JPH11320046A - Immersion nozzle for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion nozzle for casting, with which at the time of pouring molten metal such as molten steel into a mold, such trouble as clogging in the inner hole of a nozzle is avoided and also, fluid condition of the molten metal such as the poured molten steel in the mold is suitably controlled and thus, excess disturbance and variation of the molten metal surface are avoided and in this way, a metal cast such as high quality steel ingot can be obtd. SOLUTION: An immersion nozzle 1 for pouring molten metal into mold, is provided with an inner hole 2 for passing the molten metal and a molten metal spouting part 4 having plural opening holes formed in the molten metal flowing passage communicated with the end part of the inner hole part 2, and in the outer peripheral wall of the nozzle. A step part 3 is formed in the inner hole 2 of the nozzle and also, the horizontal cross sectional shape of the molten metal flowing passage in the spouting part is formed as a sector shape from the inner hole side to the opened hole.

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 molten metal for casting into a mold, and more particularly, to a casting immersion nozzle for injecting molten metal such as molten steel into a mold. In addition to avoiding problems such as blockage of the inner hole, the flow state of the molten metal such as injected molten steel in the mold is appropriately controlled to prevent excessive disturbance and fluctuation of the molten metal surface, thereby preventing 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 steel is suppressed.

[0002]

2. Description of the Related Art Conventionally, casting using molten metal, for example,
In continuous casting of steel or the like, a molten metal is injected from a tundish into a mold through a dipping nozzle. When pouring molten steel from the immersion nozzle into the mold, a fixed amount of molten steel is poured smoothly into the mold without causing blockage, flow rate change, drift, etc. It is important to appropriately control the flow state of the fluid. In other words, avoiding a drastic liquid level fluctuation such as a so-called “hot run” suppresses the deterioration of cast steel quality due to the incorporation of non-metallic inclusions, the incorporation of powder or air bubbles, etc., and is extremely important in obtaining good quality cast steel. is important.

Conventionally, the shape of the nozzle has been improved so as to avoid such blockage, irregular flow rate change, drift, etc. in the immersion nozzle 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 Laid-Open No. 4-63551, Japanese Utility Model Laid-Open No. 4-455, Japanese Utility Model Publication No. 61-72361, Japanese Utility Model Application Publication No.
No. 88, Japanese Utility Model Publication No. 59-22913, Japanese Utility Model Publication No. 5
In JP-A-7-18043 and the like, by providing various steps or constrictions in the inner hole of the immersion nozzle to increase the flow velocity in the inner hole, the flow velocity near the meniscus where the molten steel flow tends to stagnate is increased, There has been disclosed a proposal for avoiding blockage of the flow passage in the inner hole, irregular fluctuation of the flow rate, and drift.

Japanese Utility Model Application Laid-Open No. 53-14650 discloses that the position of the intersection of the center lines of a plurality of discharge holes in the direction of the short side wall of the mold is deviated from the center of the nozzle body, and is located on the opposite short side wall side. There is disclosed an invention which has a gist of a "tandish immersion nozzle positioned eccentrically", that is, a proposal for improving a flow state of molten metal in a mold by shifting a nozzle immersion position with respect to a mold. In addition,
Japanese Unexamined Patent Publication Nos. 2892 and 53-578 also disclose proposals for improving the flow state of molten metal by specifying the position and direction of the discharge opening of a dipping nozzle with respect to a mold. Further, Japanese Patent Publication No. Hei 8-18117 discloses an invention of a molten metal level fluctuation control device for controlling the molten steel level by applying an electromagnetic force to the molten steel in order to control the level fluctuation.

