JPH093522A - Refractory-coated lance - Google Patents

Abstract

PURPOSE: To prevent cracking of a refractory coat on a refractory-coated lance. CONSTITUTION: In the refractory-coated lance of which the surrounding of a core metal 6 is coated with the refractory 8, a metal satisfying <=8×10<-6> K of the average coefficient of linear expansion in the temp. range of 100-500 deg.C at the time of using 20 deg.C as the reference, is used as the core metal. By this constitution, the crack of the refractory-coated lance is not developed and the durable using times of the coated lance can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory-coated lance used for blowing a treating agent into molten metal such as hot metal or molten steel during refining in a ladle or a hot metal container.

[0002]

Refractory coated lances are used to immerse a molten metal in a vessel and blow a gas for stirring the molten metal or a flux of refining agent with the gas into the molten metal.

The gas blown into the molten metal from the refractory-coated lance becomes bubbles in the molten metal, and the bubbles rise in the molten metal due to the difference in specific gravity from the molten metal, and the molten metal is agitated on the way. And it adsorbs inclusions in the molten metal. The refining flux blown into the molten metal from the refractory-coated lance reacts with impurities in the molten metal, such as sulfur and phosphorus in the hot metal, and then floats on the surface of the molten metal to remove the impurities. . Further, the flux floating on the surface of the molten metal covers the surface of the molten metal and has the functions of preventing heat radiation from the surface of the molten metal and absorbing inclusions floating in the molten metal.

When the processing of the molten metal in the container is completed,
The refractory coated lance is removed from the molten metal and allowed to cool in the refractory coated lance yard.

The refractory-coated lance has a gas blowing port near the lower end of a cored bar made of a metal tube, and the outside of the cored bar is coated with a refractory. Gas and flux are charged from the upper end of the cored bar, and are blown into the molten metal from the gas blowing port at the lower end.

[0006]

[PROBLEMS TO BE SOLVED BY THE INVENTION]
Since it is repeatedly used intermittently in the harsh use environment as described above, the service life is low.

The reason why the refractory-coated lance has a low service life is that cracks are generated in the refractory due to imbalance in thermal expansion of the core and the refractory, and the refractory is separated from the core before being melted and damaged. is there. That is, when the refractory-coated lance is immersed in the molten metal, the refractory receives heat from the molten metal and its temperature rises, but the core metal is cooled by the blowing gas. On the other hand, after processing the molten metal, until the next processing of the molten metal, the refractory coating lance is allowed to cool while blowing gas is stopped in the refractory coating lance storage area,
The cored bar receives heat from the refractory and is heated to expand, and conversely, the refractory is cooled from the surrounding atmosphere and the cored bar and contracts.
In this way, an imbalance in thermal expansion of the core metal and the refractory material occurs, which causes cracks in the refractory material and separates from the core metal before the refractory material melts.

In order to solve this problem, JP-A-59-
The method shown in Japanese Patent No. 145720 has been proposed.
This method involves stirring and refining the molten metal with a refractory-covered lance, then cooling the core metal of the refractory-covered lance waiting in the refractory-covered lance storage area by flowing a cooling gas at room temperature or lower to cool the core. It prevents the gold from expanding due to the heat of the refractory.

However, in this method, in addition to the gas for treating the molten metal, a gas cooling device for cooling the core metal of the refractory-coated lance is required, and there is a problem that the facility becomes complicated. . Further, if the core metal is excessively cooled to allow the cooling gas to flow through the core metal, the refractory material of the refractory-coated lance is also excessively cooled, so that cracks occur in the refractory material due to thermal shock and the service life is reduced. There was a problem of doing.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 3-111510, the core metal is covered with a castable containing 1 to 20% by weight of a hollow refractory heat insulating material to enhance the heat insulating effect and increase the temperature of the core metal. Although it is to prevent it, the temperature of the core metal can be suppressed to 500 ° C or less at most,
It does not prevent the core metal from expanding.

