高品質ニッケル基超合金メルティング・ストックの溶製に関する研究

概要

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Fundamental experiments were performed on the production of high quality melting stocks, and the following results were obtained.(1) CaO lining is more favorable than MgO or Al2O3 lining to attain low [O] level in melting Al, Ti-bearing nickel base superalloys.(2) Nitrogen desorption rate under high vacuum (4×10-3Torr) is 1.7-2.7 times as large as the one under low vacuum (1×10-2Torr).(3) The lower the refining temperature is, the lower [O] level is attained in vacuum refining of Al, Ti-bearing nickel base superalloys.(4) By using the nozzle of 20mmID×120mm, it is possible to avoid the contact between casting stream and the inside wall of mold.Based on the above-mentioned results, TMD-5 nickel base superalloy melting stocks with [S], [O], [N]≤10ppm, respectively, were produced in 2 ton VIF under the condition of CaO lining, high vacuum refining (4×10-3Torr), low temperature refining after addition of reactive elements and optimization of tundish-nozzle size (20mmID×120mm).