HIGH-QUALITY MATERIAL FOR FLEXIBLE LONG PIPES AND METHOD OF MANUFACTURE THE SAME Russian patent published in 2018 - IPC C21D9/08 F16L33/00 C22C38/58 B21C37/08 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy. To provide high strength, the flexible steel pipe is made of several welded strips having base metal regions, welds and their heat affected zones having a yield strength in excess of 80 thousand pounds/inch², and made of steel containing iron and the following components, by weight %: carbon 0.17–0.35, manganese 0.30–2.00, silicon 0.10–0.30, aluminium 0.010–0.040, sulfur up to 0.010, phosphorus up to 0.015, at that the steel having a final microstructure containing a mixture of tempered martensite and bainite, the final microstructure of the flexible tube in all areas of the base metal, at the welds and in the heat-affected zones by more than 90 % by volume consists of tempered martensite, is an uniform and has a smooth distribution of fine-grained carbides.

EFFECT: high-quality material for flexible long pipes and a method of manufacturing the same are proposed.

22 cl, 18 dwg, 7 tbl