JP2002248552A - Nozzle for continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle for continuous casting having a sliding plate 5b located on the bottom of a metallurgical container, with a means restraining metal oxides from adhering to a sliding nozzle 5. SOLUTION: This invention relates to a nozzle for continuous casting having at least a passage 11 through which molten metal passes and a sliding plate 5b which is located at the lower part of the passage 11 and controls the flow volume of molten metal. The nozzle for continuous casting is provided with one or more pressure loss supplying sections of enlarged inner diameter upstream of the sliding plate 5b of the passage 11. A pressure loss section consists of an inner diameter reducing region 8 inside the passage and an inner diameter enlarging region 7 just under it. Further, the inner wall of the passage is provided with one or more screw-shaped pressure loss supplying sections 9 with a spiral groove or build-up. The nozzle for continuous casting is provided with an inert gas blowing section 10 downstream of the pressure loss supplying section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting nozzle having a sliding plate disposed at the bottom of a metallurgical vessel, and more particularly to a continuous casting nozzle for reducing metal oxide deposition on the inner wall of the sliding plate. About.

[0002]

2. Description of the Related Art When pouring a molten metal into a metal mold from the bottom of a metallurgical vessel, such as a ladle or a tundish, into a mold or the like, a sliding nozzle is arranged at the bottom of the metallurgical vessel, and the molten metal is opened and closed by opening and closing the sliding nozzle. Is adjusted and the injection is turned on and off.

[0003] The sliding nozzle is composed of two plates, an upper plate and a sliding plate, or as shown in FIG.
3, upper plate 5a, sliding plate 5
b, composed of three plates, a lower plate 5c.
When the sliding nozzle 5 is configured with three plates, the sliding plate 5b is used to adjust the opening of the sliding nozzle 5.
Only slide. FIG. 13 shows an example in which a sliding nozzle 5 composed of three plates is used. In continuous casting, tundish 1 to mold 3
The various nozzles described above, in this case, the upper nozzle 4, the sliding nozzle 5, and the immersion nozzle 6 are collectively referred to as a continuous casting nozzle.

Hereinafter, a description will be given of continuous casting of steel as an example. Molten steel contains oxygen at the end of refining. After the refining, a deoxidizing agent is added to the molten steel to convert the contained oxygen into a metal oxide, and most of the oxygen is floated and separated from the molten steel. Since some metal oxides remain in the molten steel, the molten steel injected from the tundish contains a small amount of metal oxides, and during the injection of the molten steel, the metal oxides adhere to and deposit on the walls of the sliding nozzle. It has been known. In particular, it is well known that aluminum oxide-killed steel using aluminum as a deoxidizer easily deposits and deposits a metal oxide mainly on alumina on the inner wall of the sliding nozzle during injection.
As the deposition of alumina progresses, the sliding nozzle closes and the injection of molten steel becomes impossible, so various measures for preventing adhesion are considered.

[0005] A porous refractory material is provided on the inner wall of the sliding nozzle, and an inert gas such as argon is jetted through the porous material to molten steel passing through the sliding nozzle, whereby metal oxide adheres to the inner wall of the sliding nozzle. (Hereinafter, referred to as "prior art 1").

Measures have been taken to prevent the metal oxide from adhering to the inner wall of the sliding nozzle by modifying alumina into a calcium-aluminate-based oxide having a low melting point by adding Ca to molten steel. (Hereinafter referred to as “prior art 2”).

Although not an adhesion preventing method, Japanese Patent Application Laid-Open No. H11-90593 discloses that a screw-shaped part is installed in an immersion nozzle to form a vortex in the molten steel flow in the immersion nozzle, as shown in FIG. A method of preventing the air from entering from the periphery of the sliding nozzle by applying the method is disclosed.

[0008]

Prior art 1 and prior art 2 are extremely effective measures for preventing metal oxide from adhering to the inner wall of the sliding nozzle, and are widely used. However, in the prior art 1, since the inert gas entrained in the molten steel stream is mixed into the mold, the inert gas bubbles are captured near the surface layer of the solidified slab near the surface of the molten steel in the mold, and as a result, There are quality problems such as occurrence of pock-like defects on the surface of the slab. Further, the prior art 2 has a problem that Ca addition cost is expensive and Ca content is not recognized depending on steel types.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide means for making it difficult for metal oxide to adhere to a sliding nozzle.

