Microstructural evolution during continuous galvanizing and final mechanical properties of high Al-low Si TRIP steels

摘要

Four C-Mn-0.1%Si TRIP steels with different Al contents have been studied following conventional CGL processing routes. Austenite formation, ferrite recrystallization and austenite decomposition products have been characterized by means of several techniques. It has been demonstrated that stabilization of austenite can occur without the need of an extensive bainitic formation. The enhanced formation of new ferrite during cooling from intercritical annealing to isothermal holding at 460°C is presented as a probable cause for this phenomenon. It is shown that adequate microstructure and remarkable mechanical properties (with UTS values above 1100MPa when Cr and Mo contents are increased) can be obtained in TRIP steels with moderate Al contents and using short isothermal holding times (30-60s) and temperatures fully compatible with the industrial CGL practice.