| 摘要 |
PROBLEM TO BE SOLVED: To prevent a high carbon concentration portion from being formed on the surface side in a steel pipe, even in the case of applying an elongation- rolling by inserting a mandrel bar coated with graphite base lubricator. SOLUTION: This is a method for producing the seamless steel pipe from a low carbon concentration material by using a Mannesmann mandrel mill rolling line disposing an extract sizer 11 having an inline heat treatment line. After rolling, the inner surface of the steel pipe is immediately washed and thereafter, the heat treatment is applied to execute decarburization. In this way, the portion having high carbon concentration on the surface side in the steel pipe is not formed, and since this pipe can be produced with two sets of the mandrel mill and the extract sizer without reheating, this method is excellent in the productivility and the product quality.
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