Formation and Control of Central Cracks in Alloy Steel ZKG223

Abstract

When the molten steel contains high carbon and alloy elements, the continuous casting bloom is prone to internal defects. Soft reduction is an effectively means of improvement and is widely utilized in the continuous casting process. Herein, the generation mechanism of the central cracks in alloy steel ZKG223 is analyzed in detail; that is, the tensile stress is generated by the accelerated solidification and shrinkage in the core of the bloom at the end of solidification, which acts on the dendrites and causes central cracks. In order to reduce the shrinkage stress during the solidification of the bloom, the reasonable reduction parameters of the bloom are determined by establishing a soft reduction model, and the industrial test is carried out. Through the implementation of well‐designed soft reduction, the central cracks in the bloom are significantly bridged, and the secondary dendrite spacing in the center of the bloom is shortened from 315 to 230 μm. The maximum positive and negative carbon segregation indices in the cross section of the bloom are changed from 1.039 and 0.957 to 1.020 and 0.977, respectively, which greatly improve the uniformity of element distribution and the internal quality of the bloom.