In the automotive sector, hot-dip galvanized dual-phase steels with high yield strength and tensile strengths above 1000 MPa are currently in vogue. For optimum utilization of the TRIP ((Transformation Induced Plasticity) effect, a sufficiently high amount of austenite must be stabilized in the microstructure of the material. Commonly used alloys of such steels have silicon contents above 0.8 %, which can sufficiently supress carbide precipitation during isothermal bainite formation. These silicon contents lead to crack formation during spot welding and ensure poorer surface quality due to the formation of pickles on the furnace rollers. In this master thesis, the amount of silicon in a TRIP steel is to be reduced and the potential of a partial substitution of silicon by aluminum and chromium. For this purpose, three alloys of 0.16 % carbon, 2.3 % manganese, 0.6 % silicon, with or without chromium, and varying aluminum content (0.5-0.8 %) were investigated. Dilatometer tests showed reduced carbide precipitation behavior with added aluminum. This allows enough retained austenite to be stabilized at room temperature and high elongations to be achieved. Production-like annealing cycles in a heat treatment simulator showed that the desired mechanical properties can be achieved with 0.5% aluminum. The addition of chromium has no significant effect on the amount of retained austenite because carbide precipitation during bainite formation is not affected.
|Translated title of the contribution||Substitution Of Silicon Through Aluminum in High-Ductility Steels|
|Award date||16 Dec 2022|
|Publication status||Published - 2022|
Bibliographical noteembargoed until 14-09-2027
- Retained Austenite