JP5042772B2 - Continuous casting mold - Google Patents

Description

  The present invention relates to a mold for continuous casting of molten metal having an electromagnetic coil, and relates to a mold capable of stably applying electromagnetic force to molten metal and obtaining a high quality slab for a long period of time.

  In the continuous casting of molten metal, in order to achieve stabilization of the molten metal surface, smoothing of the surface of a continuously cast slab, and increase in casting speed, for example, as disclosed in Patent Document 1, molten metal is used. Technology has been developed in which electromagnetic force is applied to the steel for casting. This is because an alternating current is supplied to an electromagnetic coil arranged so as to surround the mold and insulated with a refractory, and the meniscus portion of the molten metal in the mold is bent, and the CC powder is placed between the mold and the molten metal. It is a technique for improving surface properties by encouraging inflow and reducing the contact pressure between the mold and the slab during initial solidification.

  Patent Document 2 discloses a mold for a continuous casting apparatus having an electromagnetic coil, in which a pair of first cooling copper plates are sandwiched between a pair of second cooling copper plates and combined with a first cooling copper plate. The plate and the pair of back plates combined with the second cooling copper plate are electrically insulated via an insulator, and the mating surfaces of the first cooling copper plate and the second cooling copper plate are insulated from the mating surface. Disclosed is a continuous casting mold that is electrically insulated through an object and in which an insulator in the vicinity of the corner portion is installed within 50 mm from the corner portion of the casting surface of the first and second cooling copper plates. Yes.

  In Patent Document 3, in a continuous casting mold of a continuous casting apparatus for molten metal having an electromagnetic coil, a pair of first cooling copper plates are sandwiched between a pair of second cooling copper plates, and the first cooling copper plate and the above-mentioned The mating surface with the second cooling copper plate is electrically insulated from each other through an insulator, and is combined with the first back plate and the second cooling copper plate combined with the pair of first cooling copper plates. The second back plate is electrically insulated and fastened and fixed to each other via an insulator, and at least one of the pair of first back plates and the pair of second back plates A continuous casting mold is disclosed in which the outer peripheral surface of the plate is coated with an electrical insulator.

  Patent Document 4 discloses an electromagnetic coil (in a molten metal continuous casting apparatus in which electromagnetic force is applied in a direction perpendicular to the inner wall of the mold in the vicinity of the meniscus initial solidification portion of the molten metal in the continuous casting mold. And a pair of first back plates on a pair of first cooling copper plates, a pair of second back plates on a pair of first cooling copper plates. The cooling copper plate is combined with a pair of second back plates, and the pair of first cooling copper plates and the first back plate are movably sandwiched between the pair of second cooling copper plates and the second back plate. In the continuous casting mold configured as described above, either (or both) of the pair of first cooling copper plates and the pair of second cooling copper plates are parallel to the casting direction or inclined at 5 degrees or less from the casting direction, A cooling copper plate which is divided into two or more in the width direction, the back plate combined with the cooling copper plate divided into two or more is divided into two or more. Continuous casting molds are disclosed that are non-contacting or electrically insulated from each other.

  Patent Document 5 discloses an electromagnetic coil (in a continuous casting apparatus for molten metal in which electromagnetic force is applied in a direction perpendicular to the inner wall of the mold in the vicinity of the meniscus initial solidification portion of the molten metal in the continuous casting mold. And a pair of first back plates on a pair of first cooling copper plates, a pair of second back plates on a pair of first cooling copper plates. The cooling copper plate is combined with a pair of second back plates, and the pair of first cooling copper plates and the first back plate are movably sandwiched between the pair of second cooling copper plates and the second back plate. In the continuous casting mold configured as described above, at least one of the first and second cooling copper plates is divided into two or more in the plate width direction of the cooling copper plate, and the cooling copper plate is divided. Nickel or an alloy thereof, cobalt or an alloy thereof, chromium or an alloy thereof, iron or an alloy thereof in a range including at least a meniscus of at least a plane parallel to the casting direction among the opposed divided surfaces and the surfaces adjacent to the divided surfaces Between the coating layer provided on the dividing surface of the first cooling copper plate and the coating layer provided on the dividing surface of the second cooling copper plate. An insulator is provided, and the first and second back plates are electrically insulated from the first and second cooling copper plates, and the first back plate and the second back plate Continuous casting molds are disclosed that are non-contact or electrically insulated.

