STEEL FOR PIPELINE AND METHOD FOR ITS MANUFACTURE Russian patent published in 2023 - IPC C22C38/54 C22C38/58 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: steel sheet used for the pipeline manufacture. The steel sheet has the following composition in wt.%: C: 0.03-0.10, Si: 0.1-0.5, Mn: 1.51-1.85, P≤ 0.015, S≤ 0.00,2 Cr: 0.05-0.3, Mo: 0.05-0.20, Cu: 0.06-0.3, Ni: 0.17-0.50, Nb: 0.05-0.10, Ti: 0.005-0.02, Ca: 0.001-0.005, Al: 0.02-0.045, N≤0.006, B≤0.0002, ≤0.005, the rest is Fe and unavoidable impurities. The composition of the steel sheet satisfies the ratio 0.06≤J_C×Mn≤0.14, where the value of J_C×Mn=C⋅Mn⋅10⁴, i.e. is the product of the content of carbon and manganese, in wt.%. The sheet has a microstructure of polygonal ferrite and acicular ferrite, while the proportion of the polygonal ferrite phase is 15-39%.

EFFECT: high ductility of resulting sheets, making them suitable for subsea pipelines, pipelines crossing seismic zones, and other types of pipelines used in rough environments.

8 cl, 2 dwg, 3 tbl