STEEL WELDED PIPE OBTAINED BY CONTACT WELDING FOR FLEXIBLE CONTINUOUS PIPE AND METHOD OF ITS PRODUCTION Russian patent published in 2020 - IPC C22C38/58 C22C38/50 B21C37/08 C21D9/08 C21D9/50 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to steel pipes produced by contact welding used for production of continuous flexible pipes. Steel welded tube has the following composition, containing, wt%: C: from more than 0.10 to 0.16; Si: from 0.1 to 0.5; Mn: from 1.6 to 2.5; P: 0.02 or less; S: 0.005 or less; Al: from 0.01 to 0.07; Cr: from more than 0.5 to 1.5; Cu: from 0.1 to 0.5; Ni: from 0.1 to 0.3; Mo: from 0.1 to 0.3; Nb: from 0.01 to 0.05; V: from 0.01 to 0.10; Ti: from 0.005 to 0.05; N: 0.005 or less; Fe and unavoidable impurities – balance. Pipe has microstructure containing 2–10 vol% residual austenite and 20 vol% or less of martensite, wherein the residue is bainite.

EFFECT: produced pipes are characterized by yield point making 896 MPa or more, uniform relative elongation making 9 % or more, and high resistance of low-cycle fatigue.

3 cl, 1 dwg, 2 tbl