JP3460185B2 - Immersion nozzle for casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting immersion nozzle for injecting a molten metal for casting into a mold, and more specifically, a immersion nozzle for casting when injecting a molten metal such as molten steel into a mold. In addition to avoiding problems such as clogging of the inner hole of the mold, the flow condition of the molten metal such as molten steel in the mold is appropriately controlled to avoid excessive disturbance and fluctuation of the molten metal surface, which results in powder and air bubbles. The present invention relates to a casting immersion nozzle capable of obtaining a high-quality metal casting such as a steel ingot in which entrainment of the like is suppressed.

[0002]

2. Description of the Related Art Conventionally, casting using molten metal, for example,
In continuous casting of steel or the like, molten metal is injected from a tundish into a mold through a dipping nozzle. When pouring molten steel from the dipping nozzle into the mold, a certain amount of molten steel is poured into the mold smoothly in the middle of the dipping nozzle flow path without causing blockage, flow rate change, drift, etc. It is important to properly control the flow state of the. In other words, avoiding severe liquid level fluctuations such as so-called "hot water rampage" is very effective in preventing quality deterioration of cast steel due to the inclusion of non-metallic inclusions, inclusion of powder and air bubbles, etc., and obtaining high quality cast steel. is important.

Conventionally, the nozzle shape is improved so as to avoid such blockage in the immersion nozzle, irregular flow rate change, uneven flow, etc., and to make the flow of molten metal such as molten steel in the mold into an appropriate flow state. Many suggestions have been made. For example, Japanese Utility Model Publication No. 4-6351, Japanese Utility Model Publication No. 4-455, Japanese Utility Model Publication No. 61-72361, and Japanese Utility Model Publication No. 61-69.
No. 88, Japanese Utility Model 59-22913, Japanese Utility Model 5
In JP-A-18043, etc., various steps or constrictions are provided in the inner hole of the immersion nozzle to increase the flow velocity of the inner hole, thereby increasing the flow velocity in the vicinity of the meniscus where the molten steel flow easily stagnates. A proposal has been disclosed that avoids flow path blockage of the inner hole portion, irregular fluctuation of flow rate, uneven flow, and the like.

In Japanese Utility Model Application Laid-Open No. 53-14650, "The intersection of the center lines of a plurality of ejection holes extending in the direction of the short side wall of the mold is removed from the center of the nozzle body, and the opposite side of the short side wall is provided. An invention based on "an eccentricly positioned tundish immersion nozzle", that is, a proposal to improve the flow state of the molten metal in the mold by shifting the nozzle immersion position with respect to the mold is disclosed. In addition, actual public Sho 54
No. 2892, Japanese Utility Model Publication No. 53-578 and the like also disclose proposals for improving the flow state of the molten metal by specifying the discharge opening position and direction of the immersion nozzle with respect to the mold. Further, Japanese Patent Publication No. 8-18117 discloses an invention of a level fluctuation control device for controlling molten metal level by applying electromagnetic force to molten steel in order to control the level fluctuation of the mold.

[0005]

However, in the proposal of providing a step or a squeezed portion in the inner hole portion of the immersion nozzle, such as the above Japanese Utility Model Laid-Open No. 4-6351, the flow of molten metal in the inner hole portion becomes faster, so However, there is a technical problem that the discharge flow velocity is also increased, and the flow state in the mold is changed to deviate from the proper flow state. In addition, real public Sho 53-
In the proposal of changing or specifying the opening position and direction of the immersion nozzle with respect to the mold, such as Japanese Patent No. 14650,
In some cases, there is a risk that the fluctuation of the molten metal level of the powder line (meniscus line) will become large, and the nozzle usage time will be long, resulting in the possibility of nozzle clogging, and if clogging occurs. Had a technical problem that the initial setting flow could not be obtained. Further, in the case of Japanese Patent Publication No. 8-18117, electromagnetic force application for controlling the molten metal surface and its control means are required,
Therefore, extra equipment and cost are required.

