JP5827915B2 - Continuous casting mold - Google Patents

Description

  The present invention relates to a continuous casting mold for producing a slab while stirring molten steel flowing in a mold.

  When producing molten slabs by flowing (injecting) molten steel into a continuous casting mold, non-metallic inclusions and gases (such as bubbles) contained in the molten steel are actively levitated and removed. In order to obtain a slab excellent in quality, a continuous casting mold in which molten steel in the cavity is electromagnetically stirred has been generally applied.

  The electromagnetic stirrer prevents product defects during initial solidification by stirring molten metal with electromagnetic force.

  As a structure of a conventional continuous casting mold, Patent Document 1 discloses a shape of a cavity through which molten steel flows, and an upper center of the cavity swells outward and is narrowed downward (a part of the cavity is funnel-shaped or A continuous casting mold (in the form of a funnel) is disclosed. Thus, a continuous casting mold provided with a cavity having a funnel-shaped region in a part thereof is a mold suitable for manufacturing a thin slab having a thickness of about 30 mm to 150 mm, for example.

  Here, the continuous casting mold of the form disclosed in Patent Document 1 will be described in detail with reference to FIGS. Specifically, FIG. 8 is a plan view of the continuous casting mold as viewed from above, FIG. 9 is a diagram illustrating an assembly mode of the coil with respect to the iron core, and FIG. 10 is a view taken along the line XX in FIG. FIG. 11 is a longitudinal sectional view taken along the line XI-XI in FIG. 8 and is a longitudinal sectional view taken along a non-funnel-like region, and FIG. 12 is a view showing molten steel in the cavity. It is a figure explaining the situation which is carrying out electromagnetic stirring.

  As shown in FIG. 8, the continuous casting mold CM includes a molten steel circulating body P in which two pairs of copper side plates P1 and P1 and side plates P2 and P2 serving as cooling walls are assembled and a cavity Ca is formed therein. A cooling box B is provided outside each of the side plates P1 and P1 that are provided at the center and located on the left and right in the figure, and an electromagnetic stirring device in which a coil Co is formed on an iron core F inside the cooling box B. Q is accommodated and the whole is constituted.

  As shown in FIG. 8 and FIG. 10, the left and right side plates P1, P1 are composed of a central curved surface P1a and a plane P1b on the outer side (upper and lower sides in FIG. 8) of the curved surface P1a at the center of the side wall P1. It has a funnel-shaped region that swells outward at the top and is squeezed downward. Further, as shown in FIGS. 8 and 11, the plane P1b outside the funnel-shaped region (upper and lower sides in FIG. 8) in plan view has a non-funnel-shaped region in which the width between the left and right side plates P1 and P1 is constant. doing.

  On the other hand, the electromagnetic stirring device Q accommodated in the cooling box B is formed by winding a copper coil Co around a comb-shaped iron core F as shown in FIG. A three-phase coil that forms a U-phase, a V-phase, and a W-phase is formed. The iron core F has a rectangular cross-sectional shape orthogonal to the axial direction, and the coil Co formed around the iron core F has a rectangular frame shape.

  As shown in FIG. 10, in the funnel-shaped region, the distance t1 between the upper region of the iron core F and the curved surface P1a of the side plate P1, and the distance t2 between the lower region of the iron core F and the curved surface P1a are different. Further, as shown in FIG. 11, in the non-funnel region, the distance from the iron core F to the plane P1b of the side plate P1 is constant at t3, but this distance t3 is generally longer than the distances t1 and t2 in the funnel region. It has become.

  As shown in FIG. 10, the molten steel M provided from the nozzle N located above the funnel-shaped region flows through the cavity Ca (in the X1 direction), and is cooled and discharged from the lower opening during this flow. (X2 direction), an alternating current is provided to the three-phase coil Co from an unillustrated alternating current power source, and the molten steel M in the cavity Ca is stirred by electromagnetic force as shown in FIG.

  In this electromagnetic force agitation, as shown in FIG. 12, a reverse electromagnetic force acts on the left and right regions of the cavity Ca by the three-phase alternating current, and the molten steel M is agitated by this opposite electromagnetic force. In the funnel-shaped region, particularly in the region above the iron core F (meniscus region), the electromagnetic force increases because the distance t1 to the side plate P1a is short, and therefore the molten steel M in the region above the funnel-shaped region is greatly stirred. (Y1 direction).

