FIELD: steel making.
SUBSTANCE: invention relates to such type of steel that is employed in welded structures such as gas conduits, petroleum pipelines, as well as in high-pressure vessels. Steel according to invention contains, wt %: C 0.02-0.10, Si up to 0.6, Mn 1.5-2.5, P up to 0.015, S up to 0.003, Ni 0.01-2.0, Mo 0.2-0.6, Nb below 0.010, Ti up to 0.030, Al up to 0.070, N up to 0.0060, Fe and unavoidable impurities - the rest, provided that parameter P = 2.7C+0.4Si+Mn+0.8Cr+0.45(Ni+Cu)+2V+Mo-0.5 is within a range of 1.9 to 3.5. Microstructure of steel is mainly composed of martensite and bainite. Steel sheet is manufactured by heating casting to at least Ac3, subjecting it to hot rolling, and cooling sheet at a rate 1°C/sec to temperature not exceeding 550°C. Sheet is further used to manufacture a tube. When laying multilayer welding joint, energy absorbed in the Charpy impact test at -40°C is at least 200 J.
EFFECT: achieved elongation strength at least 800 MPa.
21 cl, 1 dwg, 9 tbl, 5 ex
