JPH07277858A - Antioxidant for carbon-containing refractory - Google Patents

Abstract

PURPOSE:To improve the durability of carbon-contg. refractories for an immersion nozzle for continuous casting, a long nozzle, etc. CONSTITUTION:This antioxidant sticks to the surfaces of carbon-contg. refractories and prevents the oxidation of the carbon-contg. refractories in a hot state. This antioxidant is blended with low m.p. frit powder and 5-40wt.% silica powder based on the amt. of the antioxidant and the surfaces of carbon-contg. refractories are uniformly coated with vitreous layers made of the resultant blend so as to produce an oxidation preventing effect over the temp. region from a low temp. to a high temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to immersion nozzles and long nozzles for continuous casting of steel in the field of metallurgy, stopper rods, thermocouple protection tubes for continuous temperature measurement, and other carbon-containing refractories.

[0002]

2. Description of the Related Art A graphite-containing refractory such as a dipping nozzle for continuous casting is usually coated with a vitreous substance on its surface to prevent oxidation or delay oxidation of the graphite contained therein.

[0003]

However, when the glass material has a high viscosity and a strong cohesive force at the temperature of use, the contact angle with graphite becomes excessively large, and if it does, cohesive peeling occurs. Further, if the viscosity of the glass material is too low, the glass material melts and flows down, and its purpose cannot be sufficiently achieved. Further, the viscosity may decrease with time, and it was extremely difficult to stably use the graphite-containing refractory for a long time.

[0004]

The present invention has been made in view of the above points, and in order to solve the above-mentioned problems, the carbon-containing refractory is adhered to the surface thereof and the carbon-containing refractory in a hot state is contained. It is an antioxidant for preventing the oxidation of refractory material, wherein a frit powder having a low melting point is blended with the above antioxidant, and silica powder is added to the above antioxidant in an amount of 5 to 40% by weight. An object is to provide a characteristic antioxidant for carbon-containing refractory materials.

[0005]

When the antioxidant of the present invention is adhered to the surface of the carbon-containing refractory material, the antioxidant is mixed with the frit powder having a low melting point so that it is coated with the glass layer at about 500 ° C. of the operating temperature, and the low temperature range is maintained. Oxidation of carbon-containing refractories can be prevented.

Further, silica powder is externally added to the above antioxidant in an amount of 5 to 40% by weight to obtain 80% by weight.
When the glass layer is maintained on the surface of the carbon-containing refractory over a high temperature range of 0 to 1000 ° C. or more, an antioxidation effect is produced, and the carbon-containing refractory can be used for a long time.

[0007]

EXAMPLES The present invention will be described below based on examples. Antioxidants for carbon-containing refractories containing graphite such as continuous casting dipping nozzles and long nozzles, stopper rods, continuous temperature measuring thermocouple protection tubes, etc. of the present invention include a frit powder having a low melting point in the antioxidant. However, silica powder is externally added to the above antioxidant in an amount of 5 to 40% by weight.

As the frit powder, SiO ₂ 60 is used.
80 wt%, Al ₂ O ₃ 5~10 wt%, Na ₂ O2
.About.7% by weight, CaO 5 to 15% by weight, PbO 2 to 5% by weight, and the vitrification temperature is lowered to about 500.degree. C. to uniformly form a glass layer on the surface of the carbon-containing refractory material in a low temperature range. To be able to cover.

Further, the above-mentioned silica powder makes it possible to maintain the glass coating on the surface of the carbon-containing refractory material in a high temperature range, and the behavior of the melting point with respect to the added amount is shown in FIG.

As can be seen from FIG. 1, the silica melting region spreads to a high temperature region with the addition amount of silica powder, and the addition amount of silica powder is 5 to 40% by weight, preferably 2%.
About 0 to 40% by weight is practical.

FIG. 2 shows the time-dependent change in contact angle at 1200 ° C. of each particle size when 20% by weight of the above silica powder was added.

The contact angle of glass having a particle size of silica powder is in the range of about 60 to 120 degrees in which the adhesion is good,
As shown in FIG. 2, particles having a particle size of 50 μm or less react with the frit in a short time and the viscosity is remarkably increased, causing aggregation and peeling of the base material.