The present invention has been made in order to solve the above technical problems, and it is a fixed amount of molten metal which does not cause irregular flow rate fluctuations and blockage of molten metal such as molten steel in the middle of the inner hole of the immersion nozzle. It is an object of the present invention to provide a casting dipping nozzle having a specific structure, which allows the molten metal to be smoothly poured into the mold and, at the time of pouring, maintains the flow of the molten metal in the mold in an appropriate state.

[0007]

According to the present invention, there is provided a casting immersion nozzle for injecting a molten metal into a mold, which communicates with an inner hole portion through which the molten metal flows down and an end portion of the inner hole portion. In the casting immersion nozzle including the molten metal flow passage and the molten metal discharge portion having a plurality of openings formed in the outer peripheral wall of the nozzle, a step portion is formed in the inner hole portion. At the same time, there is provided a casting immersion nozzle, wherein a horizontal cross-sectional shape of the molten metal flow path of the molten metal discharge portion is formed in a fan shape that widens from the inner hole toward the opening. The casting immersion nozzle of the present invention is provided with a step portion in the inner hole portion, and the horizontal cross-sectional shape of the molten metal flow path of the molten metal discharge portion is formed into a fan shape having a specific spread angle toward the opening. This is a remarkable structural feature.

In the casting immersion nozzle of the present invention, by providing a stepped portion in the inner hole portion, particularly the inner hole portion located immediately above the meniscus, the molten steel flow velocity in this portion can be increased.
As a result, alumina and other non-metallic contaminants and powders adhere to the wall surface of the flow path, and these become nuclei and the molten metal entangles and adheres to the wall surface. Irregular flow rate due to
Blockage of the flow path is avoided.

In general, starting, stopping, or adjusting the amount of molten metal supplied from the tundish to the immersion nozzle is performed by operating a sliding opening / closing device such as a slide valve provided between the bottom of the tundish and the upper part of the immersion nozzle. Be seen. Usually, the device is composed of a bottom plate and a slide plate, and the diameters thereof are 1.5 times larger than the effective diameter required for steady-state injection speed from the viewpoint of avoiding blockage due to inclusions such as alumina and other flow abnormalities. It is perforated about twice or more. Therefore, during the normal operation, the slide plate is shifted and the injection is performed in a state where the slide plate is squeezed to an effective diameter required for a predetermined injection speed.

However, since the position of the opening / closing device hole is eccentric in the injection in the throttled state, the molten metal during the injection often causes a nonuniform flow, so that the molten metal flows out from a plurality of discharge openings provided at the lower end of the immersion nozzle. A so-called one-sided flow phenomenon appears in which the amounts are uneven. As a result, in the state as it is, the molten metal flow in the mold is liable to be biased in a specific direction. However, in the casting immersion nozzle of the present invention, since the stepped portion is provided at a predetermined position at a predetermined length, the flow velocity of the molten metal flow after that portion is increased,
Since a steady turbulent state is achieved, uneven flow is eliminated, and the amount of molten metal discharged from the plurality of openings can be equalized.

On the other hand, if the stepped portion is simply provided in the inner hole of the immersion nozzle, the flow velocity of the molten metal flow is increased by the stepped portion, and the flow in the vicinity of the discharge hole is also increased.
As a result, ascending flow, entrainment flow (suction flow), etc. in the molten metal flow discharged into the mold increase, and the flow velocity of the molten metal flow hitting the inner wall of the mold increases. The rising flow, the increase in the entrainment flow, and the increase in the velocity of the molten metal flow that hits the inner wall of the mold drastically change the flow state of the molten metal in the mold, resulting in severe vertical fluctuations and disturbance of the powder line surface, and often non-metallic materials. It causes inclusion of inclusions, inclusion of powder, and inclusion of gas, which causes pinholes in the product casting. Therefore, there is a trade-off between increasing the flow velocity of the molten metal in order to suppress irregular flow rate fluctuations, clogging, uneven flow, etc. of the molten metal flowing down the inside of the immersion nozzle, and proper control of the flow state of the molten metal in the mold. In the past, it was difficult to completely solve both of them.