JP 52-32824 A JP 2003-145251 A JP 2003-145252 A International Publication Number WO2004 / 0783380 A1 JP 2007-144513 A

  Since the electromagnetic coil that generates the electromagnetic force is arranged outside the mold, the electromagnetic force acting on the molten metal inside the mold is attenuated by the induced current induced in the conductive mold. This attenuation also depends on the frequency of the alternating current used, and the higher the frequency, the greater the attenuation of the magnetic field at the mold.

  In Patent Document 1, it is described that a stainless steel lining is provided in a range including the meniscus portion of the mold so as to reduce the attenuation of the magnetic field. The attenuation of the magnetic field was inevitable.

  In the molds disclosed in Patent Documents 2 to 4, the insulation location, the electrical insulation layer, and the like are described. In short-time casting, there was no problem with attenuation of the magnetic field, but used for long-time casting. In such a case, the insulator deteriorates and the magnetic field attenuates, and the electrical insulating layer is damaged, resulting in poor durability.

  The inventors have proposed a mold disclosed in Patent Document 5, and this mold is excellent in durability without being deteriorated in insulation or damaging the electrical insulating layer even when used for a long time. However, it became clear that there was another problem when operating for a longer time. As will be described in detail later, the gap interval between the divided copper plates (distance between the surfaces of the electrical insulator applied to the divided surfaces of the respective divided copper plates, hereinafter referred to as the divided slit interval) increases as the usage time of the mold increases. The problem is that it gradually spreads. This phenomenon was remarkable at a position where the mold was subjected to a large heat load (from the meniscus height to a position around 200 mm below).

  Although the copper plate is cooled on the back or inside, the vicinity of the surface of the working surface being cast expands with heat from the molten metal. When a pair of cooling copper plates (mold short side) is divided, the short side copper plate is sandwiched between another pair of copper plates (mold long side), so the thermal expansion of the short side copper plate is in the long side copper plate. It is restrained and cannot grow freely. Therefore, when thermal expansion exceeding the elastic deformation region of the short side copper plate occurs, the vicinity of the surface of the short side copper plate is plastically deformed by thermal stress. When the temperature of the copper plate surface decreases after casting, the vicinity of the surface of the short side copper plate contracts, and a gap corresponding to the thermal stress deformation of each divided copper plate is generated in the divided slit portion. In a state where the thermal stress deformation is saturated, ideally, the slit gap opened in the cold is closed by the thermal expansion of the copper plate during casting, and after the casting again, the slit portion is opened by the contraction of the copper plate. Just by repeating, the slit gap does not expand.

  However, in practice, during casting, the split slit part is not completely closed from top to bottom, but it is considered that the closed part and the part that is slightly open are mixed. In a slightly open place, vapor or fume of molten powder used as a casting aid enters and adheres to the electrical insulator in the slit gap. The occurrence of deposits in the slit is equivalent to an increase in the copper plate width by the thickness of the deposit, and once the saturated thermal stress deformation further proceeds, the interval between the divided slits gradually increases.

  If the inside of the split slit gap is completely covered with deposits, molten metal will not enter from the working surface side of the cooling copper plate, but if there are gaps in some places, if powder breakage occurs, There is a risk of so-called hot water in which molten metal enters the gap, and stable slitting is impeded by the opening of the dividing slit. It is unavoidable to create slit gaps due to the thermal expansion of the copper plate before and after casting, so even if gaps are generated, it is necessary to eliminate foreign matter such as steam and fume entering the gap as much as possible. .

  An object of the present invention is to provide a continuous casting mold that casts by applying a magnetic field generated by an electromagnetic coil to a molten metal, and even if used for a long time, the magnetic field is not attenuated due to insulation deterioration, and stable for a long time. The object is to provide a durable mold capable of producing high quality slabs.

  The above problem is that the pressure of the gap of the split slit is the same on both the front and back of the copper plate, that is, the back plate side and the operating surface side, so it is not possible to prevent the vapor or fume generated on the operating surface side from entering the split slit, This is a problem that occurs because it enters the gap. This is solved by the continuous casting mold of the present invention described below.

