Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Producing hollow article
Patent
1997-05-27
1998-12-29
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Producing hollow article
264649, 264 81, 264309, 425449, 425470, 425DIG815, B05D 108, C04B 3565
Patent
active
058536540
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the formation of ceramic articles and to the apparatus used for the said formation. It is particularly, but not exclusively, concerned with the formation of pipes and tubes of ceramic material.
2. Description of the Related Art
Ceramic pipes and tubes have traditionally been formed from clay moulded into the desired "green" shape and then baked in an oven. These are still widely used but are not of high quality in regard to mechanical strength and ability to withstand high temperatures such that a high proportion of breakages are incurred. For ceramic pipes and tubes capable of withstanding more demanding duties, especially for such heavy duty ceramics as silicon carbide, the manufacturing methods have however become increasingly more complex. Japanese published patent specification JP-A-03-218987 describes the manufacture of a composite silicon carbide-metal pipe for such duties as combustion pipes of gas turbine engines. This manufacture first forms a layer of a uniform mixture of silicon carbide powder and carbon powder on the inner surface of a metal pipe. Excess silicon is then added and a mixed powder layer of aluminium and Fe.sub.3 O.sub.4 is laminated to the first layer to form a tubular article. The tubular article is is then subjected to very fast rotation such that a thermit reaction occurs and creating sintered silicon carbide in the first layer.
The present invention has as its object the preparation of high quality ceramic articles such as pipes and tubes while avoiding such complex procedures.
Specifically the present invention has arisen from investigations into how to apply to the manufacture of ceramic articles a technique similar to the ceramic welding process.
In "ceramic welding" a mixture of solid refractory particles and solid combustible fuel particles of a metal or semi-metal such as aluminium and silicon is projected against a target surface where the combustible particles react in an highly exothermic manner with oxygen gas to produce with the refractory particles a coherent refractory mass together with the oxide(s) produced by the reaction.
There have been many patents on ceramic welding, starting with GB patent 1,330,894 (Glaverbel). While it is known to employ ceramic welding processes to form a refractory article, for example, a block having a particular shape for use in constructing or repairing an industrial furnace, it has historically mainly been used in the in-situ repair of furnace refractories, for example the refractories used in the walls of glassmaking furnaces or coke ovens. The ceramic welding mixture is projected to the required point of repair where it produces a coherent refractory mass adhering to the furnace wall.
The refractory materials used in furnaces include such oxide materials as alumina, silica and zirconia. Refractories having a base of silicon carbide are used in certain metallurgical plant, in particular in ferrous blast furnaces or in zinc distillation columns. The combustible particles and refractory particles used in the repair mixture are usually chosen so that the coherent refractory mass is of a similar chemical composition to the furnace refractory.
SUMMARY OF THE INVENTION
According to the present invention there is provided a process for making a ceramic article from a powder mixture comprising refractory particles and combustible particles, in which the combustible particles are reacted exothermically in the presence of an oxygen-rich gas to produce the article from the refractory particles and the reaction product of the combustible particles, characterised in that the powder mixture is projected against a metal former, which is heated to a temperature of at least 850.degree. C., to produce a coherent refractory article in the shape of the former and the former is then separated from the article.
Apparatus for forming a refractory mass comprising spraying means for spraying particles of oxidizable material and refractory material together with oxy
REFERENCES:
patent: 2990601 (1961-07-01), Wagner
patent: 5013499 (1991-05-01), Willard
patent: 5061527 (1991-10-01), Watanabe et al.
Meynckens Jean-Pierre
Robert Jean-Pierre
Derrington James
Glaverbel
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