| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a homogeneous, high purity titanium ingot by using a raw material having an expanded allowable impurity concentration range without adding specified elements thereto. SOLUTION: A sponge titanium cake is produced by a Kroll process. A high purity sponge titanium lump is picked from the central part of the sponge titanium cake and is cut into a plurality of pieces of lump. The concentrations of one impurity selected from contained impurities and contained oxygen are measured for each cut lump. After that, each cut lump is arranged so as to make a gradient in the order of the measured impurity concentrations, and, welding is performed thereto. Provided that the high concentration side of the contained impurities is A, final dissolution is performed under condition that the tip of the final ingot is the part corresponding to A in the case of the impurity elements in which the distribution coefficient (S/L) between solid titanium (S) and liquid titanium (L) is >1. Alternatively, it is performed under condition that the bottom part of the final ingot is the part corresponding to A in the case of the impurity elements in which the distribution coefficient (S/L) is <1.
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