(1) In order to apply an electromagnetic force in a direction perpendicular to the inner wall of the mold near the meniscus initial solidification portion of the molten metal in the continuous casting mold, a low frequency alternating current of 10 Hz to 500 Hz is applied to the outer peripheral surface of the mold. A pair of first cooling copper plates disposed on the short side and a pair of second back copper plates disposed on the long side and a pair of second cooling copper plates disposed on the short side. Two back plates are respectively combined, and the pair of the first cooling copper plate and the first back plate are sandwiched between the pair of the second cooling copper plate and the second back plate so as to be movable. A continuous casting mold in which at least one of the first and second cooling copper plates is divided into two or more in the plate width direction, and an electric insulator is provided on the divided surface. relative to the insulation material The serial backplate surface, provided the gas introduction groove upper and lower ends are closed, a gas introduction groove in comparison with the operation surface side of the electrically insulating material during casting is pressurizable so that the positive pressure, the gas have a pressure mechanism according to, pressure ranges mold for continuous casting of molten metal, which is a 0.01MPa～0.05MPa.

  According to the present invention, when continuously casting a molten metal by applying electromagnetic force, the stability of the mold can be ensured even during long-term use, and a high-quality slab can be obtained without any operational trouble over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  In order to clarify the conventional problems, the inventors changed the first cooling copper plate 1 (short side) assembled with the divided cooling copper plate 1a as shown in FIG. 3 to the continuous casting apparatus 20 shown in FIG. Built-in and molten metal casting. 3A is a perspective view of the cooling copper plate 1, and FIG. 3B is a horizontal sectional view of the cooling copper plate 1 at the meniscus height. In addition, in Fig.3 (a), a paper surface lower direction is a casting direction.

This mold, the second width _{W 2} is 2000mm cooling copper plates 2 (long sides), a width _{W 1} of the first cooling copper plate 1 (short side) is 250 mm, height H is a dimension of 900 mm, the one The first cooling copper plate 1 is divided into two at the center of the plate width. Each copper plate 1a of the first cooling copper plate 1 divided into two was provided with a sulfide-resistant coating 5 on both as shown in FIG. That is, 0.05 mm thick nickel plating was applied to the divided surface of the cooling copper plate 1a and the surface on the back plate 3 side (a part of the surface adjacent to the divided surface). As for the working surface (the remainder of the surface adjacent to the dividing surface), as shown in FIG. A nickel-based self-fluxing alloy sprayed portion 17 having a thickness of 1 mm was provided from the bottom to the bottom. In addition, a base sprayed layer of Hastelloy C-276 (trade name of nickel-based alloy) having a thickness of 0.05 mm is formed on both divided surfaces of the divided cooling copper plate 1a by a high-speed flame spraying method, and then a plasma spraying method. Thus, a zirconia ceramic with a thickness of 0.15 mm is formed in the range from the upper end to 600 mm in the height direction, and a yttria ceramic sprayed layer with a thickness of 0.15 mm is formed in the lower range, thereby electrically insulating Object 6 was provided. Further, on the back plate 3 combined with the divided cooling copper plate 1, a base sprayed layer of Hastelloy C-276 having a thickness of 0.05 mm is formed on the surface in contact with the divided cooling copper plate 1 by a high-speed flame spraying method. A zirconia ceramic sprayed layer having a thickness of 0.15 mm was formed by a thermal spraying method, and an electrical insulating layer 7 was provided. As shown in FIG. 3B, the divided cooling copper plate 1a and the back plate 3 are assembled using an insulating washer 8, an insulating sleeve 9, and a fastening bolt 10 so that there is no electrical conduction between them. As shown in FIG. 4, it was incorporated into the continuous casting apparatus 20 and cast, and the change in insulation resistance and the change in the split slit interval were investigated.

