Cutting refractory material

Abrading – Abrading process – Utilizing fluent abradant

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451102, B24C 504

Patent

active

059613718

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BRIEF SUMMARY
The present invention relates to a method of cutting a refractory body and in particular, but not exclusively, to a method of cutting a zirconia-containing refractory body. The invention also relates to a powder mixture for use in such a method.
Refractory structures of various types, such as metallurgical furnaces, coke ovens and glass melting furnaces tend to become damaged during the course of their working lives.
Such damage may for example be manifest as slippage of one or more refractory blocks in relation to the main structure which results in an irregular surface profile, or as cracking of the refractory structure. It is in general desirable to re-establish the designed surface profile of the refractory structure, and it is also desirable to prevent further slippage of the block(s) in question and to fill any gap left by its or their displacement or cracking. In order to achieve these ends, it may be necessary or desirable to cut away any proud portion of the refractory structure. Alternatively, or in addition, it may be necessary or desirable to cut a keyway into a slipped block and/or a neighbouring block so that a key may be formed in or inserted into the keyway to prevent further slippage. Alternatively or in addition, it may be necessary or desirable to enlarge or shape any gap left by such slippage or cracking for the formation or insertion of a suitable plug. Such damage may alternatively be due to erosion of the material of the refractory structure. Such erosion tends to impart an irregular surface profile to the structure and it is often desirable to modify that surface profile before effecting a repair to the structure.
It may be necessary or desirable to form a hole in or otherwise cut a refractory structure for other purposes, for example to create openings in the wall of a furnace from outside the furnace.
The term "cutting" as used herein thus refers to removal of refractory material by means of a tool and encompasses the cutting away of a portion of the material, forming a hole or keyway in it, enlarging a hole or keyway, or creating an opening through it. The term includes "drilling", namely the formation of a rounded hole in the material.
A refractory structure can be cut mechanically, for example using a cutting wheel, drill or other edged tool, but this presents certain disadvantages for refractory repair. In order to cut the refractory and leave a surface suitable for repair, the operator would usually have to approach the cutting site quite closely, and this implies that that site would have to be at a temperature which the operator could tolerate for the time necessary to effect the cutting. This in turn implies that the refractory structure would have to be cooled from its normal operating temperature, or a temperature which is within its normal working cycle of operating temperatures. And it would have to be reheated after cutting and repair. In the case of industrial furnaces of various types, in order to avoid damage to the furnace as its refractory material contracts or expands, such cooling and reheating might have to be scheduled over a period of several days or even a few weeks, and this would accordingly represent a considerable loss in production from that furnace.
It has been proposed to repair refractory bodies by use of a "ceramic welding" technique. In this technique, the body is brought into contact, in the presence of oxygen, with a powder mixture comprising refractory metal oxide particles and fuel particles which burn in an exothermic manner by combining with oxygen to form a refractory oxide. The oxygen, usually alone, serves as a carrier gas to convey the powder mixture to the repair site. By this method a refractory mass is formed at the repair site. A particular advantage of such ceramic welding is that the repair can be effected while the refractory body is hot.
Thus, it is known from British patent specification GB 1 330 894 (Glaverbel) to form a refractory mass on a surface by projecting against the surface, at an elevated temperature and in the presen

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Oxide Ceramics, Physical Chemistry and Technology, by Eugene Ryshkewitch, Academic Press Inc., 111 Fifth Avenue, New York, NY and Academic Press Inc.)London) Ltd. 17 Old Queen Street, London S.W. 1, England. pp. 356-363. Dated: 00/00/60.

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