  On the other hand, in the non-funnel region, the distance t3 between the plane P1b of the side plate P1 and the iron core F is longer than that in the funnel region, so that the electromagnetic force that stirs the molten steel M is weaker than that in the funnel region. (Y2 direction), it is difficult to obtain sufficient stirring force in this region.

  As a result of the molten steel M not being sufficiently stirred at the end of the cavity Ca, non-metallic inclusions and gas remain in the end region of the cast slab such as a thin slab discharged from the continuous casting mold CM. Therefore, a slab excellent in surface quality as a whole product is not manufactured.

JP 9-512484 A

  The present invention has been made in view of the above-mentioned problems, and relates to a continuous casting mold having a cavity having a funnel-shaped region and a non-funnel-shaped region, and can produce a slab excellent in surface quality as a whole product. The object is to provide a continuous casting mold.

  In order to achieve the above object, a continuous casting mold according to the present invention has two pairs of side plates assembled in a frame shape to form a cavity inside thereof, and each of the pair of side plates of the two pairs of side plates is a part thereof. A funnel-shaped region that swells outward at the center and is squeezed downward, and a non-funnel-shaped region that has a constant width between the pair of side plates from the top to the bottom outside the funnel-shaped region. A molten steel circulating body in which molten steel flows from above to below, and an electromagnetic stirrer that is disposed on the outside of each of the pair of side plates and has a coil formed on an iron core. In the casting mold, the iron core has a shape corresponding to a three-dimensional shape extending from the funnel-shaped region to the non-funnel-shaped region of the pair of side plates.

  The continuous casting mold of the present invention is a mold having a cavity having a funnel-shaped region and a non-funnel-shaped region, but the iron core constituting the electromagnetic stirrer on the side of the cavity is linear like the conventional continuous casting mold. The structure in which the iron core has a shape corresponding to the three-dimensional shape extending from the funnel-shaped region to the non-funnel-shaped region of the side plate is applied. As a result, of the separation between the iron core and the side plate, the separation in the non-funnel region becomes longer than the funnel-like region, and the conventional continuous casting mold in which sufficient electromagnetic force stirring cannot be obtained in the non-funnel region. It is possible to effectively solve the problems possessed by.

  That is, the cross-sectional shape of the iron core may be any shape such as a rectangle (including a rectangle and a square), a circle, an ellipse, etc., but the separation between the iron core and the side plate is changed from the funnel-shaped region to the non-funnel-shaped region. For example, since it can be adjusted to be constant over the non-funnel region, sufficient electromagnetic force agitation can be obtained in the same manner as in the funnel region, thereby producing a slab having excellent surface quality as a whole product. Is possible.

  Here, the two pairs of side plates that define the cavity are preferably made of a metal such as copper and excellent in heat dissipation and capable of forming a cooling wall.

  For example, among two pairs of side plates that define a rectangular cavity with a planar shape, a pair of side plates that correspond to the long side has a funnel-shaped region and a non-funnel-shaped region, and an electromagnetic stirrer is provided outside the pair of side plates. A cooling box or the like is provided.

  As described above, the magnetic stirring device includes an iron core having a shape corresponding to a three-dimensional shape extending from a funnel-shaped region to a non-funnel-shaped region, a coil formed around the iron core, and an alternating current to the coil. It consists of a power supply to apply. For example, the coil constituting the electromagnetic stirrer disposed on the outside of each of the pair of side plates is composed of a U-phase, V-phase, and W-phase three-phase coil (more specifically, one is a U-phase coil) If it has, the other has a -U phase coil), both are configured to generate electromagnetic force in opposite directions.

  The back of the side plate is provided with a number of rectangular grooves or the like so that the coolant is provided here, and flows through the supply chamber or the piping for supplying the coolant to the piping in the cooling box or separately from the cooling box. A drainage chamber or the like for draining the warmed refrigerant may be provided.

