Effect of rare earth Ce on Microstructure and properties of ABS A36 ship plate

The equiaxed ferrite and pearlite can be obtained from the ABS A36 ship plate after forging and normalizing. With the increase of Ce content in the ABS A36 ship plate, the grain size of the ABS A36 steel is obviously refined and the microstructure becomes uniform. When the Ce content reaches 0.009%, the pearlite in the A36Re ship plate is obviously reduced.

The addition of rare earth in ABS A36 ship plate can not only purify grain boundaries, but also play a significant role in modifying the inclusions in the steel from strip to spherical rare earth sulfur oxides. These ellipsoidal high melting point rare earth compounds reduce the stress concentration caused by inclusion segregation, improve the tensile fracture morphology, and make dimples appear equiaxially and distribute more evenly.

When the content of Ce is 0.009%, the yield strength, tensile strength and impact toughness of A36Re ship plate are increased by 8%, 6% and 9%, respectively. The corrosion rate of A36Re ship plate is lower than that of ABS A36 ship plate. From the macroscopic observation of the rust layer, it is found that the A36Re ship plate is easy to form a black inner rust layer, which is not easy to fall off. The corrosion micro-morphology and electrochemical data analysis showed that the pitting corrosion tendency of ABS A36 ship plate was more serious, while that of A36Re ship plate was mainly uniform corrosion.

XRD analysis shows that the corrosion products of A36Re ship plate and ABS A36 ship plate are mainly iron oxides and hydroxyl iron. The corrosion rate of A36Re ship plate increases first and then decreases with the increase of corrosion time. It is found that the corrosion products of A36Re ship plate distribute more uniformly and compactly, and the resistance of rust layer is higher. XRD analysis showed that the content of protective alpha-FeOOH in A36Re ship plate increased, which improved the protective ability of rust layer to the matrix.