JPH09201660A - Nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sticking of non-metallic inclusion, such as alumina, to a nozzle, keep the suitable eroding speed, prevent the clogging of the nozzle and to display the excellent durability by specifying constituting materials in the nozzle. SOLUTION: In the nozzle for continuous casting, the refractory is composed of 10-90wt.% refractory material having a compsn. containing >=0.5wt.% at least >=1 kind among ZnO, MgO, Al2 O3 , Fe2 O3 , Ga2 O3 and mainly containing 3CaO SiO2 solid solution stabilized at the room temp., 10-40wt.% carbonaceous material and the balance the other refractory materials and is arranged at least at a part in contact with molten steel. By this constitution, the clogging of the nozzle is prevented and the durability of the nozzle is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting nozzle such as a long nozzle or a dipping nozzle used when continuously casting steel.

[0002]

2. Description of the Related Art Nozzles for continuous casting of steel are used for transferring molten steel between a pan and a tundish and between a tundish and a mold.
It plays a role in preventing molten steel contamination and turbulence in molten steel flow, and requiring long-term hot water supply. For this reason, the nozzle is required to have excellent resistance to erosion and abrasion against molten steel and slag, and to be resistant to thermal shock and molten steel pressure. It is also an important characteristic that inclusions in the metal or molten steel do not adhere to the inner wall of the nozzle. As a refractory material that satisfies these characteristics, Al ₂ O _3-
C quality is widely used, and ZrO ₂ -C quality with high corrosion resistance is often used in the powder line around the nozzle.

One of the problems of the continuous casting nozzle is clogging of the nozzle inner hole portion due to adhesion of inclusions in steel (particularly Al ₂ O ₃ ). In particular, during continuous casting of aluminum-killed steel or aluminum-silicon-killed steel, alumina, which is a deoxidation product in molten steel, adheres to the inner hole of the nozzle and the wall of the discharge hole, and gradually grows, eventually leading to nozzle blockage. Many. Furthermore, if the deposits fall off and are taken into the molten steel, the product will be degraded.

As a method for preventing the nozzle clogging, a method of blowing an inert gas such as Ar into the wall surface of the nozzle inner hole to prevent the adhesion of Al ₂ O ₃ or the like is generally used. However, even in this method, alumina may adhere and grow in the multiple casting step, leading to nozzle blockage, which is not sufficient as a countermeasure.

Attempts have been made to prevent adhesion by using a material to which alumina is unlikely to adhere as a nozzle material. As such a material, there is a ZrO ₂ —CaO—C-based material. ZrO ₂ -CaO-C refractory forms a low-melting CaO-Al ₂ O ₃ system when it contacts alumina in molten steel, and it prevents the adhesion of alumina by being appropriately melted. It is said that. However, even with this ZrO ₂ -CaO-C refractory, depending on the steel type and operating conditions, the melting loss is too large, and conversely, the melting loss is so small that alumina adhesion occurs when used for a long time, so that a stable usage condition is always present. There was a problem that I could not get it.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a continuous casting nozzle to which alumina does not easily adhere. As described above, a CaO-based material is effective as a material to which alumina does not easily adhere. However, CaO is difficult to use because it has the property of being hydrated with the moisture in the air and undergoing volume expansion to eventually collapse (digestibility), so it is used in the form of a complex with other oxides. Such calcium zirconate (CaO · ZrO ₂₎ is known as a composite oxide.

However, the amount of CaO component in CaO.ZrO ₂ is only 31% by weight in theoretical composition. In addition, the nozzle has CaO
Since a carbon material and an antioxidant are added in addition to ZrO ₂ , the CaO content in the nozzle is further reduced. As a result, the CaO / ZrO ₂ -C quality nozzles had insufficient effect of preventing CaO from adhering to alumina depending on the type of steel and the conditions of use, resulting in nozzle clogging. The present invention
It is an object of the present invention to provide a continuous casting nozzle having improved durability by increasing the amount of CaO component in a stable form to improve the function of preventing alumina from adhering and maintaining an appropriate melting loss.

