Theme I: Production and characterization of iron ore sinters for hydrogen reduction blast furnace
Chairperson: M. Hayashi (Science Tokyo)

Currently, the global steel industry is shifting toward carbon-neutral steelmaking processes. In Japan, research and development is underway to reduce CO2 emissions by increasing the H2 concentration inside blast furnaces (BF). In BF operations with high H₂ and low coke ratios, it is necessary to improve the reducibility index (RI) and reduction disintegration index (RDI) of iron ore sinters in order to maintain air permeability within the furnace. The bonding phases of iron ore sinters are composed of secondary hematite, magnetite and multi-component calcium ferrite (CF). Secondary hematite has excellent RI but poor RDI, while magnetite has excellent RDI but poor RI. In contrast, multi-component CF generally exhibits good RI and RDI, making it an important mineral phase in high-quality sinters. The committee members of ISIJ Study Group I “Production and characterization of iron ore sinters for hydrogen reduction blast furnace” (which was conducted in 2024-2026) investigated the effects of MgO addition on the formation of sinter microstructures and the quality of sinters, and conducted research on how to add MgO to produce high-quality sinters. In this session, the members were invited to report on the results of the Study Group. In addition, the reports on the relevant research findings are also invited.

Theme II: Arc heat transfer and scrap melting mechanisms
Chairpersons: S. Ueda (Tohoku Univ.), M. Nakamoto (The Univ. of Osaka), Y. Fujii (Godo Steel)

Electric arc furnace (EAF) steelmaking is becoming increasingly important as a low-carbon steel production route based mainly on scrap. Further improvement in EAF efficiency requires a quantitative understanding of scrap heating and melting, heat transfer from the arc, and slag foaming behavior.
The Research Group on “Arc Heat Transfer and Scrap Melting Mechanisms” has experimentally investigated heat transfer from the arc to metal, scrap heating and melting, and slag foaming mechanisms. These studies have provided fundamental insights into the controlling factors and interactions among these phenomena, establishing a basis for quantitative modeling of heat transfer, melting, and slag foaming in EAFs.
This discussion meeting will present the final outcomes of the research group and discuss how these findings can contribute to more efficient EAF operation. Remaining challenges, future modeling approaches, and their application to practical EAF processes will also be discussed with researchers and engineers in the field.

Theme III: Addressing sustainability challenges in the steel industry (Final report session of the study group of "Supply Chain Management in Steel and Related Industries")
Chairperson: E. Yamasue (Ritsumeikan Univ.)

Achieving carbon neutrality is one of the most important challenges facing the steel industry. However, sustainability cannot be addressed through a carbon-centered perspective alone. A wide range of interconnected issues must also be considered, including biodiversity loss associated with resource extraction, mineral resource constraints, phosphorus and nitrogen cycles, and the “resource paradox,” whereby decarbonization itself may generate additional demand for resources and new environmental burdens. Drawing on the concept of planetary boundaries, this discussion session will provide a broad overview of the sustainability challenges that the steel industry will need to confront and explore future directions for research, technology, and industrial development beyond decarbonization.

Theme IV: Advanced steel process control developed by AI and CPS
Chairpersons: Y. Ebihara (Kyoto Univ./Kyushu Univ.), M. Matsushita (JFE), In recent years, Artificial Intelligence (AI) and Cyber-Physical Systems (CPS)

have attracted considerable attention as core technologies for achieving advanced automation and labor-saving operations in manufacturing industries. Although their application in the steel industry is steadily progressing, their adoption in process control remains limited due to the complexity of process dynamics and the stringent requirements for reliability and safety.
As part of the activities of a newly established research group, this symposium aims to promote broad discussions on advanced steel process control technologies utilizing AI and CPS. Particular attention will be given to the evaluation of reliability and stability, which are critical challenges in AI-based decision-making and control. From the perspectives of both control theory and AI technologies, participants will explore future directions for research and development in this field. Furthermore, with a focus on applications to steel process control, discussions will address the potential for realizing highly reliable and efficient control frameworks through the comparison and integration of AI technologies and conventional control theory. The symposium will provide an opportunity to envision the future of next-generation process control in the steel industry.

ThemeV: Systemic optimization of energy chains: Research outcomes and future prospects
Chairpersons: H.Suwa (Setsunan Univ.), J.Mori (Nippon Steel)

This research group has been developing methodologies and enabling technologies for the "systemic optimization" of steel production systems by integrating energy, material, logistics, and exergy flows, contributing to the realization of a carbon-neutral society. As this is the final year of the research group, this discussion meeting will present research outcomes on exergy flow networks, steelworks logistics and energy simulators, operational evaluation models using probabilistic approaches, and production planning and systemic optimization models. Discussions will address the validity of the modeling methodologies, interpretation of the evaluation results, applicability to steelworks, and future research directions to assess the practical effectiveness of the research outcomes.

ThemeVI: Increasing accuracy of simulation and visualization in sheet forming process
Chairpersons: A. Segawa (KIT), A. Yanagida (TDU)

This session will feature comprehensive discussions on sheet forming simulations, reviews of constitutive laws, material property measurement techniques, and visualization technologies for deformation states.

