Comparison of contamination by non-metallic inclusions in continuous cast slabs of special low carbon steel

Abstract

The paper studies and compares the macrostructure quality of continuously cast slabs of extra low carbon steel grades DX54D, DX56D, DX57D and 006/IF during casting on a curved-type CCM with and without a vertical section. For this purpose the array of production data of casting of steel of the above mentioned grades, totaling 383 melts, was studied. At the same time, 149 melts were cast on four CCMs (conventionally named A, B, C, D) of curvilinear type with a base radius of 8 m, and 234 melts – on a machine of curvilinear type (E) with a base radius of 11 m and a vertical section of 2.7 m length. Contamination of the cast metal with non-metallic inclusions was assessed metallographically by the degree of development of the defect “point heterogeneity”. The presence of a vertical section allows to reduce the degree of development of point heterogeneity from 1.29 to 0.75 points – by 0.54 points or by 41.9% (relative). With a probability of 99.9% we can assert that the difference between the average values of point heterogeneity is not random and is limited by the presence of the vertical section of the CCM