According to the present invention, the horizontal cross-sectional shape of the molten metal flow path of the molten metal discharge portion is formed into a fan shape that expands from the inner hole toward the opening, so that the flow velocity accelerated at the step portion is re-opened at the opening. This is to solve the above-mentioned problems by lowering the temperature and avoiding the occurrence of an undesired flow state in the mold due to the discharge flow. In this case, in the rectangular mold in which the casting immersion nozzle is immersed, the melt flow discharged from the discharge opening of the nozzle immersed in the mold is exactly applied to the two corners at both ends of the short side wall of the mold. With respect to the angle β formed between the center position and the two corners at both ends of the short side wall, it is possible to obtain a particularly suitable molten metal flow state in the mold by setting the spread angle α of the fan-shaped discharge portion to satisfy the following condition. You can 2β>α> 1 / 4β

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The immersion nozzle for casting according to the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a casting immersion nozzle according to an embodiment of the present invention, FIG. 1 (a) is a vertical sectional front view, and FIG. 1 (b) is a horizontal sectional view of a nozzle discharge part. As shown in FIG. 1, a casting immersion nozzle 1 according to the present invention includes a tubular inner hole portion 2 through which molten metal flows, a step portion 3 provided therein, and an inner hole portion 2. The molten metal discharge part 4 connected to the lower end and the powder line part 7 provided on the outer peripheral wall surface of the nozzle 1 are provided. In continuous casting of steel or the like, the upper end 1a of the immersion nozzle 1 is attached to the lower part of a slide opening / closing device (not shown) which is usually a slide plate attached to the bottom plate of a tundish, and the molten metal is injected at a predetermined injection amount. It is introduced into the upper portion 2a of the inner hole portion 2 from the slide plate which is narrowed to the required aperture.

A step portion 3 is provided on the inner hole wall of the nozzle inner hole portion 2 located immediately above the powder line portion 7, and the molten metal flow speeds up the flow velocity here, and the flow path is in a steady turbulent state. It flows down and reaches the molten metal discharge part 4 connected to the lower end of the inner hole. The molten metal discharge part 4 of the present invention includes a molten metal flow path 6
As shown in FIG. 1 (b), the horizontal cross-sectional shape is formed in a fan shape that extends from the inner hole toward the opening 5. In the case of this immersion nozzle 1, two fan-shaped molten metal flow paths 6 and openings 5 are provided symmetrically with respect to a vertical plane passing through the central axis of the immersion nozzle.

In the case of the molten metal discharge portion 4 of this figure, two fan-shaped molten metal flow paths 6 extending from the central portion to the opening 5 provided in the outer peripheral wall surface are each approximately 15 degrees with respect to the horizontal. It is formed to have a descending slope. Then, the flow velocity of the molten metal flow is increased by the step portion 3, the molten metal flow reaching the molten metal discharge part 4 is evenly divided into two streams by the molten metal discharge part 4, and the respective speeds are gradually reduced. The molten metal in the mold is discharged into the mold through both openings 5 and 5 in a state where the molten metal is relaxed to an appropriate discharge speed.

In the present invention, the dipping nozzle has its central axis in the vicinity of the intersection of the diagonal lines of the four corners of the mold 8 having a generally rectangular upper surface, that is, in the vicinity of the center of the mold 8, as shown in FIG. It is positioned and immersed in the mold 8, and the surface of the powder layer existing in layers on the molten metal (molten steel) interface is inserted and arranged so as to be positioned in the nozzle powder line portion 7.

In the immersion nozzle 1 of the present invention, the installation position of the stepped portion 3 provided in the inner hole 2 for the purpose of contracting the molten metal (molten steel) flow and locally accelerating the flow velocity is not necessarily the same as in the above embodiment. Is not limited to
When a step is provided in the inner hole located directly above the meniscus, the molten steel flow velocity is accelerated in this part, which causes alumina and other non-metallic impurities and powders to adhere to the wall surface of the inner hole. It is possible to further prevent the molten metal from becoming a nucleus and being entangled with and adhered to the molten metal. As a result, irregular fluctuations in the flow rate and blockage of the flow channel due to the rapid narrowing of the flow channel diameter of the adhered portion can be further avoided.

