JPS5980732A - Batch annealing device - Google Patents

Abstract

PURPOSE:To enable production of an electrical steel sheet having an excellent excitation characteristic and iron loss characteristic in the batch annealing stage of the coil of the electrical steel sheet by annealing the coil while passing the same in a region having a specific temp. gradient in an annealing furnace. CONSTITUTION:A coil of an electrical steel sheet which is completed of primary recrystallization annealing is heated from one end toward the other end to cause secondary recrystallization over the entire width of the coil in the stage of annealing said sheet. A temp. gradient of >=0.5 deg.C/cm is given to the boundary region between the primary recrystallization region and the secondary recrystallization region in a 930-1,050 deg.C temp. range to improve the excitation characteristic and iron loss characteristic of the electrical steel sheet. A bottom chamber 11 is provided in an annealing furnace for said purpose and a stationary base 31 having the outside diameter smaller than the inside diameter of the coil C is provided therein. The coil C is placed on a base plate 41, and the temp. gradient is provided in the opening part of the chamber 11 in the stage of moving the coil from the chamber 11 kept at a low temp. to the inside of an inner cover 2 kept at a high temp. to effect the secondary recrystallization with the primary recrystallization, whereby the magnetic characteristic of the electrical steel sheet C is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal coil batch annealing apparatus, and more particularly to a metal coil batch annealing apparatus in which each part of the metal coil over its width or length passes through a specific temperature range with a specific temperature gradient. This invention relates to a batch annealing device for heating.

Conventionally, a metal coil has been placed on a base plate in a commonly used metal coil annealing furnace, and a predetermined heat pattern has been applied to the metal coil to anneal the metal coil in a stationary state. For example, in the manufacturing process of unidirectional electrical steel sheets, final finish annealing (secondary recrystallization annealing) has been widely performed in a batch annealing furnace as shown in FIG.

That is, as shown in FIG. 1, the electromagnetic steel coil C is placed on the base plate 3 with the coil axis perpendicular, and the inner cover 2 is placed over it. Then, the inner cover 2 is further covered with the bell-shaped furnace body 1, and the air supply pipe 4 is connected to the inner cover 2 to provide an N2. AX.

Supply atmospheric gas such as H2 gas. And the furnace l
The coil C is heated by the electric heater 5 installed inside and the electric heater 6 placed below the base plate 3
Heating and raising the temperature of the whole at the same time and relatively uniformly. Coil C
After raising the temperature to a predetermined temperature (1150 to 1200 ° C.) and holding it for soaking, cooling gas is blown into the furnace l from the cooling gas blowing pipe 7 connected to the top of the furnace body l to cool it at a predetermined temperature 1, Complete annealing. The heated cooling gas is transferred to the cooling device 8.
After being cooled down, it is blown into the furnace body 1 again.

By the way, miniaturization of electrical equipment such as transformers using unidirectional electrical steel sheets has recently become an important issue. In order to reduce the weight of the iron core of these electrical devices, excitation characteristics (8
There has been a need for grain-oriented electrical steel sheets with further improved iron loss properties (6%) and iron loss properties.

The heat treatment method previously applied for by the present applicant (Japanese Patent Application No. 55-75)
033.56-20154.56-198443゜56
-96740), secondary recrystallization is advanced while applying a predetermined temperature gradient to the electromagnetic steel sheet coil in the boundary region between the -secondary crystal region and the secondary crystal region. That is, the heating proceeds from one end of the electromagnetic steel sheet coil, which has undergone crystal annealing, toward the other end to cause continuous recrystallization over the entire width of the coil. At this time, within the temperature range of 930 to 1050°C, the boundary area between the primary recrystallization area and the secondary recrystallization area has 0.
Heat to give a temperature gradient of 5°C or higher. According to this method, an epoch-makingly excellent B8 that could not be obtained conventionally.
It has become possible to manufacture electrical steel sheets with specific characteristics and core loss characteristics.

However, in a conventional batch annealing furnace, the temperature is increased while heating the entire coil almost uniformly as described above. Therefore, it is not possible to provide the required temperature gradient to the metal coil in the boundary area.

Therefore, in annealing a metal coil, this invention involves heating the metal coil while applying a predetermined temperature gradient to a specific region.
The present invention aims to provide a batch annealing device that can raise the temperature.

The batch annealing apparatus of the present invention is equipped with a bell-shaped furnace body, a base plate, and an inner cover. It is located below the body.

