JP4858037B2 - Continuous casting mold and continuous casting method using the same - Google Patents

Description

  The present invention relates to a continuous casting mold capable of adjusting a magnetic field application position to an optimum position even when the magnetic brake magnetic pole cannot be installed at an optimum position in continuous casting of steel, and a continuous casting method using the same. It is.

  Usually, in continuous casting of steel, molten steel is supplied into a mold through an immersion nozzle having two discharge holes.

  FIG. 1 is a longitudinal sectional view schematically showing a flow state of molten steel in a mold in a general steel continuous casting method. As shown in the figure, the molten steel flow (hereinafter also referred to as “discharge flow”) exiting from the discharge port 2 of the immersion nozzle 1 is divided into an upward flow 21 upward and a downward flow 22 downward in the mold. Colliding with the solidified shell 5 formed in the vicinity of the short side surface of the mold.

  As the casting speed is increased, the hot water supply speed of the molten steel is increased, so that the discharge speed of the molten steel is increased and the discharge flow becomes high temperature. When the discharge flow of molten steel collides with the solidified shell 5 at a predetermined flow rate or more, the solidified shell 5 is remelted, causing defects in the slab, and further, the breakout of the slab during continuous casting operation. It can also be a cause. Further, the upward flow 21 becomes a factor that entrains the mold powder 15 in the molten steel and increases inclusions in the steel.

  As a technique for improving productivity in the continuous casting process, there is a “twin mold casting technique” in which two slabs are cast simultaneously with one strand. When this twin mold is used, the distance between the immersion nozzle and the short side surface of the mold is shortened, so that the solidification shell 5 is more likely to be re-dissolved.

  As a method for preventing the remelting of the solidified shell due to the collision of the discharge flow, it is effective to use an electromagnetic braking device that applies a braking force by applying a static magnetic field to the discharge flow using an electromagnet. Application of the electromagnetic braking device to continuous casting of steel is a known technique as disclosed in, for example, Patent Document 1. The technique disclosed in this document is to apply a static magnetic field to the flow of molten metal injected from a casting nozzle, thereby reducing the flow rate of the molten metal and dividing it into small flows, which are then solidified by the molten metal flow. This prevents melting and destruction of the shell.

  Regarding the application of the electromagnetic braking device to the twin mold, for example, Patent Document 2 discloses the following technique. That is, it has a rectangular mold including an internal partition that is divided into two sub-molds, and is disposed on one long-side side surface and on the opposite long-side side surface, and has the opposite polarity. A magnetic material in the magnet has two secondary magnets of the same polarity arranged adjacent to each other along each of the two opposite long side surfaces, This is a magnetic brake in which the submagnet has the same magnetic field direction over the entire width of the mold and generates and applies a magnetic field distributed symmetrically in both submolds.

  However, in the technique disclosed in this document, when a magnetic field is applied to the immersion nozzle, the discharge flow of the molten steel becomes asymmetrical or an upward flow along the nozzle is generated. As a result, the surface quality of the slab deteriorates.

  In addition, since the optimum magnetic field application position in the case of using an electromagnetic braking device varies depending on the shape, position, mold width, etc. of the immersion nozzle, a method of controlling the magnetic field application position has been studied.

  For example, in Patent Document 3, a movable iron core (movable core) divided into a plurality of casting directions and / or a casting width direction is used, and each of the plurality of movable iron cores is independently applied to a cast piece by a driving mechanism. A technique for controlling the magnetic force of a molten steel flow in a mold to obtain a desired magnetic field distribution by enabling advancement and retraction is disclosed. However, in the technique disclosed in the same document, since the movable iron core cannot move in the casting direction or the long side width direction of the mold, it is not possible to freely change the magnetic field distribution in the casting direction or the long side width direction of the mold. Impossible.

  Furthermore, in Patent Document 4, a pair of long mold sides is formed so as to form static magnetic fields opposite to each other in the mold long side facing direction with the immersion nozzle immersion position in the long mold width direction in the continuous casting mold as a boundary. Disclosed is a molten metal braking device in which a plurality of pairs of electromagnets are arranged in parallel in the long side width direction of the mold on each back side, and a continuous casting method using the same. The technique disclosed here can freely adjust the strength of the static magnetic field in the mold long side width direction. However, with this technique, when the core of the electromagnetic coil cannot be installed at the position where the strongest magnetic field is to be applied, sufficient braking force cannot be applied to the molten steel. The structure must be complicated.

