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: Methods for controlling blowing, controlling the slag formation and predicting sloping in the blowing of molten pig iron in LD converter are carried out by measuring acceleration of the horizontal movement of a detector, such as a lance provided in the converter, which is caused only by the slag impinging against the lance, by an accelerator, integrating the measured values to obtain integrated average values at every several seconds, and programming the integrated average values in a computer.

Abstract: The method of sequential continuous-casting of the different grade of steel according to the present invention comprises the steps of: stopping the pouring of a first grade of molten steel into a mold and the drawing of cast slab; immersing a columnar steel stock being circular or polygonal in cross section and equipped with guiding jigs into the substantially center portion of the first grade of molten steel in said mold; forming a solidified phase around said cooling material; and merging said solidified phase in a solidified shell developed from the wall of the mold to form a solidified layer shutting the upper portion off the lower portion of the first grade of molten steel.