Announcement of the winners of the paper awards to be presented in 2024.

Because lamellar cementite in pearlite has low crystal symmetry and is fine structure, it has been very difficult to analyze its crystal orientation over a wide range. In this study, the authors solved this problem by intentionally spheroidizing and coarsening cementite and established a method to analyze the crystal orientation of cementite accurately and extensively using SEM/EBSD. As a result, it was experimentally clarified that at least three independent crystallographic orientation relationships coexist in pearlite within one specimen, and further that discontinuous transitions in the crystallographic orientation relationships tend to occur at the colony boundary where the growth direction of lamellar cementite changes. Based on this experimental fact, it was also demonstrated that the use of multiple crystallographic orientation relationships with different parallelism between ferrite and cementite provides a high degree of freedom in lamellar orientation, and thus enables the equiaxed growth of pearlite.

As described above, this paper clarifies the diversity of the pearlitic transformation, a fundamental phase transformation of iron and steel, from a crystallographic viewpoint, and is a valuable study that deepens our understanding of the phase interface precipitation phenomenon, which is a basic technology for manufacturing high-strength steel. It is highly evaluated both academically and industrially, and is therefore appropriate for the Sawamura Award.

As effective use of iron scrap becomes more and more important, control of Sn, which is a tramp element, is one of the important issues. In this paper, focusing on the control of Sn in molten stainless steel, the interaction coefficients of Mo, B, Ni, Ti and Nb with Sn in Fe-Cr alloys were measured by very careful experiments. The experiment is based on an equilibrium experiment using Ag that shows two-liquid phase separation from Fe-Cr alloy, and skillfully utilizes the relationship in which the activities of each component between the two phases are equal. The obtained experimental results were compared with the values estimated by the regular solution model. Authors have steadily measured precise and valuable thermodynamic data, which can be highly evaluated. The effects of adding Cr to molten iron have been investigated in detail and reported results that greatly contribute to the recycling and circulation of stainless steel in promoting decarbonization and energy conservation. This paper has high academic and industrial value, and is expected to develop further in the future, and thus is well worthy of the Sawamura Award.

MgO-C bricks are important refractory and are used for the inner linings of Basic Oxygen Furnace and the ladle slag line. The main components of MgO and graphite could easily react with each other under high temperatures and the reaction could cause the degradation of the refractory structure and decrease the service life. Therefore, it is necessary to estimate the reaction rate quantitatively to suppress the reduction of the durability.

However, the modeling approach to the reaction has been difficult due to the existence of MgO particles of various sizes in the refractory. As a result, the reaction has been limited to the qualitative interpretation and the proposal of the reaction model has been expected to enable the qualitative estimation.

In the paper, a novel mathematical model was successfully established by the combination of the shrinkage core model and MgO particle size distribution which was expressed by the statistical distribution functions. Moreover, the model was applied to the experimental results, and it was clarified that the reaction could be promoted in the refractory containing finer particles. The fundamental findings could lead to a breakthrough in the research field of refractory and the industrial application is much expected.

As the reason described above, this extraordinary paper is recognized as one of the most valuable papers in terms of both industrial and academic point of view, and thus is well worthy of the Sawamura Award.

During Lüders band propagation in medium-Mn steels, hierarchical deformation heterogeneities exist, namely, strain partitioning, deformation-induced martensitic transformation in austenite, formations of the deformation bands and mesoscopic Lüders front. However, their effects on Lüders band propagation are not clear, and therefore, multi-scale characterization from the microstructure-scale plasticity to the macroscopic scale is indispensable.

