KR20090121339A - Continuous casting device of slab and its continuous casting method - Google Patents

Abstract

A continuous casting device of slab for producing a high quality slab in which flaw of a product is suppressed by controlling turbulence of molten metal flow in a continuous casting mold. Its continuous casting method is also provided. The continuous casting device (10) comprises a submerged nozzle (11) where the central axis of ejection openings (13) provided on the opposite sides of a tubular body (18) is set within a predetermined range, and a continuous casting mold (12) where electromagnetic stirrers (15) are provided in wide long piece members (21, 22) forming a space section (23) having a rectangular cross-section, and produces a slab by supplying molten metal (14) into the casting mold (12) through the ejection openings (13) of the submerged nozzle (11) and solidifying the molten metal while stirring by means of the electromagnetic stirrers (15). Upper end position of the ejection opening (13) is set below the lower end position of the electromagnetic stirrer (15), and a magnetic shielding plate (16) for regulating a magnetic field being generated is provided at a lower position of each electromagnetic stirrer (15). Assuming the thickness in the height direction of the core (24) of the stirrer (15) is h, the interval s in the height direction of the magnetic shielding plate (16) and the electromagnetic stirrer (15) is set in the range of h/5-h.

Description

Continuous casting apparatus of slab and continuous casting method thereof [CONTINUOUS CASTING DEVICE OF SLAB AND ITS CONTINUOUS CASTING METHOD}

The present invention relates to a continuous casting apparatus and a continuous casting method for injecting molten metal into a continuous casting mold through an immersion nozzle and producing a slab.

Conventionally, in continuous casting of a slab, for the purpose of improving the product quality of the slab, an electronic stirring device is provided in a continuous casting mold (hereinafter referred to simply as a mold), and is discharged through a discharge hole of the immersion nozzle. A method of electronic stirring the molten steel supplied into a mold and generating swirl flow in the mold has been used.

For example, Japanese Unexamined Patent Application Publication No. 7-314104 discloses an electronic stirring device installed in a mold so that the position of the molten steel bath surface is within the range from the core center of the electronic stirring device to the upper end of the core. The method of giving and casting is disclosed.

Further, Japanese Laid-Open Patent Publication No. 2004-42062 discloses a position where the discharge port portion of the immersion nozzle is lower than the lower end position of the electromagnetic coil of the electromagnetic stirring apparatus when the casting is performed by applying flow to molten steel in the mold by the electronic stirring apparatus. The installation method is disclosed.

Further, in Japanese Unexamined Patent Publication No. 7-256414, although the cast steel to be manufactured is an annular cast steel (a kind of bloom) different from the slab, an electromagnetic coil of a moving magnetic field system is disposed on the entire outer circumference of the mold. The continuous casting apparatus in which the electromagnetic shielding material is arrange | positioned under the coil is disclosed.

However, the above-described prior art still has the following problems to be solved.

In the method of Unexamined-Japanese-Patent No. 7-314104, as shown in FIG. 7, the site | part of which the direction of the molten steel flow (henceforth a stirring flow) formed by the electronic stirring device and the discharge flow from an immersion nozzle is reverse direction is shown. In this case, interference of the flow occurs, bubbles and inclusions are mixed into the slabs by stagnation, or powder mixing of the slabs occurs due to fluctuations in the water surface due to disturbance of molten steel in the interference region. Therefore, there exists a possibility that slab cleanliness may fall and a product quality may fall.

In addition, in the forward portion where the direction of the molten steel flow and the discharge flow are the same, the discharge flow of the immersion nozzle is increased, the penetration depth of the bubbles and inclusions is increased, and the floating is inhibited. There is a fear that bubbles and inclusions adhere to the coagulation shell and cause product defects at the location.

The problems of the reverse direction and the forward direction occur in the mold at the same time, and both cause the deterioration of product quality. In addition, in the method of Japanese Unexamined Patent Publication No. 2000-42062, since a magnetic field is formed below the electromagnetic coil, the above-described interference of the flow of the stirring flow and the discharge flow and the increase of the discharge flow are caused, as described above. There is a risk of impairing separation of air bubbles and inclusions.

As a means for solving the problems of the aforementioned JP-A-7-314104 and JP-A-2004-42062, although the continuous casting apparatus disclosed in JP-A-7-256414 can be considered, The manufacturing target of Japanese Patent Laid-Open No. 7-256414 is an annular cast steel, and has the following difference from the slab of the present invention.

Molds for making annular casts generally have an inner diameter of about 300 mm or less, and are considerably smaller than molds for producing slabs (eg, thickness: about 120 mm to 300 mm, width: about 800 mm to 1800 mm), The relationship between the molten steel flow by the electronic stirring in the mold and the discharge flow from the immersion nozzle is completely different.

