Comparison on Microstructures and Mechanical Properties of High Strength-Toughness Hull Steel with Normal and Controlled Rollings

Normal rolling and controlled rolling processes were carried out on 550 MPa rank high strength-toughness hull plate steel with same chemical composition, and microstructures and mechanical properties of the steel after rolling were compared. The results show that microstructures of the steel after rolling with two kinds of processes were ferrite and M/A island, the grain size of the steel with controlled rolling was a little smaller, and the content of ferrite was higher. Strength and elongation of the steel after rolling with two kinds of processes had little difference, but the steel with controlled rolling had higher low temperature impact energy at -40 ℃, which was 2.4 times of impact energy of the steel with normal rolling.