Abstract: A gaseous atmosphere having a predetermined composition is formed near an injected molten metal flow and an injection nozzle of the atmospheric gas so as to manufacture a thin metal strip exhibiting excellent surface property. A thin strip manufacturing apparatus includes an injection nozzle 1 for injecting a molten metal onto a cooling roll 2, an atmospheric gas injection nozzle 3 for injecting an atmosphere having a predetermined composition, a sensor 5 for measuring the concentration of the atmospheric gas, a control device 6 for adjusting a flow rate of the atmospheric gas on the basis of the output of the sensor 5, a cover 4 for maintaining the concentration of the atmospheric gas, and a heating device for preventing cooling of the injection nozzle 1.

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.

Abstract: In a top-and-bottom blown converter having a plurality of tuyeres arranged at the bottom of converter housing, a monitoring sub-lance is vertically movable within a region defined beween vertical planes passing through parallel lines horizontally spaced a distance of 300 mm from a tuyere aligning line.

Abstract: In the top-and-bottom blown converter steel making process, a process is provided wherein the position of the bottom-blowing tuyeres is set such that the maximum X.sub.0 among the distances X between the respective tuyreres and the center of the converter bottom is up to 1.3 times the horizontal distance Y between the central vertical axis of the converter and the outermost boundary of a hot spot region developed on the molten iron surface by the top-blowing oxidizing gas from the lance. By setting the position of the bottom blowing tuyeres in this manner, the interference of the bottom-blowing gas with the top-blowing gas is promoted to enhance the agitation between the slag and the metal to reduce the concentration of iron value (T.Fe) in the slag, thereby improving the iron yield.

Abstract: In the operation of a top-and-bottom blown converter, top-blowing oxygen gas is blown such that the center of a hot spot created by the oxygen gas jet from each of the nozzles of a top-blowing multi-nozzle lance is positioned outside a bubbling region of the molten metal surface which rising bubbles of gas from bottom-blowing tuyeres reach.

Abstract: A tuyere for blowing an agitating gas into molten steel is arranged in the bottom of an oxygen top-blown converter in order to improve the refining effect of molten steel and has a ratio of blow sectional area S (cm.sup.2) to inner peripheral length L (cm) of not more than 0.17, preferably not more than 0.125.

Abstract: In a method for cooling tuyeres when molten iron is refined by blowing a refining gas containing oxygen, and by setting tuyeres below or above the meniscus of iron bath in a vessel for refining the molten iron, wherein concentric tuyeres are used and a refining gas containing oxygen gas is blown through the inner pipe of the concentric tuyere and a fluid for protecting the tuyeres is blown through the outer pipe of the tuyere so that the protecting fluid surrounds the refining gas in a sheath form to cool the top ends of the tuyeres, the protecting fluid being a mixture of gaseous or liquid carbon dioxide and carbon fine particles.