Immersion pyrometer with protective structure for sidewall use

Abstract

Temperature sensing apparatus for use in the sidewall or bottom of a vessel for containing molten metal. A temperature sensing element is mounted within a sheath which is provided with a sacrificial coating to protect the sheath from premature oxidation such as may occur during a gas-flame pre-heat cycle. The sheath which is being protected against premature oxidation by the sacrificial coating is a composite of a closed end metal tube and a plurality of porous cermet layers of aluminum oxide-chromium oxide-molybdenum with the concentration of molybdenum decreasing in proceeding from the inner cermet layer to the outer cermet layer. The outer cermet layer of the sheath is covered by a ceramic layer of aluminum oxide. The sacrificial coating consists of a layer of zirconium oxide in combination with and covered by a layer of fibrous alumina. The sacrificial coating is typically destroyed by the end of a pre-heat cycle.

Dependencies are inferred from the claim text.