JPH1024358A - High air-tightness packing material for refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sealness of joining part of nozzles and to prevent the invasion of the air over the whole casting by using a high air-tightness packing material composed of at least one or more kinds of refractory powder and fibers and adding a specific quantity of metal having high m.p. and high combination with oxygen to the refractory. SOLUTION: The high air-tightness packing material for refractory composed of at least one or more kinds of refractory powder and fibers and adding 0.1-50wt.% metal having high m.p. and high combination with the oxygen, is used. By the constitution, since the sealness between the nozzles is improved and the effect is continued, the oxidation of molten steel is prevented over the whole casting time, and the quality of a cast slab is improved and the yield is improved. Further, various unsteady operations caused by the clogging of nozzle can be eliminated and the good operability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packing material interposed between refractory materials to prevent air from penetrating into a molten metal.

[0002]

2. Description of the Related Art In continuous casting of steel, the supply of molten steel from a tundish into a mold is shifting from a stopper system to a sliding nozzle system having a high flow rate controllability. In the case of the sliding nozzle method, the nozzle on the tundish, the sliding nozzle,
It is composed of an intermediate nozzle and an immersion nozzle, and a packing material is used at the joint between the nozzles to prevent air from entering.

When the nozzles are joined to function as one system, the role of the packing material is extremely important. If a sufficient sealing effect cannot be obtained, air may enter from between the nozzles to oxidize molten steel. Problems arise. For this reason, as described in Japanese Patent Publication No. 60-15592, a packing material to which a low melting point metal such as Al is added has been developed for the purpose of enhancing the sealing property of the packing material. It has a certain effect.

[0004]

When a low melting point metal is added to a packing material, the metal melts during use and reacts with oxygen in the air that has permeated the packing material, so that the sealing property of the packing material is improved. . However, if Al is used as the low melting point metal, for example, a strong Al ₂ O ₃ oxide film is formed on the surface of Al with the elapse of the casting time, and the diffusion of oxygen is inhibited, so that the oxidation reaction stops. For this reason, the sealing property of the packing material is high in the early stage of casting, but after the casting time has elapsed, the addition of Al is no longer possible.
Sealability is reduced.

In view of these problems, an object of the present invention is to provide a packing material capable of improving the sealing performance of a nozzle joint and preventing air from entering the entire casting.

[0006]

SUMMARY OF THE INVENTION The present invention comprises at least one kind of refractory powder and a fiber, and comprises a metal having a high melting point and a high oxygen binding property in an amount of 0.1 to 50% by weight. The present invention relates to a highly airtight packing material for refractories characterized by being added.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, in the case of a sliding nozzle system, a space between a tundish and a mold is constituted by a nozzle above the tundish, a sliding nozzle, an intermediate nozzle and a dipping nozzle.
The molten steel flows at a high flow rate of about s.

For this reason, if the sealing property of the nozzle joint portion is poor, air enters due to the ejector effect of the molten steel flow and reacts with Al in the molten steel to generate inclusions. 4Al (molten steel) +. 3O ₂ (in air) = 2Al ₂ O ₃ (in the molten steel) (1)

[0009] The Al ₂ O ₃ inclusions formed in this way not only reduce the cleanliness of the molten steel, but also adhere to the inner wall of the nozzle and cause clogging of the nozzle. Therefore, ensuring the sealing performance between the nozzles is a very important issue from the viewpoints of both quality and operation of the slab.

The present inventors have conducted detailed studies on a method of adding a metal to a packing material used for a nozzle joint and fixing oxygen in the air that has penetrated in order to improve the sealing property between nozzles. Have been. As a result, it has been found that by adding a metal having a high bonding property to oxygen and a high melting point to the packing material, the sealing property of the nozzle joint is significantly improved.

When a packing material having a high bonding property with oxygen and a high melting point metal, for example, Ti (melting point: 1680 ° C.) is used, oxygen in the air that has entered the nozzle joint at the start of casting becomes (2) Reacts with Ti according to the formula:
It is fixed in the packing material as TiO ₂ . Ti (in the packing material) + O ₂ (in the air) = TiO ₂ (in the packing material) (2)

For this reason, oxygen does not penetrate into the molten steel,
The oxidation of the molten steel represented by the reaction of the formula (1) does not occur. As the casting time elapses, the reaction of the formula (2) proceeds, and a TiO ₂ oxide film is formed on the surface of the added Ti. This oxide film is relatively porous and easily permeates oxygen. Ti (melting point 1680 ° C.) is used at the nozzle operating temperature (1300
(° C.), and is separated from the Ti surface by volume expansion when changing to TiO ₂ (solid state), so that the surface of Ti is always kept in contact with oxygen, and (2)
The reaction of the equation proceeds without stopping.

