Compositions: ceramic – Ceramic compositions – Pore-forming
Patent
1994-10-31
1996-01-09
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Pore-forming
501 80, 501 81, 252 62, C04B 3800, C04B 3810
Patent
active
054829046
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a heat-insulating refractory material for suppressing heat dissipation, which is used for the surfaces of refractories of linings in an industrial furnace or the surfaces of refractories for steel casting.
BACKGROUND ART
As refractories for steel casting, into which molten steel at about 1500.degree. C. is poured, there has been used a graphite containing refractory composition of high thermal shock resistance. The refractory composition has a high thermal conductivity because of the contained graphite, and it allows a large amount of heat dissipation from the outer surface thereof. The graphite containing refractory composition is pre-heated before being used to prevent the generation of cracks due to abrupt thermal change; however, these prevention abilities are limited because the temperature is rapidly dropped for a period of time from the completion of heating to the beginning of casting.
To cope with the above problem, for example, Japanese Unexamined Utility Model Publications Nos. SHO 55-43616 and SHO 60-34354 disclose a method of attaching Al.sub.2 O.sub.3 --SiO.sub.2 or Al.sub.2 O.sub.3 --SiO.sub.2 --CaO based ceramic heat-insulating fibers on the surfaces of refractories. This method, however, is disadvantageous in that while the contained fibers provide high heat resistance and heat-insulation, the fibers, which have sizes in the order of several microns and are harmful to the human body, are set loose in the atmosphere when the heat causes loss of the binder.
As a means for obtaining a general heat-insulating structure in place of the above ceramic heat-insulating fibers, a monolithic refractory material mixed with organic fibers lost by heating may be proposed. However, to obtain a good heat-insulating effect with only organic fibers, a large amount of the organic fibers must be added, which has the disadvantage of significantly reducing the strength of the refractory material.
The subject to be solved by the present invention is to provide a heat-insulating refractory material, which does not contain environmentally and hygienically problematic ceramic heat-insulating fibers, only contains organic fibers to the extent necessary to improve adhesive rate upon spraying, and can nevertheless achieve a specified heat-insulating effect.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished under the basic premise that it becomes possible to achieve an excellent heat-insulating effect without any of the above disadvantages by coating a foaming material of high heat-insulating effect on the refractory surfaces of linings of an industrial furnace or the surfaces of refractories for steel casting, and then foaming the coated material by heating or by the heat of molten steel.
Namely, the present invention includes a heat-insulating refractory material, which is composed of a mixture containing 2-50 wt % of a foaming material foamed by heat at 400.degree.-1500.degree. C. and 50-98 wt % of a refractory powder, a liquid binder which is added to the mixture in an amount of 20-250 wt % on the basis of the weight of the mixture.
A glass powder softened and molten at 400.degree.-1500.degree. C. may be further added in an amount of 0.1-100 wt % on the basis of the above mixture; or organic fibers lost by heating, such as yarns, pulp cotton, or vinylon fibers may be further added in an amount of 0.01-5 wt % on the basis of the above mixture to enhance the adhesive rate upon spraying.
The foaming raw material may include shirasu, vermiculite, obsidian, pearlite, pitch stone, expanded shale, fly ash and the like. In particular, obsidian or pearlite is desirable to generate a number of bubbles by the addition of a small amount. The added amount of the foaming material is required to be in the range from 2 to 50 wt %. When it is less than 2 wt %, the foamed amount is insufficient to achieve the desired heat-insulating effect. When it is more than 50 wt %, the excessive foamed amount imperils the strength required for the heat-insulating refr
REFERENCES:
patent: 4446040 (1984-05-01), Samanta
patent: 4608087 (1986-08-01), Yoshino et al.
patent: 5252526 (1993-10-01), Whittemore
patent: 5360771 (1994-11-01), Delvaux et al.
Hagiwara Shozou
Hamaguchi Setsunori
Kawabe Hideaki
Kuga Koji
Bell Mark L.
Krosaki Corporation
Marcheschi Michael
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