Development of high strength steel sheet products by back-annealing
The aim of this project was to develop and evaluate high-strength steel sheet products where the hardening introduced during cold rolling is retained to a significant degree by incomplete recrystallisation, a treatment that has been termed 'back-annealing'. The investigation included a wide range of low carbon and stainless steels. An initial round robin exercise helped to coordinate the experimental procedure in the different partners' laboratories. This phase of the work also revealed that only very modest improvements in the strength-ductility balance are possible when using simple, low-strength steel compositions. Further development was therefore directed towards back-annealing of more complex steel grades, having incompletely recrystallised ferrite matrices, including: - micro-alloyed steels containing niobium or titanium to provide precipitation hardening; - dual phase steels having martensite as a second phase; - TRIP steels having austenite as a second phase; - stainless steels with both traditional chemistries and new high Mn-N variants. Significant improvements were obtained in the combination of strength and formability from tensile tests in several of these cases. In particular, it appears that bending and hole flanging properties can be improved for high strength sheet. Fatigue strength was improved for the stainless steel but apparently not for the back-annealed dual phase steel. Computer modelling has been developed to predict annealing kinetics and mechanical behaviour of the heat treated products. Depending on the applications, the approaches were chosen to be either physical/analytical or artificial neural network models.
Bibliographic Reference: EUR 22811 EN (2007), 118 pp. Euro: 25
Availability: Katalogue Number: KI-NA-22811-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 978-92-79-05265-1
Record Number: 200719208 / Last updated on: 2007-07-05
Original language: en
Available languages: en