That is, in the electronic stirring flow in the mold for manufacturing the annular cast iron, the electromagnetic coil used for the electronic stirring is provided along the entire circumference of the mold wall surface to form a swirl flow (see FIG. 2 of JP-A-7-256414). . Therefore, the molten steel discharge flows from the immersion nozzle do not cause two problems that cause interference and acceleration of the flow of the molten steel flow due to electromagnetic stirring in the mold and the discharge flow from the immersion nozzle. This is because the discharge port of the immersion nozzle is arranged so as to be straight down as in JP-A-7-256414.

Moreover, the mold which manufactures an annular cast piece is a structure in which an electromagnetic coil is arrange | positioned around a mold, and the installation for manufacturing slabs like the electronic stirring apparatus which opposingly arranged in the wide long piece member (two mold surfaces). The configuration is completely different from.

In addition, the use of the slab is a thin plate material, rolling is carried out with a large thickness reduction ratio, and high quality is required, as represented by the outer plate for automobiles, so that fine foreign matter such as powder, bubbles and inclusions in the slab It becomes a product defect. Therefore, the level of demand for product quality is very high compared to the annular cast.

As mentioned above, not only the problem of Unexamined-Japanese-Patent No. 7-314104 and Unexamined-Japanese-Patent No. 2004-42062 does not generate | occur | produce in the continuous casting apparatus of Unexamined-Japanese-Patent No. 7-256414. There is no solution.

This invention was made | formed in view of such a situation, and the slab continuous casting apparatus which can suppress the disturbance of the flow of molten metal in the continuous casting mold, and can manufacture the slab of favorable quality with few product defects, and its continuous casting method The purpose is to provide.

The present invention is to achieve the above object as follows.

(1) In the continuous casting apparatus of the slab according to the first invention according to the above object, discharge ports are provided on both side sides of the lower part of the cylindrical body forming a flow path of molten metal, and the discharge cores are formed with a shaft center. Is provided with an immersion nozzle having a range of 60 degrees downward from the horizontal direction to the horizontal direction, and at least one pair of electronic stirring devices disposed opposite to the wide long member forming the space portion. A slab is produced by providing a continuous casting mold, supplying molten metal into the continuous casting mold through the discharge port of the immersion nozzle, and stirring and solidifying the molten metal in the continuous casting mold by the electronic stirring device. In the continuous casting device, the upper end position of the discharge port of the immersion nozzle is located at a position lower than the lower end position of the electronic stirring device. In the lower position of each said electronic stirring apparatus, the magnetic shield plate which adjusts the magnetic field produced by this electromagnetic stirring apparatus is provided, and when the thickness of the height direction of the core of the said electronic stirring apparatus is h, the said magnetic The space | interval of the height direction of a shielding board and the said electronic stirring device shall be in the range of h / 5 or more and h or less.

(2) In the continuous casting apparatus of the slab according to the first invention, the upper position of the magnetic shield plate is set to a position lower than or equal to the upper position of the discharge port of the immersion nozzle, and the lower position of the magnetic shield plate is the immersion nozzle. It is preferable to set it as the position below the lower end position of the said discharge opening of.

(3) In the continuous casting apparatus of the slab which concerns on 1st invention, it is preferable to make length in the height direction of the said magnetic shielding plate into the range of 50 mm or more and 200 mm or less, and to make the thickness 10 mm or more.

(4) In the slab continuous casting apparatus according to the first invention, the ratio d / D of the inner width d of the discharge port of the immersion nozzle to the inner width D of the immersion nozzle is within the range of 1.0 or more and 1.7 or less. It is desirable to set.

(5) The continuous casting method of the slab which concerns on the 2nd invention which concerns on the said objective manufactures the slab using the continuous casting apparatus of the slab which concerns on 1st invention.

(6) In the continuous casting method of the slab according to the second invention, the casting speed of the slab is preferably 1.0 m / min or more.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side sectional view of the casting mold for continuous casting used for the continuous casting apparatus of the slab which concerns on one Embodiment of this invention.

FIG. 2 is a plan view of a mold for continuous casting of the slab of FIG. 1. FIG.

It is explanatory drawing which shows the relative positional relationship of an electronic stirring device, an immersion nozzle, and a magnetic shield plate, and the flow of molten steel in a mold.

It is explanatory drawing which showed the influence which the distance of an electronic stirring device and a magnetic shield plate has on the molten steel in a mold.

It is explanatory drawing which shows the relative positional relationship of an electronic stirring device, an immersion nozzle, and a magnetic shield plate, and the flow of molten steel in a mold.

4B is an explanatory view showing the effect of the relative position between the discharge port of the immersion nozzle and the magnetic shield plate on the molten steel in the mold.