[0005]

However, in a proposal in which a step or a throttle portion is provided in the inner hole of the immersion nozzle as disclosed in Japanese Utility Model Application Laid-Open No. 4-6351 or the like, the flow of hot water in the inner hole becomes faster, so that the mold flows to the mold. There is also a technical problem that the discharge flow speed of the mold is increased, and the flow state in the mold is changed to deviate from the proper flow state. Also,
In the proposal of changing or specifying the opening position and direction of the immersion nozzle with respect to the mold, such as No. 14650,
In some cases, not only is there a risk that the level of the molten metal on the powder line (meniscus line) surface will increase, but also the nozzle usage time will be prolonged, and as a result, the nozzle is likely to be clogged. Has a technical problem that an initial setting flow cannot be obtained. Furthermore, in the case of Japanese Patent Publication No. Hei 8-18117, it is necessary to provide an electromagnetic force for controlling the molten metal surface and a control means therefor.
That requires extra equipment and cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and a fixed and proper amount of molten metal such as molten steel does not occur in the middle of an inner hole of an immersion nozzle without irregular flow rate fluctuation or blockage. It is an object of the present invention to provide a casting immersion nozzle having a specific structure capable of smoothly pouring a molten metal into a mold and, at the time of pouring, maintaining the flow of the molten metal in the mold in an appropriate state.

[0007]

According to the present invention, there is provided an immersion nozzle for casting for injecting molten metal into a mold, wherein the nozzle communicates with an inner hole through which the molten metal flows and an end of the inner hole. In a casting nozzle having a molten metal flow path and a molten metal discharge portion having a plurality of openings formed in the nozzle outer peripheral wall, a step portion is formed in the inner hole portion,
A casting immersion nozzle is provided, wherein a horizontal cross-sectional shape of the molten metal flow path of the molten metal discharge section is formed in a sector shape that extends from the inner hole side toward the opening. In the casting immersion nozzle of the present invention, a step portion is provided 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 in a fan shape having a specific spreading angle toward the opening. Is a striking structural feature.

In the casting immersion nozzle of the present invention, the stepped portion is provided in the inner hole portion, particularly the inner hole portion located immediately above the meniscus, so that the flow speed of molten steel in this portion is increased,
As a result, alumina and other non-metallic contaminants, powder, and the like adhere to the flow path wall surface, and these become nuclei, and the molten metal becomes entangled and adheres to the flow path. Irregular flow rate caused by
Blockage of the flow path and the like are avoided.

Generally, the start and stop of the supply of molten metal from the tundish to the immersion nozzle or the adjustment of the amount of molten metal are performed by operating a slide opening and closing device such as a slide valve provided between the bottom of the tundish and the upper portion of the immersion nozzle. Will be Usually, the apparatus is composed of a bottom plate and a slide plate, and their diameters are 1.5 times smaller than the effective diameter required for a steady injection speed from the viewpoint of avoiding clogging by inclusions such as alumina and other flow abnormalities. It is perforated about twice or more. Therefore, during normal operation, the slide plate is displaced, and the injection is performed in a state where the slide plate is set to a state where the effective diameter required for a predetermined injection speed is reduced.

However, in the injection in the throttled state, the position of the opening / closing device hole is eccentric, so that the molten metal during injection is often deflected, so that the molten metal flows out from a plurality of discharge openings provided at the lower end of the immersion nozzle. The so-called one-sided flow phenomenon in which the amounts are unequal appears. As a result, in the state as it is, the flow of the molten metal in the mold is likely to be deviated in a specific direction. However, in the casting immersion nozzle of the present invention, since the step 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 set, the drift is eliminated, and the molten metal discharge amount from the plurality of openings can be equalized.

On the other hand, simply providing a step in the inner hole of the immersion nozzle increases the flow velocity of the molten metal flow and the flow near the discharge hole by the step as described above.
As a result, ascending flow, entrainment flow (suction flow), and the like in the molten metal flow discharged to 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 flow velocity of the molten metal flow hitting the inner wall of the mold drastically change the flow state of the molten metal in the mold, resulting in severe vertical fluctuations and disturbances of the powder line surface, often resulting in non-metallic It causes inclusion of inclusions, entrapment of powder, entrapment of gas which causes pinholes in product castings, and the like. Therefore, increasing the flow rate of the molten metal flow in order to suppress irregular flow rate fluctuation, blockage, drift, etc. of the molten metal flowing down in the inner hole of the immersion nozzle and proper control of the flow state of the molten metal in the mold are two trade-offs. Conventionally, it has been considered difficult to completely solve the two.

