SEAMLESS STEEL PIPE FOR MULTISTAGE OIL CYLINDER AND ITS MANUFACTURING METHOD Russian patent published in 2021 - IPC C22C38/44 C21D9/08 C21D8/10 B21C37/06 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to a seamless steel pipe used for the manufacture of multistage oil cylinders. The pipe is made of steel having the following chemical composition, wt. %: C 0.24-0.30, Si 1.20-1.40, Mn 1.20-1.40, P ≤0.015, S ≤0.010, Al 0.025-0.055, Mo ≤0.15, Cr ≤0.15, Ni ≤0.15, Cu ≤0.20, the rest is Fe. The pipe has a tensile strength limit of 750-830 MPa, yield strength of 650-730 MPa, tensile elongation of ≥18%, a Charpy impact energy absorption coefficient for a standard sample of 10×10 with a V-shaped incision at a temperature of -20°C ≥39 J, the surface hardness of the steel pipe is 210-260 HBW.

EFFECT: wear resistance and tightness indicators are provided to prevent hydraulic oil leaks caused by frequent use of cylinders, as well as high level performance at low temperatures.

10 cl, 7 tbl, 4 ex