| 摘要 |
PURPOSE:To stably obtain the titled pipe with the irreducible minimum C content required by regulating the C content in the composition of a seamless steel pipe according to a specified formula including the desired upper limit of yield strength and by directly quenching the steel pipe immediately after rolling. CONSTITUTION:The C content in the composition of a seamless steel pipe is limited to a range defined by the formula and the steel pipe is directly quenched immediately after rolling. In the formula, X is the desired upper limit of yield strength (kg/mm<2>) and Y is the C content (wt%). By this method, a refined seamless line pipe having such a low yield ratio as <=about 85% can be manufactured stably and surely with the irreducible minimum C content required.
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