PURPOSE: To reduce the development of defect in a product by arranging pressurizing ram fixing refractory heat insulating material at the lower end thereof and pressing the ram to the top part of a steel ingot within the specific time after completing solidification of the steel ingot.
CONSTITUTION: To a mold 2 on the base plate 3, the pressurizing ram 5, which applies the mechanical pressing down at the upper part, is arranged. Further, the refractory heat insulating material 6 is fixed at lower face of the ram 5. The molten steel is poured into the mold 2 and solidified and just after that, the pressurizing ram 5, which is preheated within 10 min. and held at about 1000°C to the lower end part 6, is descended, and pressed down to the steel A just after solidifying. By this method, the pressing force is acted on the steel A as plastic deformable just after solidifying and the developments of porous defect and cracking are prevented with compressive stress. Thereafter, as the porous defect and cracking in the steel ingot are reduced, the development of the defect in the product is reduced.
Saito, Kenji
Nozaki, Tsutomu
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