JPS59232976A - Dry spray material for thermal repairment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry spraying material for hot repairs that has particularly excellent corrosion resistance.

Conventionally, various wet or dry spraying materials have been used for hot spraying repairs of metal smelting furnaces such as converters and electric furnaces, but conventional spraying materials have various drawbacks, including poor corrosion resistance. There is a drawback. In other words, wet spraying materials are made by adding anhydrous inorganic salts such as phosphates and silicates as binders to refractory aggregate whose particle size has been adjusted, and mixing it with water in a spraying claw to develop stickiness and make it adhere. However, because it contains a large amount of water, the refractory structure of the sprayed material becomes porous, deteriorating its corrosion resistance, and it also causes thermal spalling on the lining of converters, etc. There are drawbacks.

In addition, dry spraying materials include those using thermosetting resin powder such as phenol resin or urethane resin as a binder, those using a combination of the above resin powder and pitch powder such as coal pitch or petroleum pitch, magnesium sulfate, borosilicate, etc. There are known methods that use powdered water-containing inorganic substances such as sand that melt at relatively low temperatures. However, among the above, those using thermosetting resin powder have a large volatile content, low volatilization temperature, and low ignition temperature, so foaming and combustion occur during spraying, making the sprayed material fireproof. The disadvantage is that the material structure becomes extremely porous and corrosion resistance deteriorates. In addition, pitch powder has similar properties to thermosetting resins, although pitch has lower volatile content, higher volatilization temperature, and higher flammability temperature than thermosetting resins. However, like the above, it also has the disadvantage of becoming porous and deteriorating its corrosion resistance. In order to improve the above-mentioned disadvantages of using thermosetting resins and pitch, attempts have been made to suppress combustion by using N2 gas instead of air as a carrier gas, but this method has not been sufficiently effective. It has not been done. In addition, for products using powdered hydrated inorganic substances, since hydrated inorganic substances generally have a significantly higher melting temperature than thermosetting resins, it is necessary to It is necessary to use a large amount of the material, and in this case, since the nuclear material has a very high water content, there is a drawback that the water content in the structure increases during spraying, making it porous and reducing corrosion resistance.

In order to eliminate the above-mentioned drawbacks of conventional spray materials, the present inventor conducted intensive research on dry spray materials, and used pitch powder, which has less foaming and combustion than thermosetting resins. In addition, since the foaming phenomenon and the porous structure due to combustion cannot be avoided with pitch powder alone, we considered using inorganic salts that do not cause foaming and produce a highly viscous melt.In other words, inorganic salt melt The idea was to prevent pitch from foaming due to its high adhesive strength and to prevent υ combustion by coating the pitch with the melt.In this case, since the melting temperature of inorganic salts is very high, In this case, a sufficient amount of melt is not formed even in hot conditions, and certain measures are required to melt inorganic salts.

The present inventor further continued his research and discovered that the inorganic salts can be easily melted by compounding the inorganic salts and graphite. In other words, when considering the supply of heat to sprayed materials, radiation is considered to be the main source of heat transfer, so compared to the fire-resistant materials used for sprayed materials, the ability to absorb radiant heat is much higher, and the specific gravity is higher! By combining inorganic salts with graphite, which has a large specific surface area and absorbs a large amount of heat during spraying at the same particle size as fire-resistant materials, the melting heat of the inorganic salts is sufficiently supplied, resulting in foaming of the pitch. It was also found that the effect of preventing combustion phenomena was obtained, and the structure became denser. In addition, in order to compound inorganic salts and graphite, which are inherently less reactive, it is necessary to simultaneously grind and mix the two. Some of the mechanical energy generated is thermal energy μ
Energy, which is converted into chemical energy, was converted into adhesion energy, and it was discovered that inorganic salts and graphite adhere to each other. In fact, observation of the fine structure of the pulverized mixture of graphite and inorganic salts revealed strong adhesion between the two, indicating that the above treatment can simultaneously achieve adhesion and pulverization of graphite.

As a result of further research based on the above-mentioned various findings, the present inventor found that when specific amounts of pitch powder and the above-mentioned mixed pulverized material are used as a binder, it is possible to prevent the structure from becoming porous (the structure becomes densified). The inventors have discovered that by doing so, a dry spraying material with particularly excellent corrosion resistance can be obtained, and the present invention has been completed.

That is, the present invention provides a hot-temperature heating system characterized in that 8 to 80 parts by weight of pitch powder and 2 to 14 parts by weight of a mixed pulverized product of inorganic salts and graphite are blended as a binder to 100 parts by weight of refractory aggregate. Pertains to dry spraying materials for repairs.

The fire-resistant aggregate in the present invention is not particularly limited, and any materials commonly used for this type of spraying material can be used, such as magnesia, dolomite, lime, chromium, amiumina, spinet, carbonized silicon, waxite, silica,
Examples include chamotte, zircon, metal aluminum, metal silicon, etc., and one or more of these are used after adjusting the particle size. The particle size adjustment may be the same as the adjustment normally performed for this type of spray material, but just to be sure, to give an example, a particle size of about 5 to 1 mm may be adjusted to 0 to 6 mm.
It is common to use about 0% by weight, about 0 to 80% by weight of particles with a particle size of about 1 to 0.074 mm, and about 10 to 50% by weight of particles with a particle size of about 4 mm or less.

The pitch powder in the present invention has a fixed carbon content of 55
% by weight or more is preferable from the viewpoint of generating carbon pounds, and it may be either coal-based or petroleum-based. The particle size is preferably on the order of B mm or less. The amount used is 8 to 80 parts by weight per 100 parts by weight of the refractory aggregate.

If it is less than 8 parts by weight, adhesion will decrease due to insufficient liquid phase.
If the amount exceeds 80 parts by weight, the adhesion will decrease due to the flow-down phenomenon due to excessive liquid phase.

