JPH10328797A - Immersion nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the clogging of a nozzle and the development of remaining material, to improve the yield and also, to improve the quality of a cast slab by forming the thickness of inner hole body of an immersion nozzle at the lower end part thinner than that at the upper end part of the immersion nozzle. SOLUTION: The outside of the inner hole body 2 is formed thinner as a linear sloping state toward a molten steel spouting hole 6 at the lower part of the immersion nozzle 1 to form the lower end part thinner than the upper end part. Argon gas, etc., is blown from a gas blowing pipe 4 communicated with a gas blowing gap 3 in the inner hole body 2 and thus, can uniformly be blown into a nozzle hole 5 from the whole surface of the inner hole body 2. By this structure, the stuck-deposition of Al base inclusion in the poured molten steel passed through the nozzle hole 5 on the surface of the inner hole body 2 is reduced, and the molten steel pouring into the molten steel 7 in a mold from the molten steel spouting hole 6 is uniformized to avoid the enclosure of powder, etc., and the quality of the cast slab is improved and also, the yield can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion nozzle for continuous casting.

[0002]

2. Description of the Related Art In continuous casting, molten steel is injected through an immersion nozzle that is immersed in molten steel in a mold. The Al-based inclusions in the inside adhere and accumulate and gradually become a closed state, which hinders the injection of molten steel. As shown in FIG. 2, gas is blown into the inner wall of the nozzle hole 5 of the immersion nozzle 1 to provide the inner hole body 2 in order to prevent the Al-based inclusions in the molten steel from adhering and depositing.
Gas is blown from a gas blowing pipe 4 through the gap 3 of the inner hole 2, and while molten gas is blown from the inner hole 2 into the nozzle hole 5, molten steel is injected from the nozzle discharge hole 6 through the nozzle hole 5 into the mold. Injection into molten steel 7 is disclosed in
No. 40, for example.

[0003]

As described above, when the inner body 2 is provided on the inner wall of the nozzle hole 5 of the immersion nozzle 1 and the molten steel is injected into the molten steel 7 in the mold while blowing gas into the nozzle hole 5, The flow rate of gas blown from the entire surface of the hole 2 becomes uneven. Accordingly, Al-based inclusions adhere to and deposit on the surface of the inner body 2 where the blown gas has a low flow rate, and the molten steel flow injected into the mold is deflected, thereby deteriorating the quality of the slab by, for example, entraining powder. There are issues such as The present invention has been made in order to advantageously solve such a problem, and by adjusting the thickness of the inner hole body provided on the inner wall of the nozzle hole of the immersion nozzle, the entire surface of the inner hole body is almost uniformly formed. It is an object of the present invention to provide a continuous casting immersion nozzle capable of injecting gas to reduce the adhesion and deposition of Al-based inclusions in molten steel injected into the surface of an inner hole body and reliably preventing clogging of a nozzle hole. Is what you do.

[0004]

A feature of the present invention is a continuous casting immersion nozzle characterized in that the inner hole body of the immersion nozzle is formed thinner at the lower end than at the upper end of the immersion nozzle. is there.

[0005]

As described above, since the immersion nozzle is immersed in the molten steel in the mold and injects the molten steel, the static pressure of the molten steel on the entire surface of the inner body of the immersion nozzle is determined by the molten steel surface (meniscus) of the molten steel in the mold. Since the pressure increases as the depth increases, the pressure increases as approaching the lower end portion (discharge hole) of the immersion nozzle. For this reason, the flow rate of the gas blown out from the bore becomes lower as the static pressure of the molten steel becomes higher, because the gas flow is hindered by the static pressure.
Therefore, there is no gas flow that repels the Al-based inclusions to be adhered in the low flow rate portion of the gas flow from the inner body of the immersion nozzle, and the Al-based inclusions in the injected molten steel adhere to and accumulate on the surface of the inner body and are immersed. The nozzle hole of the nozzle gradually becomes closed, and the molten steel injection flow from the nozzle discharge hole into the molten steel mold drifts to degrade the quality of the slab.

Thus, in the immersion nozzle of the present invention, the portion where the molten steel static pressure is high on the front surface of the inner wall of the inner wall of the nozzle hole of the immersion nozzle, that is, the thickness of the inner hole at the lower end of the immersion nozzle is determined by the upper end of the immersion nozzle. By forming thinner than the part
The purpose is to make the flow rate of the gas blown out from the entire surface of the inner body substantially uniform, eliminate the low flow rate portion of the gas, and reduce the adhesion and deposition of Al-based inclusions on the surface of the inner body.

[0007] As described above, in a portion where the thickness of the inner hole is reduced, the gas passage resistance of the inner hole decreases accordingly. Therefore, even if the molten steel static pressure is high, the molten steel static pressure is low and the gas flow rate is almost the same as the thick portion of the inner hole thickness,
Since the blowout gas flow rate becomes substantially uniform over the entire surface of the bore, the adhesion and deposition of Al-based inclusions on the surface of the bore can be reliably reduced and clogging of the immersion nozzle can be prevented. The generation of surplus material due to clogging is reduced, the yield is improved, and the drift of the molten steel injected into the mold is prevented, so that the quality of the cast slab can be improved.