On the other hand, if the particle size is as large as 400 to 1000 μm, the reaction with the frit is insufficient and the viscosity is low, so that the particles flow down from the substrate.

Therefore, the particle size of the silica powder is 50 to 50.
Particles having a particle size of 400 μm are effective in maintaining good viscosity for a long time.

The above-mentioned antioxidant is mixed with an appropriate amount of sodium silicate water glass or an organic sizing agent, and water, and frit powder and silica powder are mixed uniformly to obtain a uniform mixture on the surface of the carbon-containing refractory. It can be applied, sprayed, or dip-attached in the shape of a circle.

[0016]

[Example of use] An antioxidant having a compounding ratio shown in Table 1 was applied to the surface of a long nozzle, which is a carbon-containing refractory used for continuous casting, and was used in an actual machine. One heat was 100 minutes, the long nozzle was preheated at 500 to 800 ° C. for 90 minutes before use, and then used for casting. The surface temperature at the time of casting was 900 to 1800 ° C, although it varied depending on the site.

Antioxidant effect comparison table

[Table 1]

In the present invention No. 1, 30% by weight of silica powder having a particle diameter of 50 to 400 μm was added to the above frit. After the use of 4 heats, the formation of the glass layer on the surface was good, so that 8 heats were used further,
A glass layer was uniformly formed on the surface with gloss, there was no pinhole, and no oxidation of the nozzle was observed.

Comparative Example No. 1 contained no silica powder, but after 4 heats were used, the glass layers were scattered little by little on the surface, and the nozzles were uniformly oxidized to about 10 mm. There was no antioxidant effect.

Comparative Example No. 2 was obtained by adding 30% by weight of silica powder having a particle size of 50 μm or less, after using 4 heats.
The glass layer is fluttered on the surface and the nozzle is 5-1
It has an oxide layer with irregularities of about 0 mm, and does not have an antioxidant effect.

Comparative Example No. 3 was obtained by adding 30% by weight of silica powder having a particle diameter of 400 to 1000 μm, and after using 4 heats, the glass layer was scattered around the silica powder on the nozzle surface. Since the nozzle has an oxide layer having irregularities of about 5 to 10 mm, it has no effect of preventing oxidation.

Although the long nozzle for continuous casting has been described above, the same applies to the immersion nozzle, stopper rod and the like.

[0023]

As described above, in the present invention, since the frit powder having a low melting point is blended with the antioxidant, it is coated with a glass layer at a temperature of about 500 ° C. to prevent the carbon-containing fire resistance in the low temperature range. It can prevent the oxidation of things.

Since silica powder is added to the above antioxidant in an amount of 5 to 40% by weight, 800 to 10
When the glass layer is maintained on the surface of the carbon-containing refractory over a high temperature range of 00 ° C or higher, the antioxidation effect is produced
The carbon-containing refractory can be used for a long time.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the addition amount of silica powder of the present invention and its molten state,

FIG. 2 is a time-dependent change state diagram of the contact angle of the particle size of the silica powder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuzo Mabune 2 Kawasaki Furnace Co., Ltd., 1576, East Offshore, Nakahiro, Ako City, Hyogo Prefecture

Claims (2)

[Claims] 1. An antioxidant which adheres to the surface of a carbon-containing refractory and prevents oxidation of the carbon-containing refractory in a hot state, wherein a frit powder having a low melting point is added to the antioxidant, Silica powder is externally applied to the above antioxidant in an amount of 5 to 40
An antioxidant for a carbon-containing refractory, which is characterized by being added by weight%. 2. The frit powder is a compounding ingredient of 60 to 80% by weight of SiO _2, 5 to 10% by weight of Al ₂ O ₃ , _{2 to} 7% by weight of Na ₂ O, 5 to 15% by weight of CaO, and _{2 to} 5% by weight of PbO. 20 silica powder with a particle size of 0.05-0.4 mm
~ 40 parts by weight, sodium silicate or organic paste,
The antioxidant for carbon-containing refractories according to claim 1, which is obtained by adding an appropriate amount of water and mixing the mixture.