JPH07214257A - Pouring device for continuous casting - Google Patents

Abstract

(57) [Abstract] [Purpose] A pouring device for continuous casting, which is effective in eliminating casting defects that lead to deterioration of slab quality by effectively suppressing stagnation of molten steel flow near the immersion nozzle. Develop and propose. In a pouring device provided with a dipping nozzle and a pair of flow restricting plates arranged in parallel with the long side wall of the mold in the upper area of the discharge port including the molten metal surface, 5 on each side parallel to the long side wall of the mold that sandwiches the nozzle
A pair of flow restricting plates arranged in series at intervals of 60 mm,
It is suspended through a flow control plate holding frame attached to the lower part of the tundish, and this flow control plate is supported so that it can be steady by an attitude control guide fixed to the upper part of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouring device for continuous casting used when pouring molten steel in a tundish into a mold.

[0002]

2. Description of the Related Art Conventionally, in continuous casting of steel, injecting molten steel into a mold, an immersion nozzle is attached to the molten steel outlet at the bottom of the tundish, and the lower part of this immersion nozzle is immersed in the molten steel in the mold. In this state, the two nozzles are provided at the lower part of the dipping nozzle to discharge into the mold.

By the way, in the case of a known general two-hole type immersion nozzle, as shown in FIG. 1 (a), the molten steel 5 flowing out from the discharge ports 2 and 2'is partially shown by an arrow 8a. To
A downward descending flow follows along the wall surface, and the remaining part rises to a molten steel surface flow as indicated by an arrow 8b. Usually, the inclusions in the molten steel float on the rising flow, and the floating inclusions are adsorbed by the molten powder 3 floating on the surface of the molten steel, whereby the inclusions are removed from the molten steel. The molten powder 3 flows between the inner wall surface of the mold 4 and the outer surface of the solidified shell 6 to ensure smooth lubrication of these.

The molten steel flow injected from the tundish into the mold 4 through the immersion nozzle 1 is basically the above-described downward flow 8a and upward flow (molten steel surface flow) 8b, but it particularly collides with the mold wall surface. Then, the molten steel surface flow 8b which has been reversed is a flow from the short side of the mold toward the dipping nozzle 1 along the molten metal surface. Therefore, in the vicinity of the immersion nozzle 1, this flow encounters another molten steel flow and collides with each other, forming a stagnant region 9 as shown in FIG. 1B.

When such a stagnation of the molten steel surface flow 8b occurs, the heat supply to the molten powder 3 floating on the molten metal surface becomes insufficient and the melting of the powder powder is hindered.
As a result, the powder consumption is reduced, and not only the lubrication effect is insufficient, but also the amount of inclusions to be adsorbed by the powder and discharged from the mold is reduced. That is, since the inclusions are accumulated in the stagnation region 9 of the molten steel inversion flow and remain as they are without being discharged, the bubbles and inclusions are trapped in the initial solidified shell generated in this part to cause a slab surface defect. It will be.