It is explanatory drawing which shows the relative positional relationship of an electronic stirring device, an immersion nozzle, and a magnetic shield plate, and the flow of molten steel in a mold.

5B is an explanatory diagram showing the effect of the length of the magnetic shield plate on the electromagnetic force.

It is explanatory drawing which shows the flow of molten steel in a mold.

6B is an explanatory view showing the effect on the molten steel in the mold by variously changing the spacing and casting speed of the electronic stirring device and the magnetic shield plate.

It is explanatory drawing which shows the flow of molten steel in the casting for continuous casting which concerns on a prior art.

EMBODIMENT OF THE INVENTION For understanding of this invention, embodiment which actualized this invention is described below, referring an accompanying drawing.

Here, FIG. 1 is a sectional side view of the continuous casting mold used for the slab continuous casting apparatus which concerns on one Embodiment of this invention, and FIG. 2 is a top view of the continuous casting mold of this slab.

As shown in Fig. 1 and Fig. 2, the continuous casting device of the slab (hereinafter also referred to only as the continuous casting device) 10 according to the embodiment of the present invention is an immersion nozzle 11 and a mold for continuous casting (hereinafter, A molten steel (an example of molten metal) 14 in the mold 12 through the discharge port 13 of the immersion nozzle 11, and the molten steel in the mold 12. It is an apparatus which solidifies while stirring 14 by the electronic stirring apparatus 15 provided in the mold 12, and manufactures slab, The electromagnetic stirring apparatus 15 in the mold 12 below the electromagnetic stirring apparatus 15. The magnetic shield plate 16 which adjusts the magnetic field produced | generated by () is provided. It demonstrates in detail below.

The immersion nozzle 11 is provided in the bottom part of the tundish (not shown) which stores molten steel, and has the cylinder 18 which forms the flow path 17 of molten metal, The lower part of this cylinder 18 Discharge ports 13 are provided on both sides of the side. Here, although the flow path has a circular cross section (which may be an elliptical cross section), the discharge port may be, for example, a circular cross section, an elliptical cross section, a square cross section (square or rectangle), or a polygonal cross section, and one or more on one side of the cylinder. Can be formed. At this time, when the shape of the discharge port is a circular cross section, the inner width thereof is a diameter, and in other shapes, it is the diameter when the cross-sectional area is the area of a circle. It is the diameter in the case of the area of a circle.

In addition, the direction of the axial center of the discharge port 13 ranges from the horizontal direction, that is, from 0 degrees (preferably 15 degrees downward to the horizontal direction) to 60 degrees downward (preferably 40 degrees) to the horizontal direction. Set to. Here, when the axial center of the discharge port is set in an area exceeding 60 degrees downward with respect to the horizontal direction, that is, when directed downward (including the direct road), inclusions and bubbles enter the interior of the slab and internal defects are formed. . In addition, when the direction of the axial center of the discharge port is set upward with respect to the horizontal direction, a strong upward flow is formed, and powder mixing is encouraged.

The ratio d / D of the inner width d of the discharge port 13 to the inner width D of the cylinder 18 of the immersion nozzle 11 forming the flow path 17 is set within a range of 1.0 or more and 1.7 or less. It is preferable. The inner width D of the cylinder 18 is, for example, about 50 mm or more and 90 mm or less (here, 70 mm). Here, when ratio d / D is less than 1.0, the inner width D of the cylinder 18 becomes large with respect to the inner width d of the discharge port 13, and the flow velocity of the discharge flow from the discharge port 13 is too high. Since it becomes faster, it becomes difficult to obtain the effect of the stirring flow by the electronic stirring device 15. Therefore, it is impossible to expect to further improve the product quality of the slab to be manufactured.

On the other hand, when ratio d / D exceeds 1.7, the inner width D of the cylinder 18 becomes small with respect to the inner width d of the discharge port 13, and the flow velocity of the discharge flow from the discharge port 13 is small. Since this becomes late, the remarkable effect by the magnetic shield plate 16 becomes difficult to appear.

As mentioned above, although the ratio (d / D) of the inner width d of the discharge port 13 and the inner width D of the cylinder 18 was made into 1.0 or more and 1.7 or less, it is preferable to set an upper limit to 1.5, and to 1.3. More preferably.

The continuous casting mold 12 is disposed to face each other with a pair of narrow narrow piece members 19 and 20 disposed to face each other with a horizontal gap therebetween. A pair of wide long pieces 21 and 22 are provided. Each of the piece members 19 and 20 and the piece members 21 and 22 are known in the art, for example, a cooling plate made of copper or a copper alloy in contact with molten steel, and attached to and fixed to the rear so as to flow the cooling water. It consists of a back plate.

