| 摘要 |
Disclosed are steel materials for pressure containers capable of suppressing hydrogen-induced cracking (HIC) by hydrogen sulfide (H2S) contained in a crude oil through a control of alloy compositions and process conditions together with a manufacturing method thereof. The manufacturing method of steel materials for pressure containers according to the present invention is characterized by comprising; (a) a step of reheating to a SRT(Slab Reheating Temperature) : 1100 ~ 1250°C of steel slabs containing in weight %; carbon (C) : 0.14 ~ 0.18%, silicon (Si) : 0.3 ~ 0.4%, manganese (Mn) : 1.1 ~ 1.3%, soluble aluminum (S_Al) : 0.01 ~ 0.05%, copper (Cu) : 0.1 ~ 0.2%, niobium (Nb) : 0.01 ~ 0.02%, boron (B) : 0.0001 ~ 0.0005%, nickel (Ni) : 0.15 ~ 0.25%, chromium (Cr) : 0.15 ~ 0.25%, calcium (Ca) : 0.0015 ~ 0.0040%, nitrogen (N) : less than 0.005% , hydrogen (H) : less than 0.0003% in addition a balance of iron (Fe) and unavoidable impurities; and (b) a step of hot-rolling of the reheated steel slabs under a condition of FRT(Finish Rolling Temperature) : 850 ~ 950°C ; and (c) a step of first cooling of the hot-rolled steel slabs; and (d) a step of normalizing heat treatment of the first cooled steel; and (e) a step of second cooling by the normalizing heat treated steel materials in a vertical stacking. [Reference numerals] (AA) START; (BB) END; (S110) Slb reheating (SRT : 1100 ~ 1250°C); (S120) Hot rolling (FDT : 850 ~ 950°C); (S130) Primary cooling (air cooling); (S140) Normalizing heat treatment (840 ~ 940°C); (S150) Secondary cooling (40 ~ 110°C/hr) |
