STEEL MATERIAL FOR MAIN PIPES, METHOD OF ITS PRODUCTION AND METHOD FOR MANUFACTURING MAIN PIPES Russian patent published in 2021 - IPC C21D8/02 C21D7/13 C22C38/18 

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to a method for producing a steel plate for a main pipe, methods for producing the main pipe, a steel plate for the main pipe, which can be used to produce main pipes used for transporting oil and natural gas and for the manufacture of subsea pipelines. A steel plate was obtained having a tensile strength of 570 MPa or more, a compressive strength of 440 MPa or more, and a thickness of 30 mm or more. Heating is carried out to a temperature in the range from 1000°C to 1200°C. Hot rolling is carried out with total rolling reduction outside the recrystallization temperature range of 60% or more, with overall rolling reduction in the temperature range (final rolling temperature + 20°C) or less of 50% or more. The final rolling temperature ranges from the Ar₃ transformation temperature or higher to 790°C or lower. Thereafter, accelerated cooling is carried out from the starting Ar₃ transformation temperature or higher at a cooling rate of 10°C/s or more until the surface temperature of the steel plate reaches 300°C to 500°C.

EFFECT: invention provides a steel material for the main pipe having a large wall thickness of 30 mm or more, high strength required for the use of the steel material in subsea pipelines, excellent low temperature toughness and DWTT performance in dropping weight burst test.

4 cl, 3 tbl, 25 ex