JP5790276B2 - Directional electrical steel sheet production line and induction heating device - Google Patents

Description

  The present invention relates to a production line for producing a grain-oriented electrical steel sheet and an induction heating apparatus for induction heating a metal material.

FIG. 8 is a view showing a main part of a conventional hot rolling line.
In FIG. 8, 21 is a rough rolling process, 22 is a coil box, and 23 is a finish rolling process. The slab 24a (rolled base material) is heated and soaked to about 1250 ° C. in a heating furnace 26 (not shown in FIG. 8), and then rolled in the rough rolling step 21. By passing through the rough rolling step 21, the slab 24a has a thickness of about several hundreds [mm] to about two hundreds and several tens [mm] to about twenty [mm] to about 40 [mm]. become.

  The coil box 22 is provided between the rough rolling process 21 and the finish rolling process 23. The coil box 22 has a function of winding the rolled base material (transfer bar 24b), which has been all rolled in the rough rolling step 21, into a cylindrical coil having a hollow center part. The coil box 22 also has a function of rewinding (sending out) the wound transfer bar 24b to the finish rolling step 23 side.

  The coil box 22 is provided for the purpose of soaking and keeping warm the transfer bar 24b. In the finish rolling step 23 after the rough rolling step 21, the time for processing the base material to be rolled is relatively long, such as about several minutes. Further, the heat energy of the base material to be rolled (transfer bar 24b) is lost mainly by radiation. By winding the transfer bar 24b in a cylindrical shape by the coil box 22, the surface area of the base material to be in contact with the outside air can be greatly reduced as compared with the plate shape. By providing the coil box 22, the temperature of the transfer bar 24b about to enter the finish rolling step 23 can be kept high and uniform.

  FIG. 9 is a diagram showing a main part of a conventional production line for grain-oriented electrical steel sheets. FIG. 9 corresponds to the conventional hot rolling line in which an intermediate heating furnace 25 is added. 26 is a heating furnace.

A grain-oriented electrical steel sheet is a steel sheet in which the easy axis of magnetization of an iron crystal is oriented in a specific direction. The grain-oriented electrical steel sheet can reduce iron loss, and is used, for example, in the iron core of electrical equipment such as a transformer.
As conventional technology of grain-oriented electrical steel sheets, for example, there is one described in Patent Document 1 below.

  In order to manufacture the slab 24a as a raw material for the grain-oriented electrical steel sheet, first, pure iron is heated to a melting point or higher to make a liquid. Next, several [%] impurities such as silicon are added to pure iron and stirred, and then cast to be solidified. This solidified product is the slab 24a. The slab 24a is a polycrystalline body in which various crystals such as a face-centered cubic lattice having a relatively high impurity solubility limit and a body-centered cubic lattice that hardly dissolves impurities are mixed. Such a state is called a solid solution. Moreover, the main component of the polycrystal which comprises the slab 24a after casting is called a parent phase crystal.

  The slab 24a extracted from the heating furnace 26 is formed into a hot coil through a rolling process and an orientation control process in the hot rolling line shown in FIG. The production line for grain-oriented electrical steel sheets is composed of a hot rolling line, a cold rolling and heat treatment line. FIG. 9 shows only the hot rolling line positioned in the upstream process of the cold rolling and heat treatment line. In the hot rolling line, the base material to be rolled is made thinner while performing orientation control so that the easy axis of magnetization of the iron crystal is aligned in one direction as much as possible. And after the process of a hot rolling line is complete | finished, a to-be-rolled base material is provided to the cold rolling and heat processing line of a downstream process. For hot coils that are semi-finished products manufactured in a hot rolling line, a process called erosion is performed mainly in a heat treatment line. In this phagocytosis process, a crystal having an easy axis of magnetization in the same direction displaces surrounding crystals to a crystal having the same structure as itself. Thereby, the grain-oriented electrical steel sheet with little iron loss which is a final product can be obtained.

  Specifically, the slab 24a extracted from the heating furnace 26 is first rolled in the rough rolling step 21 of the hot rolling line. When compressive strain is applied in the thickness direction by rolling, the slab 24a dislocations in the length direction of the slab 24a and becomes finer.

  When the slab 24a to which the compressive strain is applied is left for a long time, a parent phase crystal grows due to recrystallization and aging. At this time, if the temperature of the slab 24a is appropriately adjusted, a crystal structure containing a large amount of the additional impurity element that has reached the solid solution limit can be precipitated around the grown parent phase crystal. Crystals with easy axes can be selectively grown. This process is called an alignment control process (or simply alignment control).

The orientation control process is performed in the intermediate heating furnace 25. The intermediate heating furnace 25 can perform orientation control during the rough rolling step 21, for example, between the first rolling mill 27 and the second rolling mill 27 provided in the rough rolling step 21. Is provided. The slab 24a extracted from the heating furnace 26 is conveyed to the intermediate heating furnace 25 when the first rolling mill 27 finishes the rough rolling step 21.
In addition, the rolling process performed before an orientation control process is called a pre-rolling process (the process is a pre-rolling process).

