Perspective high-strength pipe steel with increased corrosion cold resistance

Abstract

The scientists of Nosov Magnitogorsk State Technical University developed the new steel with 0.08C-1.50Mn-1.20Cr-0.06Nb-0.04Ti alloying system. Phase transformations of undercooled austenite were examined via dilatometric analysis using Gleeble 3500 complex. Metallographic analysis of the structure, which is forming during continuous cooling, is carried out. Thermokinetic and structural diagrams of steel were built. The conditions of controlled rolling and accelerated cooling of the developed steel are suggested; they provide increased strength (ı т =520-560 N/mm 2 , ı в =600-673 N/mm 2 ; į 5 =26-23.5 %; HBW 207-229), cold resistance down to -70 °С (KCV -70 =252-245 J/cm 2 ; KCU -60 =330-295 J/cm 2 ), as well as increased corrosion resistance in carbon dioxide and hydrogen sulfide environments (HIC, SSC). Providing of such favourable combination of properties makes it possible to use the new steel for manufacture of pipes of different strength classes in oil and gas industry, for operation in the Far North regions.