Papers by Author: Masahiro Kawakami

Abstract: Direct electrolysis of Ti and its alloys has been attempted by the process using a DC-ESR unit. The concept of the process is explained in detail, and the expected key issues are commented. Liquid Ti metal was obtained in a CaF2-CaO-TiO2 bath, and electrolysis by using a new type of the electrolytic cell was also tried. Ti-Al alloy was successfully deposited in a CaF2-CaO-TiO2-Al2O3 bath, whereas Ti-Si alloy was not obtained in a CaF2-CaO-TiO2-SiO2 bath yet. Ti-Fe alloy was extracted in CaF2-CaO-TiO2-FeO bath of a particular composition. A common correlation between the cathodic current efficiency and the average consumed electric power seen in the Ti, Ti-Al and Ti-Fe electrolysis suggested the importance of sufficient temperature in the process. The bath composition also affected the temperature through the change in the electric conductivity of the bath.

Abstract: The ionic valence of Ti changed with electrorefining process of Ti in a bath equi-molar mixture of NaCl-KCl containing TiCl_n (n=2 or 3); The average valence was about 2.3 initially, and became about 2.1 after electrolysis. The cathodic current efficiency was getting better with electrolysis. It should be necessary to maintain the average ionic valence lower for efficient electrolysis in the molten salt. The dominant Ti ion and its electrode reaction changed with the addition of NaF-KF in the molten salt; The average valence shifted from about 2 to about 3, and the total amount of Ti in the bath decreased. The result indicates the disproportionation reaction: 3Ti²⁺ = Ti + 2Ti³⁺ is induced by the fluoride addition. The quantity of electricity for Ti deposition changed consequently, and the purity of the Ti deposit was also affected.

Abstract: A method for preheating steel scraps using waste heat in a continuous casting process was proposed. Experiment and numerical analysis were carried out to examine the ability of scrap preheating and to determine the factors affecting the rise in scrap temperature. Coupled natural convection-radiation heat transfer was solved by three-dimensional FEM. The distance and the constant were found to influence the sample's temperature rise greatly. The overall Nusset number can be obtained as Nu₀=(-0.33α*D*^0.8+7.08)Ra^0.15t*^-1- 32.4D*-^0.99α*^-1.98 *-1.98