| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a cast billet having little porosity without applying rolling reduction to the cast billet after casting, and a method for producing a seamless steel tube having little internal flaw by using the round cast billet. SOLUTION: This method for producing the cast billet having little porosity by adjusting the chemical composition so as to satisfy the following formula, to a Cr steel containing 1-40 mass% Cr, and casting. Cr+3Mo+Nb+4V+7-(190 C+120N+4Ni+8Cu+4Si+2W+12Al)>=0.
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