HIGH-STRENGTH STEEL PLATE FOR ACID-RESISTANT PIPELINE AND METHOD OF PRODUCING STEEL PLATE, HIGH-STR

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FIELD : metallurgy. SUBSTANCE : invention relates to metallurgy, namely to high-strength steel plate used for production of acid-resistant pipeline. Plate has a chemical composition containing the following, wt. % : C : from 0.02 to 0.08; Si : from 0.01 to 0.50; Mn : from 0.50 to 1.80; P : from 0.001 to 0.015; S : from 0.0002 to 0.0015; Al : from 0.01 to 0.08; Mo : from 0.01 to 0.50; Ca : from 0.0005 to 0.005; at least one component selected from a group consisting of Nb : 0.005 to 0.1 and Ti : 0.005 to 0.1, optionally at least one component selected from a group consisting of Cu : 0.50 or less, Ni : 0.10 or less, Cr : 0.50 or less, V : from 0.005 to 0.1, Zr : from 0.0005 to 0.02, Mg : from 0.0005 to 0.02 and rare-earth metal : from 0.0005 to 0.02, the rest are Fe and unavoidable impurities. Microstructure of steel at depth of 0.25 mm from the surface of the steel plate is a bainitic microstructure having a dislocation density of 1.0 × 1014 to 7.0 × 1014 (m-2). Vibrations of Vickers hardness at depth of 0.25 mm from the surface of the steel plate make 30 HV or less, Vickers hardness variation in the plate thickness direction is 30 HV or less, and tensile strength is 520 MPa or more. EFFECT : plate has high resistance to hydrogen cracking and high resistance to sulphide corrosion while maintaining high strength, viscosity and weldability. 3 cl, 1 dwg, 2 tbl