermodynamic calculation. The experimental results further confirm the correctness of the theoretical analysis.
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  Influence of delta phase precipitation on static recrystallization of cold-rolled Inconel 718 alloy in solid solution treatment

  Neng-yong Ye, Ming Cheng, Shi-hong Zhang, Hong-wu Song, Hong-wei Zhou

  钢铁研究学报(英文版). 2019, 26(2): 148-153.
  https://doi.org/https://doi.org/10.1007/s42243-018-0219-8

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  Due to the improvement in fatigue strength of cold-rolled blades, the static recrystallization behavior of cold-rolled Inconel 718 alloy in the solid solution treatment was investigated with the methods of optical microscopy and electron backscattered diffraction. The effect of δ phase precipitation on the static recrystallization process was also analyzed. The results show that δ phase preferentially precipitates comparing to static recrystallization. Affecting by the δ phase preferential precipitation process, sub-grain migration is the main nucleation mechanism in the static recrystallization of cold-rolled Inconel 718 alloy at 980 °C. Meanwhile, strain-induced boundary migration also exists as an aided nucleation mechanism when the rolling reduction is less than 30%.
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  Softening and recrystallization behavior of a new class of ferritic steel

  Xiang-yu Xu, Jian-zhe Li, Xue-min Wang, Wei Zhang, Qian-nan Liu, Cheng-jia Shang

  钢铁研究学报(英文版). 2019, 26(2): 154-161.
  https://doi.org/https://doi.org/10.1007/s42243-019-00230-0

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  In order to clarify the recrystallization mechanism of low-density δ-ferrite steel Fe–4Al–2Ni, interrupted and single-pass compression tests were carried out. In this regard, five deformation temperatures (750–950 at an interval of 50 °C) and different hold time were selected. It was observed that the softening and recrystallization fraction was enhanced with increased deformation temperature and hold time. The original grain boundaries were the preferred nucleation sites for recrystallized grains, and recrystallization had an impact on obtaining homogeneous and fine-grained structure. Recrystallization in the ferritic alloy commenced after a significant degree of softening, and the softening associated with recovery was appreciably less. The optimum rolling deformation temperature was identified to be greater than 900 °C.
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  Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior

  Tao Liu, Mu-jun Long, Wen-jie He, Deng-fu Chen, Zhi-hua Dong, Xian-guang Zhang

  钢铁研究学报(英文版). 2019, 26(2): 162-172.
  https://doi.org/https://doi.org/10.1007/s42243-018-0187-z

  摘要 ( ) PDF全文   可视化   收藏

  A combined model to predict austenite grains growth of titanium micro-alloyed as-cast steel during reheating process was established. The model involves the behaviors of austenite grains growth in continuous heating process and isothermal soaking process, and the variation of boundary pinning efficiency caused by the dissolution and coarsening kinetics of second-phase particles was also considered into the model. Furthermore, the experimental verifications were performed to examine the prediction power of the model. The results revealed that the mean austenite grains size increased with the increase in reheating temperature and soaking time, and the coarsening temperature of austenite grains growth was 1423 K under the current titanium content. In addition, the reliability of the predicted results in continuous heating process was validated by continuous heating experiments. Moreover, an optimal regression expression of austenite grains growth in isothermal soaking process was obtained based on the experimental results. The compared results indicated that the combined model in conjunction with precipitates dissolution and coarsening kinetics had good reliability and accuracy to predict the austenite grains growth of titanium micro-alloyed casting steel during reheating process.
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  Deformation behavior and microstructural evolution in ultra-high-strength dual-phase (UHS-DP1000) steel with different strain rates

  Mei Xu, Hui Li, Rui-ting Jiang, Di Tang, Hai-tao Jiang, Zhen-li Mi

  钢铁研究学报(英文版). 2019, 26(2): 173-181.
  https://doi.org/https://doi.org/10.1007/s42243-018-0213-1

  摘要 ( ) PDF全文   可视化   收藏

  The dynamic tensile behavior and deformation mechanism of ultra-high-strength dual-phase (UHS-DP1000) steel were investigated over a wide range of strain rates from 10^-4 to 10³ s^-1. As the strain rate increases, the transition strain decreases from 2.73 to 1.92, and the martensite plastic deformation starts earlier. At strain rate of 10^-4–0.5 s^-1, the inhomogeneous plastic deformation ability increases because the dislocation density in the ferrite matrix increases. This leads to a decrease in uniform elongation and an increase in fracture elongation. When the strain rate increases from 0.5 to 500 s^-1, the amount of mobile dislocation increases, which is the main reason for the enhancing uniform elongation and fracture elongation. Meanwhile, because the dislocation motion resistance rapidly increases, the yield strength and ultimate tensile strength also increase. When the strain rate is higher than 500 s^-1, the hardening behavior caused by the dislocation motion resistance has not been offset by softening due to the mobile dislocation and adiabatic heating. The voids at the early stage of deformation could not uniformly form and grow, and thus the homogeneous plastic deformation ability decreases.
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  Control of wall thickness and surface morphology of tungsten thin wall parts by adjusting selective laser melting parameters