  The insulation resistance value between the divided cooling copper plates 1a before use measured by a normal mega tester is 83 MΩ, and the divided slit interval measured using a microscope with a magnification of 200 from the working surface side at a position 150 mm from the upper end of the mold. Was 15 μm. Thereafter, every 200 hours of casting, the insulation resistance between the divided copper plates and the interval between the divided slits at a position 150 mm from the upper end of the mold were measured. The measured insulation resistance and split slit spacing were 52 MΩ and 30 μm after 200 hours, 15 MΩ and 42 μm after 400 hours, 12 MΩ and 68 μm after 600 hours, and 8 MΩ and 105 μm after 800 hours, respectively. After 1000 hours, the values changed to 6 MΩ and 175 μm, respectively.

The mold was disassembled and a detailed investigation was conducted. When the divided cooling copper plate 1a is removed from the back plate 3 and the divided surface is observed, an electrical insulator applied to each divided surface over a range from about 30 mm above the meniscus height to about 200 mm below the meniscus height. There was a foreign object on the top. When a horizontal cross section of a portion 150 mm high from the upper end of the mold was cut and the cross section was observed, no damage such as cracks or chips were found in the film of the electrical insulator 6, and there was no damage between the copper plate and the thermal spray coating. Although peeling was not seen and it was healthy, a deposit of several tens of μm was observed on the electrical insulator 6. As a result of analysis, this deposit is an oxide mainly composed of SiO ₂ or CaO, and it is clear that the CC powder used in casting penetrated into the split slit gap from the operating surface side. It was.

  From the above results, when foreign matter enters the slit opening caused by deformation of the copper plate 1a generated by thermal expansion and contraction of the divided cooling copper plate 1a during and before and after casting, and adheres to the slit surface, the slit interval becomes large. It turns out that it opens. In order to prevent foreign matter from entering from the working surface when the slit is opened, the pressure on the back plate 3 side is increased on the front and back of the split slit portion compared to the molten steel surface side, and foreign matter is introduced from the molten steel surface side. It is only necessary to prevent intrusion.

  FIG. 1 is an example of an embodiment of the present invention corresponding to a variable width mold, for continuous casting in which a cooling copper plate 1 is divided into two in the plate width direction and an electrical insulator 6 is provided on the opposing divided surface. 3 is a perspective view showing an assembled state of a mold 21. FIG. The pair of first cooling copper plates 1 (short sides) are assembled so as to be movably sandwiched between a pair of second cooling copper plates 2 (long sides) attached to the second back plate 4. The cylinder 12 attached to 3 allows the width to be changed during casting. The back plate 3 attached to the first cooling copper plate 1 and the back plate 4 attached to the second cooling copper plate 2 are assembled so as not to cause electrical continuity by making no contact. An electromagnetic coil 11 for applying an electromagnetic force to the molten metal in a direction perpendicular to the inner wall of the mold is provided on the outer periphery of the mold 21 in the vicinity of the meniscus portion of the molten metal in the mold 21. The electromagnetic coil 11 is energized with a low frequency alternating current of 10 Hz to 500 Hz.

  FIG. 2A is a perspective view showing a surface of the back plate 3 to which the divided cooling copper plate 1a is attached. A groove 13 for feeding pressurized gas is formed at a position facing the divided surface of the cooling copper plate. A pipe 15 is provided for feeding pressurized gas into the pipe. FIG. 2 (b) shows a horizontal section near the upper end of the mold with the cooling copper plate 1a divided into the back plate 3, and FIG. 2 (c) shows piping for feeding pressurized gas into the grooves 13. FIG. 2 (d) shows a horizontal section of a portion where a groove 13 for feeding pressurized gas is formed. FIG. As shown in FIG. 2, a groove 13 is provided on the surface of the back plate 3 opposite to the slit of the divided cooling copper plate 1a, and a pressurized gas is fed into the groove 13 so that the front and back of the divided cooling copper plate 1a, that is, the back A pressure difference can be applied between the plate 3 side and the working surface side. At this time, if the groove 13 is provided from the upper end to the lower end of the back plate 3, gas escapes from the upper end or the lower end. Therefore, the groove 13 provided in the back plate 3 is closed at the upper end and the lower end as shown in FIG. Need to be. By doing so, in the split slit portion, a pressure difference is generated between the back plate 3 side and the operating surface side, and a gas flow from the back plate 3 side to the operating surface can be generated in the slit gap, so that the operating surface side Intrusion of foreign matter from can be prevented.