According to the present invention, the molten metal flow path of the molten metal discharge section is formed into a fan-shaped shape which expands from the inside toward the opening, so that the flow velocity accelerated at the step portion is again reduced at the opening. This is to solve the above-mentioned problem by lowering the flow to avoid the appearance of an undesired flow state in the mold due to the discharge flow. In this case, the flow of the molten metal discharged from the discharge opening of the nozzle immersed in the mold just hits two corners at both ends of the short side wall of the mold,
The spreading angle α of the fan-shaped discharge portion is set so as to satisfy the following condition with respect to the angle β formed between the center position of the rectangular mold in which the casting immersion nozzle is immersed and the two corners at both ends of the short side wall. Then, a particularly suitable flow state of the molten metal in the mold can be obtained. 2β>α> １ ／ β

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The casting immersion nozzle of 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 longitudinal sectional front view, and FIG. 1 (b) is a horizontal sectional view of a nozzle discharge portion. As shown in FIG. 1, a casting immersion nozzle 1 according to the present invention includes a tubular inner hole 2 through which a molten metal flows, a step 3 provided therein, It has a molten metal discharge part 4 connected to the lower end, and a powder line part 7 provided on the outer peripheral wall surface of the nozzle 1. In continuous casting of steel or the like, the upper end 1a of the immersion nozzle 1 is attached to a lower portion of a sliding opening / closing device (not shown) usually composed of a slide plate or the like attached to a bottom plate of a tundish. Is introduced into the upper portion 2a of the inner hole portion 2 from a slide plate which is squeezed and opened to a required aperture.

A step portion 3 is provided on the inner wall of the nozzle inner hole portion 2 located immediately above the powder line portion 7, and the flow rate of the molten metal is increased here, and the flow of the molten metal flows in a steady turbulent state. And flows down to reach the molten metal discharge section 4 connected to the lower end of the inner hole. The molten metal discharge section 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-shaped shape that extends from the inner hole 2 side toward the opening 5. In the case of the 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 center axis of the immersion nozzle.

In the case of the molten metal discharge section 4 shown in FIG. 1, two fan-shaped molten metal flow paths 6 extending from the center to the opening 5 provided on the outer peripheral wall have an angle of about 15 degrees with respect to the horizontal. It is formed to have a downward slope. Then, the flow rate of the molten metal flow is increased by the stepped portion 3, and the molten metal flow reaching the molten metal discharge portion 4 is equally divided into two flows by the molten metal discharge portion 4, and the respective speeds are gradually reduced. The molten metal in the mold is discharged from the openings 5 and 5 into the mold in a state where the flow state of the molten metal in the mold is reduced to an appropriate discharge speed.

In the present invention, as shown in FIG. 2, the immersion nozzle has its central axis near the intersection of each diagonal of the four corners of the mold 8 having a generally rectangular upper surface, ie, near the center of the mold 8. It is immersed in the mold 8 while being positioned, and is inserted and arranged so that the surface of the powder layer existing in a layer on the molten metal (molten steel) interface is located in the nozzle powder line section 7.

In the immersion nozzle 1 of the present invention, the position of the step 3 provided in the inner hole 2 for the purpose of reducing the flow of the molten metal (molten steel) and locally increasing the flow velocity is not necessarily the same as that in the above embodiment. Although it is not limited to the position,
If a step is provided in the inner hole located directly above the meniscus, the flow rate of molten steel in this portion is increased, and thereby alumina and other non-metallic impurities and powder adhere to the wall surface of the inner hole and the like. In addition, it is possible to further prevent the molten metal from being entangled with the nucleus and adhering thereto. As a result, irregular fluctuation of the flow rate and blockage of the flow path due to the sharp narrowing of the flow path diameter at the adhering portion can be further avoided.

