US 4,721,534 A · Immersion pyrometer

Abstract

A protective sheath for a temperature sensing device for use in determining the temperature of molten metals. The temperature sensing device, such as a thermocouple, is encased in a molybdenum tube which is coated with successive porous layers of molybdenum, a plurality of layers of Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 --Mo in a decreasing concentration of Mo in proceeding from the inner to the outer layers, and a layer of substantially pure Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3. The Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 layer may be covered with an outer coating of a material, such as boron nitride, to protect the Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 layer from attack by slag. Alternating layers of Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 and boron nitride may be applied as outermost sacrificial layers.

Claims32

Dependent claims

A protective sheath for a temperature sensing device comprising:

(a) a metal tube having one closed end to provide a cavity for a temperature sensing device;
(b) a series of protective layers comprising at least two cermet layers consisting essentially of Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 --Mo covering the outer surface of said metal tube, the concentration of molybdenum in the at least two cermet layers decreasing in proceeding from the inner to the outer layers, and each of said cermet layers having a porosity of from about 4% to about 33%;
(c) a ceramic layer of substantially pure Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 covering the outermost of the at least two cermet layers, said ceramic layer having a porosity of from about 4% to about 33%.

Dependencies are inferred from the claim text.

Immersion pyrometer

Life of this patent

Immersion pyrometer

Life of this patent

Abstract

Claims32