Method and apparatus for treating metal

Abstract

The apparatus disclosed is intended primarily for use in practicing the disclosed method of introducing additives into a molten metal bath contained in a typical ladle or vessel mounted in an upright position with an open mouth at its upper end. The total apparatus includes mechanisms which may be conventional for producing a continuous stream of a fluidized mixture of a carrier gas and solid additive material in particulate form. Various solid additives are introduced into molten pig iron or steel, including aluminum, magnesium, calcium carbide, rare earths, columbium, boron, molybdenum, and many others for such purposes as deoxidizing, desulfurizing, alloying, controlling grain structure, etc. The novel portion of the apparatus includes a discharge tube mounted in upright attitude and extending down into the open mouth of the vessel. The upper inlet end of the tube is flow-connected to the source of the fluidized mixture and the lower discharge end is spaced a selected distance above the bath to eject a free stream of the mixture down toward the bath. The velocity of the stream is so chosen that the energy of the solid particles is sufficient to cause them to penetrate into the bath and the energy of the gas is insufficient to enable it to penetrate into the bath so that it spreads out radially. To prevent the gas from flowing over the whole surface of the bath and causing violent disturbances and splashing, a tubular shield is arranged to surround the stream and extend into the bath. The shield confines the gas to a minor portion of the surface area of the bath and causes the gas to reverse direction and flow out of the open upper end of the shield.