The present invention has been made in order to solve the above problems, and a refractory in which a refractory of a refractory-coated lance does not crack even if the core metal expands due to the heat of the refractory. A coated lance is provided.

[0012]

The refractory-coated lance of the present invention is a refractory-coated lance in which a core metal is coated with a refractory, and the refractory-coated lance is 100 ° C. to 500 ° C. based on 20 ° C.
Average linear expansion coefficient in the temperature range up to ℃ 8 × 10 ^-6 /
A metal having a K or less is used as the core metal. However, K has shown absolute temperature here.

A second invention of the present invention is the same as the first invention, wherein 100 ° C to 500 ° C based on 20 ° C.
It is characterized in that a metal having a difference between the maximum value and the minimum value of the average linear expansion coefficient in the temperature range up to 3 × 10 ⁻⁶ / K or less is used as the core metal.

[0014]

The inventors measured the temperatures of the refractory surface and the core metal surface during the use of the refractory-coated lance for blowing nitrogen gas in the dephosphorization treatment of the hot metal and during standby in the refractory-coated lance storage area. Here, the temperature measurement position on the refractory surface was set at a position 10 mm from the refractory surface. Refractory coating lance diameter is 3
00 mm, core diameter is 90 mm, processing time is 19 minutes,
The waiting time is 24 minutes. FIG. 5 shows the measurement results. The refractory surface temperature rises from the start of the hot metal dephosphorization treatment, but the refractory surface temperature begins to drop immediately after the end of the treatment. On the other hand, the surface temperature of the core metal also starts to rise with the start of the treatment, but unlike the refractory surface, the temperature continues to rise for about 10 minutes after the treatment.
This is because the core metal is cooled because nitrogen gas is blown during the treatment, whereas the core metal is not cooled because nitrogen gas is stopped after the treatment and is heated by the heat stored in the refractory. is there.

In this measurement result, the surface temperature of the core metal fluctuates between the minimum value of 150 ° C. and the maximum value of 450 ° C. during processing and during standby.

Conventionally, carbon steel has been used for the core metal,
According to the Metals Data Book 116 edited by the Japan Institute of Metals (published by Maruzen Co., Ltd.), the average linear expansion coefficient of carbon steel increases as the temperature increases and the carbon concentration is 0.23% or less, as shown in Table 1. The average linear expansion coefficient of so-called ordinary carbon steel from 0 ° C to 500 ° C is 13.9 to 14.2 × 10 ^-6 / K.
It has become.

The average linear expansion coefficient α between the temperatures t ₁ and t ₂ is given by the equation (1). α = (1 / l ₀ ) × (l ₂ −l ₁ ) / (t ₂ −t ₁ ) ... (1) where l ₀ is the length at 0 ° C. and l ₂ is the length at temperature t ₂ K Then, l ₁ is the length at the temperature t ₁ K, and 20 ° C. (293 K) is adopted as t _{1 in} the present application. That is, the average linear expansion coefficient in the present application is a value obtained by converting the expansion coefficient when heated from 20 ° C. to a certain temperature per 1K of temperature. In Table 1, the average linear expansion coefficient is calculated based on 0 ° C., but there is no great difference in the average linear expansion coefficient from the case of 20 ° C. of the present application.

[0018]

[Table 1]

On the other hand, the average linear expansion coefficient of the refractory material in the operating temperature range is generally 8 × 10 ^-6 / K or less.

If there is a difference in the average linear expansion coefficient between the refractory material and the metal core metal, the expansion of the refractory material cannot catch up with the expansion of the core metal when subjected to thermal cycles during processing and standby, Cracks occur in the refractory. In particular, the surface temperature of the refractory immediately after the treatment is lowered, and cracks are likely to occur when the temperature of the core metal is increased.

