Study of a new type ductile iron for rolling: Deformation tests (2)

On the basis of the designed composition, a new type of ductile iron bars with the composition of 3.62% C, 2.92% Si, 1.57% Mn, 0.061% P, 0.013% S, 0.024% RE and 0.021% Mg were prepared in a horizontal continues casting equipment. Plastic deformation resistance of this material was tested; the results indicate that the plastic deformation resistance is in the range of 280-310 MPa under the experimental conditions. Suitable deformation parameters for this new type ductile iron were provided. Rolling experiments from bar to plate, and from bar to bar were carried out. The rolling results reveal that this new type ductile iron is of good rolling performances. During the rolling of plate, the one pass compression ratio and the total compression ratio are up to 1.39 and 3.90, respectively. In the course of rolling of bar, the total section compression ratio is up to 4.47. Bars with the dimension of Ø 24.6 mm × 500 mm, which is of good quality, were prepared by pass rolling. By adjusting the cross rolling parameters, Ø 35 mm, Ø 40 mm and Ø 60 mm grinding balls were produced. By die forging technology, Ø 80 mm grinding balls, of which the microstructure is composed of bainite, small amounts of martensite, residual austenite and carbide, were obtained. The surface hardness of the balls is about HRC58, and the falling times are over 40,000.