A metallurgical dart includes an enlarged refractory head having a top, a bottom, and a central through hole extending from top to bottom of the head and lined with a metallic sleeve, with a portion of the lining sleeve projecting beyond the top and/or bottom of the head; an elongate tail of refractory material with an external and/or internal metallic element and of external diameter slightly less than the internal diameter of the lining sleeve, such that the tail can pass, as a close fit, through the lining sleeve of the head; and at least one crimped or other joint between the metallic element of the tail and the projecting portion of the lining sleeve, to fix the head and tail together.
A dart has a metal bar 1 passing through a ceramic, shaped, dart head 2 and then through a cylindrical ceramic dart stem 3. A sleeve 4 of a carbonaceous or reactive material is provided about the stem 3 or a layer of that material can be formed on the lower face 5 of the dart head 2 (at the interface of the steel and slag). A block or sleeve 6 of suitable reactive material could be positioned on the top face 7 of the dart. The reactive material could be cardboard or paper, or a reactive metal, such as aluminum or magnesium. In each case a chemical reaction with the molten steel will result in an updraft in the steel which clears slag from the area of the tap hole.
An improved vortex inhibitor for separating slag from molten metal during the discharge of molten metal through a nozzle includes a uniform castable refractory body with a generally tapering shape, a hollow chamber within the body and an elongated sacrificial member. The hollow chamber receives the sacrificial member or a mount for the sacrificial member. The refractory body and the sacrificial member combination in molten metal has a specific gravity less than the specific gravity of molten metal and is positioned narrow end downward when supported in molten metal. The hollow chamber can fill with molten metal to form a core that aids in orienting the body in a narrow end downward position. The sacrificial member align the with the area in which the vortex forms and minimizes interference with the flow through the discharge nozzle. The body preferably includes swirl obstructing surfaces.