In order to solve such a problem, some conventional techniques as described below have been proposed. A method has been considered in which argon gas is blown into the immersion nozzle to accelerate the flow rate of the molten steel discharged into the mold, thereby eliminating the stagnation of the molten steel flow described above. However, in the case of this technique, there is a possibility that the surface of the molten metal becomes wavy and the powder is involved, which rather causes an increase in casting defects. In addition, in the case of this method, since the initial solidified shell is easily broken and the molten steel has to be solidified in the lower part of the mold and the secondary cooling zone, there is a drawback that the increase in the flow rate is limited. A method has been proposed in which an electromagnetic coil is attached to a mold to generate a magnetic field in the molten steel in the mold, and the Lorentz force is used to stir the molten steel to utilize the electromagnetic stirring technology. However, this method has a drawback that the equipment cost is extremely high. (Japanese Patent Laid-Open No. 63-33157) Japanese Patent Laid-Open No. 63-235050 proposes a method of mounting a flow restricting plate on the outside of the immersion nozzle body and forming a swirling flow along the flow restricting plate on the molten metal surface. ing. However, in the case of this conventional technique, since the molten steel discharge port is opened in the direction parallel to the long side wall of the mold, it is not possible to completely avoid the collision of the molten steel flow generated near the immersion nozzle. However, there was a drawback that it was less effective. Japanese Unexamined Patent Publication (Kokai) No. 5-14685 discloses a method for overcoming the problems of the above-described technique, "2 in a portion which is immersed in molten steel in a continuous casting mold and is a lower immersed portion.
In a dipping nozzle having individual discharge ports, a pair of flow restricting plates disposed above the discharge ports including the molten metal surface are provided on the mold long side wall from the outer side surface of the nozzle body toward the short side walls. And project each discharge port against the flow restrictor plate.
We propose a submerged nozzle characterized by being opened in the direction of ° ~ 60 °. However, even in the case of this conventional technique, it is not possible to completely avoid the influence of the molten steel flow, and eventually the entire nozzle is vibrated or the nozzle is twisted in the circumferential direction to change the direction of the flow restrictor plate. There was a problem that the flow direction was not controlled.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to effectively prevent the above-mentioned problem of the prior art, that is, the stagnation of the molten steel flow generated near the immersion nozzle, to achieve the casting slab. We are developing and proposing a pouring device for continuous casting that is effective in eliminating casting defects that cause deterioration of quality. Another object of the present invention is to cast molten steel having a higher degree of cleanliness and improve the life of the nozzle by devising the positional relationship between the nozzle and the flow control plate. Still another object of the present invention is to provide a guide for controlling the attitude of the flow restricting plate so that the flow restricting plate always maintains the correct attitude to ensure an appropriate molten steel flow (swirl flow). It occurs in the vicinity of the meniscus. Still another object of the present invention is to use molybdenum zirconia as the material of the flow control plate,
The purpose is to eliminate the influence of buoyancy and ensure stable holding of the flow control plate.

[0008]

[Means for Solving the Problems] In order to improve the surface quality of a slab and to realize stable molten steel casting, the present inventors have taken countermeasures by reproducing molten steel flow in a mold by a water model experiment. It was In the course of such an experiment, the above-mentioned Japanese Patent Laid-Open No. 5-14
The relationship between the nozzle and the flow control plate disclosed in Japanese Patent No. 6851, the method for holding the flow control plate, the material of the flow control plate, etc. were examined. As a result, the inventors have come up with a means for solving the problems associated with the following gist structure.

That is, according to the present invention, (1) the lower part is immersed in molten steel in a continuous casting mold, and two discharge holes are formed in the lower part in a direction oblique to the long side wall of the mold. In a pouring device comprising an immersion nozzle provided with an outlet and a pair of flow restricting plates arranged in parallel with the long side wall of the mold in the upper area of the discharge port including the molten metal surface, the immersion nozzle comprises: A pouring device for continuous casting, characterized in that the flow control plates are arranged in series apart from each other, and an attitude control guide is attached to the flow control plates. (2) An immersion nozzle in which the lower part is immersed in molten steel in a continuous casting mold, and two discharging ports are provided in the lower part in the oblique direction with respect to the long side wall of the mold, In a pouring device provided with a pair of flow restricting plates arranged in parallel to the mold long side wall in the upper area of the discharge port including the molten metal surface, with respect to the immersion nozzle, the mold long side sandwiching the nozzle. A pair of flow control plates, which are arranged in series at intervals of 5 to 60 mm on both sides parallel to the wall, are suspended via a flow control plate holding frame attached to the lower part of the tundish, and this flow control is performed. The casting machine for continuous casting is characterized in that the plate is supported by a posture control guide fixed to the upper part of the mold so as to be steady. (3) Immersion nozzle in which the lower part is immersed in molten steel in a continuous casting mold, and two discharge ports are provided in the lower part in the direction of 10 to 20 ° to the long side wall of the mold. And a pair of flow restricting plates arranged in parallel to the long side wall of the mold in the upper area of the discharge port including the molten metal surface, in a pouring device, the mold sandwiching the nozzle with respect to the immersion nozzle. A flow control plate in which a pair of flow control plates made of molybdenum zirconia are arranged in series on both sides parallel to the long side wall at intervals of 5 to 15 mm, and the flow control plates are attached to the lower part of the tundish. A pouring device for continuous casting, characterized in that it is suspended through a holding frame and is supported so as to be able to prevent steady movement via a posture control guide fixed to the upper part of the mold. Is.