  And in patent document 5, on the back surface of both long sides of a casting_mold | template, from the fixed core which has a width equal to the width | variety of both long sides, the coil wound around the periphery, and the iron core surrounding the outer peripheral surface In the continuous casting mold provided with the electromagnet, the core member is provided so as to be movable and can be removed in the horizontal direction through a gap between the fixed core and a spacer is provided in the gap between the movable core member and the fixed core. An electromagnetic brake device is disclosed that is disposed to form an electrostatic magnetic field in a molten metal in a mold. However, in the technique disclosed in this document, the moving core has the same width as the fixed core, and is disposed over the entire surface in the mold long side width direction. It cannot be moved.

Japanese Patent Publication No. 2-20349 (page 3, column 5, line 44 to column 6, line 35) JP-T-2001-521444 (claims, page 13, line 16 to page 14, line 18) Japanese Patent Publication No. 7-45093 (claims, page 2, column 3, lines 41 to 50, etc.) JP-A-11-347697 (Claims [0028] to [0033], etc.) JP-A-5-277645 (claims, paragraphs [0007], [0008], etc.)

  As described above, the conventional technique for applying the electromagnetic braking force to the molten steel discharge flow from the immersion nozzle into the mold has the following problems. In other words, in order to prevent deterioration of the slab surface quality due to the turbulence of molten steel flow in the mold due to the application of a magnetic field to the immersion nozzle, it is necessary to avoid the position of the immersion nozzle and to arrange the magnetic poles of the electromagnetic braking device There is. However, when ancillary equipment is arranged on the long side of the mold, such as a twin casting mold partition fixing device, the equipment interferes with each other. The problem is that it cannot be placed at the optimum position.

  The present invention has been made in view of the above problems, and the magnetic pole of the electromagnetic braking device is used for flow control of molten steel due to the shape of the mold or the interference of the equipment position with the device arranged around the mold. An object of the present invention is to provide a continuous casting mold capable of applying a magnetic field to an optimal position even when it cannot be installed at an optimal position, and a continuous casting method using the same.

  In order to solve the above-mentioned problems, the present inventors have studied a continuous casting mold capable of adjusting a magnetic field application position to an optimum position and a continuous casting method using the same, and the following (a) to (c): As a result, the present invention was completed.

  (A) The reason why the conventional electromagnetic braking device has the core installed at the position where the magnetic field is to be applied is as follows. In other words, in order to effectively apply a magnetic field to the molten steel flow, it is important to prevent a decrease in magnetic flux density due to magnetic flux leakage. For that purpose, it is effective to make the magnetic path a continuous linear shape. For this reason, the shape of the core (a cored object magnetized inside the electromagnet) in the electromagnetic braking device has to be a continuous linear shape.

  (B) Considering the situation of (a) above, the part on the long side of the mold of the core of the electromagnetic braking device is the core of the core around which the electromagnetic coil is wound (hereinafter also referred to as “main body core”). By shifting the position from the position in a direction perpendicular to the core axis of the core, the application position of the magnetic field to the molten steel flow is moved while suppressing the decrease in the magnetic flux density within the allowable range of the performance of the electromagnetic braking device. Can do.

  (C) Based on the knowledge of (b) above, a core (hereinafter referred to as “separation core”) in which the portion on the long side of the mold is partially inserted or penetrated in the thickness direction of the backup plate among the cores of the electromagnetic braking device. The central axis of the cross section is shifted in the width direction of the long side of the mold and / or the height direction of the mold with respect to the central axis of the cross section of the “main body core”. The magnetic field can be applied to the optimum position for applying a braking force to the discharge flow of the molten steel in the mold without causing interference of the equipment position with the apparatus.

The present invention has been completed based on the above findings, the gist lies in the continuous casting method shown in the following (1) shown in cast-type contact and for continuous casting (2).

(1) A continuous casting mold capable of twin casting by disposing a partition device in a mold, which is disposed outside a long side copper plate which constitutes a long side of the mold and has a cooling structure therein, A backup plate for supporting the long side copper plate, a partition fixing device arranged on the extension line of the partition device outside the backup plate, and an electromagnetic braking device for applying a braking force to the discharge flow of the molten steel in the mold; A body core in which the electromagnetic braking device is disposed outside the backup plate, a separation core that is partially inserted or penetrated in a thickness direction in a part of the backup plate, and the body is composed of a wound electromagnetic coil core, the main body core is disposed so as to straddle the in partition fixing device in a width direction of the mold long sides, said electromagnetic coil and before In contact with the middle partition locking device, further wherein with the cross-sectional central axis of the body core and the cross-sectional center axis of the separation core is displaced in the width direction of the mold long sides, wherein the separation core long side of the mold Is in contact with the partition device on the projection plane in a direction perpendicular to the plane , and is close so that the distance between the end surface on the separation core side of the main body core and the end surface on the main body core side of the separation core is 10 mm or less A casting mold for continuous casting, characterized by being arranged as follows.

