Effects of Thermal Gradients and Rotational Flows on Grain Growth in 22 t Steel Ingots

Heavy ingots arc widely used in many industrial fields. The coarse grains formed during the process of ingot solidification influence the properties and fracture behaviors of the final products. The coarse grain growth was simulated under different thermal gradients. A 30Cr2Ni4MoV steel ingot was melted in a cubic crucible with dimensions of 15 cm x 10 cm x 23 cm, and the cooling conditions on each side of the crucible were controlled by different thermal curves. The influences of thermal gradients and rotational flows on grain growth in heavy steel ingots were then investigated both numerically and experimentally. The results showed that when the amplitude of the rotation angle was 60 degrees, the metal was solidified under a reciprocating horizontal rotational condition when the angular velocity was 10 (degrees)/ls or 20 (degrees)/s. As the thermal gradient increased, the lengths of the primary columnar grains increased, and the diameters of equiaxed grains decreased. When the direction of flow rotation was perpendicular to the direction of grain growth, the columnar grain zone was nearly eliminated, and the average diameter of equiaxed grains was 0.5 mm.