Optimization of heat treatment of TRIP steels

In transformation induced plasticity (TRIP) steels, proper microstructure is essential. The TRIP effectprovides the material with high plasticity owing to high volume fraction of ductile phases (ferrite andaustenite) in microstructure. In consequence, it provides high hardening through deformation andtransformation. The hardening is caused by transformation of retained austenite to martensite. Suitablemicrostructure for TRIP effect can be obtained by either thermomechanical or heat treatment. Presentpaper describes development of an intercritical annealing technology, which guarantees fine-grainedmicrostructure formation consisting of appropriate fractions of ferrite, lower bainite and retainedaustenite. Such structure is suitable for further cold forming with TRIP effect hardening