Further, the shape of the step portion 3 is not particularly limited as long as the above object can be achieved,
It may be formed in any shape including a spiral shape, but in general, a step thickness of 3 to 10 mm and a length of 50
It is more preferable to form it in an annular cylindrical shape of about 200 mm to 200 mm. Further, the step portion 3 may be installed in one step or a plurality of steps. In this case, as the flow velocity of the molten metal (molten steel) flow due to the step portion 3 becomes faster, the spread angle of the fan-shaped molten metal flow channel 6 is correspondingly set larger. The molten metal discharge part 4 having the fan-shaped molten metal flow path 6 of the present invention relaxes the molten metal flow velocity accelerated by the stepped portion 3 to a flow velocity capable of maintaining a proper molten metal flow state in the mold 8. After that, it acts to eject the liquid toward the peripheral wall of the mold.

The spread angle α of the fan-shaped molten metal flow path 6 is, as shown in FIG. 2, the opening 5 of the nozzle 1 immersed in the both ends of the short side wall of the rectangular mold 8 in the mold 8.
Make sure that the molten metal discharged from the mold hits the mold 8
With respect to the angle β formed by the center point of and the both corners of the mold 8,
It is preferable to set the divergence angle α of the fan-shaped molten metal flow path 6 within a range that satisfies the following condition, and thereby a particularly preferable molten metal flow state in the mold can be obtained. 2β>α> 1 / 4β

The spread angle α of the fan-shaped molten metal flow path 6
Is more than 2β, the melt flow discharged from the opening 5 of the immersion nozzle 1 hits the wall surface near the midpoint of the long side of the mold and the meniscus surface (powder line surface) is agitated, which is not preferable. On the other hand, when α is smaller than 1 / 4β, the molten metal flow hitting the corners is reduced and the effect is halved.

The constituent material of the immersion nozzle of the present invention is
It is not particularly limited, and a refractory material that is usually used for this kind of nozzle constituent material can be used. For example, a refractory made of alumina / graphite, zirconia / graphite, zirconia / graphite / boron nitride, etc. can be used for the nozzle body.

[0022]

[Examples] As "Example 1 and Comparative Examples 1 to 3" and "Example 1", the immersion nozzle shown in FIG.
30 mm, inner hole diameter 70 mm, stepped portion of 5 mm in wall thickness, 150 mm in length inside the inner hole immediately above the powder line portion, the discharge portion is a symmetrical fan-shaped discharge portion 2 that expands toward the opening.
Individual pieces, a spread angle α = 25 degrees, a discharge section flow path inclination of 15 degrees with respect to the horizontal, and an opening of 70 × 80 mm) were prepared. As “Comparative Example 1”, the immersion nozzle shown in FIG. 3 (nozzle length and inner hole diameter are the same as those of Example 1, there is no step difference in inner hole, two discharge sections are straight-shaped, and a flow path is inclined) 15 degrees and the opening was 70 × 80 mm). As “Comparative Example 2”, the immersion nozzle shown in FIG.
Same as Example 1, with the same steps as in Example 1, two discharge sections having a straight discharge shape, a flow channel inclination of 15 degrees, and an opening of 70 ×.
80 mm) was prepared. As “Comparative Example 3”, the immersion nozzle shown in FIG. 5 (nozzle length and inner hole diameter are the same as in Example 1, there is no step difference in the inner hole portion, and two fan-shaped discharge sections similar to those in Example 1 are used for the discharge section). , Channel inclination is 15 degrees, opening is 70 × 80m
m) was prepared.

Each nozzle is placed at the center position of the mold shown in FIG. 2 (rectangle: size: 300 × 1800 mm, angle β = 19 degrees between the center of the mold and both end portions of the short side wall).
Dipping as shown in FIG.
on / min. Was poured into the mold. Table 1 shows the results of confirming the usage status of each nozzle for 6 charges and about 300 minutes.

