OIL AND GAS FIELD SEAMLESS PIPE FROM MARTENSITE STAINLESS STEEL AND METHOD OF ITS MANUFACTURING Russian patent published in 2012 - IPC C22C38/48 C22C38/58 C21D9/08 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: pipe is produced from steel containing the following, wt %: 0.020 or less C, 10 - 14 Cr, 3 or less Ni, 0.05 or less N, 0.03 - 0.2 Nb or, not necessarily, 1.0 or less Si, 0.1 - 2.0 Mn, 0.020 or less P, 0.010 or less S, 0.10 or less Al, Fe and unavoidable admixtures - balance. A pipe is heated to hardening temperature equal to temperature A_c3 of conversion or higher, and then cooled down to the range of temperatures of 100°C or below with the cooling speed, appropriate speed of cooling on air or higher. Tempering is carried out, heating the pipe at 550°C or higher with subsequent cooling. Produced pipes have a tempered martensite structure, in which the amount of the released Nb makes 0.020 % or higher, high strength at the level of 95 sq. pound/sq. inch (665-758 MPa) and higher low-temperature impact strength with transition temperature from viscous damage to brittle vTrs -40°C or lower, and may be exposed to hot straightening, after which heterogeneity of yield point makes not more than 15 MPa.

EFFECT: production of an oil and gas field seamless pipe from martensite stainless steel of higher strength and higher low-temperature impact strength.

18 cl, 5 tbl