  In the orientation control step, the slab 24a is retained in the intermediate heating furnace 25 for a relatively long time (for example, several tens of minutes). For this reason, the intermediate heating furnace 25 is often installed outside the hot rolling line shown in FIG. With such a configuration, while the slab 24a is heated and kept in the intermediate heating furnace 25, in the rough rolling step 21 and the finish rolling step 23, the production of varieties other than grain-oriented electrical steel sheets (for example, ordinary steel) is performed. It can be carried out. Moreover, the furnace temperature of the heating furnace 26 is set to a temperature suitable for manufacturing a product other than the grain-oriented electrical steel sheet, for example, about 1250 [° C.]. Thereby, it becomes possible to raise the operation rate of a line.

  On the other hand, the temperature suitable for the orientation control step is 1300 [° C.] or higher. For this reason, after the slab 24a for grain-oriented electrical steel sheets is heated to about 1250 [° C.] in the heating furnace 26 and pre-rolled in part of the rough rolling step 21 (compressed strain is added). Then, it is reheated in the intermediate heating furnace 25 and maintained at a desired temperature of 1300 [° C.] or higher. When the orientation control step is completed, the slab 24a is returned from the intermediate heating furnace 25 to the rough rolling step 21 and rolled for the remaining number of passes in the pass schedule of the rough rolling step 21.

  FIG. 10 is a block diagram of the intermediate heating furnace shown in FIG. The intermediate heating furnace 25 heats and keeps the slab 24a in the middle of the rough rolling step 21, that is, in a plate-like state. The intermediate heating furnace 25 shown in FIG. 10 is of a type that heats the slab 24a by induction heating.

The main part of the intermediate heating furnace 25 is constituted by, for example, a heating and insulation container 28, a solenoid coil 29, a high-frequency power converter 30, a charging machine 31, and a hearth 32.
The heat insulation container 28 is for accommodating the slab 24a inside. The heat insulation container 28 is provided above the hearth 32. The hearth 32 is supported by the charging machine 31 so as to be movable in the vertical direction, and constitutes a bottom lid of the heat and heat insulation container 28. That is, when the hearth 32 is moved upward by the charging machine 31 and attached to the heated and insulated container 28 from below, the internal space of the heated and insulated container 28 is sealed, and a predetermined airtightness is ensured. The solenoid coil 29 is wound around the heated and insulated container 28. The high frequency power converter 30 is connected to the solenoid coil 29.

  When the preliminary rolling process is completed, the slab 24a is transported to the intermediate heating furnace 25 having the above-described configuration, and is placed on the upper surface of the hearth 32 in a standing state. In the intermediate heating furnace 25, when the slab 24 a is placed on the hearth 32, the hearth 32 is moved upward by the charging machine 31, and the slab 24 a is charged into the heated and insulated container 28. When the lower surface side of the heated and insulated container 28 is closed by the hearth 32, the inside of the heated and insulated container 28 is ensured to have predetermined airtightness.

When the slab 24a is stored inside the heat insulation container 28, in the intermediate heating furnace 25, the solenoid coil 29 is excited by the high frequency power converter 30 to generate an alternating magnetic field, and an eddy current is generated in the slab 24a. Thereby, the slab 24a is heated inside the heat insulation container 28. In order to efficiently generate an eddy current in the slab 24a, it is desirable that the frequency of the alternating magnetic field is high. However, if the frequency is too high, the magnetic flux does not penetrate into the slab 24a due to the skin effect, so the high-frequency current is set to about 300 [Hz].
Further, when the slab 24a is heated, the inside of the heat insulation container 28 is filled with an inert gas or a reducing gas to prevent an oxide film (scale) from being formed on the surface of the slab 24a.
Patent Document 2 below discloses a conventional technique for an intermediate heating furnace.

When the orientation control step is completed, the slab 24a is returned to the rough rolling step 21, and the remaining pass schedule is performed in the rough rolling step 21.
When all the rough rolling processes are completed in the rough rolling step 21, the base material to be rolled (transfer bar 24 b) is wound by the coil box 22 into a hollow cylindrical shape at the center. Thereafter, the material to be rolled is rewound in the coil box 22 and supplied to the finish rolling process 23 side.

  In the finish rolling step 23, the base material to be rolled is finish-rolled at once in a short time by a continuous finish rolling machine 33 composed of 4 to 7 stands. Thereby, the easy axis of magnetization of the crystal of the base material to be rolled is dislocated and oriented in one direction. When the finish rolling step 23 is completed, the base material to be rolled is cooled with water while appropriately controlling the cooling rate, and the easy axis of magnetization is fixed in one direction.

Japanese Patent Application Laid-Open No. 2006-265685 JP-A-6-17131

  In the hot rolling line shown in FIG. 9, the pass schedule of the rough rolling step 21 is generally about 5 to 7 passes. Increasing the number of pre-rolling passes can reduce the number of passes performed after the orientation control step. However, since the slab 24a becomes longer each time the rolling process is performed, there is a problem that if the number of passes of the preliminary rolling process is increased, a long intermediate heating furnace 25 must be constructed.

  In reality, it is difficult to manufacture a long and heat-resistant container 28 with high airtightness and a long solenoid coil 29. For this reason, conventionally, the furnace length of the heated and insulated container 28 is set to about 15 [m], and the length of the slab 24a charged into the heated and insulated container 28 is set to about 11 [m] at the maximum.

