Research progress on 316L stainless steel fabricated via laser powder bed fusion and its corrosion resistance
Zhang Yinling;An Yukun;Zong Ran;Wang Yuanxin;Laser Powder Bed Fusion(LPBF) technology, due to its high design freedom and near-net-shape forming capability, has become an effective means for manufacturing complex 316L austenitic stainless steel components. However, the unique ultra-fast melting and solidification kinetics process of this technology leads to significant heterogeneity in the material's microstructure, easily inducing Cr/Mo element segregation at cell boundaries and residual stress concentration, which significantly reduces the stability of the passive film and increases the susceptibility to pitting initiation and the risk of stress corrosion cracking. Therefore, adjusting and optimizing the forming process to simultaneously improve mechanical and corrosion-resistance properties and establishing the relationship between processing technology, microstructure, and corrosion performance are crucial for the mass production of repeatable and high-performance LPBF-316L stainless steel components. Nevertheless, current research on the influence mechanisms of alloy solidification and recrystallization during the LPBF process on the corrosion resistance of 316L stainless steel remains insufficient. This review comprehensively elaborates on the influence of powder raw materials and preparation strategies on inherent defects such as porosity and unfused zones, microstructure evolution, and corrosion resistance in LPBF-316L. It analyzes three key corrosion inducers: porosity, cellular structure, and residual tensile stress, and proposes solutions including multi-scale process parameter collaborative regulation, post-processing techniques, and raw material modification. Finally, future research directions are outlined, including cross-scale corrosion mechanism studies and engineering applicability investigations.
Influence of rare earth lanthanum addition on inclusions and mechanical properties of 2.0 GPa ultra-high strength steel
Zhang Yunfei;Zhan Dongping;Li Jihang;Jiang Zhouhua;The effects of adding different mass fractions of rare earth La on the inclusions, microstructure, and mechanical properties of 2.0 GPa ultra-high strength steel, which was smelted by a vacuum induction furnace, have been investigated by means of a metallographic microscope, scanning electron microscope, EBSD analysis, XRD diffraction, and tensile and impact tests. The results reveal that as the mass fraction of La increases from 0(no addition) to 0.003 2% and then further to 0.022% in the steel, inclusions evolve from MgO·Al_2O3 to LaAlO3-La_2O_2S complex, and later to rare earth composite oxysulfides LaS-La_2O_2S. The volume fraction of retained austenite after aging is from 1.85% to 3.05% and then to 5.17%, with the improvement rates of 64.9% and 69.5%, respectively. The Charpy impact energy increases from 11.9 J to 14.1 J and then to 15.3 J, with the improvement rates of 18.5% and 8.5%, respectively. Rare earth La plays a key role in modifying and spheroidizing inclusions in the steel, and increases the volume fraction of retained austenite, leading to a significant increase in impact energy. However, when La is excessively added to a mass fraction of 0.022%, the yield strength of the steel decreases from 1.596 GPa to 1.476 GPa, with a decrease of 0.120 GPa. It is concluded that the optimal addition of rare earth La is 0.003 2%, in this case, contributing to a noticeable increase in the toughness of 2.0 GPa ultra-high strength steel.
Effect of CaO on solution-loss kinetics of cokes in CO_2+20%H_2O atmosphere
Zhang Shuaiyu;Dou Minghui;Han Jiawei;Luo Yunhong;Feng Zhiyang;Sun Zhang;To investigate the solution-loss properties of high-reactivity cokes in a hydrogen-rich blast furnace, the solution-loss processes of basic coke(BC) and high-reactivity coke with CaO(BC+Ca) at 1 000, 1 100, 1 200 ℃ under CO_2+20%H_2O(volume fraction, the same below), N_2+20%H_2O, and CO2 atmosphere were studied. The kinetics of Boudouard reaction ■ and water-gas reaction ■ were analyzed by detecting the mole percent of CO and H2 in the off-gas, to study the effect of CaO on the solution-loss kinetics of cokes in a CO_2+20%H_2O atmosphere. The results show that the Boudouard reaction rates of BC and BC+Ca cokes in CO_2+20%H_2O atmosphere are lower than those in CO2 atmosphere, and the water-gas reaction rates of BC and BC+Ca cokes are also lower than those in N_2+20%H_2O atmosphere, which indicates that there is a competition between the reactions of H_2O and CO2 with cokes. The Boudouard reaction rate and the water-gas reaction rate of BC+Ca coke are larger than those of BC coke, which shows that CaO has a catalytic effect on both reactions. CaO addition can decline Ea for the Boudouard reaction about 22.1～24.5 kJ/mol and Ea for the water-gas reaction about 37.8～38.9 kJ/mol. Furthermore, the ratio C(kH/kC) of the water-gas reaction rate constant to the Boudouard reaction rate constant is proposed to characterize the competitiveness of H_2O to CO2. The results show that the catalytic effect of CaO on the water-gas reaction is stronger than that of the Boudouard reaction, which increases from 6.1% to 20.0% compared with the C value of coke at 1 000～1 200 ℃. The silica-aluminate existing states of Ca in cokes are calcium aluminosilicates, which effectively improve the competitiveness of H_2O to CO2.
