JPH0463033B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a coating material for a lining base material in a tundish for continuous casting. [Prior art] Dry spraying method, A coating of basic refractory material is applied using a wet spraying method, troweling method, etc. In recent years, there has been an increasing demand for increasing the continuous casting ratio in the steelmaking process, improving the quality of steel, and extending the life of tandem lining materials. In order to reduce this, efforts are being made to improve insulation and reduce weight. Light-weight heat-insulating coating materials have lower thermal conductivity than conventional high-density coating materials, and this heat-insulating effect provides benefits such as extending the life of the base material and improving disassembly by making metal removal easier. At the same time, it is possible to reduce the amount of use due to the weight reduction, and it is also possible to reduce the overall cost of the tundish. Conventionally, the following measures have been mainly taken to reduce the weight of this coating material. One method is to use a foaming agent in combination with the refractory material to generate foam in the matrix during kneading with water, thereby lowering the bulk specific gravity of the material. Used as a material for wet spraying. The other type uses organic or inorganic fibers in combination to achieve a low bulk specific gravity by dispersing the fibers in the matrix, and is mainly used as a material for dry spraying methods. However, conventional weight reduction measures all involve creating voids in the coating material matrix to lower the bulk specific gravity of the entire material, which causes problems such as structural deterioration of the matrix, lack of strength, and reduced corrosion resistance. There are limits to weight reduction. For this reason, improvements have been made in foaming systems by making the foam finer using foam stabilizers and the like, and in fiber systems by using short fibers, but neither of these efforts has led to a sufficient effect. Therefore, recently, there have been attempts to reduce the weight of the coating material by reducing the weight of the aggregate itself, as described in, for example, Japanese Unexamined Patent Publication No. 62-252363. [Problem to be solved by the invention] However, conventional lightweight aggregates have a large average pore diameter and low strength, so there is a problem that they turn into powder during mixing or transportation. When used as a material, there is a drawback that rebound loss increases. The purpose of the present invention is to solve the problem of pulverization due to low strength when using lightweight aggregate when reducing the weight of tundish coating materials, and to provide lightweight aggregates with excellent heat insulation properties and excellent penetration resistance from slag and molten steel. The object of the present invention is to provide an ultra-lightweight coating material that can reduce the baking reaction with the base material. [Means for Solving the Problems] The coating material of the present invention uses lightweight magnesia aggregate with a bulk specific gravity of 2.0 or less, an average pore diameter of 10 μ or less, and a firing temperature of 1450°C or more. This has achieved weight reduction that exceeds the limits of insulation insulation weight reduction. [Function] The present invention replaces part or all of conventionally used aggregates with a bulk specific gravity of 2.5 to 3 or more, such as magnesia clinker, spinel clinker, and dromica clinker, with a lightweight magnesia aggregate with a bulk specific gravity of 2.0 or less. As a result, lightweight insulation can be achieved using aggregate particles, making it possible to achieve lightweight insulation while maintaining matrix density, improving performance such as corrosion resistance and strength compared to conventional lightweight insulation coating materials. It is something that Furthermore, by mixing the coating material of the present invention with conventional foamed or fiber-containing coating materials, it becomes possible to achieve lightweight insulation that exceeds the previous limits. The bulk specific gravity of the lightweight magnesia aggregate to be blended is 2.0.
Must be below. Moreover, if the size is larger than that, the effect of weight reduction will be small. In addition, in order to maintain sufficient slag resistance and molten steel penetration resistance by applying the coating material, the average pore diameter must be 10μ or less, and the aggregate must not collapse during mixing or transportation. In order to provide sufficient strength and stabilize workability, the firing temperature must be 1450°C or higher. If the firing temperature is lower than 1450℃, as shown in Table 1, there will be no strength, so the spraying workability will not be stable, the limit usage amount of lightweight magnesia will not exceed 60%, and the bulk specific gravity of the construction object will be insufficient. does not decrease. On the other hand, if the firing temperature is set to 1450°C or higher, good spray workability can be obtained even if 100% lightweight magnesia is used, and bulk specific gravity can be significantly reduced (lightweight insulation). In addition, when the average pore diameter exceeds 10μ, as shown in Table 2, in products made of 100% lightweight magnesia,
Despite the effect of lightweight insulation, the large pore size facilitates the penetration of slag components and molten steel, resulting in an increase in the amount of erosion loss, and the thickness of molten steel and slag that has not penetrated is thin. It is also inferior to lightweight insulation types (fiber-based). On the other hand, those with an average pore diameter of 10μ or less can suppress the penetration of slag components and molten steel, and can exhibit better insulation effects and corrosion resistance than conventional lightweight insulation types (fiber-based). The strength of the aggregate is 0.5 with a particle size of 3.0 mm or less.
When a cylinder with a diameter of 50 mm is filled with aggregate of 50 mm or more in size and a load of 100 kg/cm ² is applied using a compression tester, it is preferable that the pulverization rate is 50% by weight or less as the amount passing through 32 meshes. . Further, the above-mentioned coating material of the present invention can be used alone, but it can also be used in combination with one or more types of aggregates such as fused magnesia clinker, seawater magnesia clinker, and calcined natural magnesite clinker. Of course, it is also possible to use the above-mentioned foaming and fiber-based insulation and weight reduction. In order to achieve the weight reduction effect by using the coating material of the present invention in combination with the above-mentioned aggregate, it is necessary to mix at least 10% by weight of the lightweight magnesia aggregate having the above-mentioned characteristics. The use of the above-mentioned lightweight magnesia aggregate is 10 out of the total amount.