  (2) A continuous casting method characterized by using the casting mold for continuous casting described in (1) above and casting by applying a braking force to a discharge flow of molten steel in the mold.

  In the present invention, “single casting” means casting in which one slab is cast with one strand, and “twin casting” refers to casting two slabs with one strand as described above. Means casting.

  In addition, “closely arranged” means to arrange with an interval of 10 mm or less. This is to minimize the decrease in magnetic flux density acting on the discharge flow of molten steel.

  In the description of the present specification, the “magnetic pole” means a magnetized core or a portion where a winding line exists in the core.

  According to the continuous casting mold and the continuous casting method using the same according to the present invention, the magnetic pole of the electromagnetic braking device is used for the flow control of the molten steel due to the interference of the equipment position with the shape of the mold or the device arranged around the mold. Even when it cannot be installed at the optimum position, the application position of the magnetic field can be adjusted to the optimum position. Therefore, the present invention can contribute to a stable casting operation in which the flow of molten steel in the mold is controlled to an optimum state and casting of a high quality slab with reduced surface defects and occurrence of breakout are prevented.

  As described above, the present invention includes a backup plate and an electromagnetic braking device that applies a braking force to the discharge flow of the molten steel in the mold, and the main body core in which the electromagnetic braking device is disposed outside the backup plate, the backup plate A separation core that is partially inserted or penetrated in the thickness direction in a part thereof, and an electromagnetic coil wound around the body core, and a cross-sectional central axis of the main body core and a cross-sectional center of the separation core A continuous casting mold in which the shaft is shifted in the mold long side width direction and / or height direction, and the end surface on the separation core side of the main body core and the end surface on the main body core side of the separation core are arranged close to each other , And a continuous casting method using the same. Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

  FIG. 2 is a view schematically showing an example of arrangement (invention example) in which the continuous casting mold of the present invention is applied to a twin mold. FIG. 2 (a) is a plan view, and FIG. 2 (b). These are DD longitudinal cross-sectional views of the same figure (a). As shown in FIG. 5A, since the partition fixing device 10 is disposed, the main body core 7 of the electromagnetic braking device 6 cannot be installed at a position immediately before the partition 9. Therefore, the separation core 8 is installed at a position (d = 40 mm in FIG. 3A) whose central axis of the cross section is shifted by 40 mm from the central axis of the main body core in the direction of the partition 9.

  In the example of the embodiment shown in FIG. 2, the inner dimension of the mold short side 3 is 260 mm, the inner dimension of the mold long side 4 for one mold is 1100 mm, the width of the partition 9 is 220 mm, and the thickness of the backup plate 11 is The width of the main body core 7 of the electromagnetic braking device 6 is 250 mm, the height is 350 mm, the width of the separation core 8 is 250 mm, the height is 350 mm, and the width of the electromagnetic coil 12 (the thickness of the winding) is 40 mm. It is. The meniscus is located at a position of 100 mm downward from the upper end of the mold, and the main body core 7 and the separation core 8 have a height of 100 mm below the molten steel meniscus 16 (L = 100 mm in FIG. ).

  The outer diameter of the immersion nozzle 1 is 148 mm, the distance between the mold short side surface of the partition 9 and the outer surface of the immersion nozzle is 226 mm, the position of the tip of the immersion nozzle is 280 mm below the molten steel meniscus 16, and the mold thickness is 40 mm. It is.

  A magnetic material can be used as the core material of the electromagnetic coil 12, and the use of a magnetic steel sheet material or electromagnetic soft iron is optimal. As a material for the backup plate, a non-magnetic material can be used. For example, use of stainless steel represented by SUS304 is suitable.

  The separation core 8 may be an integrated core that is continuous with the main body core 7, but it is easier to handle them if both cores are separated. When both cores are separated, the material of the separation core 8 may be different from the material of the main body core 7. When an iron-based material is used for the separation core 8, the material is preferably a magnetic steel plate material or electromagnetic soft iron, but there is no functional problem as long as it is a magnetic material. These steel materials can also be used.

  The electromagnetic braking device 6 and the mold are spaced from the end surface on the main body side of the separation core 8 and the end surface on the separation core side of the main body core 7 from the viewpoint of minimizing a decrease in magnetic flux density when the electromagnetic braking device is used. Is installed close to each other so that the distance is 10 mm or less. The distance between the both end faces is preferably 5 mm or less, and more preferably, the both end faces are installed so that they are in close contact with each other.

