GB2101985A

GB2101985A - Refractory sealing material

Info

Publication number: GB2101985A
Application number: GB08120830A
Authority: GB
Inventors: Masaru Takashima
Original assignee: Aikoh Co Ltd
Current assignee: Aikoh Co Ltd
Priority date: 1981-07-06
Filing date: 1981-07-06
Publication date: 1983-01-26
Also published as: GB2101985B; DE3127556A1; AU7445281A; SE8104268L

Abstract

A refractory sealing material comprises 50 to 90% by weight of refractory fillers having a particle size of less than 0.1 mm in terms of dry content 1 to 10% by weight of refractory fibrous materials, and 9 to 50% by weight of plasticizers, and the mixture is molded into the form of board or film after a suitable able amount of a liquid has been incorporated.

Description

SPECIFICATION Refractory sealing material The invention relates to refractories, and particularly to a refractory sealing material which is used to fill in voids in the linings of furnaces and vessels in which molten metals are treated.

In a conventional method of filling up such voids or gaps there is used a pastry mixture in which mortar, i.e. powdery refractory, is mixed with a binder and water and they are kneaded.

The pastry mixture is filled into the voids or gaps where it is dried maturally or by heating. Since the mixture produces water when drying, however, cracks are likely to occur. Further, such a filler is inferior in hot strength to the circumferential lining material so that an erosion occurs at the joints. Such erosion is particularly bad in vessels which are brought into contact with molten metal. In those parts of a tundish where molten metal flows ingress of the melt into joint portions of the tundish is generally prevented by applying a board-like joint filler to the seams of the lining board. However in such a method an adhesive is applied between the solid surfaces.

This does not usually give a sufficiently good seal.

The object of the invention is to prevent as much as possible the life of the lining from becoming short, which is caused by shrinkage or release, by overcoming the weaknesses of the conventional mortar or joint board adhesion and using a plastic, board- or film-like refractory filler when filling up the voids or gaps thereby to bring the solid surfaces into a closer contact.

Accordingly, the present invention provides a refractory sealing material in the shape of a board of a film which homogeneously contains 50 to 90% by weight of one or more refractory fillers selected from silica, siliceous sand, olivine, chamotte, alumina, corundum, mullite, magnesia, dolomite, spinel, chromite, zirconia, titania, zinc oxide, brick and slag, each having a particle size of less that 0.1 mm in terms of dry material, 1 to 10% by weight of one or more refractory fibrous materials selected from asbestos, rock wool, slag wool, glass wool, kaolin fiber, alumina fiber, magnesia fiber, silicon carbide fiber and carbon fiber, and 9 to 50% by weight of one or more plasticizers selected from water glasses, kibushi clay, gairome clay, kaolin, bentonite, starch, dextrin, glue, gum arabic, resins, latex and rubbers; together with a suitable amount of one or more liquids selected from water, alcohols, esters and hydrocarbons and suitable for kneading and moulding the resultant mixture into a board or a film.

The refractory fillers in the composition of the invention provide a pressure resistance and improve the heat resistance by coating the surface of said refractory fibrous materials. Said fillers are suitably selected, depending on the molten metals which is to contact the refractory, from acid refractories such as siliceous sand, silica, zirconia and titania; neutral refractories such as chamotte, alumina, corundum, mullite, olivine and chromium oxide; basic refractories such as magnesia, dolomite, spinel and zinc oxide; and the powders of brick and slag based thereon.

Preferably the particle size is smaller because of easier formation of uniform structure when the product is formed, but with particle sizes of less than 0.1 mm it is possible to maintain the structure almost uniform and roll it sufficiently thinly to form films. If the content of the refractory fillers is less than 50%, the refractory property of the product is insufficient thereby shortening the life of the product, while if the content of the refractory filler is in excess of 90% the content of fibrous materials relatively decreases whereby the anti-collapsible property is lowered to an unacceptable extent.

