JPH0512063B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a coating material that is sprayed onto the inner circumferential surface of the lining of a tundish. (Prior Art) In tundishes used in continuous steel structures, a coating material is provided on the inner circumferential surface of the lining for the purpose of extending the life of the refractory lining and facilitating metal cutting. The conditions required for this coating material include not contaminating molten steel, not exploding during preheating, and having excellent corrosion resistance. For example, JP-A-52-62128 proposes a coating material in which an inorganic alkali phosphate salt and ceramic fiber are added to a basic refractory aggregate. This type of coating material has effects such as high corrosion resistance due to the basic refractory aggregate and explosion prevention due to the addition of fibers. (Problems to be Solved by the Invention) Traditionally, coating materials have been mainly applied by troweling, but recently spraying has become popular in order to speed up the work and ensure safety. Additionally, in order to improve the operating rate of tundishes, hot construction is carried out in which the inner lining is sprayed without being sufficiently cooled. Since spraying does not require a worker to enter the furnace, hot construction is becoming more popular as spraying becomes more popular. However, although there was no problem at room temperature, if the temperature of the lining surface was 100 to 300 degrees Celsius or higher,
With conventional coating materials, water vapor pressure causes them to swell and bulge inward. There was a problem that the blisters coarsened the coating structure and significantly reduced corrosion resistance. It is difficult to solve the above problem with the method disclosed in Japanese Patent Application Laid-Open No. 52-62128. (Means for Solving the Problems) The present inventors have conducted repeated research in order to solve the above-mentioned drawbacks in spray coating materials. As a result, when using powdered sodium silicate as a binder and adding slaked lime and magnesium sulfate as hardeners in a material made by adding a binder and short fibers to basic refractory aggregate, blistering occurs during high-temperature construction. We have completed the present invention by confirming that this does not occur. That is, in the present invention, 0.5 to 10 parts of powdered sodium silicate to 100 parts of basic refractory aggregate,
This is a tundish spray coating material consisting of a mixture of 0.05 to 7 parts of slaked lime, 0.05 to 7 parts of magnesium sulfate, and short fibers of slaked lime and a binder. The reason why the coating material of the present invention does not swell is because the water vapor generated by the residual heat of the lining dissipates from the voids formed by the short fibers.
This is to prevent swelling from occurring due to water vapor pressure. This is because it hardens quickly after spraying and develops strength earlier than conventional materials. FIGS. 1 and 2 are graphs of the results obtained by measuring the curing speed of magnesia based coating materials by changing the types of binders and curing agents based on the penetration depth. Figure 1 shows room temperature (20
Figure 2 shows measurements taken at temperatures up to 25°C (300°C). The time when the penetration became 10 mm or less was considered to be cured. The proportions of the binder and curing agent are both parts by weight relative to 100 parts by weight of the magnesia clinker aggregate. In the graph, the smaller the penetration, the greater the hardening of the coating material. A Binder: Powdered soda silicate 3 parts Hardening agent: Slaked lime 2 parts Hardening agent: Magnesium sulfate 2 parts B Binder: Powdered sodium silicate 3 parts Hardening agent: Slaked lime 4 parts C Binder: Powdered sodium silicate 3 parts Hardening Agent: Magnesium sulfate 4 parts As is clear from the graphs in Figures 1 and 2, it is confirmed that A, which is a combination of powdered sodium silicate, slaked lime, and magnesium sulfate, has the fastest curing speed. . This combination is shown below.
It is thought that the two reactions occur simultaneously and their synergistic effect promotes curing. Na ₂ O・nSiO ₂ ＋Ca(OH) ₂ ＋mH ₂ O →CaO・nSiO ₂・mH ₂ O↓＋2NaOH Na ₂ O・nSiO ₂ ＋MgSO ₄ ＋mH ₂ O →nSiO ₂・mH ₂ O↓＋Na ₂ SO ₄ ＋MgO↓ On the other hand, B to C have slow curing speeds and cannot be put to practical use. A combination of powdered sodium phosphate, slaked lime, and magnesium sulfate may be used as a binder other than the above, but as shown in Comparative Example 5, which will be described later, explosion occurs during preheating even when fibers are added. This is thought to be because the floating sodium phosphate component on the surface of the coating material forms a viscous coating due to preheating, sealing the surface of the coating material and closing the escape path for water vapor. Further, powdered sodium phosphate (NaPO ₃ ) is not preferable because it elutes P ₂ O ₅ which is a source of contamination of molten steel. The basic refractory aggregate used in the present invention is conventionally one or more selected from magnesia clinker, dolomite clinker, spinel clinker, lime clinker, and the like. A part of the material may be replaced with a refractory material other than the basic refractory aggregate, but this is not preferred from the viewpoint of cleaning the steel. Further, the magnesia clinker, dolomite clinker, etc. may be either synthetic or natural products. As usual, the particle size of the aggregate is adjusted to coarse, medium, or fine to make it suitable for spraying construction. The following additives are in proportion to 100 parts by weight of the basic refractory aggregate, and all units are parts by weight. Powdered sodium silicate (Na ₂ .nSiO ₂ ) serves as a binder. For example, since it does not contain P ₂ O ₃ like powdered sodium phosphate, it is preferable from the standpoint of cleaning molten steel. Types of powdered sodium silicate include sodium metasilicate, No. 1 sodium silicate, No. 2 sodium silicate, and No. 3 sodium silicate, and one or more selected from these can be used. If it is less than 0.5 parts, it will not be effective as a binder, and if it exceeds 10 parts, corrosion resistance will decrease. More preferably, it is 1 to 5 parts. The combination of slaked lime and magnesium sulfate acts as a hardening agent for the powdered sodium silicate. The ratio is 0.05 to 7 parts.