As a result, a space 23 having a rectangular cross section in the horizontal direction is formed inside. In addition, the space portion 23 has a length of the short side of the horizontal cross section, for example, about 120 mm to 300 mm, and a length of the long side about 800 mm to 1800 mm, for example, and the fragment member 19 with respect to the long piece members 21 and 22. , 20) can be slid to make the interval variable or fixed.

The above-mentioned well-known conventional electronic stirring apparatus 15 is provided in the upper side (in detail, a back plate) of the long piece members 21 and 22, respectively.

This electronic stirring apparatus 15 winds the electromagnetic coil 25 in the core 24 which laminated | stacked the several sheets of electronic steel sheets, and arrange | positions it in the casing (not shown) made of metal (for example, stainless steel). . Therefore, the lower end of the electronic stirring device 15 means the lower end of the casing. In addition, since the casing of an electromagnetic stirring apparatus is not shown in FIG. 1, although it appears as showing the lower end of an electromagnetic coil, as mentioned above, the lower end of an electromagnetic stirring apparatus is a lower end of a casing. The electronic stirring device 15 may be provided at least one (that is, a pair) in each of the long piece members 21 and 22. Here, when installing two or more (that is, two or more pairs) in each electromagnetic stirring apparatus, it arrange | positions in the width direction (namely, the long side direction of a long piece member, the long side direction in the horizontal cross section of a space part) of a long piece member. .

In addition, the thickness h of the height direction of the core 24 of the electromagnetic stirring apparatus 15 is about 100 mm or more and 300 mm or less (here, 200 mm).

In the space portion 23 of the continuous casting mold 12, the immersion nozzle 11 is disposed so that the discharge port 13 faces the fragmentary members 19 and 20 [at this time, the discharge port of the immersion nozzle 11 ( 13) the upper end position of the electronic stirring device 15 below the lower end position], and the molten steel 14 is supplied into the mold 12 through the discharge port 13 of the immersion nozzle 11, and the mold The molten steel in (12) is stirred with the electronic stirring device 15. As a result, molten steel flow, i.e., stirring flow, is formed in the mold 12 in the clockwise or counterclockwise direction about the immersion nozzle 11, and the slab is manufactured while solidifying the molten steel.

However, when manufacturing the slab in this way, as shown in Fig. 7, the molten steel flow due to the magnetic field is formed to the lower side of the electromagnetic coil 25, that is, the stirring flow and the discharge port 13 of the immersion nozzle 11 A problem arises due to the influence of the interference of the discharge flows from and the acceleration of the discharge flows along with the stirring flow. Therefore, the production of slabs with many product defects and deteriorated product quality cannot be avoided.

Therefore, in order to actively alleviate this influence, the magnetic shielding plate 16 or more equal to or greater than the same length is disposed in the width direction of the electromagnetic stirring device 15 at the position below the electronic stirring device 15, and the mounting position thereof is also adjusted. By optimizing, good casts with few product defects are produced.

The magnetic shield plate 16 may be made of, for example, an electronic steel sheet that does not pass a magnetic field, but may be made of iron or ordinary carbon steel. In addition, when it consists of iron or general carbon steel, since it generates heat by induction heating of an electromagnetic stirring apparatus, it is set as a water-cooled structure.

In addition, the reason for arrange | positioning the upper end position of the discharge port 13 of the immersion nozzle 11 mentioned above in the position below the lower end position of the electronic stirring device 15 is as follows.

Since the direction of the discharge port shaft center is in the range of 60 degrees downward from horizontal to horizontal, if the upper end position of the discharge port 13 is placed above the lower end position of the electronic stirring device 15, even if a magnetic shield plate is provided, It is because interference and acceleration occur that are hard to do.

When the thickness of the height direction of the core 24 of the electromagnetic stirring device 15 is h, this magnetic shield plate 16 has the space | interval of the height direction of the magnetic shield board 16 and the electromagnetic stirring device 15 ( s), i.e., the interval between the upper end of the magnetic shield plate 16 and the lower end of the casing of the electronic stirring device (also the same) is h / 5 [hereinafter, also referred to as (1/5) h] or more and h or less. It is provided in the long piece members 21 and 22 so that it may be in the range of. At this time, the magnetic shield plate 16 also depends on the thickness of the cooling plate constituting the long piece members 21 and 22, but is 50 mm or more and 100 mm or less on the molten steel contact surfaces 26 and 27 of the long piece members 21 and 22. Install in back plate within range.

Here, when the space | interval s of the height direction of the magnetic shield plate 16 and the electronic stirring device 15 is less than h / 5, the magnetic shield plate 16 and the electronic stirring device 15, ie, the core 24, The distance becomes too close, and the required stirring force in the area where stirring is required is reduced by the magnetic shield plate 16, and the target product quality cannot be secured.

