Bainitic steels for new rail materials
In the present project, coordinated by Centro Sviluppo Materiali (CSM) and carried out with the contributions of Centre for Research in Metallurgy (CRM) and VoestAlpine (VAS), the following topics were investigated : morphology, transformation characteristics and properties of bainite, possibly mixed with a low amount of lath martensite, as compared to conventional pearlite structures ; steel chemical compositions suitable to achieve the optimum bainitic structure able to develop hardness values higher than 400 HB, minimum tensile strength of 1400 MPa, good wear resistance and enough ductility ; weldability of the new bainitic steels. High-Si Cr-Mo and low-Si Cr-Mo-B-Ti steels (both 0.4% carbon by mass) were investigated. These steels can develop fully bainitic microstructures under controlled accelerated cooling down to bainite region temperature, followed by pseudo-isothermal treatments in still air down to a strengthening temperature. Thermo-microstructural models were applied to predict microconstituent volume fractions after phase transformation. After chemistry and process adjustment with outputs from laboratory tests and thermal-microstructural models, full-scale tests on hot-forged rail head made of selected steels were performed. Wear performance and rolling contact fatigue was studied by tribologic tests performed on a rolling-sliding ring-on-ring tribometer and full-scale equipments. Bainite showed to have a much better behaviour than pearlite: carbide-free bainite microstructures gave the best results. Weldability was studied reproducing the typical Flash Butt Welding cycle of rail. A fully bainitic microstructure can be reproduced in the heat affected zone by applying controlled cooling after welding. Guideline to manufacture and weld bainitic rails were given.
Bibliographic Reference: EUR 22081 EN (2006), 189 pp. Euro: 25
Availability: Katalogue Number: KI-NA-22081-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-02085-4
Record Number: 200719267 / Last updated on: 2007-07-10
Original language: en
Available languages: en