US 12,227,815 B2
Seamless steel pipe having desirable sulfuric acid dew-point corrosion resistance, and method for manufacturing same
Masao Yuga, Tokyo (JP); Hiroyuki Takai, Tokyo (JP); Yasumasa Takemura, Tokyo (JP); and Mitsuhiro Okatsu, Tokyo (JP)
Assigned to JFE Steel Corporation, Tokyo (JP)
Appl. No. 17/623,919
Filed by JFE Steel Corporation, Tokyo (JP)
PCT Filed Jun. 12, 2020, PCT No. PCT/JP2020/023144
§ 371(c)(1), (2) Date Dec. 30, 2021,
PCT Pub. No. WO2021/005960, PCT Pub. Date Jan. 14, 2021.
Claims priority of application No. 2019-127602 (JP), filed on Jul. 9, 2019.
Prior Publication US 2022/0411890 A1, Dec. 29, 2022
Int. Cl. C21D 9/08 (2006.01); C21D 1/28 (2006.01); C21D 6/00 (2006.01); C21D 8/10 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/58 (2006.01)
CPC C21D 9/085 (2013.01) [C21D 1/28 (2013.01); C21D 6/004 (2013.01); C21D 6/005 (2013.01); C21D 6/008 (2013.01); C21D 8/105 (2013.01); C22C 38/002 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/58 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A seamless steel pipe having desirable sulfuric acid dew-point corrosion resistance,
the seamless steel pipe having a composition that consists of, in mass %, C: 0.02 to 0.12%, Si: 0.010 to 1.00%, Mn: 0.10 to 2.00%, P: 0.050% or less, S: 0.004% or less, Al: 0.010 to 0.100%, Cu: 0.03 to 0.80%, Ni: 0.02 to 0.50%, Cr: 0.55 to 1.00%, Sb: 0.005 to 0.20%, optionally Sn: 0.005 to 0.5%, and the balance Fe and incidental impurities, and satisfying the following formula (1),
1.7×Cu*+11×Cr*+3.8×Sb*≥13.5 . . . (1),
where Cu*, Cr*, and Sb* represent average concentrations of Cu, Cr, and Sb, respectively, in mass %, as measured in a region 0.5 to 2.0 mm away from an outer surface of the steel pipe toward a center of a wall thickness of the steel pipe,
the seamless steel pipe having a yield strength of 230 MPa or more, and a tensile strength of 380 MPa or more.