On the other hand, when the space | interval s exceeds h, even if the distance of the height direction of the magnetic shield plate 16 and the electronic stirring device 15 becomes too far, and the necessary stirring force mentioned above can be ensured, it will be discharged and stirring Interference and acceleration of the discharge flow cannot be prevented and the target product quality cannot be secured.

As mentioned above, although the space | interval s of the height direction of the magnetic shield plate 16 and the electronic stirring device 15 was h / 5 or more and h or less, it is preferable to set an upper limit to 4h / 5, and to set it to 3h / 5. More preferred.

The magnetic shield plate 16 preferably has the length x in the height direction within a range of 50 mm or more and 200 mm or less, and the thickness thereof is 10 mm or more. Moreover, it is preferable to make the length of the magnetic shielding plate 16 the width direction equal to or more than the width direction length of the electromagnetic stirring apparatus 15.

Here, when the length x of the height direction of a magnetic shield plate is less than 50 mm, the residual influence of the leakage magnetic field below the magnetic shield plate becomes large. On the other hand, when the length x of the height direction of a magnetic shielding plate exceeds 200 mm, the leakage magnetic field from the lower side of a magnetic shielding plate becomes small, and the improvement effect of the stirring flow by a magnetic shielding plate becomes low. . As mentioned above, although the length x of the height direction of a magnetic shielding board was set in the range of 50 mm or more and 200 mm or less, it is preferable to set a minimum to 70 mm, and to make an upper limit 170 mm, and it is more preferable to set it as 150 mm.

In addition, since the magnetic field generated from the electronic stirring device 15 can be adjusted by setting the thickness of the magnetic shielding plate to 10 mm (preferably 20 mm) or more, the upper limit value is not specified. In consideration of workability and economical efficiency when installed at (21, 22), it is preferable to be 100 mm or less.

In addition, the installation position of the height direction of the magnetic shield plate 16 makes the upper position of the magnetic shield plate 16 into the position below the upper position of the discharge port 13 of the immersion nozzle 11, and the magnetic shield plate 16 It is preferable to make the lower end position of) into a position below the lower end position of the discharge port 13 of the immersion nozzle 11. The length x in the height direction of the magnetic shield plate 16 is longer than the inner width d of the discharge port 13.

Here, when the magnetic shield plate is disposed at an upper position above the upper position of the discharge port, that is, above the upper end of the discharge port, the flow from the discharge port of the immersion nozzle does not directly act. Since the magnetic shielding plate is provided in an area where the magnetic shielding plate is not formed, problems with interference and acceleration with the stirring flow do not occur, but the stirring area by the electronic stirring device arranged at a predetermined distance from the upper end of the magnetic shielding plate is conversely reduced. Rather, it deteriorates the surface quality of the slab.

Further, when the lower end position of the magnetic shield plate is positioned above the lower end position of the discharge port, as a method of reducing the adverse effects of the discharge flow and the stirring flow, it is considered to deepen the immersion depth of the immersion nozzle into the mold. In this case, however, it is necessary to make the length of the cylinder of the immersion nozzle excessively long, and the casting preparation work on the immersion nozzle is not practical, and problems such as interference with other facilities also occur.

As mentioned above, although the upper end position of the magnetic shield plate was made into the position below the upper end position of the discharge port of the immersion nozzle, and the lower end position of the magnetic shield plate was made into the position below the lower position of the discharge port, the upper position of the magnetic shield plate was It is preferable to install as close as possible to the upper position of the discharge port.

Next, the continuous casting method of the slab which concerns on one Embodiment of this invention is demonstrated.

When manufacturing a slab, molten steel is supplied to a tundish (not shown), and molten steel is supplied from the tundish to the casting 12 for continuous casting through the immersion nozzle 11. Moreover, the slab manufactured is sent to the downstream side, stirring and solidifying the molten steel 14 in the casting 12 for continuous casting with the electronic stirring device 15. As shown in FIG.

At this time, the casting speed (drawing speed) of the slab is usually 0.8 m / min or more, but in order to obtain the effect of the present invention remarkably, it is 1.0 m / min or more, preferably 1.2 m / min or more, 1.4 m More preferably, it is more than / min. Thereby, the productive efficiency of slabs can be improved than before.

In addition, although the upper limit of the slab casting speed is not prescribed | regulated, it is about 2.5 m / min as an upper limit possible in the state of the art, for example.

<Example>

Next, the Example performed in order to confirm the effect of this invention is demonstrated.

