PRODUCTION OF CONTINUOUSLY CAST INGOT HAVING GOOD SURFACE CHARACTERISTIC

PURPOSE:To prevent surface flawing with a steel of which the Cp value calculated by the specific equation has a prescribed value by using casting powder contg. C at a high ratio to adjust the Cp value in the surface layer part of an ingot to a specific range. CONSTITUTION:The integranular cracking of the continuously cast ingot is largely affected by the grain size of austenite (gamma) grains and the formation of the coarse austenite (gamma) grains during solidifying and cooling accelerates considerably the intergranular cracking of the ingot. The carbon equiv. Cp of the steel contg. Mn, Ni, Ca and N is calculated by the equation. The Cp value in the surface layer part of the ingot is adjusted to the range higher than 0.23 by using the casting powder having >=(5-6%) and up to about 20% content of C with the steel of which the Cp value is in a 0.13-0.23 range. The Cp value in the surface layer part of the ingot moves to a range where the cracking arises to the smaller extent. The cracking of the ingot is thus prevented.