Importance

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Abstract

A porous plug for treating molten metal is characterized by a porous refractory body having an axis and a wear detection refractory element in transaxial juxtaposition with the porous refractory body over a portion of the axial height of the body, the wear detection refractory element having an emissive power different from that of the porous refractory body to provide a discernible indication of the extent of wear of the porous refractory body. The wear detection refractory element may be in the form of a porous refractory insert internally located within the porous refractory body or a non-porous refractory sleeve surrounding the porous refractory body, or combinations thereof. The insert or sleeve may have top end faces located at the minimum melt down height of the porous plug whereby when the plug melts down sufficiently to expose the top end face of the insert or sleeve indicating that the plug is at the end of its useful life, the plug at high temperature after use will vary in brightness across its top surface thus permitting detection of such end of the plug life through observation of the brightness pattern resulting from the different emissive powers of the body and insert or sleeve.

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First Claim