| 摘要 |
PURPOSE: A method of manufacturing high strength hot rolled steel strip with low susceptibility of sulfide stress corrosion cracking (SSCC) suitable for use as pipelines transporting sour oil is provided. CONSTITUTION: The method includes the steps of reheating a steel slab comprising C 0.03 to 0.12 wt.%, 0.50 wt.% or less of Si, Mn 0.5 to 1.50 wt.%, 0.020 wt.% or less of P, 0.005 wt.% or less of S, Ca 0.0010 to 0.0050 wt.%, Cu 0.2 to 2.0 wt.%, Ti 0.01 to 0.07, Nb 0.01 to 0.07 wt.%, one element selected from the group consisting of V 0.01 to 0.07 wt.%, 1.0 wt.% or less of Ni, 1.0 wt.% or less of Cr and 1.0 wt.% or less of Mo, a balance of Fe and incidental impurities at 1100 to 1250°C; hot rolling the steel slab, wherein cumulative reduction ratio at higher than 1000°C is greater than 60 % and finish hot rolling temperature is 900 to 950°C; cooling the hot rolled steel sheet to the temperature range of 550 to 450 at a cooling rate of 6 to 13°C/sec, followed by air cooling; and heat treatment at 550 to 650°C.
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