  The molten steel is cooled by the side plate that defines the cavity in the process of flowing the molten steel, and the molten steel is discharged from the cavity while starting to harden sequentially from the outer periphery in the flowing process. A slab having a shape and a dimension corresponding to the shape of the outlet is produced.

  Then, the electromagnetic stirrer operates in the flow process in the cavity, and the molten steel is stirred by the electromagnetic force, and the nonmetallic inclusions and gas contained in the molten steel are removed. In particular, in the continuous casting mold of the present invention, the same level of electromagnetic force is provided to the molten steel over the entire region from the funnel-shaped region to the non-funnel-shaped region. A cast slab that is agitated by electromagnetic force and has excellent surface quality as a whole product can be produced.

  Here, the continuous casting mold according to the present invention can include a plurality of embodiments as described below. In one form thereof, the iron core has a rectangular cross-sectional shape, and the coil has a rectangular frame shape in cross-sectional shape, and the coil is inclined from above to below in the funnel-shaped region. The non-funnel region is disposed in a vertical posture, and the separation between the iron core and the side plate is constant from the funnel region to the non-funnel region.

  The iron core is twisted in the vicinity of the boundary between the funnel-shaped region and the non-funnel-shaped region, for example, so that the rectangular cross-section having an axis that fits the three-dimensional shape from the funnel-shaped region to the non-funnel-shaped region. Can be an iron core.

  In the funnel-shaped region, the iron core having a rectangular cross section is disposed in an inclined posture from above to below, and the coil having a rectangular frame-shaped cross section is also disposed in an inclined posture so as to conform to the inclined posture of the iron core. On the other hand, in the non-funnel-shaped region, the iron core having a rectangular cross section is disposed in a vertical posture, and the coil having a rectangular frame cross section is also disposed in a vertical posture so as to match the vertical posture of the iron core. In this way, the coil placement posture changes between the funnel-shaped region and the non-funnel-shaped region, and the iron core is disposed so that the separation between the iron core and the side plate is constant from the funnel-shaped region to the non-funnel-shaped region. Has been.

  That is, in the funnel-shaped region, the side on the side plate side of the iron core constituting the rectangular cross-section from the top to the bottom is always the same distance as the side plate (for example, the separation is t). Are arranged so that the side on the side plate side of the iron core is the same distance t.

  In this way, in all the regions of the funnel-shaped region and the non-funnel-shaped region, and the distance between the iron core and the side plate is constant from the upper region to the lower region of the side plate, The same degree of electromagnetic force can be applied to the molten steel in all regions of the funnel region (including the depth direction in the cavity).

  Further, as another embodiment of the continuous casting mold, the iron core has a parallelogram shape in a funnel-shaped region, and a rectangular shape in a non-funnel-shaped region, and the coil has a funnel shape. The cross-sectional shape is a parallelogram frame shape in the shaped region, and the cross-sectional shape is a rectangular frame shape in the non-funnel shaped region, and the separation between the iron core and the side plate is constant from the funnel-shaped region to the non-funnel shaped region. Can be mentioned.

  Regarding the cross-sectional shape of the iron core, the cross-sectional shape in the funnel-shaped region is a parallelogram, more specifically, an iron core having a parallelogram-shaped cross-section with the same inclination as the upward-downward inclination in the funnel-shaped region is applied. In addition, a coil having a parallelogram frame shape is applied so that the coil also matches the cross-sectional shape of the iron core.

  According to this embodiment, in the funnel-shaped region, an electromagnetic core having a parallelogram cross section having an angle suitable for the inclination of the side plate in this region and a coil having a parallelogram frame-shaped cross section around it are arranged. An unnecessary space (dead space) that may be generated in the cooling box that accommodates the stirring device can be eliminated.

  In addition, the orientation of the coil changes between the funnel-shaped region and the non-funnel-shaped region, and the iron core is disposed so that the distance between the iron core and the side plate is constant from the funnel-shaped region to the non-funnel-shaped region. Thus, similar to the continuous casting mold of the form described above, the same degree of electromagnetic force can be applied to the molten steel in all the regions of the funnel-shaped region and the non-funnel-shaped region.