If it is less than % by weight, there is a problem in terms of the effect of lightweight insulation, and there is no effect of the blend, but even if all of the conventional aggregate is replaced, there is no problem in terms of slag penetration resistance and corrosion resistance. . When the coating material of the present invention is used as a dry spraying material, the particle size of the magnesia aggregate needs to be 1.5 mm or less in order to suppress ribald loss during spraying construction. When using the coating material of the present invention as a troweling or wet spraying material, the particle size of the magnesia aggregate must be 5 mm or less in terms of workability of troweling or suppression of ribaud loss during wet spraying. Therefore, the effect of lightweight insulation can be increased by using a foaming agent in combination. When preparing the coating material of the present invention, a binder, a curing agent, a thickener,
This is done by adding and mixing fibers. As the binder, one type or a combination of two or more of various phosphates such as various sodium phosphates, calcium phosphates, magnesium phosphates, potassium phosphates, and aluminum phosphates, and various silicates such as sodium silicate, potassium silicate, and lithium silicate are used. . As the hardening agent, one or a combination of two or more of calcium hydroxide, calcium carbonate, gypsum, Portland cement, alumina cement, magnes lag, dicalcium silicate, various calcium phosphates, etc. is used. Further, as the fibers used in the present invention, one type or a combination of two or more types of organic fibers such as cotton, synthetic fiber pulp, and paper, and inorganic fibers such as ceramic fibers, glass fibers, and asbestos are used. In particular, as thickeners used in troweling and wet spray coating materials, various clays, organic glues, various silicates, phosphates, etc. are used, and as blowing agents, for example, lignin sulfonic acid, etc. is used. [Example] Example 1 Table 4 shows that, as a dry spraying material, the aggregate part was composed of a combination of lightweight magnesia A and B shown in Table 3 with particle size adjustment and seawater magnesia clinker with particle size adjustment. Binder:Curing agent is 2:1, the amount added is changed depending on the volume of the aggregate part, and the minimum amount of organic fiber necessary for workability or lightweight insulation is mixed. M
After spraying, it was dried in a dryer at 110°C for 24 hours. The quality of this sample was measured according to JIS-R2205 and JIS-R2213. Next, add a similar sample to the first
It was set on the lining of a high frequency induction furnace as shown in the figure. In the figure, 1 is a sprayed material sample, 2 is a C/S=1 slag, 3 is pig iron, 4 is MgO stamp material, and 5 is Kosil. Slag with C/S=1 and 7kg of pig iron are heated to 155℃ in a high frequency induction furnace with this lining.
After holding for 3 hours while replacing 300 g of slag every 30 minutes, the slag line erosion rate and penetration of slag and molten steel were observed. As seen in Table 4, D
In the case of ~H and K~M, a sufficient weight reduction effect can be seen, whereas in the case where no lightweight magnesia is mixed at all or the amount of lightweight magnesia aggregate is small (conventional example C) , weight reduction is not sufficient. In the fiber-based lightweight insulation type (Conventional Example B), compared to the conventional type (Conventional Example A), the unpermeated thickness of slag and molten steel increases due to the lightweight insulation, but a decrease in strength is observed. On the other hand, the type (Example D) that uses the minimum amount of organic fiber necessary for workability (same as the conventional type) and uses 20% lightweight magnesia A has almost no decrease in strength or deterioration in erosion resistance, and is lightweight and insulating. The effect is the same as that of the conventional lightweight insulation type. This shows that a lightweight insulation effect can be obtained while maintaining the density of the matrix structure. Also,
20% less lightweight magnesia A in the same material system
Although the loss rate increased slightly by using the above, the effect of lightweight insulation was further increased (Example E,
F). At this time, the particle size of magnesia A is set to 2
When the thickness was less than mm, rebound loss increased and workability decreased (Examples G and H). Lightweight magnesia B
In the types using (Comparative Examples I and J), since the firing temperature of lightweight magnesia is low, the strength of the clinker itself is low, and the bulk specific gravity of the spray-formed sample decreases little, so the lightweight insulation effect is small. Furthermore, because the average pore diameter was large, the erosion rate increased. By combining lightweight magnesia A with conventional technology (fiber insulation) (Examples K, L, M), it is possible to reduce the weight beyond the previous limits, and the decrease in strength and erodibility is also lower than that of conventional lightweight insulation types. Similarly, it can withstand use in an actual furnace. This resulted in a significant reduction in basic unit consumption and a heat insulating effect. Example 2 Table 5 shows examples in which the coating material of the present invention was used as a wet spray material. As in the case of Example 2, a binder, a thickener, or a foaming agent was added to the aggregate composed of a combination of lightweight magnesia A whose particle size was adjusted as shown in Table 3 and seawater magnesia clinker whose particle size was also adjusted. Mixtures N to T containing the minimum amount of organic fiber necessary for workability are mixed with a mortar mixer for 3 minutes using a mortar mixer with the amount of water necessary to obtain workability, and then mixed with a pressure feeder to the tip of the nozzle. send the materials,
After blowing the material away with air at the tip of the nozzle and spraying it onto the designated metal frame, it is dried in a dryer at 110℃ for 24 hours. This sample is JIS-
Quality was measured according to R2205 and JIS-R2213.
Next, a similar sample was set on the lining of the high frequency induction furnace shown in Figure 1, and C/S = 1 slag and 7 kg of pig iron were added.
After melting at 1550°C and holding for 3 hours while replacing 300 g of slag every 30 minutes, the slag line erosion rate and penetration of slag and molten steel were observed. Here, as in the case of the dry sprayed material of Example 1, compared to the conventional type (Conventional Example N), the types (Examples O, P, Q) in which lightweight magnesia A was replaced with normal seawater magnesia, There was only a slight decrease in strength and an increase in the rate of erosion, and the lightweight insulation effect was improved. At this time, the particle size of lightweight magnesia does not need to be 1.5 mm or less unlike dry spraying, and by combining it with conventional technology (foam insulation) (Examples S and T), it is possible to achieve lightweight magnesia that exceeds the previous limit. It became possible to

