RT Journal Article
SR Electronic
A1 Zurnadzhy, Vadym
A1 Chabak, Yuliia
A1 Petryshynets, Ivan
A1 Efremenko, Alexey
A1 Sili, Ivan
A1 Sagirov, Ruslan
A1 Efremenko, Vasily
T1 Advancing the ductile behaviour of heavy-wall API X70 pipeline steel by a "Slab/Sheet" thickness ratio increase
JF Manufacturing Technology Journal
YR 2024
VO 24
IS 5
SP 843
OP 854
DO 10.21062/mft.2024.090
UL https://journalmt.com/artkey/mft-202405-0015.php
AB The present work was aimed at studying the effect of a "Slab/Sheet" thickness ratio (SSTR) on the microstructure and mechanical properties of API 5L X70 steel sheets intended for heavy-wall oil/gas pipelines. The 25 mm-thick and 40 mm-thick steel sheets were rolled from the cast slabs of different thicknesses (250 mm and 300 mm) and their mechanical properties were compared. The sheets were subjected to thermo-mechanical controlled processing followed by accelerating cooling, resulting in the structure of quasi-polygonal/acicular ferrite with minor amounts of granular pearlite and martensite-austenite constituents. Increasing the cast slab thickness significantly improved the ductility and low-temperature impact toughness of steel sheets regardless of their thickness. Specifically, a total elongation increased by 3-6 points (up to 26-28 %); an absorbed impact energy (tested at -20 °C) - in 1.5-1.8 times (up to 300-370 J); the DWTT shear area (at -20 °C) - in 1.6-2.1 times (up to 81-91.7 %). The properties advancement under SSTR increase was associated with an additional refinement of ferrite grains and better homogenization of cast structure under deeper hot deformation.