2019 Sawamura Award and Distinguished Article Award

Separation and recovery of phosphorus from steelmaking slag is an important research subject related to decrease of slag generation and resource utilization. On the other hand, phosphorus recovery is becoming more and more important in the near future because high iron phosphate ore is expected to be used and steelmaking slag with high phosphorus oxide concentration is expected. Phosphorus oxide in the slag is concentrated to a soluble C₂S–C₃P solid solution, which enables selective elution of phosphorus. In this paper, steelmaking slag containing a high concentration of phosphoric acid is used to investigate the effect of K2O addition on phosphorus recovery by leaching, and a steelmaking process using high P ore is proposed. Through detailed experiments, the influential factors in the leaching and precipitation processes were investigated, and the control method for phosphorus recovery was clarified. A solid containing 30% phosphorus oxide was recovered by separation and calcination of the precipitate, indicating that it could be used as a phosphate fertilizer. In addition, the leaching residue could be recycled.

This paper deals with very important engineering themes, taking into account the steelmaking process at the blast furnace integrated steelworks, and the experiments are detailed and the development in practical use is clear and can be evaluated. It can be highly evaluated in both academic and technical aspects, and it can be judged that the paper is suitable for the Sawamura Award.

This paper describes the effect and mechanism of crystallization on heat transfer of mold flux used in a continuous casting of steelmaking process.

The apparent thermal conductivities including radiation conduction were measured on glassy and crystallized mold flux samples under steep temperature gradients using a new original experimental apparatus. In the experiment, the apparent thermal conductivity of Inconel 600 and fused silica were measured in comparison with that of mold flux. Moreover a heat transfer calculation model about solid mold flux film has been developed and discussed using the obtained experimental data of mold flux. Especially it was clarified that the thermal conductivity increased with the increase of the crystallization rate in the temperature range from room temperature to 350℃. Moreover the apparent thermal conductivity of the glassy layer increased to 1.54 (W/m/K) for 1.32 (W/m/K) of the crystal layer in the temperature range from 500℃ to 600℃. And then the effect of radiation on the apparent thermal conductivity was clarified quantitatively by this paper.

A lot of valuable basic data about heat transfer of mold flux used in continuous casting process were collected and analyzed by the new original experimental facilities and mathematical calculation model. Therefore, this paper is considered to be valuable with respect to not only academic but also industrial point of view, and hence is worthy of the Sawamura Award.

Clogging of submerged entry nozzle in continuous casting process is a severe technical issue directly affecting production efficiency and product quality. Although various mechanisms have been proposed as reasons of nozzle clogging, its consensus has not been achieved.

Establishment of the efficient production technology is desired.

The present paper focused on the possibility of oxidation of Ti and Al in molten steel by CO gas produced from the reaction between C and SiO₂ contained in nozzle material. Firstly, the phase diagram for the Fe_tO-Al₂O₃-TiO_x system under reducing atmosphere was estimated by CALPHAD method, and the formation of liquid oxide was thermodynamically predicted. Secondly, lab-scale experiments holding molten Fe, Fe-Al, Fe-Ti, or Fe-Al-Ti alloy under CO atmosphere in Al₂O₃ crucible at 1560℃ were conducted to observe the reaction behavior at the interface between molten steel and nozzle material, and distribution of products. Formation of the Fe_tO-Al₂O₃-TiO_x liquid oxide was observed as estimated from the phase diagram, and Al₂O₃ oxide was entrapped in the liquid oxide. Reaction mechanism was deduced from above experimental facts and estimated phase diagram, and the nozzle clogging mechanism was proposed.

This paper reports the excellent findings which can provide fundamental and concrete countermeasures to prevent nozzle clogging. The achievement is highly evaluated from both academic and practical aspects. This paper is worthy of the Sawamura Award.

There is a growing demand for use of low grade iron ores, i.e., iron ores with high content ratio of gangue (SiO₂, Al₂O₃) or fine ores, etc., as burden of BF from the viewpoints of lack of high grade iron ores or expensive cost. Reduction disintegration often proceeds through crack generation and propagation caused by volume expansion due to the reduction of iron ore from hematite to magnetite, and it is concerned about increasing pressure loss with decreasing permeability in the blast furnace (BF). In this case, the high productivity and stable operation of BF can’t be maintained. The authors tried to apply acoustic emission (AE) method for a detailed in-situ observation of BF burden materials by a combinational experimental of reduction disintegration, and found that gaseous species (H₂ and CO) had a large influence on crack generation and propagation of sample by measuring a large number of AE_s during initial and later reduction stages. Moreover, they revealed that crack generation and propagation of samples were strongly influenced by thermal stress generated during cooling stage. They first could evaluated RDI values quantitatively by apply AE method. These obtained results leads to quantitatively evaluation of reduction disintegration behavior, and it is expected to establish new technology of stable operation of BF.

