Strategies for Producing Dual-Phase Steel Using Niobium Microalloying

摘要

Dual phase steel is nowadays widely applied in automotive construction as hot rolled and cold rolled grades. The strength and elongation of DP steels are principally determined by the ratio of ferrite and martensite in the microstructure. However, for practical forming in the press shop additional properties are important such as bendability and hole expansion ratio. These characteristics relate to the morphology and distribution of phases in the microstructure. Niobium microalloying can influence not only the strength of DP steels but also particularly the phase morphology and homogeneity leading to significant improvement of the mechanical properties. The paper will show processing strategies involving Nb microalloying in DP steel production. The metallurgical mechanisms induced by Nb are discussed in detail. In particular the beneficial effect of Nb for producing low-carbon (<0.1%C) DP steels is pointed out.