Research progress on brazing of Inconel 718 superalloy
Chen Jiacheng;Cai Quan;Zhao Pu;Zhu Mengmeng;Luo Kunjie;Xia Yuanhang;Yan Jiuchun;Inconel 718 alloy is a key precipitation-strengthened nickel-based superalloy used in aerospace and energy power fields. The fabrication and in-service repair of precision components, such as aero-engine turbine blades and combustors, highly depend on brazing technology. The surface oxide film of the alloy easily leads to poor wettability of brazing fillers, and the thermal cycle during brazing tends to cause base metal softening and stress cracking, bringing great challenges to the design of brazing fillers and process control. This paper focuses on three core problems in the brazing of Inconel 718 alloy: wettability, base metal softening, and stress cracking, analyzing their mechanisms and improvement strategies. It systematically summarizes the composition, metallurgical behavior, and selection criteria of nickel-based and precious metal-based brazing filler systems. It clarifies the influence of brazing parameters such as temperature, holding time, and joint gap on the microstructure and properties of joints, as well as the performance strengthening mechanism of post-brazing heat treatment, and looks forward to the future development direction of Inconel 718 alloy brazing technology.
A prediction model of blast furnace slag viscosity based on response surface methodology
Zhang Haochen;Liu Zhenggen;Tong Kuixing;Wang Ziyu;Zhang Xu;Employing the response surface methodology(RSM) and central composite design(CCD), the effect of binary basicity R2, MgO mass fraction, and Al_2O3 mass fraction on the blast furnace slag viscosity has been systematically investigated, and a slag viscosity prediction model has been developed. The results show that R2, w(MgO), and w(Al_2O3) all significantly influence slag viscosity, with the order of influence being w(Al_2O3)>w(MgO)>R2. The established mathematical model(i.e., prediction model) has a correlation coefficient of 0.979 5, enabling accurate prediction of slag viscosity changes with different factors. When the blast furnace slag has an R2 of 1.19, w(MgO) of 7.79%, and w(Al_2O3) of 12.39%, the actual viscosity closely matches the predicted value, with an average error of only 4.30%, proving the model′s accuracy and reliability.
Splashing behavior of converter based on VOF-DPM bidirectional conversion model
Tang Xudong;Qi Fengsheng;Li baokuan;Liu Zhongqiu;Aiming at the challenge of accurate quantitative prediction of splashing behavior in the converter top-blowing process, a mathematical model for converter splashing based on a bidirectional VOF-DPM conversion. This model establishes a bidirectional conversion criterion between the VOF(volume of fluid) continuous phase and the DPM(discrete phase model) discrete phase, and accurately characterizes the interface instability induced by the impact of the top lance jet on the gas-liquid interface of the molten bath, the conversion process from the continuous liquid phase to discrete splashing droplets, as well as the conversion process from the discrete phase droplets back to the continuous liquid phase when discrete phase droplets fall into the molten bath. On this basis, full trajectory tracking and quantitative statistics of splashing droplets are realized. Based on the established model, a systematic study is carried out on the influence laws of top-blowing flow rate and top lance height on splashing behavior. The results show that within the range of working conditions investigated in this study, the optimal regulation effect of splashing can be obtained at a top-blowing flow rate of 7.40 m3/h and a top lance height of 105.5 mm.
Optimization and application of asymmetric tundish structure
Zhao Wenjing;He Longlong;Chen Min;Xu Lei;A combination of physical modeling and numerical simulation has been employed to investigate the effects of different flow-control schemes on the molten steel flow field and temperature field within the tundish. The results indicate that under water-model conditions, the response time and peak time of the two streams in the original scheme differ significantly, the consistency between the two streams is poor, and the average dead-zone volume fraction is as high as 33.45%. After increasing the dam height and enlarging the distance between the dam wall and the dam, the consistency of the two streams is markedly improved, and the average dead-zone volume fraction decreases to 14.55%. Practical application results show that the temperature difference of the molten steel above the two nozzles in the tundish decreases from 4～6 ℃ to 2～3 ℃, and the total oxygen content in the cast billet is reduced by approximately 27.9%. These findings illustrate that the optimized scheme effectively enhances the metallurgical performance of the tundish and improves the quality of the cast billet.
Isothermal kinetics of carbothermal reduction of magnesium oxide from magnesite
Meng Qinglong;Zhang Yu;Li Jinna;Pang Yun;Zhuang Yanxin;Xing Pengfei;In order to promote the industrialization of magnesium preparation by carbothermal method, the isothermal reduction method was used to explore the isothermal carbothermal reaction mechanism of magnesium oxide prepared from magnesite. The effects of temperature and dough-making pressure on the reduction rate of magnesium oxide were systematically investigated, and the isothermal kinetic parameters and apparent activation energy of the carbothermal reaction were further calculated. The results show that 96.17% reduction could be realized by the briquetting reaction for 60 min at 1 773 K and 10 MPa dough-making pressure. In the temperature range of 1 623～1 773 K, the kinetics can be divided into two stages, namely 0～20 min and 30～60 min. Both phases are controlled by three-dimensional diffusion with apparent activation energies of 206.98 kJ/mol and 238.08 kJ/mol, respectively.
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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