  The range of the groove 13 is indispensable to include a region where the heat load of the cooling copper plate 1 is high, and is desirably provided in a range from 50 mm above the meniscus height to 250 mm below the meniscus height, and has an upper end and a lower end. You may provide in the whole range.

  The gas used for pressurization may be any gas such as air, nitrogen, argon or the like.

  Since the front surface (working surface side) of the split slit portion is atmospheric pressure, the back of the split slit portion (back plate 3 side) may be a pressure slightly higher than that. Therefore, the pressure applied to the gas fed into the groove 13 may be higher than the atmospheric pressure by 0.01 MPa or more. If the pressure is set too high, the gas will spout out from the slit gap to the molten steel side, which may affect the solidification of the molten layer of CC powder and the molten metal. Up to pressurization is preferred. The pressure of the gas may be measured by providing a pressure gauge 14 on the pipe 15 connected to the back plate 3.

  In addition, in the structure of the electrical insulator provided in the division | segmentation surface of the division | segmentation cooling copper plate 1a, or the joint surface of the cooling copper plates 1 and 2, the coating material, coating method, durability of the cooling copper plates 1 and 2 for improving sulfur resistance As the material and application method of the electrically insulating material having the property, those shown in Patent Document 5 may be used as they are.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  For example, as an example of the pressurizing mechanism, the groove 13 is provided in the back plate 3 and the pressurized gas is fed into the groove 13 so that the pressure on the back plate 3 side is higher than the pressure on the operating surface side. The pressurizing mechanism is not limited to this, and any system may be used as long as it can generate a pressure difference between the front and back of the split slit.

  In the mold of the present invention, the cooling copper plates 1 and 2 can be cooled by machining slits in the cooling copper plates 1 and 2 and providing water channels between the cooling copper plates 1 and 2 and the back plates 3 and 4. A well-known method can be employed such as providing a cooling water channel by making a through hole in the cooling copper plates 1 and 2.

  Further, for the intermediate portion and the lower end portion in the height direction of the working surface of the cooling copper plates 1 and 2, commonly used nickel plating, cobalt-nickel plating, self-fluxing in order to improve corrosion resistance and wear resistance. Needless to say, it is better to apply alloy spraying.

  In the mold having the dimensions of the second cooling copper plate 2 (long side) having a width of 2000 mm, the first cooling copper plate 1 (short side) having a width of 250 mm, and a height of 900 mm, the first cooling copper plate 1 is a plate. A mold was divided into two at the center of the width. Both of the first cooling copper plates 1a and 1a divided into two are provided with 0.05 mm thick nickel plating on the dividing surface and the surface on the back plate 3 side (a part of the surface adjacent to the dividing surface). For the surface (the remainder of the surface adjacent to the split surface), 0.05 mm thick chrome plating is provided in the height direction, 300 mm from the upper end, and 1 mm thick nickel-based self-fluxing alloy from the 300 mm height to the lower end. Thermal spray was provided. On both divided surfaces of the divided cooling copper plate 1, a base sprayed layer of Hastelloy C-276 (trade name of nickel-based alloy) having a thickness of 0.05 mm was formed by a high-speed flame spraying method, In the horizontal direction, a 0.15 mm thick zirconia ceramic is formed in the range from the upper end to 600 mm, and a 0.15 mm thick yttria ceramic sprayed layer is formed in the range from the upper end to 600 mm to the lower end. Was provided. Further, the back plate 3 combined with the divided cooling copper plate 1 is provided with a groove 13 having a width of 6 mm and a depth of 5 mm in a range from a height of 20 mm to 880 mm from the upper end at a position opposite to the divided slit. 13 is provided with a hole 19 penetrating the back plate 3 for measuring the pressure of the gas in the pipe 15, the valve 16 and the groove 13 for connecting to a device for sending the compressed gas into the hole 19. The pressure gauge 14 was attached (refer FIG.2 (c)). A base sprayed layer of Hastelloy C-276 having a thickness of 0.05 mm is formed by a high-speed flame spraying method in a range excluding the groove 13 on the surface of the back plate 3 that is in contact with the divided cooling copper plate 1, and then a thickness is formed by a plasma spraying method. A 0.15 mm zirconia ceramic sprayed layer was formed. These divided cooling copper plate and back plate 3 were assembled so that there was no electrical continuity between them, and incorporated into a continuous casting apparatus for casting. In the casting, the casting was performed by feeding argon having a pressure 0.02 MPa higher than the atmospheric pressure into the groove 13 from the pipe 15 connected to the groove 13 provided in the back plate 3.