  As can be understood from the above description, according to the continuous casting mold of the present invention, the electromagnetic stirrer arranged on the side of the cavity is configured with respect to the mold having the cavity having the funnel-shaped region and the non-funnel-shaped region. Since the iron core has a shape corresponding to the three-dimensional shape extending from the funnel-shaped region of the side plate to the non-funnel-shaped region, the same level of electromagnetic force is generated in all regions of the funnel-shaped region and the non-funnel-shaped region. It can be applied to the molten steel, so that a slab excellent in surface quality can be manufactured as a whole product.

It is a top view of embodiment of the continuous casting mold of this invention. It is the figure explaining the assembly | attachment aspect of the coil with respect to an iron core. It is the III-III arrow line view of FIG. 1, and is the figure which showed together the condition where the molten steel distribute | circulates in the cavity. It is the IV-IV arrow line view of FIG. 1, and the figure which showed the condition where the molten steel is distribute | circulating in the cavity. It is a figure explaining the situation where the molten steel is being stirred by the electromagnetic force within the continuous casting mold. It is the longitudinal cross-sectional view which showed other embodiment of the electromagnetic stirring apparatus. It is the figure which showed the analysis result regarding the magnetic flux density distribution in the longitudinal direction of a cavity. It is a top view of embodiment of the conventional continuous casting mold. It is the figure explaining the assembly | attachment aspect of the coil with respect to an iron core. FIG. 9 is a view taken along the line XX of FIG. 8 and shows a situation in which molten steel is circulating in the cavity. FIG. 9 is a view taken along the line XI-XI in FIG. 8 and shows a situation in which molten steel is circulating in the cavity. It is a figure explaining the situation where the molten steel is being stirred by the electromagnetic force within the continuous casting mold.

  Hereinafter, embodiments of a continuous casting mold of the present invention will be described with reference to the drawings. Although the illustrated example shows the structure of the cooling box in a simplified manner, it is needless to say that it may be a continuous casting mold provided with a cooling box provided with a mechanism for supplying a refrigerant to the side plate. .

(Embodiment of continuous casting mold)
FIG. 1 is a plan view of an embodiment of a continuous casting mold according to the present invention, and FIG. 3 is a view taken along the line III-III in FIG. 1 and shows a situation in which molten steel is circulating in the cavity. FIG. 4 is a view taken in the direction of arrows IV-IV in FIG. 1 and shows a situation in which molten steel is circulating in the cavity. FIG. 5 is a diagram for explaining a situation in which molten steel is stirred by electromagnetic force in a continuous casting mold.

  A continuous casting mold 100 shown in FIG. 1 has a molten steel circulating body 10 in which two pairs of copper side plates 1 and 1 and side plates 2 and 2 serving as cooling walls are assembled in a frame shape and a cavity Ca is formed therein. A cooling box 5 is provided on the outside of each of the side plates 1 and 1 that are provided in the center and located on the left and right sides in the figure, and an electromagnetic stirring device in which a coil 4 is formed on an iron core 3 inside the cooling box 5. 20 is accommodated and the whole is constituted. The constituent elements of the electromagnetic stirring device 20 include an AC power source (not shown) that applies an AC current to the coil 4.

  As shown in FIGS. 1 and 3, the left and right side plates 1, 1 are composed of a central curved surface 1 a and a flat surface 1 b outside (upper and lower sides in FIG. 1). It has a funnel-shaped region that swells outward above la (inflow side of molten steel M) and is squeezed downward (outflow side of molten steel M). Further, as shown in FIGS. 1 and 4, the width between the planes 1 b and 1 b of the left and right side plates 1 and 1 is constant in the height direction outside the funnel-shaped region in plan view (up and down side in FIG. 1). A non-funnel-like region.

  The electromagnetic stirrer 20 accommodated in the cooling box 5 is formed by winding a copper coil 4 around a comb-shaped iron core 3 as shown in FIG. 2, and the left and right electromagnetic stirrers 20, 20 are respectively A three-phase coil (two-pole three-phase AC coil) forming a U phase, a V phase, and a W phase is formed.

  Moreover, the cross-sectional shape orthogonal to the axial direction of the iron core 3 is a rectangle, and the coil 4 formed around the iron core 3 has a rectangular frame shape in cross-section.

