PURPOSE: To prevent generation of a tone sheet in the stage of removing a steel ingot from a mold for casting a steel ingot by using thinly a material which is different from the material of the mold and has a low yield point to constitute the part of the lower inside surface of the mold where the tone sheet is liable to arise.
CONSTITUTION: A core 9 for forming the inside surface of a mold for casting a steel ingot is erected on a flat plate-shaped drag 8 and a master mold 10 is disposed to form a space 12 for forming the mold to enclose said core mold. A cast iron for the casting mold is then poured through a runner 11 and a sprue 13 into the space 12 to cast the mold. A mold coating material 14 mixed with powder of ferrosilicon is used in the part of the lower outside circumferential surface of the mold 9 where a tone sheet is liable to arise. The molten cast iron poured into this part forms the material consisting primcipally of ferrite having a low yield point to 0.2W1mm thickness as the cementite in the pearlite base is decomposed to ferrite and graphite by ferrosilicon. The generation of the tone sheet on the lower inside surface of the mold is obviated in the stage of drawing the steel ingot cast by using such mold.
TAKAGI MASATADA
SAKAMOTO NOBUHIRO
Next Patent: METHOD FOR REPAIRING CRAZING OF CASTING MOLD FOR MAKING INGOT