OIL CYLINDER STEEL PIPE AND MANUFACTURING METHOD THEREFOR

WIPO Patent Application WO/2023/093802

A1

An oil cylinder steel pipe and a manufacturing method therefor. In addition to 90 wt% or more of Fe and inevitable impurities, the oil cylinder steel pipe further comprises the following chemical elements in percentage by weight (wt%): C: 0.16-0.3%, Si: 0.15-0.5%, Mn: 1.2-1.8%, Nb: 0.02-0.04%, Mo: 0.1-0.2%, and optionally Ti: 0.015-0.03% and B: 0.0015-0.0035%. According to the present invention, after the steel pipe is tensioned and quenched, different stepped cooling processes are adopted respectively, the distribution of phase change and thermal stress on the whole wall thickness of the oil cylinder steel pipe is controlled by increasing the rigidity and straightness level of the steel pipe, the distribution of ferrite in the microstructure of the oil cylinder steel pipe is controlled, the residual stress of the oil cylinder steel pipe is effectively reduced, cracking of the inner wall is avoided, and therefore the oil cylinder steel pipe with high strength and low residual stress is obtained, the yield strength of the oil cylinder steel pipe is greater than or equal to 600 MPa, the tensile strength is greater than or equal to 730 MPa, and the residual stress is less than or equal to 50 MPa.

SUN WEN (CN)
GAO ZHAN (CN)
MA YANNAN (CN)
ZUO HONGZHI (CN)

PCT/CN2022/134015

June 01, 2023

November 24, 2022

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BAOSHAN IRON & STEEL (CN)

C22C38/00; C21D8/10

CN105925883A	2016-09-07
CN103060715A	2013-04-24
CN103498105A	2014-01-08
US20140299235A1	2014-10-09
JPH07233416A	1995-09-05

WATSON & BAND INTELLECTUAL PROPERTY AGENT LTD. (CN)

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