[0010]

The present invention is as follows. (1) A continuous casting nozzle having at least a flow path 11 through which a molten metal passes, and a sliding plate 5b provided at a lower portion of the flow path to adjust a flow rate of the molten metal. The pressure loss imparting portion whose inner diameter is increased upstream of the sliding plate 5b
A nozzle for continuous casting characterized by being provided at more than one location. (2) The pressure loss imparting portion is formed by forming a raised portion 8 around the inner wall of the flow path and increasing the inner diameter immediately below the inner diameter of the raised portion (1). The nozzle for continuous casting as described. (3) The pressure loss imparting section described in (1), wherein the groove 7 is formed around the inner wall of the flow path, and the inner diameter of the groove is made larger than the inner diameter immediately above. Nozzle for continuous casting. (4) The continuity according to the above (1), wherein the pressure loss applying section is formed by making the inner diameter of the sliding plate larger than the inner diameter of the flow path or increasing the inner diameter of the flow path from the middle. Nozzle for casting. (5) A continuous casting nozzle having at least a flow channel 11 through which the molten metal passes, and a sliding plate 5b provided at a lower portion of the flow channel to adjust the flow rate of the molten metal, A continuous casting nozzle comprising one or more screw-shaped pressure loss applying portions 9 having spiral grooves or ridges. (6) The continuous casting nozzle according to any one of (1) to (5), further including an inert gas blowing unit 10 downstream of the pressure loss applying unit.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of the study of the present inventors, it has been found that the higher the flow rate of the molten metal, the more the metal oxide adheres to the portion, and the sliding nozzle is controlled by adjusting the opening for controlling the injection flow rate. By being given an aperture,
It has been found that the molten metal reaches the maximum flow rate and the adhesion is likely to proceed preferentially. This is considered to be because the flow rate of the metal oxide increases as the flow rate of the molten metal increases, so that the frequency of contact of the metal oxide with the inner wall of the sliding nozzle increases. As a means of reducing the flow rate of the molten metal in the sliding nozzle, it is effective to reduce the level of the molten metal in the tundish, but if the level of the molten metal is simply reduced, the tundish is accordingly reduced. It is well known and undesirable that the floating capacity of the molten metal is reduced and the floating time of the molten metal is impaired and the quality of the metal is deteriorated. In view of such circumstances, as a result of earnest research and development of means for effectively reducing the flow rate of molten metal in the sliding nozzle while securing the surface level of the tundish, the present invention has been realized.

The gist of the present invention is that the kinetic energy of the molten metal is depleted by passing the molten metal through the flow path resistance portion before reaching the sliding nozzle, and thereby the molten metal passes through the sliding nozzle. Is to decrease the flow rate of the particles to reduce the adhesion.

In the above (1) of the present invention, as shown in FIG. 1 to FIG. 4, one or more pressure loss imparting portions having an enlarged inner diameter called an inner diameter enlarged portion 7 are provided. As a result, the pressure loss applying section becomes a flow path resistance section, and the kinetic energy of the molten metal is consumed by passing through the flow path resistance section,
Thereby, the flow velocity when passing through the sliding nozzle is reduced to reduce the adhesion.

As shown in FIG. 1 (2) of the present invention, the pressure-loss applying section is provided with a raised section 8 on the inner wall of the flow path in the upper nozzle 4 upstream of the sliding nozzle 5. It can be configured by providing at least one or more inner diameter enlarging portions 7 in which the inner diameter immediately below the raised portion is larger than the inner diameter. The enlarged inner diameter portion 7 acts as a flow path resistance portion, and can effectively consume the kinetic energy of the molten metal 2, thereby reducing the flow velocity of the molten metal 2 in the sliding nozzle 5 and reducing the adhesion. FIGS. 9 and 10 schematically show the state of flow in the enlarged inner diameter portion 7. The generation of a vortex in the enlarged inner diameter portion 7 effectively consumes the kinetic energy of the molten metal 2 and reduces the flow path resistance. Department. The shape of the inner diameter enlarged portion 7 may be a stepped shape as shown in FIG. 9 or a tapered shape as shown in FIG. FIG. 4 is an overall view of a case where the shape of the inner diameter expanding portion 7 is tapered. Even if the inner diameter expanding portion 7 and the inner diameter reducing portion 8 are tapered as shown in FIG. According to this, particularly when the spread angle of the taper is 6 ° or more, a vortex is generated in the taper, thereby effectively acting as a flow path resistance portion.

