Compositions: ceramic – Ceramic compositions – Refractory
Patent
1982-03-18
1984-01-17
Poer, James
Compositions: ceramic
Ceramic compositions
Refractory
501153, 501154, C04B 3510
Patent
active
044264577
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to optical pyrometry applied in measuring the temperature of molten metals, and particularly to a composition of and a method for producing materials used for manufacturing a light guide assembly for transmitting thermal radiation from the molten metal to the pyrometer through the lining of a metallurgical vessel. More specifically, the invention is concerned with a refractory powder for use as a protective filler in a light guide assembly incorporating a corundum light-transmitting member, and a method of producing same.
BACKGROUND ART
To improve the operational reliability of light transmitting devices without making their construction more complex, is a problem still to be solved in the art of optical pyrometry.
The great number of patents granted in various countries (cf. USSR Authors' Certificates Nos 146,533 Int. Cl..sup.2 G OIK 1/00, 1961, and 271,067 Int. Cl.sup.2 G 01/J 5/02, 1970, U.S. Pat. No. 3,745,834, FRG Pat. No. 2,338,532) indicates that the above problem still exists and that attempts have been made to solve it. Generally, the prior art light transmitting device comprises a light transmitting member made from a light-permeable corrosion-resistant refractory material such as for instance, quartz or synthetic corundum, and a tube wherein said light-transmitting member is disposed. The space between the inner surface of the tube and the light-transmitting member is filled with a refractory powder. When in use the device is mounted in the lining of a metallurgical vessel so that one end (exposed end) of the light-transmitting member is in contact with a melt, and the opposite end extends through the lining outside the vessel and is optically connected to a pyrometer.
Although a great many attempts have been made to improve the operational reliability of a light guide assembly, this has not yet occurred. This, perhaps, can be explained by the fact that in the prior art apparatus, only principal structural members of the light transmitting device were improved without changing the composition of the refractory powder. At the same time it is worth mentioning that the light guide assembly is operated under conditions of thermal shock (sharp changes in the temperature of the exposed end of the light-transmitting member) and high temperature gradients along the exposed end. Under such conditions the role of a refractory powder as protective means is increasing in importance. Therefore, with a decrease in the thickness of the lining and an increase in the temperature of the melt within the metallurgical vessel, stricter requirements are placed upon the protective refractory powder, since in this case the temperature gradient through the depth of the lining increases.
As a refractory powder, for instance, alkali-free heat resistant oxides are used (cf. Austria Pat. No. 280,650 Int. Cl.sup.2 G 01K 1/16, Apr. 27, 1970). In particular zirconium dioxide (ZrO.sub.2) and aluminum oxide (Al.sub.2 O.sub.3) are most extensively used for this purpose. In the apparatus according to this patent, the powder is used in the same form as it is produced, that is, without preliminary treatment.
It is to be noted that the most efficient light-transmitting members at present are those made from synthetic (monocrystalline) corundum. However, in the course of operation of light guide assemblies having a corundum light-transmitting member and filled with a powder of any of the above two oxides, there arise a number of difficulties.
First, when in use, and in particular at the sintering temperature of the lining, the aluminum oxide powder tends to fuse with the corundum of the light-transmitting member, thereby preventing free displacement of the light-transmitting member within the refractory material, and thus increasing the probability of damage to it.
It should be noted in this connection that although the corundum light-transmitting member has the same chemical composition as the refractory powder, the former is a monocrystal while the latter is in the form of a polycrys
REFERENCES:
patent: 4251279 (1981-02-01), Ekdahl
Chugunny Evgeny G.
Zhukov Leonid F.
Institut Problem Litiya Akademii Nauk Ukrainskoi SSR
Poer James
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