Analysis on Microstructure and Properties of Cold-rolling Automotive Applications TRIP Steel with 1．20％Si

摘要

The TRIP steel with 1. 20% Si was appropriately hot rolled,cold rolled,annealed and quick cooled. Results suggested that the yield ratio of trial steel is 0. 58 with low yield strength (390 MPa) and high tensile strength(670 MPa). Especially for good elongation(28.0%) and n value(0. 230) ,they proved that the TRIP steel possesses excellent formability. They are beneficial that the microstructure contains ferrite,which is excellent in ductility,and a second hard phase small island martensite. The presence of retained austenite in the ferrite -boundary will enhance even further the total elongation by TRIP effect. The volume fraction of retained austenite is 6.2% from the quantitative Xray diffraction analysis. As a result,further improvement can be achieved by TRIP effect,i. e. strain induced transformation of retained austenite to martensite. The TRIP steel with excellent mechanical properties will be elected in emphases for the automotive applications to attain weight reduction and to improve the impact safety of vehicles.