[0008]

[Means for Solving the Problems] The present inventors have investigated a CaO-based material which contains a large amount of CaO component excellent in the effect of preventing adhesion of alumina and which has solved the problems of dusting and hydration reaction due to transition. As a result, a specific metal oxide was solid-dissolved
We focused on the effectiveness of 3CaO · SiO ₂ solid solution. That is, when the composition of 3CaO · SiO ₂ composition was directly baked without any additive, as shown in the following equation, CaO and α′-2Ca were decreased when the temperature was lowered.
It decomposes into O ・ SiO _2, and α'-2CaO ・ SiO ₂ generated at this time is α '
→ Because it becomes dust (dusting) due to abnormal expansion during γ transition, it cannot be used as a refractory material. 3CaO ・ SiO ₂ → CaO + α'-2CaO ・ SiO ₂ α'-2CaO ・ SiO ₂ → γ-2CaO ・ SiO ₂

Here, when a specific metal oxide is added and melted or fired, the high temperature phase is stabilized at room temperature to produce 3CaO.SiO.
_{2 A} solid solution is obtained. Being stabilized, this material avoids the problems of decomposition and dusting found in pure 3CaO.SiO ₂ . Moreover, since it is stable against hydration reaction, it is easy to handle. Also CaO / ZrO ₂
Since it contains a CaO component in an amount more than twice that of, excellent anti-adhesion properties of alumina are expected.

The inventors of the present invention used the above refractory material as the material for the continuous casting nozzle and combined it with an appropriate amount of carbonaceous material. As a result, it was possible to effectively prevent the adhesion of alumina, and at the same time, the melt loss rate. The present invention has been completed by finding that the above can be suppressed appropriately.

That is, the nozzle for continuous casting of the present invention is Zn
At least one of O, MgO, Al ₂ O ₃ , Fe ₂ O ₃ , and Ga ₂ O ₃ is 0.
Refractory material mainly containing 3CaO ・ SiO ₂ solid solution stabilized at room temperature containing 5 wt% or more 10-90 wt% and carbonaceous material 10-
A refractory material containing 40% by weight and the remainder being other refractory material is disposed at least at a portion in contact with molten steel.

[0012]

The refractory material used in the present invention is Zn.
The main component is a 3CaO.SiO ₂ solid solution in which one or more of O, MgO, Al ₂ O ₃ , Fe ₂ O ₃ , and Ga ₂ O ₃ are solid-dissolved. This solid solution, by the metal oxide is a solid solution to that of 3CaO · SiO ₂ compositional ratio, the decomposition and dusting as seen in pure 3CaO · SiO ₂ for high-temperature phase is stabilized at room temperature Do not wake up. To obtain this solid solution, as an example, 0.5% of one or two or more of the above metal oxides is added to a mixture having a composition of 3CaO.SiO _2.
Electrofused with more than wt% or 14
There is a method of firing at a temperature of 00 ° C or higher, preferably 1600 ° C or higher. When the amount of metal oxide is less than 0.5% by weight, 3CaO ・ SiO ₂
As it is not stabilized, it decomposes and becomes dust. The upper limit of these amounts is not particularly limited, but if the addition amount increases, it leads to a decrease in corrosion resistance due to a decrease in CaO components and an increase in low-melting components and a decrease in alumina adhesion properties, and therefore a metal oxide. Is preferably 10% by weight or less, and more preferably 5% by weight or less. When the metal oxide is dissolved alone, the transformations to be stabilized are not exactly the same,
In both cases, the high-temperature phase was stabilized at room temperature. 3CaO ・ SiO ₂
A solid solution can be obtained. As an example of forming a solid solution of two or more kinds of metal oxides, when adding Al ₂ O ₃ and MgO, 54CaO
Monoclinic 3CaO ・ SiO with a mineral composition of 16SiO ₂・ Al ₂ O ₃・ MgO
_{2 A} solid solution can be obtained.

The refractory material used in the present invention is the above-mentioned 3CaO.
- is a SiO ₂ solid solution mainly formed, but if the amount that is produced in the manufacturing process, mixing, CaO, 2CaO · SiO _2, 3CaO
・ It does not matter if other minerals such as Al ₂ O ₃ are included.