[0008] As described above, as the molten steel static pressure on the front surface of the inner body of the immersion nozzle becomes higher, the thickness of the inner body becomes thinner. For example, the thickness of the inner body is changed from the upper end to the lower end (discharge hole) of the immersion nozzle. It is preferable in terms of manufacturing to form a thin linearly inclined shape toward ()), but it is also possible to form an inclined thin shape in a shape such as a stepped shape or a curved shape. Also, in the case of forming such an inclined thin film, if it is formed on the inner side of the inner body (contact surface of the molten steel), the contact resistance with the molten steel flow increases, and the molten steel discharge flow (the molten flow) into the mold is increased. ) May be non-uniform in the width direction of the mold, which is not preferred.

As described above, an example of the relationship between the molten steel position in the mold of the inner body of the immersion nozzle and the volume of the inner hole is shown by a mathematical expression.

Qx = α / L (PH−P) = α / L (PH−ρgx) (1) From P = ρgx (1) L = α / gx (PH−ρgx) (1) 2) However, qx: Gas flow rate at a distance X in the vertical direction from the surface of molten steel in the mold α: Constant (value determined by pore diameter and porosity of inner body) L: Inner body thickness PH: Inner body gas blowing gap P : Static pressure of molten steel over the entire bore body ρ: Density of molten steel g: Gravitational acceleration of molten steel In view of the above, the distance X in the vertical direction (toward the tip of the immersion nozzle) from the surface of molten steel in the mold of the immersion nozzle positioned in the molten steel in the mold Accordingly, the gas flow rate gx can be made constant by changing the inner hole thickness L. That is, the flow rate of the blown gas can be made constant over the entire surface of the inner body, and the adhesion and deposition of Al-based inclusions on the entire surface of the inner body can be reliably reduced.

[0010]

Next, examples of the present invention will be described. In FIG. 1, the thickness of the inner body 2 of the immersion nozzle 1 is made thinner at the lower end (on the molten steel discharge hole 6 side) than at the upper end of the nozzle 1. For example,
As shown in the figure, the outer side of the inner hole body 2 is formed to be thin linearly inclined toward the lower end portion (the molten steel discharge hole 6) of the immersion nozzle 1,
The lower end is formed thinner than the upper end. Gas (argon gas or the like) is blown from a gas blowing pipe 4 communicating with the gas blowing gap 3 of the inner hole 2, whereby the gas can be uniformly blown from the entire surface of the inner hole 2 into the nozzle hole 5. The adhesion and deposition of Al-based inclusions in the molten steel passing through the hole 5 on the surface of the inner body 2 is reduced, and the molten steel discharge hole 6 is reduced.
This makes it possible to uniformly inject molten steel into the molten steel 7 in the mold to avoid entrainment of powder or the like, improve the quality of cast slabs, and increase the yield.

Next, an operation example of continuous casting using the immersion nozzle according to the present invention will be described together with a comparative example.

[Table 1]

[0012]

[Table 2] (continuation of Table 1)

Note 1: The length of the bore in the molten steel was determined by immersing the bore in the molten steel downward from the surface of the molten steel by positioning the dipping nozzle into the molten steel in the mold to inject the molten steel into the mold. Length. Note 2: The thickness of the inner hole body was formed such that the outer side of the inner hole body was inclined and linearly reduced from the upper end to the lower end. Note 3: For continuous casting, slab thickness 245 mm, width 800 mm
Was cast by a curved continuous casting apparatus. Note 4: Cast molten steel component: C: 0.04%, Mn: 0.2
5%, Si: 0.01%, P: 0.01%, S: 0.0
1%, Al: 0.035%, remaining unavoidable impurities and F
e. Note 5: Use argon gas (normal temperature) as the gas to be blown into the bore. Note 6: The casting amount is the amount of slab that was cast without the generation of extra material due to clogging of the immersion nozzle. Note 7: The thickness of the adhered substance is the thickness of the adhered substance adhered to the surface of the bore when casting 900t.

[0014]

According to the immersion nozzle of the present invention, the clogging of the nozzle can be significantly reduced, the generation of surplus material can be reduced, the yield can be improved, and the quality of the slab can be improved. Further, the frequency of nozzle replacement due to clogging of the immersion nozzle is reduced, so that the operation rate of the continuous casting apparatus can be increased and the productivity can be improved. Further, excellent effects can be obtained such that the operation can be performed without additional work, and the operation can be performed without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional immersion nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion nozzle 2 Inner body 3 Gas injection gap of inner body 4 Gas injection pipe 5 Nozzle hole of immersion nozzle 6 Molten steel discharge hole of immersion nozzle 7 Molten steel in mold

Claims (3)

[Claims] 1. An immersion nozzle for continuous casting, wherein the inner hole body of the immersion nozzle is formed to be thinner at the lower end than at the upper end of the immersion nozzle. 2. The immersion nozzle for continuous casting according to claim 1, wherein the outside of the inner hole is formed thin. 3. The immersion nozzle for continuous casting according to claim 1, wherein the thickness of the inner hole body is formed so as to be linearly thinner toward the lower end of the immersion nozzle.