  The separation core 8 and the body core 7 are preferably installed so that at least 10% of the cross section of the main body core overlaps with the cross section of the separation core, more preferably the cross section of the main body core. It is good to install so that 50% or more of the cross-section of the separated core overlaps.

  FIG. 2 shows an example in which the magnetic field application position is moved in the width direction of the long side of the mold, that is, in the horizontal direction, but the magnetic field application position is moved in the mold height direction, that is, in the casting depth direction. Also good.

Example 1
In order to confirm the effect of the present invention, the present invention example to which the present invention is applied, the comparative example to which the present invention is not applied, and the electromagnetic brake device can be arranged at an ideal position without the partition fixing device in the mold The distribution of magnetic flux density was compared in each case. Distribution of magnetic flux density was performed by numerical analysis simulation, and the analysis results were compared.

  FIG. 3 is a plan view schematically showing an example (comparative example) of an arrangement in which the present invention is not applied to a mold having a partition fixing device, and FIG. 4 is an electromagnetic diagram in a mold having no partition fixing device. It is a top view which shows typically the example when the core of a braking device can be arrange | positioned in an ideal position. The numerical analysis simulation is performed for the arrangement example shown in FIG. 2 for the example of the present invention, for the arrangement example shown in FIG. 3 for the comparative example, and for the example shown in FIG. 4 for the ideal arrangement example. It was. The winding current of the electromagnetic coil was 600 A, and the number of turns was 100.

  Table 1 shows the side surface of the short side of the partition shown in FIGS. 2, 3 and 4 (position indicated by B in each figure) and the side face of the partition side of the immersion nozzle (position indicated by C in each figure). ) Shows the comparison of magnetic flux density.

  FIG. 5 is a diagram showing a comparison of magnetic flux density distributions in the mold long-side width direction in the AA longitudinal section in FIGS. 2, 3, and 4.

  As described above, in order to cast a slab excellent in surface quality by applying a braking force to the discharge flow of molten steel from the immersion nozzle, the magnetic flux density at the position where the immersion nozzle is present is low, and the mold short side of the partition It is important to adjust the distribution of magnetic flux density so that the magnetic flux density at the position of the side surface becomes high.

  According to the results of Table 1 and FIG. 5, in the comparative example in which the present invention is not applied, the side position of the submerged nozzle (by C in the figure), compared with the case where the core of the electromagnetic braking device is disposed at an ideal position. The magnetic flux density is high at the position shown, and the magnetic flux density is low at the short side surface position (position indicated by B in the drawing) of the partition.

  On the other hand, in the example of the present invention to which the continuous casting mold of the present invention is applied, a distribution shape having a low magnetic flux density at the side surface position of the immersion nozzle and a high magnetic flux density at the side surface of the mold short side of the partition is obtained. Yes. The magnetic flux density distribution shape of the above-described example of the present invention is close to the magnetic flux density distribution shape obtained when the core of the electromagnetic braking device can be arranged at an ideal position. As shown in Table 1, in the example of the present invention, compared to the comparative example, the magnetic flux density applied to the side position of the immersion nozzle is reduced by 0.05 T (500 Gauss) or more, and the side surface of the mold short side of the partition is reduced. The magnetic flux density at the position could be increased by 0.03 T (300 Gauss) or more. Therefore, the distribution shape of the magnetic flux density in the example of the present invention is an optimum distribution shape for casting a slab excellent in surface quality by applying a braking force to the discharge flow of molten steel from the immersion nozzle.

(Example 2)
An example in which the continuous casting mold of the present invention is applied to single casting of slabs having different widths will be described. A general steel continuous casting mold is manufactured so that the short side of the mold is movable in the direction opposite to the short side, and slabs having different widths can be cast. Since the optimum application position of the magnetic field also changes according to the width of the slab to be cast, the method of moving the application position of the magnetic field using the continuous casting mold of the present invention is effective.

  FIG. 6 is a diagram schematically showing an example in which the continuous casting mold of the present invention is applied to a single mold and the magnetic field application position is moved closer to the center in the long side width direction of the mold. (A) is the top view, The figure (b) is DD longitudinal cross-sectional view of the figure (a). FIG. 7 is a diagram schematically showing an example in which the continuous casting mold of the present invention is applied to a single mold and the magnetic field application position is moved to the mold short side in the mold long side width direction. (A) is a plan view, and (b) is a DD longitudinal sectional view of (a).