First, the influence which the distance s of the height direction of an electromagnetic stirring device and a magnetic shield plate has on the molten steel in a mold is demonstrated, referring FIG. 3A and FIG. 3B. 3A shows the relative positional relationship between the electronic stirring device, the immersion nozzle and the magnetic shield plate, and the flow of molten steel in the mold at that time. Here, the upper end position of the discharge port of the immersion nozzle and the lower end position (lower end of the casing) of the electronic stirring device are coincident with each other. 3B has shown the cleanliness rating of the slab manufactured at this time. This cleanliness rating evaluates the number of defects (for example, inclusions, powders, bubbles, etc.) of the slab after casting, and in detail, the sample (30 mm x 30 mm) polished every 1 mm from the slab surface is produced, After polishing, the film is divided into 30 lengthwise and horizontally to secure 900 inspection areas of 1 mm x 1 mm, and the number of defects is counted with an optical microscope for the 900 inspection areas, and the numerical value is proportional to the number of defects (pieces / cm 2). . In other words, if the cleanliness rating is high, the product quality is lowered, and if it is low, the product quality is good (the same is true below).

In the test conditions, the upper end position of the discharge port of the immersion nozzle is placed at the lower end position of the casing of the electronic stirring device, the inner width D of the cylinder is 70 mm, the d / D is 1.0, and the axis of the discharge port is horizontal (O degrees). ), The length x in the height direction of the magnetic shield plate was fixed at 100 mm and the thickness was 30 mm, and the casting speed Vc of the slab was 1.4 m / min.

As apparent from FIG. 3A, it can be seen that the flow of molten steel changes as the interval s in the height direction of the electronic stirring device and the magnetic shield plate is narrowed (moving the magnetic shield plate upward). Moreover, it turns out that the change of the flow of molten steel becomes small by widening the space | interval s of the height direction (moving a magnetic shield plate downward) (relationship of a solid line and a dotted line in FIG. 3A).

Specifically, as is clear from FIG. 3B, the gap s in the height direction of the electronic stirring device and the magnetic shield plate is narrowed (moving the magnetic shield plate upward), and less than 1/5 of the core thickness h. In the case of using the distance, the flow velocity of the front surface of the electronic stirring device is also affected, and the necessary stirring force cannot be provided.

Next, when the space | interval s of the height direction of an electronic stirring device and a magnetic shielding plate is h / 5 or more and h or less, the stirring force of an electronic stirring device below is obtained, obtaining the required stirring force on the whole surface of an electronic stirring device. It can reduce, and it can prevent interference and acceleration with the discharge flows from the discharge port of the immersion nozzle. Finally, when the distance s in the height direction between the electronic stirring device and the magnetic shielding plate is set to exceed the core thickness h, the stirring force below the electronic stirring device cannot be reduced, and the discharge port of the immersion nozzle is discharged. Interference and acceleration with the discharge flow cannot be prevented.

That is, the magnetic shield plate is provided below the electromagnetic stirring device, and the spacing s in the height direction between the electronic stirring device and the magnetic shield plate is provided in the above-mentioned proper range, so that the cleanliness of the slab surface affecting the product quality. Where necessary to improve the agitation can be precisely stirred above the required agitation force, it was confirmed that can improve the cleanliness rating.

Next, the influence of the relative positions of the magnetic shield plate and the discharge port of the immersion nozzle on the molten steel in the mold will be described with reference to FIGS. 4A and 4B. Here, FIG. 4A shows the relative positional relationship between the electronic stirring device, the immersion nozzle and the magnetic shield plate, and the flow of molten steel in the mold at that time, and FIG. 4B shows the cleanliness rating of the slab manufactured at this time.

In the test conditions, the interval s in the height direction between the electronic stirring device and the magnetic shield plate was 2h / 5, the inner width D of the cylinder was 70 mm, the d / D was 1.0, and the axis of the discharge port was horizontal (O degree). The length in the height direction of the magnetic shield plate was fixed at 100 mm and the thickness was 30 mm, and the casting speed (Vc) of the slab was 1.4 m / min.

As apparent from Embodiment 1 shown in Figs. 4A and 4B, the upper position of the magnetic shield plate is disposed below the upper position of the discharge port of the immersion nozzle (the upper end of the discharge port is positioned 40 mm above the upper end of the magnetic shield plate). Arrangement | positioning), the interference of discharge flow and stirring flow, and acceleration of discharge flow by some stirring generate | occur | produced, and the cleanliness rating could be made less than 3 which is the cleanliness rating in the absence of a magnetic shield plate, By depositing deposits (e.g., inclusions or reaction products) at the discharge port, the axis of the discharge port is varied and the cleanliness rating is not stabilized.