The shape of the step 3 is not particularly limited as long as the above-mentioned object can be achieved.
It may be formed into any shape including a spiral shape and the like, but generally, the step thickness is 3 to 10 mm and the length is 50 mm.
More preferably, it is formed in an annular cylindrical shape of about 200 mm. In addition, the step portion 3 may be provided in one or more steps. In this case, the spreading angle of the fan-shaped molten metal flow path 6 is set to be larger as the flow velocity of the molten metal (molten steel) flow by the step portion 3 becomes faster. The molten metal discharge section 4 having the sector-shaped molten metal flow path 6 of the present invention reduces the molten metal flow velocity accelerated by the step 3 to a flow velocity at which the flow state of the molten metal in the mold 8 can maintain an appropriate state. Then, it acts to discharge toward the peripheral wall of the mold.

As shown in FIG. 2, the divergent angle α of the fan-shaped molten metal flow path 6 is set at the opening 5 of the nozzle 1 immersed in the mold 8 at the corners at both ends of the short side wall of the rectangular mold 8.
Mold 8 so that the flow of molten metal discharged from
And the angle β formed by the two corners of the mold 8
It is preferable to set the spread angle α of the fan-shaped molten metal flow path 6 within a range satisfying the following condition, whereby a particularly suitable molten metal flow state in the mold can be obtained. 2β>α> １ ／ β

The spread angle α of the fan-shaped molten metal flow path 6
Is larger than 2β, the molten metal flow discharged from the opening 5 of the immersion nozzle 1 collides with the wall near the middle point on the long side of the mold, and the meniscus surface (powder line surface) is stirred. When α is smaller than 1 / 4β, the flow of the molten metal hitting the corner is reduced, and the effect is reduced by half.

The constituent material of the immersion nozzle of the present invention is as follows:
There is no particular limitation, and refractory materials 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 Example 1 and Comparative Examples 1 to 3 The immersion nozzle (nozzle length 7) shown in FIG.
30 mm, inner hole diameter 70 mm, thickness 5 mm, 150 mm length step inside the inner hole just above the powder line part, the discharge part is a symmetrical fan-shaped discharge part 2 expanding toward the opening.
(Spread angle α = 25 degrees, discharge section flow path inclination 15 degrees with respect to the horizontal, and opening 70 × 80 mm) were prepared. As “Comparative Example 1”, the immersion nozzle shown in FIG. 3 (nozzle length, inner hole diameter is the same as in Example 1, no inner hole step, two straight discharge parts, and the flow path inclination is 15 °, an opening of 70 × 80 mm) was prepared. As “Comparative Example 2”, the immersion nozzle (nozzle length and inner hole diameter shown in FIG.
Same as Example 1, with a step similar to that of Example 1, the discharge part is two straight discharge parts, the flow path inclination is 15 degrees, and the opening is 70 ×
80 mm). As “Comparative Example 3”, the immersion nozzle shown in FIG. 5 (nozzle length, inner hole diameter is the same as in Example 1, no inner hole level difference, and two discharge sections having the same fan shape as Example 1 in the discharge section) , Channel inclination is 15 degrees, opening is 70 × 80m
m) was prepared.

Each nozzle is positioned at the center of the mold shown in FIG. 2 (rectangle: size: 300 × 1800 mm, angle β = 19 degrees between the center of the mold and both corners of the short side wall).
As shown in FIG. 2, the molten steel was immersed in a 5.1 t throughput.
on / min. Was injected into the mold. Table 1 summarizes the results of confirming the usage status of each nozzle for 6 charges for about 300 minutes.