  In the example shown in FIGS. 6 and 7, the separation core is composed of a magnetic part and a non-magnetic part. Here, for example, electromagnetic soft iron can be used for the magnetic part, and stainless steel such as SUS304 can be used for the non-magnetic part. Similarly to the example of FIG. 2 in which the continuous casting mold of the present invention is applied to the twin mold, it is possible to use a mold of a type in which a separation core made of a magnetic material is fitted into a backup plate. In some cases, each time the position of the separation core is changed, it is necessary to replace the entire backup plate fitted with the separation core, which increases costs and man-hours.

  On the other hand, if the method shown in FIGS. 6 and 7 is used, only the magnetic part and the non-magnetic part of the separation core are exchanged while the same backup plate is used without exchange. By moving the position of the magnetic part, the magnetic field can be applied to the optimum position for applying a braking force to the molten steel discharge flow in the mold.

  According to the continuous casting mold and the continuous casting method using the same according to the present invention, the magnetic pole of the electromagnetic braking device is used for the flow control of the molten steel due to the interference of the equipment position with the shape of the mold or the device arranged around the mold. Even when it cannot be installed at the optimum position, the magnetic field application position can be adjusted to the optimum position. Therefore, the present invention can be widely applied in a casting process as a continuous casting mold and a continuous casting method capable of stably casting a high quality slab with reduced occurrence of surface defects and the like.

It is a longitudinal cross-sectional view which shows typically the flow state of the molten steel in the casting_mold | template in the general continuous casting method of steel. It is a figure which shows typically the example (invention example) of the arrangement | positioning which applied the casting mold for continuous casting of this invention to the twin mold, The figure (a) is a top view, The figure (b) is the figure ( It is DD longitudinal cross-sectional view of a). It is a top view which shows typically the example (comparative example) of arrangement | positioning which does not apply this invention to the casting_mold | template which has a partition divider. It is a top view which shows typically the example which could have arrange | positioned the electromagnetic braking device in the ideal position of the casting_mold | template which does not have a partition divider fixing device. It is a figure which compares and shows distribution of the magnetic flux density of the casting_mold | template long side width direction in the AA longitudinal cross section in FIGS. FIG. 2 is a diagram schematically showing an example in which the continuous casting mold of the present invention is applied to a single mold and the magnetic field application position is moved closer to the center in the mold long side width direction, and FIG. FIG. 4B is a longitudinal sectional view taken along the line DD of FIG. It is a figure which shows typically the example which applied the casting_mold | template for continuous casting of this invention to a single casting_mold | template, and has moved and arrange | positioned the application position of a magnetic field to the casting_mold | template short side of a casting_mold | template long side width direction. FIG. 4B is a plan view, and FIG. 2B is a DD longitudinal sectional view of FIG.

Explanation of symbols

1: immersion nozzle, 2: discharge port,
3: Mold short side, 4: Mold long side,
5: Solidified shell 6: Electromagnetic braking device
7: body core, 8: separation core,
9: Partition, 10: Partition fixing device,
11: Backup plate, 12: Electromagnetic coil,
13: Magnetic part of the separation core, 14: Non-magnetic part of the separation core,
15: Mold powder, 16: Meniscus of molten steel,
21: Upflow, 22: Downflow

Claims (2)

A continuous casting mold capable of twin casting by arranging a partition device in the mold,
The long side of the mold is arranged outside the long side copper plate having a cooling structure, the backup plate supporting the long side copper plate, and the outside of the backup plate is arranged on the extension line of the partition device A partition fixing device, and an electromagnetic braking device that applies a braking force to the discharge flow of the molten steel in the mold,
A body core in which the electromagnetic braking device is disposed outside the backup plate, a separation core that is partially inserted or penetrated in a thickness direction in a part of the backup plate, and Consisting of a rotated electromagnetic coil,
The main body core is disposed so as to straddle the partition fixing device in the width direction of the mold long side,
The electromagnetic coil and the partition fixing device are in contact with each other;
Further, the cross-sectional central axis of the main body core and the cross-sectional central axis of the separation core are shifted in the width direction of the mold long side , and the separation core is in a projection plane in a direction perpendicular to the long side of the mold. In contact with the partition device ,
And the casting mold for continuous casting characterized by arrange | positioning closely so that the space | interval of the end surface by the side of the separation core of the said main body core and the end surface by the side of the main body core of the said separation core may be 10 mm or less.   A continuous casting method using the casting mold for continuous casting according to claim 1 and casting by applying a braking force to a discharge flow of molten steel in the casting mold.

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