4A and 4B, when the upper position of the magnetic shield plate is disposed at the upper position of the discharge port of the immersion nozzle, the interference between the discharge flow and the stirring flow, and the stirring flow It was confirmed that the acceleration of the discharge flow due to this can be prevented and the cleanliness rating can be improved.

4A and 4B, when the lower end position of the magnetic shield plate is set to a position 40 mm above the lower end position of the discharge port, the interference between the discharge flow and the stirring flow, and the stirring flow Although it was confirmed that acceleration of the discharge flow due to this can be prevented and the cleanliness rating can be improved, there are the following problems.

Usually, the dipping depth of the dipping nozzle is about 200 mm to 300 mm, but in Example 3, the dipping depth of the dipping nozzle is 400 mm to 500 mm or more, and as a result, the length from the top of the mold to the tip of the dipping nozzle is about 600 mm to 700 mm. Becomes Therefore, if the weight of the immersion nozzle is considerably heavy and at the same time the immersion nozzle is attached to the tundish, the start operation and the end operation of the continuous casting are performed in order to prevent collision between the immersion nozzle and peripheral devices such as molds. Since the lifting stroke of the tundish is increased, and the immersion nozzle is excessively raised to be avoided and transported, it is not practical in practical operation.

Next, the influence which the length x of the height direction of a magnetic shield plate has on the molten steel flow in a mold is demonstrated, referring FIG. 5A and FIG. 5B. Here, FIG. 5A shows the relative positional relationship between the electronic stirring device, the immersion nozzle and the magnetic shield plate and the flow of molten steel in the mold at that time, and FIG. 5B shows the electromagnetic force at this time. In addition, the electromagnetic force of the vertical axis | shaft shown in FIG. 5B makes the electromagnetic force acting on the area | region deeper than the upper position of the discharge opening of the immersion nozzle in the absence of the magnetic shield plate shown in FIG. 5A (dotted line in drawing) set to 1.0 (the diagonal line in FIG. 5A). Attenuation of the electromagnetic force at the time of changing the magnetic force which causes stirring flow of a negative area) and the length (x) of the height direction of a magnetic shield plate is shown. In addition, the test conditions set the space | interval s of the height direction of an electronic stirring device and a magnetic shield board to 2h / 5, and fixed the thickness of the magnetic shield board to 10 mm.

As is apparent from FIG. 5B, it has been confirmed that as the length x in the height direction of the magnetic shield plate becomes longer, the electromagnetic force becomes smaller. In particular, by setting the length in the height direction of the magnetic shielding plate within the range of 50 mm or more and 200 mm or less, the effect of the magnetic shielding plate is economically obtained, while the interference of the discharge flow and the stirring flow and the acceleration of the discharge flow due to the stirring flow are accelerated. It was confirmed that it can prevent.

Next, the influence of the slab casting speed on the molten steel in the mold will be described with reference to FIGS. 6A and 6B. Here, FIG. 6A shows the flow of molten steel in the mold, and FIG. 6B shows the cleanliness rating of the slab manufactured by variously changing the spacing in the height direction and the casting speed of the electronic stirring device and the magnetic shield plate.

In the test conditions, the upper end position of the discharge port of the immersion nozzle is disposed at the lower end position of the electronic stirring device, the inner width D of the cylinder is 70 mm, the d / D is 1.0, the axis of the discharge port is horizontal (O degree), and the magnetic shield plate. The length in the height direction of 100 mm, the thickness was fixed to 30 mm.

As shown in Fig. 6A, the discharge flow from the discharge port on one side of the immersion nozzle increases with increasing casting speed. As a result, in the area where stirring flows and discharge flows interfere, nonuniformity of flow velocity occurs, for example, mixing of powder and disturbance of hot water surface is encouraged, and product defects resulting from steelmaking increase.

In addition, the discharge flows from the discharge port on the other side of the immersion nozzle also increase as the casting speed increases. As a result, in the acceleration region, the penetration depth of the inclusion becomes deeper (the injury effect cannot be obtained), resulting in an increase in product defects due to steelmaking.

From the above-described results and shown in FIG. 6B, when the distance s in the height direction between the electronic stirring device and the magnetic shielding plate is within the range of (1/5) h or more and less than h, the casting speed of the slab is increased. Also, while obtaining the necessary stirring force by the electronic stirring device, it was confirmed that the interference between the discharge flow and the stirring flow and the acceleration of the discharge flow due to the stirring flow can be prevented, and the cleanliness rating can be improved.

In particular, by increasing the casting speed of the slab to 1.0 m / min, 1.4 m / min, and further 1.6 m / min, it was possible to obtain a result in which the effect of the present invention was more remarkable.