[0010]

As described above, the pouring device for continuous casting according to the present invention, as shown in FIG. 2a, is mainly installed in the bottom portion of the tundish (not shown) and has two openings opened in opposite directions. Used to inject the molten steel in the tundish into the mold 4 through a pair of molten steel discharge ports 2 and 2 '
From a hole type immersion nozzle 1 and a pair of flow restricting plates 7A and 7B which are arranged in series on both sides parallel to the long side wall of the mold that sandwiches the immersion nozzle 1 with a constant interval (d). It is configured.

With respect to the immersion nozzle 1, one of the features of the present invention is that the discharge ports 2 and 2'opened at symmetrical positions are opened in a direction parallel to the long side wall of the mold as in the conventional case. Instead of forming holes, a constant angle, for example, 5 ° to the flow restricting plates 7A, 7B and the long side wall of the mold in the circumferential direction of the nozzle.
By opening the holes in the direction deviated within the range of 60 °, the discharge flow itself from the nozzle of the molten steel 5 is discharged in a direction that swirls from the beginning, whereby the main body of the immersion nozzle 1 is centered. The swirling flow is also formed on the molten metal surface.

In such a submerged nozzle 1, the opening direction of the discharge ports 2 and 2'is displaced from the direction of the flow restricting plates 7A and 7B by 5 ° to 60 ° in the circumferential direction of the nozzle. Since a hole is opened toward, a clean weak swirl flow is generated over the entire area of the mold. Therefore, the stagnation of the molten steel flow around the nozzle body on the molten metal surface is completely eliminated. As a result, the inclusion of inclusions at a specific position does not occur, and the powder 3 due to the decrease in the temperature of the molten steel is used.
It also eliminates the reduction of the consumption amount of. As a result, the ability of the powder 3 to remove inclusions can be prevented from decreasing, and casting defects due to inclusions accumulated on the molten metal surface can be effectively prevented.

By making the discharge direction of the discharge ports 2 and 2'at an angle with respect to a flow restricting plate installed parallel to the long side wall of the mold, swirling around the immersion nozzle 1 on the molten metal surface. A stable flow is generated, but this molten steel swirl flow 8a, 8b
Varies depending on the direction of the openings of the discharge ports 2 and 2 ′. For example, the swirling flow velocity gradually increases by increasing the opening angle θ and reaches the maximum at 20 °.
When it exceeds 20 °, it tends to decrease gradually thereafter. In order to reduce the influence on other casting conditions, the angle range of the discharge ports 2 and 2'in the present invention is preferably 10 ° to 20 °.

The flow restricting plates 7A and 7B must be constructed so as not to obstruct the flow of the molten steel discharge flow. For this reason, the lower end is the upper end edge of the discharge port. on the other hand,
The upper end of the flow control plate is higher than the height at which the surface of the molten metal and the powder floating on it are separated, and it is necessary to have a height for suspending and supporting it by a flow control plate support frame, as described later. The width of the flow restricting plates 7A, 7B is about half the distance from the outer peripheral surface of the immersion nozzle to the short side of the mold, that is, the inner diameter on the long side is D
In this case, 0.3 Dmm to 0.6 Dmm is preferable.

The flow restricting plates 7A and 7B are spaced apart from each other in relation to the immersion nozzle body and are arranged in parallel with and in series with the long side wall of the mold in the center of the mold in the thickness direction. To be installed. For example, the flow control plates 7A, 7B
In order to suspend the flow control plate at the above-mentioned predetermined position, as shown in FIG. 2, a flow restricting plate holding frame 10 having fixing parts 10a and 10b is attached to the bottom of the tundish, and the flow restricting plate is fixed to the fixing part 10a. ,
It is preferable to suspend and support the molten steel 5 in the mold in a dipped state via 10b.

Further, the flow control plates 7A and 7B have a pair of postures fixed to the upper end of the mold corresponding to the flow control plates so as to alleviate the influence of the swirling flow of the molten steel in the mold and to maintain the flow control plates in the correct posture. It is preferable that the control guides 11a and 11b are supported so as to be steady. For example, as shown in FIG.
A pair of attitude control guides 11a, 11b are fixed to the upper end surface of the mold 4, and the attitude control guides 11a, 11b are provided with guide grooves 11g, 11g 'in which the flow restricting plates are loosely fitted.
The flow restricting plate is fitted in this groove, or as shown in FIG. 4a, the flow restricting plate is projected and fixed leaving a gap where the flow restricting plate is located, and is loosely sandwiched by the posture control guides 12a and 12b, and shakes. It is preferable to support it so that it can be stopped.

