| 摘要 |
PURPOSE:To obtain a steel material having extremely excellent hydrogen induced crack resistance steel material which scarcely causes a hydrogen resisting induced crack under a severe sour environment by hot-working a cast fillet by which contents of S, O and Ca of a position corresponding to the final solidified part satisfy a prescribed relational equation. CONSTITUTION:A steel material excellent in hydrogen induced crack resistance (HIC resistance) is obtained by hot-working a cast billet by which contents of S, O and Ca of a position corresponding to the final solidified part, namely, the center segregation zone of the cast billet satisfy a relational equation. As for said hot-working, a steel material which shows more excellent HIC resistance is obtained by executing it in an austenite temperature area of <=1,200 deg.C, or in an austenite/ferrite two phase coexistent temperature area of >=Ar1 temperature and <=Ac3 temperature, by >=20% section reduction rate. This steel material shows extremely excellent HIC resistance under a wet environment (sour environment) containing H2S or CO2, too, especially, under a sour environment containing them in high density. |