In this paper, the characteristics of Lüders deformation of an Fe-5Mn-0.1C alloy that was cold-rolled and intercritically annealed are investigated from macro and micro multi-scale. On the macro scale, the thickness and growth of the Lüders band are determined using a digital image correlation (DIC), and in-situ SEM observation (micro level) is performed on the Lüders front. The following new findings have been obtained from the relationship between stress-strain diagrams and micro-level observations. The elastic region in the vicinity of the elastic-plastic interface has a local stress greater than the macroscopic lower yield stress, due to inhomogeneous microstructure, residual stress, notch effect, etc. As a result, the initiation of deformation bands occurs in the elastic region (stress below the upper yield point). After macroscopic yielding, the thin deformation bands grew via band branching, thickening, multiple band initiation, and their coalescence. Based on these observations, a model for discontinuous Lüders band propagation has been proposed.

This paper clarifies the behavior of Lüders deformation in medium-Mn steels, which are attracting attention as next-generation high-tensile steels, using multiscale in-situ observation, from both experimental and theoretical aspects, and is of high academic and engineering significance, making it suitable for the Sawamura Award.

Intergranular and quasi-cleavage fracture are important for hydrogen embrittlement of steels. Effect of hydrogen on intergranular fracture has been well investigated. On the other hand, the crystallographic feature of the fracture surface is not clear for hydrogen-related quasi-cleavage fracture.

In the paper, three dimensional image and crystallographic feature of serrated markings on the quasi-cleavage fracture surface were investigated. In the quasi-cleavage fracture relating with plastic deformation, {011} plane which has largest resolved normal stress imposed on the plane was selected as a fracture surface and longitudinal direction of serrated markings were almost parallel to <110> and <112> direction. The result indicates that the direction of serrated markings has close relationship with the direction of vacancy lines nucleated by jog-dragging of screw dislocation. This means that not only the slip deformation but also the vacancies induced by hydrogen-enhanced plastic deformation is important for understanding of hydrogen embrittlement.

This study provides importance of the resolved normal stress imposed on the fracture surface for discussion of hydrogen-related quasi cleavage fracture mechanism, which has academic and technological significance. Therefore, this paper is worth well to the Sawamura Award.

Currently, new efforts (hydrogen reduction steelmaking, molten iron oxide electrolysis, biomass ironmaking, etc.) are being made in the global steel industry to achieve carbon neutrality by 2050. Under these circumstances, this paper is related to NEDO's COURSE50 project, which aims to achieve a 10% carbon reduction in the blast furnace process in relation to the future carbon neutrality. Although qualitative effects of reducing of carbon rate by hydrogenous gas injection, top gas recycling, and use of high reducibility sinter have been predicted, quantitative effects in the actual blast furnace process have not been reported. In this paper, the effects of COG injection into the blast furnace, shaft gas circulation after CO2 separation from the top gas, and the use of high reducibility sinter are quantitatively demonstrated using a pilot test blast furnace, clearly showing a very high level of technical content. It also has sufficient realism for social implementation for application to actual blast furnaces. Furthermore, the technological developments described in this paper are expected to make a significant contribution to carbon reduction in blast furnace processes not only in Japan but also in the world.

Based on the above, this paper is judged to be worthy of the Sawamura Award because it quantitatively demonstrates the carbon reduction effect of blast furnaces using a new technology, it is of a high technical level, it is expected to have a ripple effect on researchers around the world toward the realization of carbon neutrality, and it is also of a high academic level.

According to growing demand of high-quality steel, secondary refining has become even more important where precise prediction is expected on composition change, agglomeration and floating behaver of inclusions in molten steel; however, systematic understanding has not been established due to variety of controlling factors. This paper well investigates these complex phenomena by applying “coupled reaction model” to composition change of inclusion in molten steel to clarify the controlling mechanism for precise prediction and further elucidation of agglomeration and floating behavior of inclusions has been also made by applying physical properties. Reaction with refractories, formation of spinel compounds as well as desulfurization reaction have been well practically investigated to find good agreement with the results of ladle operation. Coupled reaction model has ever been applied to the prediction of hot metal pretreatment; however, its application to secondary refining process has been firstly made using thermodynamic equilibrium theory, kinetics as well as physical properties with novelty. Hence, this paper has been extensively referred and widely influenced many possible refining processes and accordingly deserves the Distinguished Paper Award.