Further, as the material of the flow restricting plates 7A and 7B, zirconia graphite, zirconide, molybdenum zirconia, etc. are preferable since they have excellent melting resistance. In particular, molybdenum zirconia has a specific gravity of 7.2 to 8.5, which is larger than that of molten steel, so that push-back due to buoyancy does not cause displacement of the holding position of the flow control plate, and stable pouring work can be secured. Therefore, it is more preferable.

With respect to the immersion nozzle 1, the flow restricting plates 7A and 7B are arranged in series on both sides of the long side wall of the mold sandwiching the nozzle at intervals of 5 to 90 mm. . This spacing is because if the space exceeds 90 mm, the flow control effect is lost. On the other hand, if the space is less than 5 mm, collision may occur due to the influence of the mold oscillating. More preferably 5
The range is 60 mm, more preferably 5 to 15 mm.

[0019]

[Example] 60 tons of SUS304 molten steel, 154 mm on the short side,
Using a mold with a long side of 1070mm, molten steel temperature 1510 ℃, casting speed
Under a casting condition of 880 to 930 mm / min, a pouring experiment was conducted by a continuous casting machine using the pouring device of the present invention and the conventional pouring device.

Example 1 A flow control plate made of zirconia carbon (l: 250 mm, t: 20 m)
m, h: 200 mm) at a predetermined position in the mold, that is, through the flow restricting plate holding frame shown in Fig. 3, and the immersion nozzle (outer diameter: 90 mmφ, outlet diameter: 40 mmφ, outlet inclination angle: 10 °) outer peripheral surface Were suspended and supported at a distance of 10 mm from the above, and the molten steel was poured into the mold from the tundish through the immersion nozzle. As a result, the displacement of the flow control plate was slight even after 7 hours of operation, and there was no distortion of the nozzle. In addition, the melting loss of the flow control plate is 0.5-
At 1.0 mm / H, there were no particular problems.

Embodiment 2 According to the above-mentioned Embodiment 1, not only the flow restricting plate support frame is used but also the middle part of the flow restricting plate is fixed to the upper surface of the mold.
It was supported by the attitude control guide shown in (1) so that it could be steady, and the molten metal was poured in the same manner. As a result, there was no displacement of the flow control plate and no distortion of the nozzle even after 7 hours of operation.

Example 3 In accordance with Example 1 above, an experiment was carried out using a material for the flow restricting plate made of molybdenum zirconia. As a result, the stability of the flow control plate was dramatically improved, there was no displacement of the flow control plate and no nozzle distortion even after 8 hours of operation, and the damage to the nozzle and the flow control plate was very slight. It was

Conventional Example 1 Immersion Nozzle (Outer Diameter: 90 mmφ, Discharge Port Diameter: 40 mmφ, Discharge Port Inclination Angle: 10 °) From the outer peripheral surface toward the mold short side wall, parallel to the long side wall, made of alumina carbon A pair of flow control plates (l: 200 mm, t: 20 mm, h: 200 mm) were projected, and the molten steel was poured from the tundish into the mold through such a flow control plate fixed type immersion nozzle. As a result, only 30
Distortion occurred between the nozzle and the flow restricting plate in minutes, the flow restricting effect was decreased, the flow beside the nozzle stagnated, and the mold temperature was decreased at the nozzle side. It is considered that this is because the entire nozzle was displaced from the mounting position due to the force of pushing back the molten steel and the collision of the molten steel flow. Moreover, the nozzle and the flow control plate are severely melted, and the life is reached by the operation for 1 hour, which is controlled by the melting speed of the slag line. The rate of erosion was 6 to 7 mm 3 / hour.

