HIGH-STRENGTH PIPE MADE OF LOW-CARBON PRE-PERITECTIC MOLYBDENUM-CONTAINING STEEL FOR OIL AND GAS PIPELINES AND METHOD OF ITS MANUFACTURE Russian patent published in 2018 - IPC C22C38/12 C21D8/10 F16L9/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, in particular to the production of high-strength seamless steel pipes from low-carbon pre-peritectic steels used for main oil and gas pipelines. Pipe is obtained from steel containing, wt%: carbon less than 0.08; manganese – 1.20–1.70; vanadium – 0.040–0.10; niobium – 0.030–0.070; molybdenum – 0.10–0.25; aluminium – 0.005–0.060; nitrogen – 0.005–0.015; iron and unavoidable impurities – the balance. Content of carbon, manganese and molybdenum in the steel is in the ratio ([C]+[Mn]/6-[Mo]/5)≤0.26 and provides a ferrite potential of not less than 1. Pipe is obtained by hot deformation and subsequent heat treatment. Hot deformation of the pipe is carried out at a temperature of 900÷1,300 °C. Heat treatment is carried out by heating under austenitisation to a temperature A_C3+(30÷45) °C, cooling in water and subsequent high-temperature tempering at a temperature of A_C1-(30÷100) °C with a holding time of at least 2 minutes per 1 mm of the pipe wall thickness, which provides a microstructure consisting of finely dispersed low-carbon secondary sorbite.

EFFECT: obtaining pipes with demand strength and viscoplastic characteristics.

2 cl, 1 dwg