  In addition, if the length of the slab 24a when extracting from the heating furnace 26 is shortened, the number of passes of the preliminary rolling process can be increased and the number of passes performed after the orientation control step can be reduced. However, if the length of the slab 24a when extracting from the heating furnace 26 is shortened, the length of a semi-finished product (hot coil) that can be manufactured from one slab 24a is shortened. Furthermore, even if the length of the slab 24a when extracting from the heating furnace 26 is shortened, the time required for the rough rolling step 21 is not so shortened, and the productivity of the hot rolling line is greatly reduced. For this reason, conventionally, the length of the slab 24a when extracting from the heating furnace 26 is made as long as possible, and the number of passes in the pre-rolling step is limited (for example, to about 1 pass).

  For this reason, conventionally, the easy axis of the crystal properly oriented in the orientation control step may be dislocated again in a random direction by the subsequent rough rolling process. That is, the conventional manufacturing method has a problem that it is difficult to manufacture a grain-oriented electrical steel sheet with a small iron loss.

This invention was made in order to solve the above-mentioned subject, The objective is providing the manufacturing line which can manufacture a directional electrical steel sheet with few iron losses, without enlarging an installation. That is.
Moreover, the other objective is to provide the induction heating apparatus which can have the said effect in the production line of a grain-oriented electrical steel sheet.

A production line for grain-oriented electrical steel sheets according to the present invention is a production line for producing grain-oriented electrical steel sheets, and is provided between a rough rolling process and a finish rolling process of a hot rolling line, A coil box that is wound in a cylindrical shape with a hollow center, and an induction heating device that heats the transfer coil formed by the coil box in a cylindrical shape . The induction heating device includes a support base and a support base. A cradle roll on which a transfer coil is mounted, and a drive device for driving the cradle roll. A plurality of cradle rolls are rotatably provided on the support base, and the drive device is a transfer device. When the coil is heated, the cradle roll is driven to rotate the transfer coil and the transfer So that the end portion of the base member disposed on the outer periphery of yl does not contact the cradle roll is intended to separate the cradle rolls from the transfer coil in accordance with the position of the end portion.

An induction heating device according to the present invention is an induction heating device that heats a plate-shaped metal material wound in a cylindrical shape with a hollow center portion in a cylindrical shape, and includes a hollow portion and a peripheral portion of the metal material . the outer, a solenoid coil disposed along the width direction of the metal material, a support base, rotatably provided on the support base, a cradle roll metal material is placed, a drive device for driving the cradle rolls And exciting means for exciting the solenoid coil to heat the metal material, and a plurality of cradle rolls are rotatably provided on the support base, and the driving device drives the cradle roll when the metal material is heated. Thus, the metal material is rotated, and the cradle roll is separated from the metal material in accordance with the position of the end so that the end of the metal material disposed on the outer peripheral portion does not contact the cradle roll. It is intended to make.

  According to this invention, in a production line for grain-oriented electrical steel sheets, grain-oriented electrical steel sheets with less iron loss can be produced without increasing the size of the equipment.

It is a figure which shows the principal part of the manufacturing line of the grain-oriented electrical steel plate in Embodiment 1 of this invention. It is a perspective view which shows the induction heating apparatus with which the manufacturing line of FIG. 1 was equipped. It is a side view which shows the induction heating apparatus with which the manufacturing line of FIG. 1 was equipped. It is a rear view which shows the induction heating apparatus with which the manufacturing line of FIG. 1 was equipped. It is a figure for demonstrating operation | movement of the induction heating apparatus with which the manufacturing line of FIG. 1 was equipped. It is a figure which shows the principal part of the manufacturing line of the grain-oriented electrical steel plate in Embodiment 2 of this invention. It is a figure for demonstrating the function of the induction heating apparatus in Embodiment 2 of this invention. It is a figure which shows the principal part of the conventional hot rolling line. It is a figure which shows the principal part of the manufacturing line of the conventional grain-oriented electrical steel sheet. It is a block diagram of the intermediate heating furnace shown in FIG.

  The present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the following description, overlapping contents are appropriately simplified or omitted.

Embodiment 1 FIG.
1 is a diagram showing a main part of a production line for grain-oriented electrical steel sheets according to Embodiment 1 of the present invention.
The electromagnetic steel sheet includes a directional electromagnetic steel sheet and a non-oriented electromagnetic steel sheet. FIG. 1 shows a hot rolling line for producing a grain-oriented electrical steel sheet. A grain-oriented electrical steel sheet is a steel sheet in which the easy axis of magnetization of an iron crystal is oriented in a specific direction. The grain-oriented electrical steel sheet can reduce iron loss, and is used, for example, in the iron core of electrical equipment such as a transformer. A production line for grain-oriented electrical steel sheets is composed of an upstream hot rolling line and a downstream cold rolling and heat treatment line. In the present embodiment, only the hot rolling line will be described, and description of the cold rolling and heat treatment lines will be omitted.

As shown in FIG. 1, the hot rolling line includes a heating furnace 1, a rough rolling process 2, a coil box 3, an induction heating device 4, a finish rolling process 5, a water cooling device 6, and a coiler 7.
The manufacturing method of the slab 8a (rolled base material) that is a raw material of the grain-oriented electrical steel sheet is the same as the conventional method. That is, in order to manufacture the slab 8a, first, pure iron is heated to a melting point or higher to make a liquid. Next, impurities such as silicon are added to pure iron by several [%] and stirred, and then cast and solidified, and cut from several [m] to several tens [m].

