MANUFACTURE METHOD OF STEEL SHEET FOR PIPES WITH INCREASED DEFORMATION CAPACITY Russian patent published in 2018 - IPC C21D8/02 C22C38/00 C22C38/58 

FIELD: metallurgical engineering.

SUBSTANCE: steel sheet 15-40 mm in thickness with a yield strength of more than 480 MPa, used in the production of electrically welded pipes, a slab of steel containing, wt %: carbon 0.04-0.08, silicon 0.10-0.30, manganese 1.60-1.85, chromium no more than 0.30, nickel 0.20-0.40, molybdenum 0.10- 0.25, copper not more than 0.30, aluminium not more than 0.05, niobium 0.03-0.06, titanium 0.010-0.020, vanadium not more than 0.01, sulfur no more than 0.003, phosphorus not more than 0.013, iron and the inevitable impurities - the rest, are heated to 1100-1200°C, are subjected to rough rolling at 950÷1050°C, then finishing rolling at 700÷820°C with a total reduction of 75÷85%, after which the resulting sheet is cooled at a rate of 20÷35°S/s to 300÷500°C, and then in air to a temperature of not more than 150°C. The sheet has a microstructure consisting of bainite, polygonal ferrite, and also "second phases" in the form of a martensite-austenite component and degenerate perlite.

EFFECT: increased deformation capacity of steel sheet.

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