In the present invention, the above refractory material is used in the range of 10 to 90% by weight, preferably 30 to 90% by weight. This usage is
If it is less than 10% by weight, the effect of preventing adhesion of alumina cannot be sufficiently obtained, and if it exceeds 90% by weight, thermal shock resistance and corrosion resistance are impaired.

The carbon material is added to impart heat shock resistance and corrosion resistance, and is scaly graphite, earth graphite, artificial graphite, carbon black, petroleum coke, carbon fiber, mesophase car. Although bon etc. can be used, it can be said that natural scaly graphite is optimal in view of its characteristics. If the amount of the carbon material is less than 10% by weight, the corrosion resistance and thermal shock resistance will be insufficient, while if it exceeds 40% by weight, the structural deterioration of the refractory material will easily proceed and the abrasion resistance will be reduced. Therefore, the carbon material is used in the range of 10-40% by weight.

In the present invention, other refractory materials can be used in combination with the above constituent materials. Examples of refractory materials that can be used in combination include calcium zirconate, zirconia, zircon, magnesia, alumina, spinel, fused silica, and the like. Among these, it is particularly preferable to use CaO-containing calcium zirconate or CaO stable zirconia because the corrosion resistance can be improved without impairing the effect of preventing adhesion of alumina. When using these refractory materials, use them within the range of 80% by weight or less. If the amount exceeds 80% by weight, the amount of 3CaO.SiO ₂ solid solution used decreases, and the characteristic of preventing alumina adhesion is impaired, which is not preferable.

Further, in the present invention, an antioxidant can be added in order to prevent the oxidation of the carbonaceous material and improve the hot strength of the refractory. As such a material, one kind or two or more kinds can be used from metal materials such as metals and alloys and non-oxide materials such as carbides, nitrides and borides. For example, metal materials such as Al and Si and A
Use alloys such as l-Si, Al-Mg, Al-Si-Mg, and non-oxide materials such as B ₄ C, SiC, TiC, WC, BN, AlN, Si ₃ N ₄ , ZrC. . The antioxidant is in the form of fine particles or powder in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the refractory material.
If this amount is less than 0.1 parts by weight, the effect of preventing oxidation and strength development cannot be obtained, and if it exceeds 10 parts by weight, the thermal shock resistance and the melt damage resistance are deteriorated.

In manufacturing the nozzle of the present invention, a binder such as pitch or phenol resin is added to a raw material mixture prepared in a predetermined ratio, and the mixture is kneaded and then molded into a nozzle shape by a rubber press or the like. Baking at a temperature of 800 ° C or higher in a non-oxidizing atmosphere. The present invention has a structure in which a refractory material of the material specified in the present invention is disposed at least in a portion of the inner wall of the nozzle where the molten steel flow contact surface has a thickness of 2 mm or more. Therefore, it is of course possible to form the entire nozzle only with the material specified in the present invention, but for example, the base is made of Al ₂ O ₃ -C and the powder is
It is also possible to dispose a ZrO ₂ -C substance on the line and to configure a portion of the molten steel flow contact surface having a thickness of 2 mm or more with the material of the present invention.
Known sintering agents and fibers may be added as long as the effect of preventing adhesion of alumina is not impaired.
After firing, impregnation treatment may be performed with tar, pitch, phenol resin or the like.

A large amount of CaO contained in the refractory material used in the present invention is A in the molten steel at the interface between the molten steel flow and the nozzle.
By reacting with l ₂ O ₃ to form a CaO-Al ₂ O ₃ -based low melting point compound, which floats in the molten steel, alumina adhesion to the nozzle wall is effectively prevented. Since the CaO content is high, the reaction is performed efficiently, and it not only prevents the adhesion of alumina but also has a cleaning function to remove impurities in the steel. Further, the melting loss also gradually progresses on average while maintaining the lubricity of the nozzle wall depending on the amount of CaO, so that an appropriate melting loss rate can be maintained. Furthermore, as a result of adding thermal shock resistance and corrosion resistance due to the addition effect of the carbonaceous material, it is possible to prevent clogging of the continuous casting nozzle and significantly improve durability,
Sufficiently applicable to multi-continuous casting.