  Specifically, the entire slab 8a is heated and soaked to about 1250 [° C.] by the heating furnace 1 and extracted onto a line (conveyer). The slab 8a extracted from the heating furnace 1 has a thickness of about a few tens [mm] to a few hundred tens [mm], for example.

  The rough rolling process 2 includes a rolling mill 9 having one stand or a plurality of stands. The rolling mill 9 may be a reversible type or an irreversible type. When the rolling mill 9 having a plurality of stands (four stands in the example shown in FIG. 1) is provided, the rough rolling step 2 may be configured by combining a reversible type and a nonreversible type.

When the slab 8a is rolled to the final pass of the pass schedule in the rough rolling step 2, the thickness is from about 20 [mm] to about 40 [mm], and the length is from several tens [m]. It will be about a few tens [m]. In addition, when the rolling process is performed to the final pass in the rough rolling step 2, the temperature of the base material to be rolled decreases from, for example, about 1000 [° C.] to about 1100 [° C.].
The base material to be rolled that has been rolled to the final pass in the rough rolling step 2 is referred to as a transfer bar.

  The coil box 3 is provided between the rough rolling process 2 and the finish rolling process 5. The coil box 3 has a function of winding the transfer bar around a hollow cylindrical coil. The coil box 3 also has a function of rewinding (sending out) the wound transfer bar to the finish rolling step 5 side.

The coil box 3 is provided for soaking and keeping warm the base material (transfer bar) to be rolled that has been processed in the rough rolling step 2. The coil box 3 is not provided with a mandrel (core bar) or the like for winding the transfer bar. The coil box 3 is wound around a cylindrical coil having a hollow center while appropriately rotating a plate-shaped transfer bar. For this reason, in the to-be-rolled base material (transfer bar) wound up by the coil box 3 in a cylindrical shape, the space in which the to-be-rolled base material does not exist in the central portion in the axial direction (the width direction of the transfer bar) (Hollow part) is formed. This hollow portion is called a coil eye.
A base material (transfer bar) to be rolled, which is wound into a hollow cylindrical shape by the coil box 3, is referred to as a transfer coil 8b.

The induction heating device 4 is for heating and keeping the transfer coil 8b formed by the coil box 3 in a cylindrical shape. In the induction heating device 4, the transfer coil 8b is maintained at about 1350 ° C. to 1400 ° C. by induction heating, and a desired crystal is grown in the transfer coil 8b. That is, in the hot rolling line, the orientation heating process is performed in the induction heating device 4.
Hereinafter, the configuration of the induction heating device 4 will be specifically described with reference to FIGS.

2 is a perspective view showing an induction heating apparatus provided in the production line of FIG. 1, FIG. 3 is a side view thereof, and FIG. 4 is a rear view thereof.
The induction heating device 4 includes a heated and insulated container 10, a transport device 11, and a heater 12.

  The heat insulation container 10 is for accommodating the transfer coil 8b inside. The heating / warming vessel 10 is formed with an inlet / outlet (not shown) for taking in / out the transfer coil 8b. In addition, the heat insulation container 10 is provided with an airtight door (not shown) for opening and closing the entrance / exit. When the hermetic door is properly closed, a predetermined hermeticity is secured in the inside of the heated and insulated container 10. The transfer coil 8b is heated and kept warm inside the heat and heat insulation container 10 in a state where the airtight door is properly closed.

  The induction heating device 4 is provided with a means (atmosphere holding means: not shown) for keeping the inside of the heating and keeping container 10 in a predetermined atmosphere. The atmosphere holding means is for preventing an oxide film (scale) from being formed on the surface of the transfer coil 8b when the transfer coil 8b is heated and kept warm. The atmosphere holding means, for example, evacuates the inside of the heated and insulated container 10 when heating and keeping the transfer coil 8b, or reduces the inside of the heated and insulated container 10 to a high temperature inert gas (for example, nitrogen gas) or reducing A scale is prevented from being formed on the surface of the transfer coil 8b by a method such as filling with gas (for example, hydrogen gas).

  The transport device 11 is for transporting the transfer coil 8b formed by the coil box 3 from the coil box 3 to the heating and warming container 10 in a cylindrical shape. The main part of the transport device 11 is constituted by, for example, a support base 13, a rail 14, and a cradle roll 15.

  The support base 13 is for supporting the transfer coil 8b. A wheel 16 that rolls on the rail 14 is rotatably provided on the lower surface of the support base 13. That is, the support base 13 is configured to be able to move along the rail 14 while supporting the transfer coil 8b. The rail 14 is laid between the coil box 3 and the heated and insulated container 10. In the present embodiment, the rail 14 is also laid inside the heated and insulated container 10. For this reason, in this Embodiment, the support stand 13 moves along the rail 14 between the coil box 3 and the inside of the heat insulation container 10. Further, the transfer coil 8b is heated and kept warm while being supported by the support base 13.

  The cradle roll 15 constitutes a portion on which the transfer coil 8b is actually placed when the support base 13 supports the transfer coil 8b. The cradle roll 15 is rotatably provided on the support base 13. In the present embodiment, a pair of cradle rolls 15 are installed on the upper surface of the support base 13 horizontally, in parallel and at the same height, with a predetermined interval. In the transport device 11 including the cradle roll 15 having such a configuration, as shown in FIGS. 2 to 4, the transfer coil 8 b has the axial direction (left-right direction in FIG. 3) coincident with the axial direction of the cradle roll 15. To be arranged. Further, the transfer coil 8 b is evenly placed on both cradle rolls 15 so that the lowermost part is disposed between the cradle rolls 15.