Moreover, as a result of testing also the ratio (d / D) of the inner width d of the discharge port of the immersion nozzle and the inner width D of the flow path, the magnetic shielding plate was made by setting the ratio d / D within the range of 1.0 or more and 1.7 or less. It was confirmed that more excellent effect can be obtained.

As mentioned above, it was confirmed that this invention can suppress the disturbance of the flow of molten steel in the casting for continuous casting, and can manufacture the slab of favorable quality with few product defects.

As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the structure described in embodiment mentioned above, Other embodiment which can be considered within the range of the matter described in a claim It also includes a variant. For example, the case where the continuous casting apparatus of the slab of this invention and its continuous casting method are comprised by combining some or all of each above-mentioned embodiment or modification, is also included in the scope of the present invention.

Continuous casting apparatus of slab as described in (1)-(4) of this invention, and continuous casting method of slab as described in (5) and (6) is below the electronic stirring apparatus provided in the long piece member of the casting mold for continuous casting. Since the magnetic shield plates are provided at intervals of a predetermined height direction, the influence of the flow of molten metal, that is, the interference of the flow of agitated and discharged from the immersion nozzle and the acceleration of the flow rate of the discharged flow can be reduced. Thereby, the disturbance of the flow of molten metal in the casting for continuous casting can be suppressed, and the slab of favorable quality with few product defects can be manufactured.

In particular, since the continuous casting apparatus of the slab described in (2) defines the installation position of the magnetic shield plate with respect to the discharge port of the immersion nozzle, the influence of the interference of the stirring flow and the discharge flow and the acceleration of the flow velocity of the discharge flow can be further reduced. Can be.

Since the continuous casting apparatus of the slab described in (3) defines the length and thickness in the height direction of the magnetic shield plate, melting in the mold for continuous casting by the magnetic shield plate while suppressing the leakage magnetic field from the magnetic shield plate. The effect of suppressing the disturbance of the flow of metal can be enhanced.

The slab continuous casting device described in (4) defines that the ratio (d / D) of the inner width D of the immersion nozzle to the inner width d of the discharge port increases the speed of the discharge flow from the discharge port excessively. While suppressing, molten metal can be stably supplied into the mold from the discharge port. As a result, the influence of the interference of the stirring flow and the discharge flow and the acceleration of the flow rate of the discharge flow, which have occurred in the past, can be reduced, and the disturbance of the flow of molten metal in the casting for continuous casting can be suppressed, so that product defects are prevented. Less good quality slabs can be produced.

In the continuous casting method of the slab described in (6), the casting speed of the slab is 1.0 m / min or more, whereby the influence of the interference of the stirring flow and the discharge flow and the acceleration of the flow rate of the discharge flow has been remarkably shown. Also with respect to speed, disturbance of the flow of molten metal in the casting for continuous casting can be suppressed. Thereby, the slab of favorable quality with few product defects can be manufactured by improving production efficiency compared with the former.

Claims (6)

Immersion nozzles are provided in the both sides of the lower part of the cylinder which forms the flow path of molten metal, and the immersion nozzle which made the axial center of this discharge port into the range of 60 degrees downward from the horizontal direction to the horizontal direction, It is provided with the casting part for continuous casting provided with the space part of rectangular cross section, and provided with the at least 1 pair of electronic stirring apparatus arrange | positioned facing the wide long piece member which forms this space part, In the continuous casting apparatus for supplying molten metal into the continuous casting mold through the discharge port of the immersion nozzle, and producing a slab while stirring and solidifying the molten metal in the continuous casting mold by the electronic stirring device,  The upper end position of the said discharge port of the said immersion nozzle is located below the lower end position of the said electronic stirring device, The magnetic shielding board which adjusts the magnetic field produced by this electromagnetic stirring device is provided in the lower position of each electromagnetic stirring device, When the thickness in the height direction of the core of the electronic stirring device is h, the interval between the magnetic shielding plate and the height direction of the electromagnetic stirring device is in the range of h / 5 or more and h or less. Casting device. The lower end position of the magnetic shielding plate is set to a position lower than the lower end position of the ejection opening of the immersion nozzle. Continuous casting device of the slab characterized in that. The slab continuous casting apparatus according to claim 1 or 2, wherein the length of the magnetic shielding plate is in the range of 50 mm or more and 200 mm or less, and the thickness thereof is 10 mm or more. The ratio (d / D) of the inner width d of the discharge port of the immersion nozzle to the inner width d of the immersion nozzle is set within a range of 1.0 or more and 1.7 or less. Continuous casting device of the slab characterized in that. The slab is manufactured using the continuous casting apparatus of the slab of any one of Claims 1-4, The continuous casting method of the slab characterized by the above-mentioned. The method of claim 5, wherein the casting speed of the slab is 1.0m / min or more.

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