1992 Fiscal Year Final Research Report Summary
Study on the Production of extra-low-oxygen titanium by Calcium -halide flux method
| Project/Area Number |
03453062
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属精錬・金属化学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
ONO Katsutoshi Kyoto University, Department of Metallurgy, Professor, 工学部, 教授 (10026049)
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| Co-Investigator(Kenkyū-buntansha) |
OISHI Toshio Kyoto University, Department of Metallurgy, Associate Professor, 工学部, 助教授 (80026145)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Titanium / Extra-Low-Oxygen / Fused Salt Electrolysis / Residual Resistivity Ratio / High parity Titanium |
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| Research Abstract |
Under co-existence of calcium and its oxide, the equiliblium oxygen content in titanium is 500 mass ppmO at 1273K^<1)2)>. The advanced methods were examined to attain the lower oxygen level from the thermodynamic viewpoints. Calcium-halide fluxes may decrease the activity of by-product CaO so efficiently that Ca-CaCl_2 and Ca-BaCl_2 fluxes were experimentally applied for the deoxidation of titanium.
Titanium wires and small pieces containing a few hundreds mass ppm were deoxidized as low as a few tens mass ppm by use of CaCl_2 flux and calcium vapor at 1273K. The oxygen sources to make worse the efficiency of the further purification of titanium were discussed and one of them was suggested to be the oxygen contamination in the flux.
Deoxidation of high purity titanium using an electrochemical technique and characterization of the obtained nearly oxygen-free titanium were carried out. High purity titanium cathode and carbon anode were immersed in molten salt (e.g. CaCl_2) at around 1223 K, and external DC voltages were applied between the electrodes. High purity titanium cathode wires containing 110 mass ppmO were deoxidized to less than 20 ppm. Trace element analysis(e.g. glow discharge mass spectrometry), micro Vickers hardness measurements, and electrical resistivity measurements were carried out to characterize the deoxidized titanium samples. The electrochemical deoxidation produced high purity titanium with a high residual resistivity ratio (rho_<298>/rho_<4.2>=155) and a low micro Vickers hardness value (64kgf/mm^2). Feasibility of deoxidation by using various molten salts such as BaCl_2 and MgCl_2 was also examined, and titanium containing about a thousand mass ppm oxygen were deoxidized to 100 - 300 ppm level by using these salts.
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