Less than 0.05 parts has no effect. When the amount exceeds 7 parts, there is almost no difference in effectiveness as a hardening agent, and corrosion resistance is reduced. More preferably, both are 0.1 to
There are 4 parts. Short fibers have the role of forming an escape path for water vapor.
No matter how strong the coating material is due to early curing, problems such as explosions may occur if there is no escape route for water vapor. The amount added and the specific material are not particularly different from conventional ones, for example, 0.05 to 5 parts. The specific material is one or more selected from organic or inorganic materials such as cotton, synthetic fiber, pulp, sepiolite, slag wool, ceramic fiber, and asbestos. The binder has the effect of imparting adhesion. For example, it is one or more selected from bentonite, fireclay, CMC, PVA, dextrin, sodium alginate, and the like. Preferably the addition ratio is
It is 0.1 to 8 parts. Further, in the present invention, other substances other than those mentioned above, such as borax as a crack prevention agent, alcohols as a dust generation inhibitor, etc., may be added within a range that does not impede the effects of the present invention. For spraying construction, a dry gun is used and water is added to create a slurry-like coating. The coating thickness shall be 5 to 50 mm. This coating material is removed every time the tandyshi is used.
Spray fresh. (Examples) Table 1 shows examples of the present invention and comparative examples thereof. Among the following tests, air permeability, porosity, presence of blisters, and presence of explosions were determined by using a dry gun to test a furnace material test tundish lined with alumina-silica monolithic refractory to a thickness of approximately 20 to 30 mm. Measurements were made on the sprayed coating material. In Table 1, *1 air permeability and *2 porosity were measured by cutting out a test piece from the sprayed coating material at room temperature and drying it. *3 Curing time is the time required for curing, with a kneaded material prepared by adding an appropriate amount of water at room temperature and having a penetration of 10 mm or less using a penetrometer. The time was measured. *4 The presence or absence of blisters was determined by spraying on the inner lining heated to a surface temperature of approximately 300°C using a gas burner and observing the presence or absence of blisters. *5 The presence or absence of explosions was determined by spraying at room temperature, preheating to approximately 1200°C with a gas burner, and observing whether explosions occurred at that time. *6 Corrosion resistance was determined by cutting out a test piece from the coating material sprayed at room temperature, and measuring the erosion loss size by a rotary erosion test using slag and molten steel as solvents. Table 1 shows an index with Comparative Example 5 set at 1.00, and the smaller the number, the larger the erosion dimension. *7 The evaluation method for P ₂ O ₅ content in steel is based on the actual
46 "Tandaiyu" spray coating,
in the steel obtained through the tundish
The amount of P ₂ O ₅ picked up was measured. As shown in the test results shown in the table, all of the examples of the present invention were free from blistering and explosion, and had excellent corrosion resistance. Furthermore, as shown by the results of the examples, it is also preferable in terms of cleaning steel. On the other hand, in Comparative Examples 1 and 2, the corrosion resistance was significantly inferior as a result of blistering. In Comparative Example 3, the proportion of magnesium sulfate was higher than the range of the present invention, and the corrosion resistance was poor. Comparative Example 4, in which short fibers were not added, and Comparative Example 5, in which powdered sodium polyphosphate was used as a binder, both exploded during preheating. Comparative example 5 further
Molten steel contamination due to elution of P ₂ O ₅ was observed.

【table】

【table】

[Table] (Results of the Invention) The present invention makes it possible to prevent blistering by using a binder and a hardening agent that do not contaminate molten steel. As described above, the present invention solves the problem of hot application of sprayed coating materials without contaminating molten steel, and has extremely great industrial value, such as improving the operating rate of tundishes and cleaning steel.

[Brief explanation of the drawing]

Figures 1 and 2 are graphs showing the curing speed of the compounded mixture using various binders and curing agents. Figure 1 shows construction at room temperature, and Figure 2 shows hot construction. .

Claims (1)

[Claims] 1 By weight, for 100 parts of basic refractory aggregate,
Powdered sodium silicate 0.5-10 parts, slaked lime 0.05-7 parts,
A tundish spray coating material consisting of a mixture of 0.05 to 7 parts of magnesium sulfate, short fibers and a binder.