  The transport device 11 is provided with a drive device (not shown) for driving the cradle roll 15. When the transfer coil 8b is heated, the drive device drives (rotates) the cradle roll 15 to rotate the transfer coil 8b. The transfer coil 8 b is placed on the cradle roll 15 such that the axial direction of the transfer coil 8 b coincides with the cradle roll 15 and the outer peripheral surface thereof is in contact with the outer peripheral surface of the cradle roll 15. For this reason, when the cradle roll 15 rotates, the transfer coil 8b rotates in the direction opposite to the rotation direction of the cradle roll 15 around the hollow portion.

  The heater 12 is for heating and keeping heat in a state where the transfer coil 8 b is placed on the cradle roll 15 of the transport device 11 inside the heat and heat insulation container 10. The main part of the heater 12 is constituted by a solenoid coil 17, a support device 18, and a high-frequency power converter 19 (excitation means).

  As shown in FIG. 2, when the transfer coil 8b is heated and kept warm, the solenoid coil 17 is disposed so as to surround the periphery of the portion disposed on the upper side of the transfer coil 8b.

  Specifically, the solenoid coil 17 is horizontally placed in the hollow portion along the width direction of the transfer coil 8b so that a part of the solenoid coil 17 penetrates the hollow portion (coil eye) formed at the axial center of the transfer coil 8b. Arranged. Further, the solenoid coil 17 is disposed on the both sides of the transfer coil 8b from the above part to the upper side, and is disposed again horizontally above the transfer coil 8b so as to face the transfer coil 8b. That is, the other part of the solenoid coil 17 extends along the width direction of the transfer coil 8b outside the outer peripheral portion of the transfer coil 8b so that a predetermined gap is formed between the solenoid coil 17 and the outer peripheral surface of the transfer coil 8b. Placed horizontally.

  The solenoid coil 17 is divided into a conductor 17a and a short circuit 17b. For example, as shown in FIG. 3, the conductor 17 a has a U-shape (sideways U-shape) in a side view and opens to one side. The short circuit 17b is for connecting between the end parts formed in the conductor 17a. By appropriately connecting the short circuit 17b between the ends of the conductor 17a, the conductor 17a and the short circuit 17b are formed in a continuous spiral shape. In other words, the solenoid coil 17 is formed in a continuous spiral.

The solenoid coil 17 (conductor 17a, short circuit 17b) is supported by a support device 18. The support device 18 supports at least one of the conductor 17a and the short circuit 17b so that the transfer coil 8b placed on the cradle roll 15 can move in the width direction.
The high frequency power converter 19 excites the solenoid coil 17 to heat the transfer coil 8b.

Next, operation | movement of the induction heating apparatus 4 which has the said structure is demonstrated.
The transfer coil 8 b formed by the coil box 3 is wound on the cradle roll 15 of the transport device 11 provided in the coil box 3. When the transfer coil 8 b is placed on the cradle roll 15, the support base 13 moves on the rail 14 and conveys the transfer coil 8 b to the inside of the heated and insulated container 10. When the transfer coil 8 b is carried into the heating and holding container 10, the hermetic door is closed, and, for example, high-temperature nitrogen gas is sent into the heating and holding container 10.

  When the support base 13 on which the transfer coil 8b is mounted is stopped at a predetermined position in the heating and heat insulation container 10, a solenoid coil 17 is formed by the conductor 17a and the short circuit 17b.

  Specifically, the transfer coil 8b is moved from one end surface side so as to approach the conductor 17a fixed to the support device 18. The conductor 17a is finally disposed such that the lower side portion of the U-shape passes through the hollow portion of the transfer coil 8b and the upper side portion crosses the upper side of the transfer coil 8b. Further, the short circuit 17b is moved by the support device 18 from the other end surface side of the transfer coil 8b so as to approach the transfer coil 8b, and is connected between the respective ends of the conductor 17a. Thereby, the solenoid coil 17 is formed so as to surround the periphery of the portion arranged on the upper side of the transfer coil 8b, and a closed electric circuit is formed.

  When the conductor 17a is appropriately short-circuited by the short-circuiting device 17b and the inside of the heated and insulated container 10 is filled with high-temperature nitrogen gas, the high-frequency power converter 19 causes the solenoid coil 17 that has become the above-described closed circuit to For example, excitation is performed with a high-frequency current of about several hundreds [Hz]. As a result, an alternating magnetic field is generated in the circumferential direction of the transfer coil 8b (in the direction of arrow A shown in FIG. 4), an eddy current is generated in the transfer coil 8b, and the transfer coil 8b is heated.

When the transfer coil 8 b is heated, the driving device drives the cradle roll 15 to rotate the transfer coil 8 b on the cradle roll 15. Since the transfer coil 8b is evenly placed on the pair of cradle rolls 15 and a sufficient gap is formed between the solenoid coil 17 and the transfer coil 8b, the transfer coil 8b is placed on the cradle roll 15. , The transfer coil 8b does not contact the solenoid coil 17.
In this state, the transfer coil 8b is kept at an appropriate temperature, and a crystal having an easy axis of magnetization in the same direction is selectively grown in the transfer coil 8b.