Further, the refractory fibrous materials are provided to link the interspaces between the aggregate particles thereby to prevent collapse of the product in an atmosphere of molten metal or gas whereby the life of one-continuous-continuous casting is completed. The fibres are more effective as their length increases. Provided they are more than about 2 mm long they give acceptable results from the cost and practical use points of view. Furthermore, most preferably different kinds of refractory fillers of the invention are chosen depending on the kind of acid, neutral or basic property of aggregate, but the refractory fibrous materials can be used any time and if the temperature is not so high they may be selected only in consideration of cost.That is, refractory fibrous materials can be selected from the less expensive fibers such as asbestos, rock wool, slag wool and glass wool as well as from the expensive and high heat-resistant fibers such as kaolin fiber, alumina fiber, magnesia fiber, silicon carbide fiber and carbon fiber. If the content of the refractory fibrous materials excess 10% this may either impede the heat resistance of the aggregate or stop the improvement of the refractory property owing to the nature of the fibrous materials, so that more than 10% content thereof is not suitable, while with less than 1% of refractory fibrous materials the fibrous materials are not sufficient to perform their role of linking the aggregate particles thereby accelerating a collapse of the product so that less than 1% content is also unsuitable.

Furthermore, plasticizers are added in order to make the product soft and workable so that it can be worked into joints or voids of different shapes. The plasticizer gives a flexibility to the product through a roll extruder or a suction type dewatering molding machine, with the plasticizer as it is or by heating it or adding a liquid such as water or organic solvent thereto thereby presenting a softness (i.e. plasticity) to the product. Therefore, the product does not fracture when it is bent or folded, and when it is applied to uneven surfaces of voids or gaps it closely contacts these surfaces without creating voids. The plasticizer according to the invention has a property which scarcely changes the volume of the product even when preheated.In the plasticizer of the invention there are homogeneously dispersed, with liquids, by mixing, water glass, chlorides of alkali metals or alkaline earth metals, water-soluble phosphate, clay, kaolin, bentonite; and starch, dextrin, glue, gum arabic, water-soluble resins, solvent-soluble resins and rubber; and high polymer compounds belonging thereto, petroleum products and dry distilled products of coal. The liquid may either be removed by drying or left as it is.

If less than 9% of plasticizer is used, a satisfactory softness is not imparted to the product, and if more than 50% of plasticizer is used the refractory property of the product is lowered so that it is not suitable.

The liquids added when mixing the materials may be water, alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, glycerol and glycol, esters such as ethyl acetate, amyl butyrate, ethyl butyrate and amyl acetate, ketones such as acetone and methyl ethyl ketone, and hydrocarbons such as gasoline, kerosene, benzene and toluene. Their kind and additive amount are determined depending on the softening degree sought under the adhesive condition when used and on the mixing properties exhibited by the materials.

The use of the sealing materials of the present invention affords protection for the refractory materials lining vessels for treating molten metals and avoids waste of fuels as well as uneven heating within heating chamber.

The refractory sealing material according to the invention is prepared in such a way that predetermined amounts of the refractory fillers and refractory fibrous materials are mixed, with the addition of a plasticizer if it is powdery, it is heated or it is added as it is gradually with the liquids, and at the time when the plasticizer has been uniformly mixed the mixture is molded in the form of board or film by rolling, or by means of extruder or suction type dewatering forming machine and then the molding is cut in proper length.If the plasticizer is solid it may be heated, while if heating is impossible (such as in thermosetting resins) a small amount of organic solvent is added to dissolve the solid or make it a coiloidal liquid, and said liquid is mixed dropwise little by little at the same time as mixing the refractory fillers and the refractory fibrous materials. The mixture thus made is extruded as in the above method and the extruded article is cut in the form of board or film. If the plasticizer is water, other solution or emulsion a mixture of solid or powdery materials is gradually added to the plasticizer while being mixed. If necessary they are further mixed with liquid so as to regulate the hardness. Molding is carried out in the same way as the above method. If the product is to be used for packing, or such like, the packing can be punched or cut out of the board or film in a desired size or shape.

The present invention will now be illustrated by the following Examples.

Table 1 shows a number of compositions in accordance with the invention and two Comparative Examples. In the Table, materials other than liquids are expressed as weight percent in terms of dry content, the liquids are expressed as parts by weight relative to solid content, and the Comparative Examples as parts by weight.