  As shown in FIGS. 1, 3, and 4, the iron core 3 disposed on the side of the side plate 1 has a shape corresponding to a three-dimensional shape extending from the funnel-shaped region to the non-funnel-shaped region of the side plate 1. ing. More specifically, in the plane axis of the iron core 3 shown in the plan view of FIG. 1, the funnel-shaped region has a curved shape, and the non-funnel-shaped region has a plane axis that is linear. On the other hand, the cross-sectional shape orthogonal to the plane axis is configured so that the cross-section is twisted in the middle, and in the funnel-shaped region, the same inclination as the curved surface 1a of the inclined side plate 1 as shown in FIG. The iron core 3 having a rectangular cross section is disposed in the posture, and in the non-funnel region, the iron core 3 having the rectangular cross section is disposed in the same vertical posture as the plane 1b of the vertical side plate 1 as shown in FIG.

  Further, the separation between the upper region of the iron core 3 having a rectangular cross section and the curved surface 1a of the side plate 1 in the funnel-shaped region is t4, and the separation between the lower region of the iron core 3 and the curved surface 1a of the side plate 1 is also the same at t4. The separation between the iron core 3 and the side plate 1b in the non-funnel region is the same at t4.

  As shown in FIG. 3, a process in which the molten steel M provided from the nozzle 6 located above the funnel-shaped region flows into the cavity Ca (in the X1 direction) and is cooled and discharged from the lower opening during this flow. (X2 direction), an alternating current is provided to the three-phase coil 4 from an unillustrated alternating current power source, and the molten steel M in the cavity Ca is agitated by electromagnetic force as shown in FIG.

  In this electromagnetic force agitation, as shown in FIG. 5, the electromagnetic force in the opposite direction acts on the left and right regions of the cavity Ca by the three-phase alternating current, and the molten steel M is agitated by this opposite electromagnetic force. In the electromagnetic casting, in the continuous casting mold 100, the iron core 3 having a rectangular cross section in the funnel region and the curved surface 1a of the side plate 1 are separated, and the iron core 3 having a rectangular cross section in the non-funnel region and the plane 1b of the side plate 1 are separated. Are the same length, the same degree of electromagnetic force is applied to the molten steel M flowing in the cavity Ca regardless of the portion.

  Then, as shown in FIG. 5, the molten steel M is stirred so as to draw a circle on the plane by the electromagnetic force applied in the funnel-shaped region (Y3 direction), and in the non-funnel-shaped region as well as the funnel-shaped region. Stirring is performed by returning the molten steel M that has entered from the funnel-shaped region to the funnel-shaped region by the electromagnetic force (Y4 direction).

  In this way, as a result of rotational stirring with the same degree of electromagnetic force over the entire funnel-shaped region and non-funnel-shaped region, nonmetallic inclusions and gas contained in the molten steel are removed from the entire molten steel. Therefore, a slab excellent in surface quality as a whole product is manufactured.

  FIG. 6 is a longitudinal sectional view showing another embodiment of the electromagnetic stirring device. The iron core 3A constituting the electromagnetic stirrer 20A shown in the figure has a parallelogram in the cross-sectional shape in the funnel-shaped region, and has a rectangular cross-sectional shape in the non-funnel-shaped region. Regarding the coil 4A, the cross-sectional shape is a parallelogram frame shape in the funnel-shaped region, and the cross-sectional shape is a rectangular frame shape in the non-funnel-shaped region. The separation between the iron core and the side plate is constant over the region (separation t4).

  As shown in the figure, applying the iron core 3A whose cross-sectional shape in the funnel-shaped region is a parallelogram, more specifically, the inclination of the curved surface 1a of the side plate 1 from the upper side to the lower side in the funnel-shaped region An iron core 3A having a parallelogram cross section having the same inclination is applied, and a coil 4A having a parallelogram frame shape is used so that the cross section of the coil 4A matches the cross section of the iron core 3A.

  According to the illustrated embodiment, in the funnel-shaped region, the parallelogram-shaped iron core 3A having an angle suitable for the inclination of the curved surface 1a of the side plate 1 in this region and the coil having the parallelogram-shaped frame cross-section around it. By arranging 4A, the dead space which may arise in the cooling box 5 which accommodates the electromagnetic stirring apparatus 20A is eliminated.