On the other hand, when low melting point Al is used as the metal, oxygen in the air can be fixed in the packing material as Al ₂ O ₃ by the reaction of the formula (3) in the early stage of the casting, as in the case of Ti. With the passage of time, the strong Al ₂
An O ₃ oxide film is generated, and the reaction of the formula (3) stops. 4Al (in packing material) + 3O ₂ (in air) = 2Al ₂ O ₃ (in packing material) (3)

This is because the low-melting-point metal is in a liquid state at the nozzle operating temperature and is easily deformed, so that the oxide film formed on the surface is not easily peeled off. Therefore, when a low melting point metal such as Al is added to the packing material,
Since the reaction of the formula (3) does not proceed continuously, the effect of improving the sealing performance by adding Al is lost with the elapse of the casting time.

As described above, the packing material is made of T
By adding a metal having a high melting point such as i and having a high binding property to oxygen, the sealing property between nozzles is improved and the effect is maintained, so that oxidation of molten steel can be prevented over the entire casting time.

[0016] The compounding of the packing material in the present invention comprises at least one kind of refractory powder and fibers.
In addition, a metal having a high melting point and a high binding property to oxygen is added.
What is necessary is just to contain 1-50 weight%. This is because when the amount of metal added is less than 0.1% by weight, the above-mentioned effect is not obtained, and
If the content is more than the weight%, the mixing ratio of the metal becomes too high, and the nozzle and the packing material are difficult to adhere to each other.

The additive metal is not limited to Ti,
Any material may be used as long as it is solid at the temperature at which the nozzle is used and has a high binding property to oxygen. For example, Zr, Cr, or the like can be used.

As the refractory powder, one or more arbitrarily selected from metal oxides, metal carbides and metal nitrides are usually used, and as the fibers, ordinary inorganic, organic, metal or the like is used. Is possible.

The present invention is not limited to the nozzle between the tundish and the mold described above, but can be applied to all refractory-to-refractory joints such as a ladle nozzle and RH. .

[0020]

The present invention will be described below with reference to examples and comparative examples. In a continuous casting facility in which the tundish-mold consists of a nozzle above the tundish, a sliding nozzle, an intermediate nozzle, and an immersion nozzle, a 2 mm thick packing material having the composition shown in Table 1 is used at the joint between the nozzles. And casting speed 1.6m / min
, Component C: 30 ppm, Si: 0.015%, Mn:
0.25%, P: 0.02%, S: 0.01%, Al:
1250t of 0.04% molten steel was cast.

In order to evaluate the amount of air oxidation at the nozzle joint between the tundish and the mold, the amount of decrease in the Al concentration in the molten steel on the tundish discharge side and in the mold was measured at the beginning of casting and during the middle of casting.

[0022]

[Table 1A]

[0023]

[Table 1B]

As shown in Table 1, at the nozzle joint between the tundish and the mold, at least one kind of refractory powder and fiber are used, and the high melting point and the bonding property with oxygen are obtained. By using the packing material to which 0.1 to 50% by weight of high Ti was added, the decrease in the concentration of molten steel between the tundish and the mold was suppressed to 4 ppm or less. As a result, nozzle clogging and inclusion defect were not generated at all.

On the other hand, Comparative Example 1 used A as the packing material.
However, since a metal having a high melting point and a high bondability with oxygen was not contained, the reduction in the Al concentration in the molten steel between the tundish and the mold during the early stage of casting was 4 ppm.
Although suppressed to the following, the effect of the addition of Al disappeared after the middle stage of casting, and the decrease in the Al concentration in the molten steel between the tundish and the mold increased significantly. As a result, inclusion defect was generated after the middle stage of casting, and nozzle clogging occurred at the end of casting.

In Comparative Example 2, since the packing material did not contain a metal having a high melting point and a high binding property to oxygen, Comparative Example 3 contained a large amount of Ti having a high melting point and a high binding property to oxygen. Since the adhesiveness between the packing material and the nozzle was lowered, the concentration in the molten steel between the tundish and the mold was significantly reduced from the initial stage of casting. As a result, inclusion defects were generated throughout the casting, and nozzle clogging also occurred from the middle stage of casting.

[0027]

As described above, by using the highly airtight packing material for refractories of the present invention, oxidation at the nozzle joint between the tundish and the mold can be prevented, so that the quality of the slab is improved. Yield is much better. In addition, various unsteady operations due to nozzle clogging can be omitted, and operability is improved.

Claims (1)

[Claims] 1. A refractory comprising at least one kind of refractory powder and a fiber, to which 0.1 to 50% by weight of a metal having a high melting point and a high oxygen binding property is added. For high airtight packing material.