ThemeVII: To solve problems of hot rolling rolls and visualization of roll interface phenomena
Chairpersons: A. Yanagida (TDU), N. Ueshima (The Univ. of Osaka)

Visualization of interface phenomena as well as mechanisms of wear and surface damage of hot rolling rolls is necessary to understand roll/workpiece phenomena in roll bytes.
In the “Research on Visualization of Rolling Roll Interface Phenomena,” research is being conducted not only by direct measurement, but also by physical simulation using numerical analysis and model experiments. At this forum, we will discuss the findings and future challenges with the audience as the final report of our research group, which was established in fiscal year 2023.

ThemeVIII: Rethinking hydrogen embrittlement: embrittlement and strengthening arising from dynamic interactions between lattice defects and solute atoms (Joint discussion session organized by the ISIJ research group and forum on hydrogen embrittlement)
Chairpersons: R. Matsumoto (The Univ. of Osaka), M. Kawamori (Kobe Steel), M. Koyama (Tohoku Univ.)

Hydrogen embrittlement has long been recognized as an important issue, yet a unified understanding of how hydrogen affects plastic deformation and fracture has not been fully established. In recent years, increasing attention has been paid to viewing the interaction between hydrogen and lattice defects, such as dislocations, grain boundaries, and vacancies, as a dynamic process involving both hydrogen diffusion and defect motion. Carbon, nitrogen, and other solute atoms that migrate either by diffusion or through the motion of lattice defects can likewise interact with defects and induce strengthening, plastic instabilities, strain localization, and, in some cases, embrittlement. Comparing these phenomena provides a useful framework for distinguishing features specific to hydrogen embrittlement from those shared more generally by deformation and fracture phenomena arising from dynamic interactions between solute atoms and lattice defects. This discussion session will bring together recent experimental, computational, theoretical, and evaluation/analysis approaches to discuss the mechanisms of hydrogen-induced strengthening and embrittlement, with particular emphasis on their general and distinctive characteristics from the viewpoint of dynamic solute–defect interactions.

ThemeIX: New frontier in pearlitic steels and materials with lamellar structure
Chairpersons: K. Kishida (Kyoto Univ.), R. Ueji (NIMS), A. Shibata (NIMS)

Pearlitic steels achieve the highest strength levels among practical steels through wire drawing, and further advances in strength and drawability are strongly desired. Meanwhile, recent studies have provided new insights into the deformation behavior of cementite and pearlitic microstructures. This symposium will highlight the outcomes of the ISIJ research project “Mechanisms of Unique Lamellar Structure Development in Drawn Pearlitic Steels” (2024–2026), together with related contributed presentations. Discussions will focus on the relationships between microstructure and mechanical properties of pearlitic steels and future perspectives in this field.

ThemeX: Microscopic and macroscopic deformation behaviors of multiphase steels
Chairperson: T. Hojo (TGU)

Multiphase steels consisting of hard and soft phases achieve excellent strength-ductility balance owing to the differences of mechanical properties and the controls of the fraction and morphologies of consisting phases. In addition, Multiphase steels undergo heterogeneous deformation both microscopically and macroscopically owing to those different phases. On the other hand, the damage (void) initiation and growth at the hard/soft phase interfaces are promoted because of the heterogeneous deformation between hard and soft phases. Since the multiphase steels are composed of several combinations of phases and mechanical properties, phase fraction and morphologies of consisting phases are controlled, researchers do not posess a consensus regarding the detailed deformation behaviors and the initiation and growth behaviors of voids in the multiphase steels.
In this symposium, the microscale and macroscale deformation behaviors and damage initiation and growth behaviors of the multiphase steels will be discussed, and researchers shear the understanding for multiscale analyses of the deformation and damage behaviors of the multiphase steels.

ThemeXI: Latest trends of chemical and physical analysis of steels -1
Chairperson: M. Ohnuma (Hokkaido Univ.)

Since most of the latest results based on advanced analysing technique are presented in the sessions for particular targets, it is sometimes difficult to share the latest technique or problem in the steel analysing techniques. Therefore, we are planning to have annual session for the advanced analysing techniques in the non-busy day of the parallel sessions.

ThemeXII: Speciation and control of Mn states and behavior in steel slag (Final report session of the study group of "Analysis of chemical configuration and morphology of manganese in steel slag")
Chairpersons: H. Eba (TCU), H. Tobo (JFE)

Manganese (Mn) is an essential element in steel production because it improves the toughness of steel. In steelmaking processes, Mn is supplied not only from iron ore but also through the addition of ferromanganese alloys. Owing to its high affinity for oxygen, a portion of the Mn is transferred to the slag phase. Consequently, Mn is considered to influence the properties of slag, and its activity and reactivity vary depending on its speciation within the slag. However, the chemical states and behavior of Mn have not been sufficiently analyzed or discussed to date. In this research group, we have analyzed the valence states of Mn, its mineral phases, and its leaching characteristics in steel slag, and have examined their relationships with slag formation conditions such as temperature.
In this discussion session, we will present the final results of the research group, summarize the overall findings, and discuss potential applications of the outcomes. We also hope to engage in active exchanges of opinions with participants, including discussions on future research directions and prospects for responding to changes in steelmaking processes and operating conditions.