Round bar tensile test specimen for sulfide stress corrosion cracking test of a steel, test method for sulfide stress corrosion cracking of steel, and seamless steel pipe having excellent resistance to sulfide stress corrosion cracking

摘要

A round bar tensile test specimen for a sulfide stress corrosion cracking test of a steel, the specimen including a parallel section, a shoulder section, and a grip section. A sectional shape of the shoulder section being formed by a curve having two or more radii of curvature. A radius of curvature R1 (mm) of a portion of the curve adjacent to the parallel section being 15 mm or more, and the radius of curvature R1 (mm) satisfying (0.22σ−119)≤R1≤100 in terms of load stress σ (MPa) of the sulfide stress corrosion cracking test. A length X1 (mm) of the portion of the curve having the radius of curvature R1 in a longitudinal direction of the test specimen satisfying X1≥√{(r/8)×(R1−r²/4)}. Additionally, other radii of curvature of the curve being smaller than the radius of curvature R1.