Comparative Test When continuously casting SUS 304 molten steel and continuously casting a slab having a thickness of 150 mm, when the pouring apparatus according to the present invention shown in FIG. 5 (a) is used, the control shown in FIG. 5 (b) is used. A molten metal pouring comparison test was carried out for the case of using a fixed flow plate immersion nozzle and the case of using a conventional immersion nozzle without a flow restrictor shown in FIG. 5 (c). The evaluation in this test was judged by the cleanliness in the slab, and the cleanliness was measured according to the method specified in JIS-G0555. The sample was cut into 5 steps in the thickness direction of the slab and 3 steps in the width direction. Then, after mirror-polishing this sample, a field of view of 20 mmφ was investigated. The results are shown in Table 1.

[Table 1]

As shown in the results in Table 1 above, the pouring apparatus according to the present invention has the best cleanliness. In addition, with the equipment of 7 continuous casting (60 tons x 7 = 420 tons, 8 tons
Time) worked effectively. However, the equipment of
The limit is 60 tons and 70 minutes, and the surface cleanliness of the central part of the slag tends to be inferior to that of the short side in the device. Therefore, grinder polishing was necessary.

[0026]

As described above, according to the present invention, the following effects can be expected. The stagnation of the molten metal flow is eliminated, the molten metal surface temperature becomes uniform, and the ability of powder to adsorb inclusions is improved. Since the flow control effect is excellent, it is not necessary to increase the discharge flow rate of the molten metal, so that the powder is not entrained. Since slab defects due to inclusions accumulated on the surface of the molten metal can be reduced, the quality of the slab is improved. The life of the equipment is long, the above effects can be obtained in continuous casting, and the equipment cost is low.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a usage state of a conventional immersion nozzle,
(a) is a longitudinal sectional view and (b) is a schematic view of molten steel flow.

FIG. 2 is an explanatory view of a usage state of the pouring device of the present invention,
(a) is a vertical sectional view, and (b) is a horizontal sectional view.

FIG. 3 is a perspective view of a flow restricting plate support frame.

FIG. 4 is a perspective view of a posture control guide.

FIG. 5 is a schematic diagram of various nozzles used in a comparative test of examples.

[Explanation of symbols]

 1 Nozzle body 2, 2'Discharge port 3 Powder 4 Mold 5 Molten steel 6 Solidification shell 7A, 7B Suppression plate 8a, 8b Molten steel flow 9 Stagnation area 10 Suppression plate support frame 10a, 10b Fixed part 11a, 11b, 12a, 12b Posture control guide 11g, 11g 'Guide groove

Claims (3)

[Claims] 1. A submerged nozzle in which a lower portion is immersed in molten steel in a continuous casting mold, and two discharge ports are provided in the lower portion in a direction oblique to a long side wall of the mold. And a pair of flow restricting plates arranged in parallel to the long side wall of the mold in the upper area of the discharge port including the molten metal surface, wherein the immersion nozzle and the flow restricting plates are provided. A pouring device for continuous casting, characterized in that the flow control plates are provided separately from each other in series, and an attitude control guide is attached to the flow control plate. 2. A submerged nozzle in which a lower part is immersed in molten steel in a continuous casting mold, and two discharge ports are provided in the lower part in a direction oblique to a long side wall of the mold. And a pair of flow restricting plates arranged in parallel to the long side wall of the mold in the upper region of the discharge port including the molten metal surface, the mold holding the nozzle with respect to the immersion nozzle. A pair of flow control plates, which are arranged in series at intervals of 5 to 60 mm on both sides parallel to the long side wall, are suspended via a flow control plate holding frame attached to the lower part of the tundish. The pouring device for continuous casting is characterized in that the flow control plate is supported so as to be steady by a posture control guide fixed to the upper part of the mold. 3. A lower part is immersed in molten steel in a continuous casting mold, and two discharge ports are provided in the lower part in the direction of 10 to 20 ° with respect to the long side wall of the mold. In a pouring device comprising a dipping nozzle and a pair of flow restricting plates arranged in parallel with the long side wall of the mold in the upper area of the discharge port including the molten metal surface, the nozzle is provided with respect to the dipping nozzle. A pair of flow control plates made of molybdenum zirconia were placed in series on both sides parallel to the long side wall of the mold, with a spacing of 5 to 15 mm, and the flow control plates were attached to the lower part of the tundish. A pouring device for continuous casting characterized in that it is suspended through a flow plate holding frame and is supported so as to be able to prevent steady movement through a posture control guide fixed to the upper part of the mold.