PURPOSE: To obtain a steel plate for electric seam welded steel pipe free from hydrogen-induced cracking in a direction perpendicular to the plate surface even under a severe low-pH environment and excellent in toughness at low temp., by providing a composition containing Ca besides C, Si, Mn, and Al respectively in the prescribed quantities and in which respective contents of O, P, and S are limited.
CONSTITUTION: The above steel plate for electric welded steel pipe has a composition which contains, by weight, 0.001W0.008% Ca besides 0.05W0.12% C, 0.10W0.40% Si, 0.3W1.2% Mn, and 0.005W0.10% Al and in which quantities of O, P, and S are limited to ≤0.0020%, ≤0.015% and ≤0.0030%, respectively. This steel plate for electric welded steel pipe is used as line pipes and shows characteristics excellent in toughness at low temp. as well as in resistance to plate surface-perpendicular-type hydrogen-induced cracking not only in the base-metal zone of a steel pipe but also in the butt seam weld zone particularly in cold districts and also even in a wet environment (sour environment) containing H2S and CO2.
TAKEZAWA HIROSHI
KONNO TAKAHARU
HAGA HIROTSUGU
