Method of preventing damage of an immersed tuyere of a decarburization

Abstract

In bottom blown oxygen steel making or in top and bottom blown combined oxygen steel making, a tip end of a tuyer immersed in molten steel is seriously damaged or melted away due to very high temperatures due to the vigorous combustion of carbon, manganese and so on by the oxygen blown into a furnace. In order to prevent such damage, hydrocarbon gas has been blown through space between an outer pipe and an inner pipe of a dual pipe tuyere or tuyeres, but such hydrocarbon gas rather excessively lowers the temperature of the molten metal adjacent to the tip end of the tuyere and often blocks the opening of the tuyere. Now, instead of blowing in hydrocarbon gas, particulate material such as limestone magnesite, dolomite and the mixture thereof are proposed to be blown into the molten metal in the decarburization steel making vessel carried by an innert gas, combustion gas, blast furnace gas, LD process gas and oxygen or a mixture of these gases. Particulate material mentioned above, when blown into the molten metal, increases the momentum of the gas flow, enhances a shielding effect, against high radiation heat by fire point, or further forms either a kind of protective layer or deposit of refractory mineral material at the tip of the tuyere thereby effectively preventing damage of the tuyere and lengthens the service life of the refining vessel. Addition of particulate material in continuously linearly or in stepwise manner has been proved to be effective for accomplishing the above-mentioned cooling and protecting effect of the particulate material.