JPS6138156B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to carbon-containing basic refractories. Carbon-containing refractories are difficult to wet with molten slag and have excellent heat-resistant spalling properties, so the scope of their use has been rapidly expanding in recent years. Carbon-containing basic refractories made by blending carbonaceous raw materials are attracting attention as materials with high corrosion resistance and spalling resistance, and are used as linings for electric furnaces, converters, ladles, secondary smelting furnaces, etc. It is well known that it has a good track record as a refractory. However, such carbon-containing basic refractories have poor bonding strength because their bond form is carbon bonds derived from phenolic resins, pitch, etc.
It has been observed that in locations subject to mechanical shock or severe abrasion of molten steel, the connective tissue of the refractory is destroyed, causing internal cracks in the refractory, resulting in peeling and wear. In order to improve the strength characteristics of such carbon-containing basic refractories, attempts have been made to add metals such as aluminum and silicon. It is true that the addition of these metals
The hot strength properties are improved, and the impact and abrasion resistance are improved, but when the metal is even slightly oxidized, the hot strength decreases rapidly, and the impact and abrasion resistance are improved. The effect almost disappears. The present inventor conducted various studies on methods for preventing the phenomenon in which carbon-containing basic refractories peel off due to cracks caused by mechanical shock, etc., and found that carbon or graphite fiber bundles were added inside the refractories. It has been found that by disposing the above-mentioned peeling wear and tear, the above-mentioned peeling wear and tear is significantly reduced. Conventionally, there have been examples of incorporating ceramic fibers into refractories, but it is difficult to disperse the fibers, and furthermore, the fibers are difficult to be fixed during blending in a stretched state, and they cannot be oriented in any direction. It was not possible to incorporate the fibers with the same amount of fiber, and the arrangement was not necessarily appropriate for stress, and the effect of adding the fibers was not sufficiently enhanced. Since these were used in the form of single fibers, this was an unavoidable problem. The fiber bundle used in the present invention is obtained by converging carbon or graphite long fibers manufactured from polyacrylonitrile, polyvinyl alcohol, coal tar pitch, etc., and has a secondary fiber diameter of 0.1 to 3 m/m.
It is within the range of Secondary fiber diameter is 0.1m/
If it is less than 3 m/m, the effect cannot be sufficiently improved, and if it exceeds 3 m/m, the filling property and structure will deteriorate, which is not preferable. It is appropriate to express the amount of such fibers added in terms of the number of fibers per cross-sectional area of the refractory, but in the case of the carbon-containing basic refractory according to the present invention, it is preferably 5 to 100 fibers per 100 cm ² of cross-sectional area. . A region of less than 5 fibers is not sufficient to improve the performance of the refractory, and a region of more than 100 fibers causes manufacturing problems and does not allow a refractory with good texture to be obtained. When arranging fiber bundles inside the refractory, it is preferable for one end to be located inside the furnace and container, such as on the molten metal contact surface, and for the other end to reach the cold end of the refractory, from the viewpoint of reinforcing effect. But that's fine. In addition, even if the fiber bundle is not continuous from one end to the other, if it is interposed from the inside of the furnace almost parallel to the cold end direction axis, it can be cut in the middle and made into multiple layers. But that's fine. The effect of the long fiber bundle according to the present invention is that it improves the bending strength or tensile strength of refractories, suppresses the occurrence of cracks due to mechanical stress, and also relieves stress in the fiber part and prevents the propagation of cracks. It is possible to prevent this. Therefore, in order to fully exhibit the above effects, it is necessary to have a strong bond between the fireproof aggregate and the fibers, and to satisfy this, a phenolic resin that has bonding properties with carbon or graphite fibers is required. , it is assumed that coal tar pitches are used as a binder. Here, the phenolic resin is obtained by reacting a phenol such as phenol, cresol, xylenol, resorcinol, etc. with an aldehyde such as formaldehyde under an acid or alkali catalyst. The aggregate used in the present invention is made by blending one or more basic raw materials such as magnesia, calcia, dolomite, and spinel with one or more carbon raw materials such as phosphorous graphite, earthy graphite, anthracite, and carbon black. However, the blending ratio of the carbon raw material is preferably in the range of 5 to 40 parts by weight from the viewpoint of refractory performance. In the present invention, the above-mentioned aggregate is kneaded by a conventional method using a carbonaceous binder such as a phenolic resin or coal tar pitch, and carbon or graphite fiber bundles are added during molding. The refractory according to the present invention can be formed by conventional uniaxial forming or isostatic press. The present invention is obtained by drying the above-mentioned molded product at 150 to 400°C or firing it at a temperature higher than that, and in the case of a molded product that undergoes a cooking process, it is impregnated with tar pit by a known method. There is nothing wrong with that. Examples are given below to explain the present invention in more detail. Example 1 Magnesia-graphite materials having the compounding ratio shown in Table 1 were kneaded using a conventional method, and then mixed using a friction press at 450 m/m×
When forming bricks of 150 to 130 m/m x 150 m/m, add a predetermined number of fiber bundles (length 450 m/m) with a secondary fiber diameter of 1 m/m, which are made by converging carbon fibers with a single fiber diameter of 12.5 μ. did.

[Table] After molding, dry at 250℃ for a day and night to produce unfired MgO-C.
Made quality bricks. Although there is no difference in quality after drying compared to additive-free products, the quality after reduction firing at 150°C, especially the bending strength, has been greatly improved. Further, even in severe spalling tests, the fiber additives according to the present invention have obtained good results.

[Table] Example 2 The Pitchbond magnesia-carbon mixture shown in Table 3 was heated and kneaded in a conventional manner, and after the kneading was cooled.

[Table] 2.5% of resol type phenolic resin was added to the outside, and the above formulation was secondarily kneaded at room temperature. When molding with a friction press after kneading (brick nizing:
450m/m x 150~130m/m x 150m/m), converging graphite fibers with a single fiber diameter of 10.5μ to create a secondary fiber with a diameter of 0.5
A predetermined amount of fiber bundles of m/m were added. After molding, it was fired at 1400°C in a reducing atmosphere, and then subjected to tar impregnation treatment. It has been demonstrated that the fiber additive according to the present invention has significantly superior strength properties and excellent resistance to mechanical stress such as impact.

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Claims (1)

[Claims] 1. Refractories for molten metal processing furnaces and container linings, including particle size-adjusted magnesia, calcia,
A carbon-containing basic refractory made by adding 5 to 40 parts by weight of a carbon raw material such as phosphorous graphite, anthracite, or carbon black to 60 to 95 parts by weight of a basic raw material such as dolomite or spinel, which has single fibers inside. A converged secondary fiber bundle of carbon or graphite fibers with a diameter of 0.1 to 3 mm or a net made of the fiber bundle is placed so that the longitudinal direction of the fiber bundle or the plane of the net is the axis from the inside of the furnace to the cold end side of the refractory. A refractory characterized in that 5 to 100 fiber bundles are arranged per 100 cm ² of cross-sectional area of the refractory so that they are substantially parallel to each other.