REHOMI, refinement and development of homogeneous microstructures through the thickness of heavy products in V steels
This research aims at studying the combination of high vanadium, nitrogen and carbon on the formation of acicular ferrite. A new cooling concept - alternate water cooling - for the in-depth cooling of heavy products was investigated and consists of a succession of passes in an accelerated cooling line. The acicular ferrite microstructures were generally difficult to obtain in laboratory experiments with industrially achievable chemical compositions or cooling cycles. The combination of high vanadium and nitrogen allows for the production of acicular ferrite microstructures. This was not associated with the foreseen improvement of the tensile or toughness properties when compared with bainitic microstructures. EBSD and image analysis of LOM were applied to separate bainite from acicular ferrite. The increase of vanadium content from 0.06 to 0.11 % smoothes the hardness gradient through the thickness. This evolution is associated with a shift to a high cooling rate of the polygonal ferrite nose in the phase transformation diagram. In terms of properties, the gain on the yield strength is about of 50MPa but, in some cases, at the expense of the toughness. Rolling schedules and chemical analyses were determined to fulfill requirements of heavy beams in vanadium steel in the as-rolled and welded conditions.
Bibliographic Reference: EUR 23876 EN (2009), 127 pp. Euro: 20
Availability: http://bookshop.europa.eu/is-bin/INTERSHOP.enfinity/WFS/EU-Bookshop-Site/en_GB/-/EUR/ViewPublication-Start?PublicationKey=KINA23876 (Catalogue Number: KI-NA-23876-EN-S)
ISBN: ISBN: 978-92-79-11699-5
Record Number: 200910525 / Last updated on: 2009-12-21
Original language: en
Available languages: en