PURPOSE: To provide a titled casting mold of a pressing method with water cooled copper plates by which a steel ingot for an extra thick plate having no inverse V segregation at all and having excellent internal quality by blowing a gas for cooling from the porous block in the lower part of the water-cooled copper plates to cool solidified shells and evacuating forcibly the gas from an upper evacuating port to increase the rate of solidification.

CONSTITUTION: An evacuating port 44 is closed 46 and a molten steel 32 is charged into a casting mold. Pressing of long side casting molds 2 is started similarly to the prior art in follow up to the shrinkage of solidified shells 34 when said shells are formed. A gas for cooling is blown at the same instant from a porous block 38 by a blower 40. The gas ascends in the gap parts between water-cooled copper plates 4 and the shells 34 and cools the shells 34. The heated gas is discharged by an evacuating port 44, an evacuating pipe 50 and an evacuating fan 52 right under a heat insulating material 36. The gas for cooling is positively passed in the gas between the steel plate and the plate 4 to increase extraction of heat by which the quantity of the heat extracted is increased by about 20% as compared with the conventional device. The quality in the steel ingot is thus improved by such increase coupled with the heat insulating effect of the material 36. H2, Ar, N2, etc. are usable in addition to air for the gas for cooling.