It is desirable that the kinetic energy of the molten metal be consumed as the number of the inner diameter enlarging portions 7 increases, but it is necessary to provide at least one portion.
In FIG. 1, there are three inner diameter enlarged portions 7, and in FIG.
Is installed in one place.

As shown in FIG. 2 (3) of the present invention, the pressure-loss applying section is provided with a groove 7 on the inner wall of the flow path in the upper nozzle 4 on the upstream side of the sliding nozzle 5, and directly above the nozzle. The inner diameter of the groove 7 is made larger than the inner diameter of the flow path 11,
The groove 7 may constitute the enlarged inner diameter part, and the flow path immediately above the groove may constitute the reduced inner diameter part 8. This inside diameter enlarged part 7
However, the same function as the inner diameter enlarged portion 7 of the above (2) is exerted, and the kinetic energy of the molten metal 2 can be effectively consumed, whereby the flow velocity of the molten metal 2 in the sliding nozzle 5 also decreases. Adhesion is also reduced.

As described in the above (4) of the present invention, the pressure loss imparting portion is formed by the sliding plate 5 from the inner diameter of the flow path 11.
It may be formed by increasing the inner diameter of b or increasing the inner diameter of the flow path 11 from the middle. FIG.
This is an example in which the inside diameter of the sliding plate 5b is larger than the inside diameter. In this case, the inner diameter of the upper plate 5a is increased together with the sliding plate 5b, and the upper plate 5a constitutes the inner diameter enlarged portion 7 and effectively functions as a flow path resistance portion. FIG. 8 shows an example in which the inner diameter of the flow path is increased from the middle. The upper half of the flow path 11 constitutes the reduced inner diameter portion 8 and the lower half constitutes the enlarged inner diameter portion 7.

Even in the case where the screw-shaped portion 9 as shown in the above (5) of the present invention shown in FIG. 5 is provided, it is not possible to effectively consume kinetic energy by generating a vortex in the molten metal 2. This is included in the present invention because it is the same as the above-described operation and effectively functions as a flow path resistance portion.

According to the present invention, the adhesion and deposition to the sliding nozzle, which is a flow rate control part and is most important for casting, is generated although the adhesion to the reduced inner diameter portion and the screw-shaped portion where the flow velocity of the molten metal becomes large occurs slightly. Is greatly reduced.

Further, as in the above (6) of the present invention, a gas blowing section 10 is provided in the vicinity of the pressure loss applying section, preferably immediately below the pressure loss applying section. Effective for preventing deposition. FIGS. 6 and 7 show an example of the invention having a gas blowing portion 10. The inert gas blown from the gas blowing portion 10 passes through the inner diameter reducing portion 8 and the screw-shaped portion 9 by buoyancy, so that the tundish 1 is removed. Therefore, while preventing the adhesion to the part, the quality problem that the inert gas is mixed into the mold does not occur.

FIGS. 1 to 8 each have an immersion nozzle 6, but since the effects of the present invention can be achieved without the immersion nozzle 6, the immersion nozzle 6 Having no is included in the present invention.

However, it should be noted that, as shown in FIG. 11, the immersion nozzle 6 downstream of the sliding plate 5b is provided with an inner diameter enlarged portion 7 and an inner diameter reduced portion 8 as shown in FIG. If the screw-shaped portion 9 is provided in the immersion nozzle 6 on the downstream side of the sliding plate 5b, the flow controllability, which is the original purpose of the sliding nozzle, is undesirably deteriorated.

[0023]

Next, an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIGS. 275 tons of molten steel tapped from a 280 ton converter was placed in a ladle, aluminum was added and deoxidized to adjust the total aluminum content to 0.030% by mass. Thereafter, RH reflux treatment was performed, and continuous casting with a slab size of 220 mm × 220 mm was attempted via a tundish. The process of adding Ca to molten steel for preventing nozzle clogging was not performed, and the casting was performed with the aim of continuous casting of three or more charges in the state shown in FIGS. 1, 3 to 7, and 11 to 13. Table 1 shows the results.