[0024]

[Table 1]

From the results shown in Table 1, in the immersion nozzle of Comparative Example 2 in which the inner hole portion has a step, but the discharge portion is not fan-shaped and straight, the discharge flow is a meniscus portion (powder line portion).
It was found that the molten steel surface was violently changed and the quality of the steel was adversely affected. On the contrary, in the immersion nozzle of Comparative Example 3 in which the discharge portion was formed in a fan shape satisfying the conditions of the present application and the inner hole portion was not provided with a step, the inner hole portion was gradually closed, resulting in an inner hole diameter. It was also confirmed that the discharge flow velocity is accelerated due to the reduction in volume and the outflow velocity initially set changes, and the effectiveness of the fan-shaped discharge flow path is lost. In order to obtain good quality steel, it is necessary to consistently maintain various conditions such as the discharge flow rate that was initially set during casting. It has not been possible to achieve this with a nozzle provided with only one of the parts, but it has been found for the first time that this can be achieved with a nozzle according to the invention which combines both means under specific conditions.

[0026]

EFFECTS OF THE INVENTION The casting immersion nozzle of the present invention has the above-mentioned specific combination configuration, and when a molten metal such as molten steel is injected into the mold, the molten steel flow has irregular flow rate fluctuations and inner holes in the nozzle inner hole portion. Not only can troubles such as blockage be avoided, but the flow state of the molten metal such as the injected molten steel in the mold is appropriately controlled, and the molten metal surface is excessively disturbed by the discharged molten steel flow.
Fluctuations are avoided, and as a result, the inclusion of non-metallic inclusions, the entrainment of powder, the entrainment of gas, etc. is suppressed, and a metal casting such as a high-quality steel ingot can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a casting immersion nozzle according to the present invention, in which (a) is a sectional view of the immersion nozzle and (b) is a sectional view taken along line AA of (a). is there.

FIG. 2 is a schematic diagram showing a dipping state of a mold and a dipping nozzle for casting.

FIG. 3A is a vertical cross-sectional view of an immersion nozzle according to Comparative Example 1 (inner hole portion has no step, discharge hole portion is straight), and FIG. 3B is a sectional view taken along line AA of FIG. Is.

FIG. 4 (a) is a vertical cross-sectional view of an immersion nozzle (with a step difference in the inner hole portion, a straight discharge hole portion) according to Comparative Example 2, and FIG. 4 (b) is a sectional view taken along the line AA of (a). Is.

FIG. 5 (a) is a vertical cross-sectional view of an immersion nozzle according to Comparative Example 3 (inner hole portion has no step, discharge hole portion has a fan shape),
(B) is an AA sectional view of (a).

[Explanation of symbols]

1 immersion nozzle 1a immersion nozzle upper end 2 Inner hole 2a inner wall 3 steps 4 Molten metal discharge part 5 openings 6 Molten metal flow path 7 Powder line section 8 molds

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichiro Mochizuki No. 1 Minamito, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory (56) Reference JP-A-8-294757 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) B22D 11/10 330 B22D 41/50 520

Claims (3)

(57) [Claims] 1. A casting immersion nozzle for injecting molten metal into a mold, comprising: an inner hole portion through which the molten metal flows, a molten metal flow path communicating with an end portion of the inner hole portion, and an outer peripheral wall of the nozzle. In a casting immersion nozzle including a molten metal discharge part having a plurality of formed openings, a step portion is formed in the inner hole part, and a horizontal cross section of a molten metal flow path of the molten metal discharge part. shape is formed from the inner bore in a fan shape spreading toward the opening, expanding horizontal cross-sectional shape of the molten metal passage of the molten metal discharge section
Ramp angle α and rectangle into which the dipping nozzle for casting is dipped
Between the center position of the mold and the two angles at both ends of the short side wall
An immersion nozzle for casting, characterized in that a relationship of 2β>α> 1 / 4β is established with an angle β formed . 2. The casting immersion nozzle according to claim 1, wherein the step portion is provided in an inner hole portion located directly above the molten metal meniscus. 3. The step portion has a step thickness of 3 to 10 mm and a length of 50 to 20 inward from the inner hole wall forming the inner hole portion.
The immersion nozzle for casting according to claim 1 or 2, wherein the immersion nozzle is formed in an annular cylinder shape of 0 mm.