MANUFACTURING METHOD OF SEAMLESS STEEL PIPE Russian patent published in 2009 - IPC C21D8/10 C22C38/48 

FIELD: processes.

SUBSTANCE: invention relates to field of thermo mechanical treatment. Steel blank, containing of, wt %: C - 0.15-0.20, Si 0.01- 0.15, inclusively, Mn - 0.05-1.0, Cr - 0.05-1.5, Mo - 0.05-1.0, Al ≤0.10, V - 0.01-0.2, Ti - 0.002-0.03, B - 0.0003-0.005 and N - 0.002-0.01, one or more components selected from group: Ca, Mg and rare earth elements in specified amount, P ≤ 0.025%, S ≤ 0.010% and Nb ≤ 0.005%, at fulfillment of conditions: C+(Mn/6)+(Cr/5)+(Mo/3) ≥ 0.43 and Ti × N < 0.0002-0.0006 × Si, the rest is Fe and admixtures, it is heated up to temperature 1000-1250°C, it is rolled with finite temperature of rolling 900-1050°C, it is tempered received steel pipe directly from the temperature not lower than transformation temperature Ar₃, it is tempered in the range of temperatures from 600°C up to transformation temperature Ac₁ or after rolling received steel pipe is additionally heated in the range of temperatures from transformation temperature Ac₃ up to 1000°C in flow line, it is tempered up to temperature not lower than transformation temperature Ar₃ and subject to abatement in the range of temperatures from 600°C up to transformation temperature Ac₁.

EFFECT: obtained pipe allows high strength and distinct, and also allows high ratio of yield limit to tensile strength and distinct resistance against PCC.

2 cl, 1 ex, 4 tbl