Abstract: Hollow metal ingots are produced by a hollow metal manufacturing apparatus comprising a mold placed on a stool, and a cylindrical metallic cooling core placed in the mold to form an annular casting space therebetween. During the casting, a cooling fluid is directly blown upon the inner surface of the core while the cylindrical metallic core is allowed to be buckled. The cooling core is constituted by an outermost metallic cylinder to be brought into contact with a molten metal, a cylindrical lattice-fashioned buckling-adjusting frame positioned in the metallic cylinder and provides passages through which the cooling fluid is passed, and a cooling fluid vessel which is positioned inside the buckling-adjusting frame and is provided with a number of cooling fluid blowing nozzles.

Abstract: A method and an apparatus for manufacturing a hollow steel ingot are disclosed, which comprise coaxially arranging a cylindrical metallic core in a center of a mold and pouring molten steel into an annular casting space defined between the core and the mold to cool and solidify it. In this case, the core is constructed with a concentric double tube consisting of inner tube and outer tube and receives in its central portion a cooling gas tank provided at the outer peripheral surface with plural outlets opening toward the inner peripheral surface of the inner tube. An inert gas is flowed through an annular gap defined between the inner tube and the outer tube, while a cooling gas is blown toward the inner peripheral surface of the inner tube.