Effect of binary basicity of slag on smelting behavior of vanadium-titanium magnetite pre-reduced pellets
Zhao Meng;Tian Hongyu;Chu Mangsheng;Tang Jue;Zhou Haoyu;Wang Yefeng;Based on thermodynamics, process mineralogy and thermal experiments, the effects of binary basicity of slag R2 [i.e. w(CaO)/w(SiO2)] on the smelting behavior of vanadium-titanium magnetite pre-reduced pellets have been systematically studied. The results of FactSage thermodynamic calculation show that increasing R2 can reduce the Ti content in molten pig iron, while having little effect on the temperature and amount of Fe and V formation. Combining the thermal experiments results and process mineralogy theory, it can be concluded that when R2 increases from 0.43 to 0.8, the recovery rates of Fe and V in the molten pig iron increase from 97.07% and 82.31% to 98.89% and 89.48%, respectively; The recovery rate of TiO2 in the molten slag increases from 93.67% to 95.21%. The formation of low melting phases reduces the degree of inclusions in the ferroalloy phase, promotes the directional migration of valuable elements, and thus improves the slag iron separation effect. When R2 is higher than 0.8, its impact on the recovery rate of valuable components is relatively small. The formation of high melting point perovskite increases the melting point, viscosity, and slag amount of the molten slag phase, thereby increasing the cost and energy consumption of EAF.
Improved black-winged kite optimization algorithm-light gradient boosting machine model to predict converter steelmaking endpoint temperature
Wu Guochao;Li Ailian;Xie Shaofeng;Inner Mongolia University of Science & Technology Office of Logistics and Capital Construction;In order to realize the accurate prediction of converter steelmaking endpoint temperature, the actual SPCC steel data collected in the field are selected. By using the 3σ principle, mean-filling method for cleaning data outliers and missing values and determining 10 input features based on gray correlation analysis and process theory, and then establishing the light gradient boosting machine(LightGBM)-based endpoint temperature prediction model for converter steelmaking, and adopting support vector machine(SVM) and extreme gradient boosting(XGBoost) model as a comparison, the adaptability of the LightGBM model in the converter data and the superiority of the prediction performance is verified. Aiming at the problem that LightGBM models require manual parameter tuning, making it difficult to improve prediction accuracy, a multi-strategy improved black-winged kite optimization algorithm(IBKA) is proposed to obtain the optimal combination of its important parameters. The results show that compared with the other five optimization models(JAYA-LightGBM, GWO-LightGBM, WOA-LightGBM, RBMO-LightGBM, BKA-LightGBM), the IBKA-LightGBM model performs optimally in terms of prediction accuracy and performance evaluation indices, and achieves better prediction results, with prediction error hit rates of 85.56% and 96.67% at ±10 ℃ and ±15 ℃, respectively, which can provide effective operational guidance for steelmaking production.
Identification and treatment of academic misconduct
To protect the right of readers and authors as well as to maintain the quality and reputation of the journal, Journal of Materials and Metallurgy adopts CNKI academic misconduct detection system for automatic detection. The general storeroom of China academic literature network will be used for academic misconduct detection, including plagiarism, forgery, falsification, improper attribution, and multiple submissions.
1. Recognition of Academic Misconduct Papers
For the paper with a repetition rate higher than 20%, the submitted paper, together with the comparison paper, will be submitted to the reviewer to determine the nature and form of the duplicated part and to give handling recommendations.
2. Handling of Academic Misconduct Papers
1) In a prudent manner, authors will be punctually notified from the editorial departmental when the paper is ultimately recognized as academic misconduct. Explanations and defenses are allowed before handling decisions are made.
2) If the paper has been accepted but has not been officially published, the author will be notified, and the paper will be rejected and disqualified in the paper processing system.
3) If the paper has been officially published, the author of the paper will be notified in written form. The acceptance qualification will be disqualified, and the online version of each database will also be revoked. The journal reserves the right to seek compensation for any loss of reputation or other damage caused to the journal.
4) For authors with serious misconducts, their names and affiliations will be published in the journal at an appropriate time together with revocation notice. The author's affiliation and other scientific and technical journals in the field will be notified.
3. Handling of authors’ dissent
If the authors have dissents with the recognition and handling results, they can apply a written application for review to the editorial department of the journal within 10 working days from the date of receiving the notice. The Journal will not accept the application after the deadline. The editorial department will be responsible for inviting experts to review the paper and making final handling opinions. The authors will be notified the final review results within 30 working days.
The above measures will be effective from the date of promulgation and will be interpreted by the Editorial Board of the Journal of Materials and Metallurgy.
Appendix: Recognition Criteria of Academic Misconduct Papers
1) Reproduction of another person's work in its original or substantially original form;.
2) Change the type of others’ work and regard the results completed by others as the results completed by themselves; or do not change the type of results, but use the components protected by copyright in the results and change the specific manifestations of the results, as their own independent results.
3) Use the protected views of others to form the whole, core or main point of his own paper as the main part or substantive part of one’s own academic paper;
4) Fabrication or falsification of research results, survey data, experimental data or documentation;
5) Citing protected ideas, programs, materials, data, etc. of others without reference notes
6) Multiple submissions.
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