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Method for producing welded steel pipe for line pipe with excellent hydrogen-induced cracking resistance, sulfide stress cracking resistance and low-temperature toughness
Method for producing welded steel pipe for line pipe with excellent hydrogen-induced cracking resistance, sulfide stress cracking resistance and low-temperature toughness
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机译：具有优异的抗氢致开裂，抗硫化物应力开裂和低温韧性的管线管焊接钢管的生产方法
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摘要
PROBLEM TO BE SOLVED: To provide a method for producing a welded steel pipe for a line pipe, excellent in HIC resistance, SSC resistance and low temp. toughness. SOLUTION: A hoop contg., by weight, 0.01 to 0.2% C, 0.03 to 0.8% Si, 0.4 to 2.0% Mn, 0.025% P, 0.002% S and 0.01 to 0.1% sol.Al, furthermore contg. one or more kinds selected from 0 to 0.5% Cu, 0 to 0.5% Ni, 0 to 1.2% Cr, 0 to 1.0% Mo, 0 to 0.15% Nb, O to 0.1l5% V, 0 to 0.15% Ti, 0 to 0.15% Zr and 0 to 0.005% B and moreover contg. one or two kinds selected from 0 to 0.005% Ca and 0 to 0.01% rare earth metal is passed through a forming roll group and is continuously formed into the shape of an open pipe. At the time of pressurizing this open pipe by a squeeze roll to butt both edges of the hoop, irradiating the butted part with a laser beam and executing abbuting welding to form into a welded steel pipe, the laser beam is applied under the conditions satisfying the inequality of 1.57.2a/v2 [Q/ 2k(Tm -T)}]2 =1.8, in the inequality, a: the thermal dliffusivity of the hoop (m/s), v: welding speed (m/s), Q: laser output (J/s), : the thermal conductivity of the hoop (J/m-s.k), k: the thickness of the hoop (m), Tm : the m.p. of the steel (K) and T: the preheating temp. (K).
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