Examples of the graphite in the present invention include scale graphite, earthy graphite, and artificial graphite for electrodes, and at least one of these is used.

Moreover, the inorganic salts in the present invention include not only various salts conventionally used as binders but also inorganic acids such as boric acid. Anhydrous ones are preferable, but even those containing water can be used because the amount used is small and the structure does not become porous. For example, sodium hexametaphosphate, sodium acid pyrophosphate, sodium tetof polyphosphate, sodium monophosphate. borates such as boric acid, borax, sodium borate, potassium borate, lithium borate, silicates such as sodium metasilicate, sodium orthosilicate, amorphous sodium silicate, etc. At least one of these can be used.

In the present invention, it is necessary to use the above-mentioned graphite and inorganic salts in a composite form, which can be achieved by mixing and pulverizing the two. The mixing ratio of the two is about 2:1 to 1:10 by weight of inorganic salts: graphite.
This is preferable from the viewpoints of adhesiveness between the two and formation of a melt of inorganic salts. The method for pulverizing the mixture is not particularly limited and can be carried out by any known means, including a vibrating mill, which has a large pulverizing effect,
It is preferable to use a ball mill or the like. In addition, the grinding conditions such as grinding time vary depending on the equipment used and are not constant, but from the viewpoint of adhesion, it is recommended to grind the mixed pulverized material until it becomes a fine powder with a specific surface area of 10 m2/f or more. preferable.

Thus, 75 mixed pulverized products in which inorganic salts and graphite are firmly adhered! can get. The amount of mixed pulverized material used is 1 part fire-resistant aggregate.
The amount is 2 to 14 parts by weight per 00 parts by weight. If the amount is less than 2 parts by weight, the adhesion will decrease, and if it is more than 14 parts by weight, the structure tends to become porous, which is not preferable.

According to the dry spraying material of the present invention, by blending the mixed pulverized product of inorganic salts and graphite, the inorganic salts can be easily melted9, thereby preventing the foaming phenomenon and combustion of the pitch as described above. It is possible to prevent the refractory structure of the material from becoming porous (that is, the structure becomes dense), resulting in the remarkable effect of significantly improving corrosion resistance. Further, the dry spray material of the present invention is extremely good in terms of adhesion, strength, etc.

Therefore, the dry spraying material of the present invention can be used in converters, electric furnaces, AOD
It is extremely suitable for hot repair of metal refining furnaces such as furnaces, VOD furnaces, R* degassing vessels, DH degassing vessels, etc.

Hereinafter, the present invention will be explained in more detail with reference to Production Examples, Examples, and Comparative Examples.

Production example 1 Sodium hexametaphosphate and scale graphite 1:1.1:2
．． Mixed at a weight ratio of 1:4 or 1:81.
Put 5 kF into a vibration mill (manufactured by Chuo Kakoki Co., Ltd., batch type), and set the vibration motor amplitude to 6 mm and rotation speed to 170 rpm.
(capacity: 2.2 kW) for about 2 hours. The specific surface area of the obtained mixed pulverized product is shown in Table 1 below.

Table 1 Examples 1 to 14 and Comparative Examples 1 to 6 Spraying the present invention or comparative dry spray materials (numbers in the tables indicate parts by weight) having the formulations shown in Tables 2, 8, and 4. was sprayed using a gun onto magnesia panel bricks in an experimental furnace whose internal temperature was maintained at 1200°C. In order to examine the adhesion of each sprayed material, the adhesion rate to the panel bricks during spraying was measured, and the adhesive strength with the panel bricks after spraying was determined.

Furthermore, the sample /1/ after spraying was collected to determine the density of the structure.
Compressive strength and corrosion resistance were investigated. The test method is shown below.

0 adhesion rate... Recover the rebound loss and measure the weight,
It was calculated according to the following formula.

0 Adhesive strength: Based on the following criteria.

○: Very strong (does not peel off even when hit with a small hammer)
.

△: Intermediate (peel off when hit with a small hammer).

×: Weak (peels off when touched).

0 porosity: Measured according to JIS 2205.

0 Water absorption rate: Measured according to JIS R2205.

O apparent specific gravity: Measured according to JIS R2205.

Zero force specific gravity: Measured according to JIS R2205.

O compressive strength: Measured according to JIS Ordinary 2206.

O Corrosion resistance test: A sample with a shape of 40 x 40 x 115 mm was used as the lining of a high frequency induction heating furnace, and
The maximum melting thickness in the 40 mm direction when held at ℃ for 8 hours (mm) is shown. As the slag, 2 kg of converter slag was used.

The results of each test are shown in Tables 5, 6 and 7.

As is clear from Tables 5, 6, and 7, the dry sprayed materials of the present invention have better adhesion, are denser, and are particularly superior in corrosion resistance and strength than the comparative materials. You can see that

Further, with the dry spraying material of the present invention, no pitch foaming phenomenon or burning was observed during spraying.

Next, using each dry spraying material of Example 6 and Comparative Example 2,
Table 8 shows the results of actual use in a top-blowing converter.

As shown in Table 8 and above, the dry sprayed material of the present invention has particularly excellent corrosion resistance, adhesion, strength, etc. compared to conventional materials, and therefore has significantly improved durability. That is clear.

(that's all)

Claims (1)

[Claims] ■ 8 to 8 parts by weight of pitch powder per 100 parts by weight of refractory aggregate.
Mixed pulverized product 2 to 14 of 30 parts by weight and inorganic salts and graphite
A dry spraying material for hot repairs characterized by containing a weight part as a binder. (2) The dry spray material for hot repair according to claim 1, wherein the inorganic salt is at least one of phosphate, boric acid, borate, and silicate.