THICK HIGH-TENSILE ACID-RESISTANT MAIN PIPE AND METHOD OF ITS MANUFACTURE Russian patent published in 2017 - IPC C21D8/10 C21D9/08 C22C38/00 C21D11/00 

FIELD: metallurgy.

SUBSTANCE: microstructure in the pipe thickness direction is 90% or more of bainite, and 1% or less of martensite-austenite in the area that extends from the position located at a distance 2 mm from the inner surface to a position located at a distance 2 mm from the outer surface. The pipe hardness thickness in the area different from the center segregation area is 220 Hv10 or less, and the hardness in center segregation area is 250 Hv10 or less. The main axis of voids, inclusions and inclusion clusters present in the area, which extend from the position located at a distance 1 mm from the inner surface to a position located at a distance of 3/16 of the pipe thickness, and the section that extends from the position located at the distance 1 mm from the outer surface to a position located at the distance of 13/16 of the pipe thickness in the direction of its thickness, are 1.5 mm or less.

EFFECT: increased resistance to hydrogen induced cracking of the main pipe with a wall thickness 20 mm or more and a tensile strength equal to 560 MPa or higher, it is made of a steel containing C, Si, Mn, P, S, Al, Nb, Ca, N and O, one or more component selected from Cu, Ni, Cr, Mo, V and Ti, Fe and unavoidable impurities are the rest.

6 cl, 3 tbl