SEAMLESS STEEL PIPE AND METHOD OF ITS PRODUCTION Russian patent published in 2019 - IPC C22C38/32 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to seamless steel pipe used in oil industry for oil and gas wells. Pipe has the following chemical composition, wt.%: C: from 0.21 to 0.35; Si: from 0.10 to 0.50; Mn: from 0.05 to 1.00; P: 0.025 or less; S: 0.010 or less; Al: from 0.005 to 0.100; N: 0.010 or less; Cr: from 0.05 to 1.50; Mo: from 0.10 to 1.50; Nb: from 0.010 to 0.050; B: from 0.0003 to 0.0050; Ti: from 0.002 to 0.050; V: from 0 to 0.30; Ca: from 0 to 0.0050; and rare-earth metal: from 0 to 0.0050, rest is Fe and impurities. Pre-austenite grain size number corresponding to the ASTM E112 standard is 7.0 or more in the area of the main pipe body except for the first end area and the pipe second end area. First pipe end area extends to 500 mm from pipe first end in axial direction of seamless steel pipe to second pipe end area, and second end region extends to 500 mm from pipe second end in axial direction of seamless steel pipe to first end of pipe. In the region of the main pipe body, the difference between the maximum value and the minimum value of the grain size number is 1.0 or less, yield point ranges from 655 to less than 862 MPa, and difference between maximum value and minimum tensile strength is 27.6 MPa or less.

EFFECT: pipe has excellent resistance to sulphide cracking under stress at suppression of variation of strength in circular and axial directions.

16 cl, 3 dwg, 4 tbl, 3 ex