[0024]

[Table 1]

The casting conditions of Inventive Example 1 are of the type shown in FIG. Achieved 5-charge casting which exceeded the target 3-charge casting. The opening of the sliding nozzle 5 during casting is 5
At the stage of charging, a slight tendency to clogging was observed, and a variation in the level of the molten metal in the mold was observed within a range of 3 mm or less. As a result of the disassembly inspection after the completion of casting, clogging was observed in the reduced inner diameter portion 8, and slight adhesion of alumina was also observed in the sliding nozzle 5.

The casting conditions of Inventive Example 2 are of the type shown in FIG. Achieved the target of 3 charge casting. The opening degree of the sliding nozzle 5 during casting shows a slight tendency to clog at the stage of the third charge, and the variation in the level of the molten metal in the mold has been recognized to be in a range of 4 mm or less. As a result of the disassembly inspection after the completion of casting, clogging was observed in the reduced inner diameter portion 8, and slight adhesion of alumina was also observed in the sliding nozzle 5.

The casting conditions of Inventive Example 3 are of the type shown in FIG. Achieved the target of 3 charge casting. The opening degree of the sliding nozzle 5 during casting shows a slight tendency to clog at the stage of the third charge, and the variation in the level of the molten metal in the mold has been recognized to be in a range of 4 mm or less. As a result of the disassembly inspection after the completion of casting, clogging was observed in the reduced inner diameter portion 8, and slight adhesion of alumina was also observed in the sliding nozzle 5.

The casting conditions of Inventive Example 4 are of the type shown in FIG. Achieved 4-charge casting which exceeded the target 3-charge casting. The opening of the sliding nozzle 5 during casting is 4
At the stage of charging, a slight tendency to clogging was observed, and a variation in the level of the molten metal in the mold was observed within a range of 3 mm or less. As a result of the dismantling inspection after the completion of casting, clogging was found in the screw-shaped portion 9 and the sliding nozzle 5
Also, slight adhesion of alumina was observed.

The casting conditions of Inventive Example 5 are of the type shown in FIG. Achieved eight-charge casting, far exceeding the target three-charge casting. The opening degree of the sliding nozzle 5 during casting did not show a tendency to clog, and a very good result was obtained in which the amount of mold level fluctuation was within 2 mm until the final casting charge. When the sliding nozzle 5 was dismantled and inspected after completion of casting, no alumina adhered to the reduced inner diameter portion 8 at all, and only slight alumina adhered to the sliding nozzle 5 was observed. Further, as a result of investigating the quality of the slab, no defect due to the injection of the inert gas was found.

The casting conditions of Invention Example 6 are of the type shown in FIG. Achieved eight-charge casting, far exceeding the target three-charge casting. The opening of the sliding nozzle 5 during casting did not show a tendency to clog, and a very good result was obtained in which the amount of mold level fluctuation was within 2 mm until the final casting charge. When the sliding nozzle 5 was disassembled and inspected after completion of casting, no alumina adhered to the screw-shaped portion 9 at all, and only slight alumina adhered to the sliding nozzle 5. Further, as a result of investigating the quality of the slab, no defect due to the injection of the inert gas was found.

The casting conditions in Comparative Example 1 are of the type shown in FIG. Immediately after the start of the first charge casting, the opening of the sliding nozzle 5 shows a tendency to clog, and the fluctuation of the mold level in the mold is also 20
mm, casting was abandoned during charging. As a result of the disassembly inspection after the completion of the casting, remarkable adhesion of alumina to the sliding nozzle 5 was observed.

The casting conditions of Comparative Example 2 are of the type shown in FIG. Immediately after the start of the first charge casting, the opening of the sliding nozzle 5 shows a tendency to clog, and the fluctuation of the mold level in the mold is also 20
mm, casting was abandoned during charging. As a result of the disassembly inspection after the completion of the casting, remarkable adhesion of alumina to the sliding nozzle 5 was observed.