In the present invention, the temperature of the core metal is 100 to 50.
The temperature of 0 ° C was set because the refractory-coated lance is repeatedly used, and therefore it is not normally left to stand until the temperature of the cored bar is cooled to 100 ° C or less, and the temperature of the cored bar is 100 ° C.
If it is less than 5, the temperature difference between the temperature of the refractory when inserting the refractory-coated lance into the molten metal and the temperature of the core metal is large, and cracks occur in the refractory, so that the object of the present invention cannot be achieved.
The upper limit of 00 ° C. is that no higher temperature is required for the purpose of the present invention.

In the temperature range of 100 to 500 ° C. which is the operating temperature of the core metal, the average linear expansion coefficient of the refractory material is close to 8 × 10 ^-6 /
By using a metal having an average linear expansion coefficient of K or less as the core metal, the expansion amount of both the refractory and the core metal due to the temperature behavior of the refractory even when subjected to a thermal cycle during processing and standby. Since the amount of shrinkage is close, cracking of the refractory can be suppressed.

Even if the average linear expansion coefficient is 8 × 10 ⁻⁶ / K or less in the temperature range of 100 to 500 ° C., if the average linear expansion coefficient changes abruptly, the average linear expansion coefficient changes abruptly. Cause cracks in refractory materials. Therefore, 100 to 5
The difference between the maximum value and the minimum value of the average linear expansion coefficient in the temperature range of 00 ° C. is preferably 3 × 10 ⁻⁶ / K or less.

[0024]

Embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the molten metal 2 is poured into the container 1, the refractory-coated lance 3 is dipped in the molten metal 2,
Gas for agitating the molten metal 2, or gas and a flux for refining the molten metal 2 are blown from the refractory coating lance 3.

Gas and flux are blown into the molten metal 2 from the refractory coating lance 3 and 4 is blown gas bubbles. The gas bubbles rise in the molten metal 2 due to the difference in specific gravity from the molten metal 2. In the middle of the process, it has a function of stirring the molten metal 2 and adsorbing inclusions in the molten metal 2. 5
Has a function of preventing heat radiation from the surface of the molten metal 2 by the slag and absorbing inclusions floating in the molten metal 2.

When the stirring and refining of the molten metal 2 in the container 1 are completed, the refractory coating lance 3 is taken out of the molten metal 2 and naturally cooled in the place of the refractory coating lance 3.

The refractory coating lance 3 has a structure as shown in FIG. The cored bar 6 has a gas blowing port 7 near its lower end. The outside of the cored bar 6 is covered with a refractory material 8. The stirring gas or the refining gas and flux is injected from the upper end of the cored bar 6 and blown into the molten metal 2 from the gas injection port 7 at the lower end.

(Embodiment 1) FIG. 1 is a cross-sectional view of a molten metal container and a refractory-coated lance showing an embodiment of the present invention, showing a case where hot metal is treated as molten metal. The capacity of the molten metal container is 200 t, the length of the refractory coating lance is 8150 mm,
The diameter of the refractory coated lance is 300 mm, the diameter of the core metal is 90 m
m, nitrogen gas was used as the stirring gas, and CaO was used as the blowing flux.

Alumina spinel castable was used as the refractory material coated on the core metal. Using this refractory-coated lance, hot metal was desulfurized. Iron-N as the core metal
i (Ni is about 30%, balance is iron) alloy,
FIG. 3 shows the relationship between the temperature and the average linear expansion coefficient with 0 ° C. as the reference. As shown in Fig. 3, the average linear expansion coefficient from 20 ℃ to 100 ℃ is 0.8 × 10 ^-6 / K, from 20 ℃ to 50 ℃.
The average coefficient of linear expansion up to 0 ° C is 7.4 × 10 ^-6 / K,
The average linear expansion coefficient in the temperature range from 100 ° C. to 500 ° C. is less than 8 × 10 ⁻⁶ / K.

The hot metal desulfurization time is 17 minutes and the standby time is 27 minutes. As a result of comparing the number of times the refractory-coated lances were used repeatedly under these conditions, the average number of times the refractory-coated lances of the present invention were used was 45, while the conventional carbon steel core bar was used. The life of the refractory coating lance using was 30 times, which was a remarkable improvement. No crack was generated in the refractory-coated lance of the present invention.