  When a predetermined time elapses from the start of heating of the transfer coil 8b and the heating and heat retaining process (that is, the orientation control process) is completed, the short circuit 17b is removed from the conductor 17a. In addition, the transfer coil 8 b is transported from the heated and insulated container 10 to the coil box 3 by the support base 13. When the transfer coil 8b is returned to a predetermined position of the coil box 3, the transfer coil 8b is rewound in the coil box 3 by a predetermined uncoiling mechanism. Thereby, a to-be-rolled base material is supplied to the finish rolling process 5. FIG.

  FIG. 5 is a view for explaining the operation of the induction heating apparatus provided in the production line of FIG. In FIG. 5, reference numeral 11a denotes a standby cradle roll and a support device connected to the transport device 11 by a coupler 11b. FIG. 5 shows a state during heating (FIG. 5A) and winding (FIG. 5B) of the transfer coil 8b.

  In the finish rolling step 5, for example, a continuous finish rolling mill 20 composed of 4 to 7 stands is provided. The water cooling device 6 is provided on the downstream side of the finish rolling process 5. The base material to be rolled supplied from the coil box 3 is rolled to a desired plate thickness in a short time by the continuous finish rolling mill 20. The base material to be rolled that has undergone finish rolling is water-cooled by the water-cooling device 6 while appropriately controlling the cooling rate, so that the easy axis of the crystal is fixed.

  The rolling base material appropriately cooled by the water cooling device 6 is taken up by a coiler 7 and then conveyed to a downstream cold rolling and heat treatment line.

  If it is a production line of the said structure, a directional electrical steel sheet with few iron losses can be manufactured, without enlarging an installation in a hot rolling line.

  That is, with the induction heating device 4 having the above configuration, the transfer coil 8b can be heated in a cylindrical shape and maintained at a temperature suitable for orientation control. It can be done after the schedule is completely finished. Therefore, unlike the conventional case, the easy axis of magnetization of the crystal whose orientation is appropriately controlled in the orientation control step is not dislocated again in a random direction by the subsequent rough rolling, and the iron loss is small. It becomes possible to manufacture a grain-oriented electrical steel sheet.

  In addition, since the transfer coil 8b can be heated in a cylindrical shape with the induction heating device 4 having the above-described configuration, even if the length of the slab 8a when extracting from the heating furnace 1 is increased, the heat insulation is performed. There is no need to lengthen the container 10. For this reason, the induction heating apparatus 4 can be reduced in size without impairing the productivity of the hot rolling line.

  In the conventional intermediate heating furnace 25 (induction heating apparatus) as shown in FIG. 10, the solenoid coil 29 is arranged so as to surround the heating and insulation container 28. In such a configuration, when the solenoid coil 29 is excited by the high-frequency power converter 30, magnetic flux is generated so as to pass through the slab 24a, the hearth 32, and the outside air. Since the magnetic resistance is large in the air, part of the magnetic flux leaks to infinity, or passes through other surrounding metals and heats them. For this reason, the conventional intermediate heating furnace 25 has a problem that the slab 24a cannot be efficiently heated.

Further, in the conventional intermediate heating furnace 25, in order to prevent the hearth 32 from being heated by eddy current, the hearth 32 is made of a nonmagnetic, high heat-resistant material and a heavy slab 24a. It had to be made of a special material with such strength that it would not buckle when placed.
Further, in the conventional intermediate heating furnace 25, the solenoid coil 29 must be disposed so as to completely surround the four sides of the slab 24a, and there is a problem that a large solenoid coil 29 is required.

The induction heating device 4 having the above configuration can solve such various problems.
That is, in the induction heating device 4, the solenoid coil 17 is disposed so as to surround the periphery of the portion disposed on the upper side of the transfer coil 8b. For this reason, when the solenoid coil 17 is excited by the high-frequency power converter 19, magnetic flux is generated in the circumferential direction of the transfer coil 8b (in the direction of arrow A shown in FIG. 4), and the magnetic field is closed by a metal having a small magnetic resistance. A circuit can be formed. That is, with the induction heating device 4 having the above configuration, the leakage magnetic flux can be reduced and the transfer coil 8b can be efficiently heated.

In addition, since most of the magnetic flux passes through the transfer coil 8b, even if the solenoid coil 17 is excited by the high frequency power converter 19, almost no eddy current is generated in the cradle roll 15. For this reason, it is not necessary to comprise the cradle roll 15 with a special material, and the induction heating apparatus 4 can be comprised at low cost.
Further, unlike the prior art, the solenoid coil 17 is not arranged around the base material to be rolled that has a plate shape, so that the solenoid coil 17 is not enlarged. If the solenoid coil 17 is small, it is easy to increase the dielectric strength.

  In the induction heating device 4 configured as described above, the cradle roll 15 heats and keeps the temperature while rotating the transfer coil 8b. For this reason, the whole transfer coil 8b can be heated uniformly, and there is no possibility that temperature nonuniformity will arise in the transfer coil 8b.

  In the conventional intermediate heating furnace 25, the slab 24a is placed on the hearth 32 and heated with the slab 24a standing. Since the hearth 32 is made of a special material as described above, it is kept at a relatively low temperature even when the slab 24a is heated. For this reason, the conventional intermediate heating furnace 25 has a problem that the heat of the slab 24a escapes from the hearth 32 in contact with the slab 24a, and the temperature distribution in the width direction of the slab 24a becomes uneven. If the slab 24a is not heated evenly, appropriate orientation control cannot be performed.