[Analysis and results of magnetic flux density distribution in the longitudinal direction of the cavity]
The inventors have modeled the continuous casting mold shown in FIGS. 1, 3 and 4 in a computer, and determined the magnitude (magnetic flux density) of electromagnetic force formed in the cavity when a three-phase alternating current is applied to the coil. The analysis to identify was done.

  With respect to the analysis model, two models are created: Example and Comparative Example. First, the dimensions of the embodiment model are as follows. The width s1 of the funnel-shaped region of the cavity Ca shown in FIG. 1 is 250 mm, the width s2 of the non-funnel-shaped region is 150 mm, and the length s3 of the funnel-shaped region in the longitudinal direction of the side plate is The length s4 in the longitudinal direction of the entire cavity Ca is 1300 mm, the length s6 of the inclined portion of the funnel-shaped region shown in FIG. 3 is 650 mm, and the length s5 of the iron core is 300 mm.

  On the other hand, the comparative example model models the continuous casting mold shown in FIGS. 8, 10, and 11 and has dimensions corresponding to the example model.

  The number of turns of the coil and the current value were the same in the example and the comparative example, and the magnitude and distribution of the magnetic flux density at a point 15 mm inside the side plate in the longitudinal direction of the cavity were specified. The analysis results are shown in FIG.

  In FIG. 7, the horizontal axis indicates the position in the longitudinal direction of the cavity, and is normalized by dividing the length from the starting point by the total length. On the other hand, the vertical axis represents the magnetic flux density, and the analysis value is normalized by dividing the analysis value by the maximum value of the analysis value of the example in both the example and the comparative example. In addition, since an alternating current is applied to both the example and the comparative example, a waveform graph with a constant period is shown particularly with respect to the example.

  From the figure, in the comparative example, the magnetic flux density at the end of the cavity is extremely weak, which means that the electromagnetic force at the end of the cavity is weak and stirring is insufficient at the end of the cavity. Yes.

  On the other hand, in the embodiment, the magnetic flux density is high in the entire region in the longitudinal direction including the end portion of the cavity. Therefore, the electromagnetic force is strong in the entire region of the cavity, and the molten steel in the cavity is sufficiently stirred as a whole. It shows that.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Side plate, 1a ... Curved surface, 1b ... Plane, 2 ... Side plate, 3, 3A ... Iron core, 4, 4A ... Coil (three-phase coil), 5 ... Cooling box, 6 ... Nozzle, 10 ... Molten steel circulating body, 20 , 20A ... electromagnetic stirring device, 100 ... mold for continuous casting, Ca ... cavity, M ... molten steel

Claims (3)

Two pairs of side plates are assembled in a frame shape to form a cavity on the inside thereof, and each of the pair of side plates of the two pairs of side plates swells outwards above the center and is squeezed downward. Molten steel that has a funnel-shaped region and a non-funnel-shaped region with a constant width between the pair of side plates on the outside of the funnel-shaped region from above to below, and the molten steel flows from above to below in the cavity. With circulation
An electromagnetic stirrer provided with a coil on an iron core, disposed on the outside of each of the pair of side plates, and a continuous casting mold,
The continuous casting mold in which the iron core has a shape corresponding to a three-dimensional shape extending from a funnel-shaped region to a non-funnel-shaped region of the pair of side plates. The iron core has a rectangular cross-sectional shape, and the coil has a rectangular frame shape in cross-sectional shape,
The coil and the iron core are disposed in an inclined posture from the top to the bottom in the funnel-shaped region, and are disposed in a vertical posture in the non-funnel-shaped region, and extend from the funnel-shaped region to the non-funnel-shaped region. The continuous casting mold according to claim 1, wherein the separation between the iron core and the side plate is constant. The iron core has a parallelogram shape in the cross-section in the funnel region, and the cross-sectional shape is rectangular in the non-funnel region.
The coil has a parallelogram frame shape in the cross-section in the funnel region, and a rectangular frame shape in the non-funnel region,
The continuous casting mold according to claim 1, wherein the distance between the iron core and the side plate is constant from the funnel-shaped region to the non-funnel-shaped region.

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