(Example 2) The same molten metal container and refractory-coated lance having the same shape as in Example 1 were used to perform the same hot metal treatment.

Alumina spinel castable was used as the refractory material coated on the core metal. Using this refractory-coated lance, hot metal was desulfurized. Iron-N as the core metal
An i-Co (Ni is about 30%, Co is about 15%, and the balance is iron) alloy, and the relationship between the temperature and the average linear expansion coefficient when this alloy is set to 20 ° C. is shown in FIG. As shown in Fig. 4, the average linear expansion coefficient from 20 ℃ to 100 ℃ is 4.2 × 1.
0 ^-6 / K, the average linear expansion coefficient from 20 ℃ to 500 ℃ is 5.8 × 10 ^-6 / K, the minimum value of the average linear expansion coefficient from 100 ℃ to 500 ℃ is about 300 ℃ At 3.8 × 10 ⁻⁶ / K and the maximum value at 500 ° C. is 5.
8 × 10 ^-6 / K, the difference between the maximum and minimum is 2 × 10 ^-6
/ K.

The desulfurization treatment of the hot metal is 17 minutes and the waiting time is 27 minutes. As a result of comparing the number of times the refractory-coated lances were used repeatedly under these conditions, the average number of times the refractory-coated lances of the present invention were used was 60, while the conventional carbon steel cored bar was used. The life of the refractory-coated lance using was 30 times, which was a marked improvement. No cracks were formed on the refractory-coated lance of the present invention.

Since the average linear expansion coefficient of ordinary metals is high, the lower limit of the average linear expansion coefficient is not limited, but 0.5
When × falls below 10 ^-6 / K, contrary not keep up with the expansion of the expansion refractory metal core, refractory from the metal core is peeled off, so easily fall off, more than 0.5 × 10 ^-6 / K desirable. Also, by providing a refractory material or the like having a high heat insulating effect on the outer peripheral portion of the core metal to improve the heat insulating effect, the surface temperature of the core metal becomes low,
Further, the service life of the refractory-covered lance is improved.

[0036]

According to the present invention, since a metal having a low average linear expansion coefficient is used for the core metal of the refractory-covered lance, cracks of the refractory-free material do not occur and the number of times the refractory-covered lance is used is extended. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram of a molten metal processing apparatus used in an example of the present invention.

FIG. 2 is a schematic view of a refractory coating lance used in an example of the present invention.

FIG. 3 is a diagram showing the relationship between the temperature of the metal core metal used in Example 1 of the present invention and the average linear expansion coefficient with 20 ° C. as a reference.

FIG. 4 is a diagram showing the relationship between the temperature of the core metal used in Example 2 of the present invention and the average linear expansion coefficient when 20 ° C. is used as a reference.

FIG. 5 is a diagram showing the relationship between the surface temperature of the refractory and the surface temperature of the cored bar during use of the refractory-coated lance and standby in the storage space and the elapsed time.

[Explanation of symbols]

 1 Molten Metal Container 2 Molten Metal 3 Refractory Coated Lance 4 Gas Bubble 5 Slag 6 Core Bar 7 Gas Inlet 8 Refractory

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuto Takahashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. A refractory-coated lance in which a core metal is coated with a refractory material has an average linear expansion coefficient of 8 × in a temperature range of 100 ° C. to 500 ° C. with reference to 20 ° C.
A refractory-coated lance characterized by using a metal having a metal content of 10 ^-6 / K or less as a core metal. However, K is an absolute temperature. 2. From 100 ° C. based on 20 ° C. to 5
The refractory material according to claim 1, wherein a metal having a difference between the maximum value and the minimum value of the average linear expansion coefficient in the temperature range up to 00 ° C of 3 × 10 ^-6 / K or less is used as the core metal. Coated lance.