TABLE 1

Comparative Comparative No.1 No.2 No.3 No.4 No.5 Example 1 Example 2 Siliceous sand - - - 70 52 Chamote - - 65 - - Mixed and Refractory kneaded as Alumina 55 - - - - 100 parts fillers in Example Magnesia - 60 - - 1 Zircon Flower - - 10 15 Asbestos 10 - - - Refractory Rock woll - 8 - - 2 fibrous Kaolin fiber - - 4 - materials Silicon Carbide fiber - - - 1 50%aqueous solution - - - 14 of sodium polyacrylate Grains of polyethylene 15 - - - 30 Plasti- 40% vinyl acetate - - 21 - cizers emulsion Powder of vinyl chlo- 20 - - - ride Natural rubber 28~ - 32 - - 16 Be MgCl2 60 parts water - - - 30 N-hexane - 20 - - liquids Benzole - 30 - - 40 Methyl ethyl ketone 30 - - - Methanol 20 - - - 500x 500x Packing 500x Film of 500 x 100 x 5mm 100x 100x of 200 100x 100 mm board.

5mm 5 mm (outside 5 mm (wide) produced in the board board diameter) board x 2 mm sequence of mix/ Shape of products x 100 (thick) ing, kneading, Mortar (inside molding, drying, diameter) and calcinig at and 3mm 500~C thickness The refractory sealing material of Examples 1, 2 and 4 in the form of a board was adhered onto a lining moistened with an aqueous solution of water glass, at a seam portion of magnesia lining boards of a 30 ton tundish for continuous steel casting, and the sealing material was preheated at 900"C. After the melt was poured in four-continuous continuous casting from a 200 ton ladle the tundish was shifted to a consolidating process. At this time the amount of wear of the lining board was observed and the influence on the permanent lining material at the lower portion was inspected every ten cycles. It was found that the molten steel did not erode in any way into the lower permanent lining material. In Comparative Example 1 there was inspected, also in ten cycles, a seal in which the seam of a lining material was filled up with a magnesia cement. The result was that the seam portion was always eroded thereby to require repair of the lower permanent lining material.

Further, at a 200 ton ladle above said tundish an argon bubbling was carried out by a porous plug, a packing board of the refractory sealing material of Example 3 was used to seal the bottom surface of the porous plug, and the porous plug was replaced. Even at regular 8 charge the sealing portion was hardly cracked at the end of the process.

A mixed and kneaded article according to Comparative Example 2 without molding as in Comparative Example 1 was applied, as mortar. to the joint with said porous plug, when it took the working time mor than 5 times.

The inspection result remained almost unchanged.

Claims

1. A refractory sealing material in the shape of a board or a film and comprising 50 to 90% by weight of a refractory filler having a particle size of less than 0. 1 mm in terms of dry content, 1 to 10% by weight of a refractory fibrous material, and 9 to 50% by weight of a plasticizer, together with a liquid suitable for kneading and then moulding the said materials into a board or a film.

2. A refractory sealing material according to Claim 1 wherein the refractory filler is one or more materials selected from silica, siliceous sand, peridotite, chamotte, alumina, corundum, mullite, magnesia, spinel, chromium oxide, zirconia, titania, zinc oxide, brick and slag.

3. A refractory sealing material according to Claim 1 or 2, wherein the refractory fibrous material is one or more materials selected from asbestos, rock wool, slag wool, glass wool, kaolin fiber, alumina fiber, magnesia fiber, silicon carbide fiber, and carbon fiber.

4. A refractory sealing material according to Claim 1, 2 or 3, wherein the plasticizer is one or more materials selected from chlorides of alkali metals or alkaline earth metals, water-soluble phosphates, clay, kaolin, bentonite; starch, dextrin, glue, gum arabic, water-soluble resins, solvent-soluble resins, insoluble resins, rubbers; and high polymer compounds belonging thereto, petroleum products and dry distilled products of coal.

5. A refractory sealing material according to any one of Claims 1 to 4, wherein the liquid .s one or more liquids selected from water, alcohols, esters, ketones and hydrocarbons.

6. A refractory sealing material according to Claim 1 substantially as described in any one of the foregoing Examples.