Effect of Deformation on the Formation of Internal Cracks in Continuously Cast Blooms

Abstract

The effect of deformation on the formation of internal cracks in a solidifying continuously cast bloom has been investigated on the basis of two kinds of deformation tests, i.e., squeezing test of 300 mm square bloom and bending test of 300 × 400 mm bloom carried out on bloom caster.
The relation between the amount of squeezing or bending and the roll load at the initiation of internal cracks was obtained for various grades of steels. Temperature range for the occurrence of internal cracks was also estimated from melting behavior of a composite rivet (Ni-embedded steel rivet) driven into a solidifying bloom together with heat transfer calculation for the solidifying shell. The internal cracks were observed to occur at temperatures of 30-40°C lower to slightly higher than the solidus. This indicates that formation of the internal cracks is closely related to the embrittlement occurring at this temperature range.
The strain caused at the internal cracks by the squeezing test was calculated by the finite element analysis, and the strain leading to the formation of internal cracks was found to be 0.3 to 0.8%, depending on the steel grades.