HIGH-STRENGTH SEAMLESS STEEL PIPE WITH HIGH RESISTANCE TO SULPHIDE STRESS CRACKING FOR OIL WELLS AND ITS MANUFACTURING METHOD Russian patent published in 2013 - IPC C21D8/10 C21D9/08 C22C38/00 C22C38/32 

FIELD: metallurgy.

SUBSTANCE: seamless steel pipe contains the following, wt %: from 0.15 to 0.50 of C, from 0.1 to 1.0 of Si, from 0.3 to 1.0 of Mn, 0.015 or less of P, 0.005 or less of S, from 0.01 to 0.1 of Al, 0.01 or less of N, from 0.1 to 1.7% of Cr, from 0.4 to 1.1% of Mo, from 0.01 to 0.12 of V, from 0.01 to 0.08 of Nb, from 0.0005 to of 0.003 B or contains additionally from 0.03 to 1.0 wt % of Cu and it has microstructure consisting of 0.40% or more of dissolved Mo and a phase of tempered martensite which is the main phase f and which has grains of primary austenite with the grain size of 8.5 or more and 0.06 wt % or more of suspended sludge of M₂C-type in the form of grain. Steel pipe material is heated to 1000-1350°C and then it is hot-rolled to seamless steel pipe of specified form, the pipe is cooled to the room temperature at speed not lower than speed of air cooling, and drawing of seamless steel pipe is performed at temperature from 665 to 740°C.

EFFECT: high resistance of pipes for oil wells to sulphide stress cracking.

15 cl, 3 tbl, 2 dwg