[0020]

Embodiments of the present invention will be described below. In preparing the 3CaO.SiO ₂ solid solution used in the examples, calcium carbonate, silica, sintered alumina and magnesia clinker were used as raw materials, and these powders were blended so as to have the chemical composition shown in Table 1. Next, this mixture was mixed, molded into a prismatic shape, and baked at 1600 ° C. for 5 hours. Furthermore, after crushing this fired product into powder, it was re-molded and
Fired for hours. Adjust the particle size of this fired product to 0.5 mm or less,
It was used to prepare a sample for evaluation. The materials 1 and 2 in which Al ₂ O ₃ or MgO was solid-solved were structurally stabilized without being dusted. On the other hand, the comparative example to which Al ₂ O ₃ or MgO was not added was not suitable as a refractory material because it became dust when the temperature was lowered in the firing process.

[0021]

[Table 1]

The samples were prepared based on the compounding ratio shown in Table 2. First, a phenol resin was added to these blends as a binder and kneaded, and then molded into a sample shape by using a rubber press. Next, this molded body is placed in an argon atmosphere.
The sample was fired at 1000 ° C for 5 hours. Table 2 also shows the evaluation results. The evaluation method was carried out according to the method shown below.

[0023]

[Table 2]

Also in the comparative example, a sample was prepared and an evaluation test was carried out in the same manner as in the example. Table 3 shows the blending ratio, the characteristics, and the evaluation results.

[0025]

[Table 3]

In each of the examples of the present invention, the amount of adhered alumina was small and the amount of wear was small. On the other hand, in Comparative Examples, except for Comparative Example 1, the amount of adhered alumina was larger than that in Examples, and the nozzle clogging was apt to occur. Comparative Example 1 that used many 3CaO · SiO ₂ is alumina adhesion, it had good resistance to wear resistance both resistance sports - was markedly inferior to the ring properties.

Next, the immersion nozzle of the composition of Example 1 and the alumina-graphite immersion nozzle of Comparative Example 4 were installed in a tundish having a capacity of 250 tons and casting was carried out. When the adhesion state of metal inclusions was examined, almost no adhesion was observed in the immersion nozzle of the present invention, whereas in the alumina-graphite nozzle the amount of inclusions was large and nozzle clogging was likely to occur. Met.

Evaluation method 1) Apparent porosity, bulk specific gravity: JIS-R2205 2) Abrasion amount (mm): A test piece cut into 30 × 30 × 170 mm was immersed in molten steel at 1600 ° C. for 2 hours, which was melted in a high frequency furnace. Then, the amount of wear was measured and obtained. 3) Spooling resistance: A test piece of 40 × 40 × 170 mm shape was immersed in molten steel at 1600 ° C for 3 minutes in a high-frequency furnace and then air-cooled for 20 minutes, repeated 10 times. Was observed. 4) Alumina adhesion rate: 1600 melted in a high frequency furnace
Add aluminum to the molten steel at ℃, 30 × 30 × in it
A 150 mm test piece was immersed for 2 hours and the adhesion state of alumina precipitated from molten steel was observed.

[0029]

EFFECTS OF THE INVENTION By using a refractory containing a 3CaO.SiO ₂ solid solution and a carbonaceous material defined in the present invention as a constituent material of a nozzle for continuous casting, non-metallic inclusions such as alumina can be efficiently attached. It is possible to prevent it and also to maintain an appropriate dissolution rate. As a result, even in use in continuous casting, excellent durability can be exhibited without causing nozzle clogging.

[0030]

[Table 1] * CSAM: 54CaO ・ 16SiO ₂・ Al ₂ O ₃・ MgO C ₂ S: 2CaO ・ SiO ₂ C: CaO

[0031]

[Table 2]

[0032]

[Table 3]

Claims (1)

[Claims] 1. A 3CaO.SiO ₂ solid solution containing at least one 0.5% by weight or more of ZnO, MgO, Al ₂ O ₃ , Fe ₂ O ₃ and Ga ₂ O ₃ and stabilized at room temperature is mainly used. Refractory material as an ingredient 10-90
A nozzle for continuous casting, characterized in that a refractory material containing 10% by weight of carbonaceous material and 10-40% by weight of carbonaceous material, and the remainder being another refractory material, is disposed at least at a portion in contact with molten steel.