The casting conditions of Comparative Example 3 are of the type shown in FIG. Immediately after the start of the first charge casting, the opening of the sliding nozzle 5 tends to be clogged, and the level change in the mold is also 20 m.
m, casting was abandoned during charging.
As a result of dismantling inspection after the end of casting, sliding nozzle 5
Marked adhesion of alumina was observed.

[0034]

As described above, it is possible to provide means for making it difficult for metal oxides to adhere to the sliding nozzle, thereby avoiding the stoppage of operation due to clogging, thereby greatly contributing to the improvement of productivity. .

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a state in which casting is performed by applying claim 2 of the present invention in a longitudinal section.

FIG. 2 is a view schematically showing a state in which casting is performed by applying claim 3 of the present invention in a longitudinal section.

FIG. 3 is a diagram schematically showing a state in which casting is performed by applying claim 4 of the present invention in a longitudinal section.

FIG. 4 is a diagram schematically showing a state in which casting is performed by applying claim 2 of the present invention in a longitudinal section.

FIG. 5 is a view schematically showing a state in which casting is performed by applying claim 5 of the present invention in a longitudinal section.

FIG. 6 is a view schematically showing a state in which casting is performed by applying claim 6 of the present invention in a longitudinal section.

FIG. 7 is a view schematically showing a state in which casting is performed by applying claim 6 of the present invention in a longitudinal section.

FIG. 8 is a diagram schematically showing a state in which casting is performed by applying claim 4 of the present invention in a longitudinal section.

FIG. 9 is a diagram schematically showing the flow of molten metal in the vicinity of a stepped inner diameter enlarged portion.

FIG. 10 is a view schematically showing a flow of a molten metal near a tapered inner diameter enlarged portion.

FIG. 11 is a view schematically showing a vertical section of a state in which casting is performed with an inner diameter enlarged portion and an inner diameter reduced portion provided downstream of a sliding plate as a comparative example.

FIG. 12 is a view schematically showing a state in which a screw-shaped portion is provided downstream of a sliding plate and casting is performed as a comparative example in a longitudinal section.

FIG. 13 is a view schematically showing a state in which general casting is performed using a sliding nozzle in a longitudinal section.

[Explanation of symbols]

 1: Tundish 2: Molten metal 3: Mold 4: Upper nozzle 5: Sliding nozzle 5a: Upper plate 5b: Sliding plate 5c: Lower plate 6: Immersion nozzle 7: Inner diameter enlarged portion (groove) 8: Inner diameter reduced portion (rise) 9) Screw-shaped part 10: Gas injection part 11: Flow path

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryoichi Kakimoto 12 Nakamachi, Muroran City Inside Nippon Steel Corporation Muroran Steelworks (72) Inventor Masanobu Suzuki 12 Nakamachi Muroran City Nippon Steel Corporation Muroran F term in steelworks (reference) 4E004 FA00 FB00 HA02 LC04 4E014 DB02

Claims (6)

[Claims] 1. A continuous casting nozzle having at least a flow path through which a molten metal passes, and a sliding plate provided at a lower portion of the flow path for adjusting a flow rate of the molten metal, wherein A nozzle for continuous casting, comprising one or more pressure loss applying portions having an enlarged inner diameter on the upstream side of the sliding plate. 2. The pressure loss applying portion is formed by forming a raised portion around an inner wall of a flow path and increasing an inner diameter immediately below an inner diameter of the raised portion. The nozzle for continuous casting as described. 3. The pressure loss imparting section according to claim 1, wherein a groove is provided on the inner wall of the flow path, and the inner diameter of the groove is made larger than the inner diameter immediately above. Nozzle for continuous casting. 4. The pressure loss applying section according to claim 1, wherein the inner diameter of the sliding plate is made larger than the inner diameter of the flow path, or the inner diameter of the flow path is made larger in the middle. Nozzle for continuous casting. 5. A continuous casting nozzle having at least a flow path through which a molten metal passes, and a sliding plate provided at a lower portion of the flow path for adjusting a flow rate of the molten metal, wherein the nozzle is provided on an inner wall of the flow path. A continuous casting nozzle comprising one or more screw-shaped pressure loss applying portions provided with spiral grooves or bulges. 6. An apparatus according to claim 1, further comprising an inert gas blowing section downstream of said pressure loss applying section.
The continuous casting nozzle according to any one of the above.