Considering the above achievements, this paper has an academic and a technical significance, and especially promises the ripple effect in the field of iron-making. Thus it is worth of the Sawamura Award.

It has long been thought that excellent hydrogen embrittlement resistance of drawn pearlitic steel is caused by its fine lamellar structure aligned in the drawing direction. However, there is no direct experimental evidence to support the mechanism, because it is very difficult to get macroscopic specimens with the tensile axis normal to the drawing direction from the drawn wire with small diameter. In the present study, authors newly applied in-situ microbending test during cathodic hydrogen charging by using focused ion beam and indentation techniques in order to directory investigate the anisotropy of hydrogen embrittlement resistant of drawn pearlitic steel. As a result, it was revealed that the hydrogen embrittlement crack propagates more easily in the direction parallel to the ferrite/cementite interface than normal to that, which suggests that the directional lamellar alignment of the pearlitic steels effectively suppresses the hydrogen embrittlement crack propagation in the radial direction of the drawn wire. Furthermore, high resolution lattice image obtained by scanning/transmission electron microscopy clearly revealed that the crack propagates along the ferrite/cementite interface, and K_C is considerably small.

Considering the above achievements, this paper is regarded as outstanding one toward uncovering the mechanism of hydrogen embrittlement, and hence worthy of the Sawamura Award.

It is useful to observe microstructure evolution directly during heat treatment and it is very important to monitor internal or phase stresses directly during transformation in order to understand the transformation mechanism. It is possible for the neutron diffraction technique to determine the phase stresses from lattice constants of the constituents.

In this paper, the authors tried to conduct in situ monitor of the phase transformation behavior from austenite during cooling in a 1.5Mn-1.5Si-0.2C steel. The experimental results among in situ neutron diffraction, dilatometry measurement and in situ X-ray diffraction were compared and the in situ neutron diffraction measurement enabled to investigate the changes in lattice constants of ferrite and austenite. And the relationships among thermal contraction, carbon enrichment in austenite and phase stresses were discussed. From the neutron diffraction data using the Eshelby inclusion theory, the generation of phase stresses, transformation strains, thermal misfit strains, and carbon enrichment in austenite during ferrite transformation were discussed. The carbon concentration for the onset of pearlite transformation was estimated and diffraction profile line broadening caused by pearlite formation was presented. The present results using the neutron diffraction experiments made clear the phase transformation behavior in a quantitative way for the first time.

From the above reasons, the academic and engineering contributions of the present paper are outstanding and this paper is worthy of the Sawamura Award.

Thermodynamic consideration is an effective procedure for prediction of inclusion composition in steelmaking process. In order to describe the activity coefficient of components in high alloy steel, the authors proposed a uniform expression by Redlich-Kister parameters, which is called Miki and Hino's formalism. In this article, the equilibrium relations between oxides and the composition of components in high alloy steel were discussed, and plant data were compared with the calculated results. It was found that Miki and Hino's formalism can be utilized for high alloy steel. That is, the authors succeeded in the calculation of the equilibrium relationship between the components of molten steel and inclusions for high alloy steel. It can consistently explain the relationship in actual steelmaking operation.

To begin with, it has much academic value that Miki and Hino's formalism can calculate the activity of components in high alloy steel by a uniform expression by Redlich-Kister parameters. Moreover, it also has a technical significance to solve the disagreement between the composition of molten steel and inclusions, which has been a major problem in steelmaking process.

With the spread of high alloy steels, the control of inclusions has become of great importance. Miki and Hino's formalism and the derived thermodynamic parameters will continue to be utilized, and further development to other multi-component systems is expected.

The paper apparently has an absolute value with an academic and a technical significance, and thus it is worth well the Distinguished Article Award.

There is increasing demand to develop structural materials with high specific strength (strength-to-density ratio), in order to reduce the weight of transportation vehicles which leads to the improvement of fuel efficiency and reduction of CO₂ emission. Lowering the density of steel by adding light elements such as Al and Si has been well-recognized as an effective approach to increase the specific strength.

The present authors systematically investigated the influence of chemical composition and heat treatment condition on the constituent phases, microstructural morphology, hardness, cold workability and tensile property at room temperature in the Fe-20mass%Mn-Al-C quaternary and Fe-20mass%Mn-Al-C-5 mass% Cr quinary alloys with a low density of less than 7.0g/cm3. As a result, low density steels exhibiting excellent combinations of high specific strength and elongation were successfully developed through a simple annealing treatment. The relation between the microstructure and mechanical property of the low-density steels was clearly summarized in a wide chemical composition range, based on phase diagrams. It was also found out that nano-size κ carbides, which precipitated during cooling from annealing temperature, significantly strengthened the steels and the α volume fraction affected the mechanical property of γ+α duplex steels. These findings have thus contributed to the development of high-strength steel with low density.

Therefore, the present paper is considered as a pioneering work in the field of high-strength steel with low density and it is worthy of the Distinguished Article Award.