Control of Mechanical Properties of Hot-dip Galvanized Ti-IF Steel Sheet

The hot dip galvanizing experiment of Ti-IF steel was carried out on a CGL line designed for the production of DQ and lower grade products. The effect of RTH strip temperature and skin-passing on the mi-crostructure, recrystallization texture and mechanical properties were investigated. The results show that, based on ULC Ti-IF steel, the hot dip galvanized sheet with excellent formability can be produced when suitable amount of excess Ti is ensured and suitable processing schedule is applied. Its yield strength, average r-value and n-value reach approximately 150 MPa, 2.5 and 0.25, respectively. However, after skin-passing, the yield strength increases obviously, the n-value and elongation decreases markedly. The n-value of final skin-passed products depends on ferrite grain size and becomes very low when the ferrite is coarsened. A strategy to ensure mechanical properties of hot-dip Ti-IF steel sheet by adjusting process parameter is discussed in terms of surface conditions of hot-dip galvanized steel sheet and application situation of customer.