  The purpose of this study was to investigate changes in insulation resistance and slit gap spacing as the casting time increased. Therefore, this mold was cast without installing an electromagnetic coil, and insulation between the first divided cooling copper plates 1 was performed. The resistance was appropriately measured using a mega tester and the slit interval was appropriately measured with a microscope having a magnification of 200 from the working surface side.

  The insulation resistance value between the divided cooling copper plates 1 before use was 80 MΩ, and the gap distance between the divided copper plates 1 (distance between the surfaces of the electrical insulators provided on the divided surfaces of the divided copper plates 1a) was 17 μm. It was. Thereafter, every 200 hours of casting, the insulation resistance and the gap spacing between the divided copper plates 1a were measured. The insulation resistance and gap spacing between the divided copper plates 1a were 48 MΩ and 30 μm after 200 hours, 19 MΩ and 40 μm after 400 hours, 11 MΩ and 45 μm after 600 hours, and 8 MΩ after 800 hours, respectively. It changed to 6 MΩ and 50 μm after 48 μm and 1000 hours, respectively. When this mold was disassembled and investigated, almost no adhesion was observed on the electrical insulator applied to the divided surface of the divided copper plate 1a, and the present invention effectively prevents foreign matter from entering the dividing slit. I found out that

  The present invention can be applied to a mold for continuous casting of molten metal having an electromagnetic coil.

It is the perspective view which showed typically the casting_mold | template for continuous casting concerning this invention. It is the figure which showed typically the state which assembled the 1st backplate of the casting_mold | template concerning this invention, and the 1st cooling copper plate to the 1st backplate, (a) is a perspective view of a 1st backplate. (B) is a horizontal cross-sectional view of the upper end of the state where the cooling copper plate is assembled to the back plate, (c) is a horizontal cross-sectional view of the pipe connection portion for feeding pressurized gas in the state where the cooling copper plate is assembled to the back plate. (D) is a horizontal sectional view of a portion excluding (b) and (c) in a state where a cooling copper plate is assembled to a back plate. It is the figure which showed typically the state which assembled the 1st cooling copper plate of the conventional casting_mold | template to the 1st backplate, (a) is a perspective view, (b) is a horizontal sectional view in meniscus height. . It is the perspective view which showed the conventional mold for continuous casting typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st cooling copper plate 2 2nd cooling copper plate 3 1st back plate 4 2nd back plate 5 Sulfide-resistant coating 6 (installed in the dividing surface of a cooling copper plate) Electrical insulator 7 (Cooling copper plate and back Electrical insulator 8) Insulating washer 9 Insulating sleeve 10 Fastening bolt 11 Electromagnetic coil 12 Cylinder 13 Groove 14 Pressure gauge 15 Piping 16 Valve 17 Nickel-based self-fluxing alloy spraying

Claims (1)

An electromagnetic coil for applying a low-frequency alternating current of 10 Hz to 500 Hz to the outer peripheral surface of the mold in order to apply an electromagnetic force in a direction perpendicular to the inner wall of the mold near the meniscus initial solidification portion of the molten metal in the continuous casting mold A pair of first cooling copper plates arranged on the short side and a pair of first back plates, and a pair of second cooling copper plates arranged on the long side and a pair of second backs The plates are respectively combined, and the pair of the first cooling copper plate and the first back plate are movably sandwiched between the pair of the second cooling copper plate and the second back plate. In the continuous casting mold, at least one of the first and second cooling copper plates is divided into two or more in the plate width direction, and an electric insulator is provided on the divided surface.
A gas introduction groove having an upper end and a lower end closed is provided on the back plate surface facing the electrical insulator, and the gas introduction groove becomes a positive pressure during casting compared to the working surface side of the electrical insulator. pressurizable, have a pressurizing mechanism by the gas, the pressure range is continuous casting mold of the molten metal, which is a 0.01MPa~0.05MPa as.

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