[0024]

[Table 1]

From the results shown in Table 1, the immersion nozzle of Comparative Example 2 in which the inner hole has a step but the discharge portion is not a fan-shaped but straight, the discharge flow is a meniscus portion (powder line portion).
It has been found that the surface of the steel fluctuates violently, adversely affecting the quality of the steel. Conversely, in the immersion nozzle of Comparative Example 3 in which the discharge portion was formed in a sector shape satisfying the conditions of the present application and no step was provided in the inner hole portion, the inner hole portion gradually closed, resulting in an inner hole diameter. In addition, it was recognized that the discharge flow velocity was accelerated due to the reduced volume, and the outflow velocity set initially was changed, and the effectiveness of the fan-shaped discharge passage was lost. In order to obtain good quality steel, it is necessary to consistently maintain the initially set conditions such as the discharge flow rate while casting is being performed. This cannot be achieved with a nozzle provided with only one of the parts, and it has been found that this can only be achieved with a nozzle according to the invention in which both measures are combined under certain conditions.

[0026]

According to the immersion nozzle for casting of the present invention, when the molten metal such as molten steel is injected into the mold by the above-described specific combination configuration, irregular flow fluctuations of the molten steel flow in the nozzle inner hole and the inner hole are not performed. Not only troubles such as clogging are avoided, but also the flow state of the molten metal such as injected molten steel in the mold is appropriately controlled so that the molten steel surface is excessively disturbed by the discharged molten steel flow,
Fluctuations are avoided, whereby mixing of non-metallic inclusions, entrainment of powder, entrainment of gas, and the like are suppressed, and a high-quality metal casting such as a steel ingot can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a casting immersion nozzle according to the present invention, wherein (a) is a cross-sectional view of the immersion nozzle, and (b) is an AA cross-sectional view of (a). is there.

FIG. 2 is a schematic view showing a immersion state of a mold and a casting immersion nozzle.

FIG. 3A is a longitudinal sectional view of an immersion nozzle (without a step in an inner hole, a straight discharge hole) according to Comparative Example 1, and FIG. 3B is a sectional view taken along the line AA of FIG. It is.

FIG. 4A is a longitudinal sectional view of an immersion nozzle (inner hole stepped, discharge hole straight) according to Comparative Example 2, and FIG. 4B is an AA sectional view of FIG. It is.

FIG. 5 (a) is a longitudinal sectional view of an immersion nozzle (without a step in an inner hole, a fan-shaped discharge hole) according to Comparative Example 3,
(B) is AA sectional drawing of (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion nozzle 1a Immersion nozzle upper end part 2 Inner hole part 2a Inner hole wall 3 Step part 4 Molten metal discharge part 5 Opening 6 Molten metal flow path 7 Powder line part 8 Mold

Continued on the front page (72) Inventor Yoichiro Mochizuki 1 Minamifuji, Ogakie-cho, Kariya-shi, Aichi Pref. Toshiba Ceramics Co., Ltd. Kariya Works

Claims (4)

[Claims] 1. A casting immersion nozzle for injecting a molten metal into a mold, comprising: an inner hole through which the molten metal flows; a molten metal flow path communicating with an end of the inner hole; and a nozzle outer peripheral wall. And a molten metal discharge portion having a plurality of formed openings, wherein a stepped portion is formed in the inner hole portion, and a horizontal cross-sectional shape of a molten metal flow path of the molten metal discharge portion is provided. Is formed in a fan-like shape that extends from the inner hole side toward the opening. 2. The immersion nozzle for casting according to claim 1, wherein the step is provided in an inner hole located immediately 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 inside the inner wall of the inner hole forming the inner hole.
The immersion nozzle for casting according to claim 1, wherein the immersion nozzle is formed in an annular cylindrical shape of 0 mm. 4. A spread angle α of a horizontal sectional shape of a molten metal flow path of the molten metal discharge portion, a center position of a rectangular mold into which the casting immersion nozzle is immersed, and two corners at both ends of a short side wall. The casting immersion nozzle according to any one of claims 1 to 3, wherein a relationship of 2β>α> 1 / 4β is satisfied with an angle β formed between them.