  Yan-jun Xie, Huai-chao Yang, Xue-bing Wang, Lin Zhao, Chun-jiang Kuang, Wei Han

  钢铁研究学报(英文版). 2019, 26(2): 182-190.
  https://doi.org/https://doi.org/10.1007/s42243-019-00234-w

  摘要 ( ) PDF全文   可视化   收藏

  The tungsten thin wall parts which were used as high-performance collimator devices were fabricated by optimizing selective laser melting laser parameters. The effect of laser power and scan rate on wall thickness and surface morphology of tungsten thin wall parts was investigated, respectively. The results indicated that the wall thickness increased with the enhancement in laser power as a linear relationship. On the contrary, the wall thickness decayed exponentially with the acceleration in laser scan rate. Meanwhile, the wall thickness of the parts fabricated by laser double-pass melting was thinner than that fabricated by laser single-pass melting. In addition, mathematic models for selecting suitable laser power and laser scan rate to fabricate specified tungsten thin wall parts were proposed. Furthermore, the effects of laser parameters on the top surface roughness, adhesive parts and hot cracks were also discussed.
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  Corrosion behavior of Ni-based coating containing spherical tungsten carbides in hydrochloric acid solution

  Shan-shan Liu, Hai-yan Chen, Xuan Zhao, Li Fan, Xiao-ming Guo, Yan-sheng Yin

  钢铁研究学报(英文版). 2019, 26(2): 191-199.
  https://doi.org/https://doi.org/10.1007/s42243-019-00240-y

  摘要 ( ) PDF全文   可视化   收藏

  A Ni-based alloy coating with 30 wt.% spherical tungsten carbide particles was prepared through plasma transferred arc welding on 42CrMo steel. The composition and microstructure of the coating were examined through X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry. The corrosion behaviors of the coating compared to the Ni coating without tungsten carbide particles and to the bare substrate in a 0.5 mol/L HCl solution were presented through polarization curves, electrochemical impedance spectroscopy (EIS) measurements and long-term immersion tests. The results demonstrated that the composite coating microstructure comprised Ni matrix, Ni-rich phase, tungsten carbide particles, W-rich phase and Cr-rich phase. The polarization curves and EIS measurements presented that a passivation film, which mainly included Ni, Cr, Fe and W oxides, was formed in the composite coating that protected the substrate from corrosion by HCl solution. In the immersion tests, a micro-galvanic reaction at the new-formed phases and Ni matrix interface caused severe pit corrosion and Ni matrix consumption. The debonding of Ni-rich and W-rich phases could be observed with the immersion time extension. The tungsten carbide particles and Cr-rich phase were still attached on the surface for up to 30 days.
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  Effect of heat treatment on cyclic deformation properties of Fe–26Mn–10Al–C steel

  He Li, Jian-ping Zhao, Zhan-yu Wang, Li Ding

  钢铁研究学报(英文版). 2019, 26(2): 200-210.
  https://doi.org/https://doi.org/10.1007/s42243-019-00239-5

  摘要 ( ) PDF全文   可视化   收藏

  Fully reversed tensile–compression low-cycle fatigue tests were performed at room temperature under strain amplitude of 0.4%. The monotonic tensile results show that Fe–26Mn–10Al–C steels are fully austenite and the optimal combination of ultimate tensile strength and total elongation was present at 950 °C with 65 GPa %. The fatigue results show that the specimen at 1050 °C has the maximum fatigue life of 162,000 cycles, which is much longer than twinning-induced plasticity (TWIP) steels of the same strain amplitude. The hot-forging specimen shows high similarity with TWIP steels with rapid initial cyclic hardening followed by cyclic softening and cyclic saturation. After solution heat treatment, it is noteworthy that, after rapid initial cyclic softening, another rapid cyclic hardening and a following decrease with fluctuation were observed at 1000 °C. It is reasonable to believe that it is caused by κ-carbides precipitated during cyclic deformation. Another interesting phenomenon is cyclic stress subsidence observed at 1050 °C during its saturation stage at the last quarter of the fatigue life, and the span is about 12.5% of whole fatigue life.
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  Evaluation of interaction between Sn and passivated stainless steel through an easy chromaticity approach

  Yan Zhao, Jian-jun Guan, Feng Liu, Ping Liang, Cong-qian Cheng, Jie Zhao

  钢铁研究学报(英文版). 2019, 26(2): 211-218.
  https://doi.org/https://doi.org/10.1007/s42243-019-00229-7

  摘要 ( ) PDF全文   可视化   收藏

  The interaction between Sn and passivated stainless steel was evaluated through an easy chromaticity approach. The microstructure of Fe–Sn intermetallics (IMCs) was observed, and their growth was inspected at different time after the interaction. The oxide film on stainless steel exposed in air locally delayed IMC growth, and the chemically passivated film protected stainless steel from Fe–Sn compound formation. To investigate the interaction mechanism, the integrity of passivated films grown on stainless steel was evaluated by chromogenic inspection. The interaction extent was related to colour measurement a*. Results indicated that the measured value of a* from the inspection decreased with the increasing exposure time, and a minimum a* value was found in chemically passivated samples. The tendency of the colour measurement was consistent with the effect of passive film on IMC growth. The interfacial reaction of passivated stainless steel with Sn was illustrated based on the integrity of the passive films.