  The induction heating device 4 having the above configuration does not cause such a problem. That is, in the induction heating device 4, since the cradle roll 15 heats and keeps the temperature while rotating the transfer coil 8b, the temperature is increased in both the width direction and the length direction (the length direction of the transfer bar) of the transfer coil 8b. The distribution can be made uniform.

  In the present embodiment, the case where the transfer coil 8b is heated and soaked on the support 13 of the transport device 11 has been described. However, this is only an example, and the transfer coil 8b may be moved from the support base 13 to the heating fixing base (support base) in the inside of the heat insulation container 10. In this case, the cradle roll 15 is rotatably provided on the fixing base for heating and is driven by a driving device.

Embodiment 2. FIG.
FIG. 6 is a diagram showing a main part of a production line for grain-oriented electrical steel sheets according to Embodiment 2 of the present invention. FIG. 6 shows the inside of the heated and insulated container 10.

  As described in the first embodiment, the transfer bar that has been rolled to the final pass of the pass schedule in the rough rolling step 2 has a thickness of about 20 [mm] to 40 [mm]. When the transfer bar is wound up by the coil box 3, its end 8c (tail end) is disposed on the outer peripheral part (outermost part) of the transfer coil 8b. That is, in the transfer coil 8b formed into a cylindrical shape by the coil box 3, a step corresponding to the thickness of the transfer bar is formed on the outer peripheral portion (the position of the end portion 8c).

  In the present embodiment, as shown in FIG. 6, three or more cradle rolls 15 are rotatably provided on the support base 13 of the transport device 11. In the following, a case where four cradle rolls 15a to 15d are provided on the support base 13 will be described as an example.

The functions of the cradle rolls 15a to 15d are the same as those in the first embodiment.
In other words, the cradle rolls 15a to 15d constitute a portion on which the transfer coil 8b is actually placed when the support base 13 supports the transfer coil 8b. The cradle rolls 15a to 15d are arranged horizontally and in parallel on the upper surface of the support base 13. The pair of inner cradle rolls 15b and 15c are arranged at the same height, and the pair of outer cradle rolls 15a and 15d are arranged at the same height at a position slightly higher than the cradle rolls 15b and 15c. .

  In the transport apparatus 11 including the cradle rolls 15a to 15d having such a configuration, as shown in FIG. 6, the transfer coil 8b is arranged so that the axial direction thereof coincides with each axial direction of the cradle rolls 15a to 15d. The Further, the transfer coil 8b is placed on the cradle rolls 15a to 15d evenly on the left and right sides so that the lowermost part is disposed between the cradle rolls 15b and 15c. When the end 8c is disposed at the upper position, all of the cradle rolls 15a to 15d are in contact with the transfer coil 8b.

  The driving device provided in the transport device 11 drives (rotates) the cradle rolls 15a to 15d and rotates the transfer coil 8b when the transfer coil 8b is heated. The transfer coil 8b is placed on the cradle rolls 15a to 15d so that the axial direction thereof coincides with the cradle rolls 15a to 15d and the outer peripheral surface thereof is in contact with the outer peripheral surfaces of the cradle rolls 15a to 15d. For this reason, the transfer coil 8b rotates in the direction opposite to the rotation direction of the cradle rolls 15a to 15d with the hollow portion as the center by rotating the cradle rolls 15a to 15d.

  Further, the cradle rolls 15a to 15d are configured to be movable between a position in contact with the transfer coil 8b (the outer peripheral surface thereof) and a position not in contact with the transfer coil 8b. When the transfer coil 8b is heated, the driving device is positioned at the end 8c so that the end 8c of the (rolled base material) disposed on the outer periphery of the transfer coil 8b does not contact the cradle rolls 15a to 15d. In addition, the cradle rolls 15a to 15d are separated from the transfer coil 8b.

  FIG. 7 is a diagram for explaining the function of the induction heating apparatus according to Embodiment 2 of the present invention. As shown in FIG. 7, the drive device rotates the transfer coil 8b to the other side (FIG. 7) by rotating the cradle rolls 15a to 15d to one side (clockwise in FIG. 7), for example, when the transfer coil 8b is heated. Then rotate counterclockwise.

  When the transfer coil 8b rotates and the end 8c approaches the cradle roll 15a, the drive device moves the cradle roll 15a to the outside (downward) before the end 8c reaches the position of the cradle roll 15a. , Away from the transfer coil 8b (FIG. 7A). At this time, the cradle rolls 15b to 15d are in contact with the transfer coil 8b, and rotate the transfer coil 8b.

  Thereafter, when the end portion 8c passes the position of the cradle roll 15a, the driving device moves the cradle roll 15a inward (upward) to contact the transfer coil 8b. Thereby, the rotational force of the cradle roll 15a is transmitted to the transfer coil 8b.

The same applies to the cradle rolls 15b to 15d.
That is, when the transfer coil 8b rotates and the end portion 8c approaches the cradle roll 15b, the driving device moves the cradle roll 15b outward before the end portion 8c reaches the position of the cradle roll 15b. Separated from the coil 8b (FIG. 7B). At this time, the cradle rolls 15a, 15c, and 15d are in contact with the transfer coil 8b, and rotate the transfer coil 8b. Then, when the end portion 8c passes the position of the cradle roll 15b, the driving device moves the cradle roll 15b inward to contact the transfer coil 8b.