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〔Effect of the invention〕

The lightweight heat-insulating tundish coating material of the present invention can have the following effects. B. Compared to conventional products, it has excellent penetration resistance of molten steel, improves corrosion resistance, or when used in combination with conventional technology, improves the heat insulation effect, has a large effect in reducing the basic unit, and reduces seizure to the base metal. The effect of reducing the amount of heat and contributing to extending the life of the base material is also extremely large. (b) Magnesia clinker, which was previously used,
By replacing part or all of an aggregate with a bulk specific gravity of 2.5 to 3 or more, such as spinel clinker or dolomite clinker, with a lightweight magnesia aggregate with a bulk specific gravity of 2.0 or less, lightweight heat insulation can be achieved using aggregate particles. It is possible to make lightweight insulation while maintaining the density of magnesia, improving performance such as corrosion resistance and strength compared to conventional lightweight insulation coatings. (d) By using it in conjunction with conventional foam and fiber-based lightweight insulation, it becomes possible to achieve lightweight insulation that exceeds previous limits.

[Brief explanation of drawings]

FIG. 1 shows a schematic cross-sectional view of a lining set of a high-frequency induction furnace used for evaluation tests of slag erosion and slag/molten steel permeability.

Claims (1)

[Claims] 1. A lightweight heat-insulating tandice coating material made of lightweight magnesia aggregate with a bulk specific gravity of 2.0 or less, an average pore diameter of 10 μ or less, and a firing temperature of 1450°C or higher. 2 At least 10% by weight of lightweight magnesia aggregate with a bulk specific gravity of 2.0 or less, an average pore diameter of 10μ or less, and a firing temperature of 1450°C or more, one or two types of fused magnesia clinker, seawater magnesia clinker, and natural magnesite fired clinker. A lightweight heat-insulating tandice coating material made by mixing up to 90% by weight of the above aggregates. 3. The lightweight thermal insulation tandice coating material according to claim 1 or 2, characterized in that the particle size of the lightweight magnesia aggregate is 1.5 mm or less, and is constructed by a dry spraying method. 4. A lightweight heat insulating tan according to claim 1 or 2, characterized in that the particle size of the lightweight magnesia aggregate is 5 mm or less, a foaming agent is used in combination, and is constructed by troweling and wet spraying methods. Dateshi coating material.