  FIG. 7 (c) shows a state where the cradle roll 15c is moved outward and separated from the transfer coil 8b, and FIG. 7 (d) shows a state where the cradle roll 15d is moved outward and separated from the transfer coil 8b. Show.

  Since the transfer coil 8b has a very large weight, for example, when the end portion 8c gets over while being in contact with the cradle roll 15a, a large impact is applied to the cradle roll 15a, the solenoid coil 17, the heating and warming container 10 and the like. End up. Further, the outer peripheral portion of the transfer coil 8b is also damaged. With the induction heating device 4 having the above configuration, the vertical movement of the transfer coil 8b caused by the end portion 8c can be reduced, the rotation of the transfer coil 8b is stabilized, and the load acting on the induction heating device 4 is greatly increased. Can be reduced.

  The rest of the configuration is the same as that of the first embodiment.

DESCRIPTION OF SYMBOLS 1,26 Heating furnace 2,21 Rough rolling process 3,22 Coil box 4 Induction heating apparatus 5,23 Finish rolling process 6 Water cooling apparatus 7 Coiler 8a, 24a Slab 8b Transfer coil 8c End part 9, 27 Rolling mill 10, 28 Heating Thermal insulation container 11 Transport device 11a Standby cradle roll and support device 11b Connector 12 Heater 13 Support base 14 Rail 15, 15a, 15b, 15c, 15d Cradle roll 16 Wheel 17, 29 Solenoid coil 17a Conductor 17b Short circuit 18 Support device 19, 30 High frequency power converter 20, 33 Continuous finish rolling mill 24b Transfer bar 25 Intermediate heating furnace 31 Charger 32 Hearth

Claims (8)

A production line for producing grain-oriented electrical steel sheets,
A coil box provided between the rough rolling process and the finish rolling process of the hot rolling line, and winding the transfer bar into a hollow cylindrical shape at the center;
An induction heating device that heats the transfer coil formed by the coil box in a cylindrical shape ,
The induction heating device includes:
A support base;
A cradle roll that is rotatably provided on the support base and on which the transfer coil is mounted;
A driving device for driving the cradle roll,
A plurality of the cradle rolls are rotatably provided on the support base,
The driving device drives the cradle roll to rotate the transfer coil when the transfer coil is heated, and prevents an end portion of a base material disposed on an outer peripheral portion of the transfer coil from contacting the cradle roll. And a directional electrical steel sheet production line for separating the cradle roll from the transfer coil in accordance with the position of the end . The induction heating device includes:
A solenoid coil disposed along a width direction of the transfer coil on a hollow portion of the transfer coil and on an outer side of the outer peripheral portion;
Exciting means for exciting the solenoid coil and heating the transfer coil;
A production line for grain-oriented electrical steel sheets according to claim 1, comprising: The induction heating device includes:
A support device for supporting the solenoid coil;
With
The solenoid coil is
A conductor that has a U-shape in side view and opens to one side;
By connecting between the ends of the conductor, a short circuit formed in a continuous spiral with the conductor;
With
The directional electrical steel sheet manufacturing line according to claim 2, wherein the support device supports one of the conductor and the short circuit so as to be movable in a width direction of the transfer coil. The induction heating device includes:
A heated and insulated container capable of accommodating the transfer coil therein;
A transfer device for transferring the transfer coil from the coil box to the inside of the heat and heat insulation container while maintaining a cylindrical shape,
A production line for grain-oriented electrical steel sheets according to any one of claims 1 to 3, comprising: The transfer device
A support base that moves between the coil box and the inside of the heated and insulated container;
A cradle roll that is rotatably provided on the support base and on which the transfer coil is mounted;
A driving device for driving the cradle roll;
With
5. The grain-oriented electrical steel sheet production line according to claim 4 , wherein the driving device drives the cradle roll to rotate the transfer coil when the transfer coil is heated. The induction heating device includes:
In order to prevent the scale from being formed on the surface of the transfer coil, an atmosphere holding means for keeping the inside of the heating and warming container in a predetermined atmosphere when the transfer coil is heated,
A production line for grain-oriented electrical steel sheets according to claim 4 . An induction heating device that heats a metal material wound in a cylindrical shape with a hollow center part in a cylindrical shape,
A solenoid coil disposed along the width direction of the metal material on the outside of the hollow portion and the outer peripheral portion of the metal material;
A support base;
A cradle roll that is rotatably provided on the support base and on which the metal material is placed;
A driving device for driving the cradle roll;
Excitation means for exciting the solenoid coil and heating the metal material ,
A plurality of the cradle rolls are rotatably provided on the support base,
The drive device drives the cradle roll to rotate the metal material when the metal material is heated, and the end of the metal material arranged on the outer peripheral portion does not come into contact with the cradle roll. An induction heating device for separating the cradle roll from the metal material in accordance with the position of the end portion . A support device for supporting the solenoid coil;
With
The solenoid coil is
A conductor that has a U-shape in side view and opens to one side;
By connecting between the ends of the conductor, a short circuit formed in a continuous coil with the conductor;
With
The induction heating device according to claim 7 , wherein the support device supports one of the conductor and the short circuit so as to be movable in a width direction of the metal material.

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