A columnar fixed base is provided coaxially within the bottom chamber and extends upward from the bottom of the bottom chamber. The fixed base has an outer diameter slightly smaller than the inner diameter of the metal coil, and has a partition located at the opening of the bottom chamber. Further, the base grate has an annular shape and is equipped with a cooling means. The base grate is supported by a support member that penetrates through the bottom of the bottom chamber and is movable up and down. The lower end of the support member is connected to a lifting drive.

In the batch annealing apparatus configured as described above, the metal coil is heated while giving a predetermined temperature gradient in a specific region [ii. First, the base grate on which the metal coil is placed is lowered, and the metal coil is placed in the bottom chamber Store inside. Then, the base grade is gradually increased. At this time, the portion of the metal coil that protrudes upward from the bottom chamber, that is, the portion that enters the inner cover, is heated by the heating means and secondary recrystallization proceeds. The part of the metal coil inside the bottom chamber remains in the state of primary recrystallization. The heating means, the rising speed of the metal coil, and the like are arranged so that the boundary area between the secondary recrystallization region and the primary recrystallization region, that is, the portion of the metal coil located near the bottom chamber opening, has a predetermined temperature gradient. In addition, adjust the cooling means for the base plate.

The batch annealing apparatus of the present invention is provided with a bottom chamber as described above, and the inner diameter of the bottom chamber is slightly larger than the outer diameter of the metal coil, and the outer diameter of the bottom chamber is a cylindrical shape with a partition portion that is slightly smaller than the inner diameter of the metal coil. A fixed base is provided within the bottom chamber. Therefore, the bottom chamber U high temperature (7) is separated from the inner cover by the metal coil and the fixed base partition.
The inside of the bottom chamber can be kept at a much lower temperature than the inside of the inner cover. Thereby, when the metal coil is sent out from the bottom chamber into the inner cover, a required temperature gradient can be given to the boundary area.

Furthermore, in the apparatus of the present invention, since the base plate is provided with a cooling means, the portion of the metal coil that reaches the bottom chamber can be maintained at a low temperature.

As a result, a large temperature gradient can be applied to the boundary area. Furthermore, in controlling the cooling it is also possible to adjust the temperature gradient to the desired value.

Examples of the present invention will be described below.

FIG. 2 is a longitudinal sectional view showing an example of the batch annealing apparatus of the present invention. In FIG. 2, the same members VC as those of the conventional device shown in FIG. 1 are given the same reference numerals, and the explanation of these members will be omitted hereinafter.

The bottom chamber 11 consists of a cylindrical body I2 having a flange 13 at the upper end and a bottom member 14, and is constructed of firebrick. The body 12 and the bottom member 14 are separated for easy disassembly and assembly, and a sand seal 15 is provided between them to prevent atmospheric air from entering the bottom chamber 11. In addition, the inner peripheral surface of the body 12 is lined with a flexible and elastic heat insulating material 16 (for example, a ceramic fiber block), and the inner diameter of the inner lining is slightly smaller than the outer diameter of the metal coil C. It is designed to slide. The bottom chamber 11 configured in this manner is supported on the floor by supports 21 at the flange 13.

The furnace body 1 is placed on a flange 13, and the space between the furnace body 1 and the bottom chamber 11 is kept airtight by the sand seal 5 and the liquid seal 26. ! In addition, the inner cover 2 is also placed on the flange 13 and sealed with a sand seal.

Inside the bottom chamber 11, a cylindrical fixed base 31 is provided coaxially with the U body 12 and protruding upward from the bottom member J4. The fixed base 31i is made of refractory bricks, and an atmospheric gas supply hole 32 passes through the center. A portion of the fixed base 31 located at the opening 17 of the bottom chamber 11 serves as a partition portion 33 . A heat insulating material 16 lined on the inner circumferential surface of the body 12 is provided on the outer circumferential surface of the partition.
The same heat insulating material 34 is attached. The outer diameter of the partition part 33 is slightly smaller than the inner diameter of the coil C, so that the inner peripheral surface of the coil C slides on the outer peripheral surface of the partition part 33. Further, the upper end of the partition portion 33 is located at the same height as the upper surface of the bottom chamber 11. The upper and lower parts of the partition part 33 each have a slightly smaller diameter, and serve as a first heating part 35 and a second heating part 37, respectively. An electric heater 36.38 is attached to each heating section 35.37. A base portion 39 is located between the lower end of the second heating portion 37 and the bottom member 14, has the same diameter as the partition portion 33, and has a heat insulating material 40 pasted thereon.

The base plate 41 has an annular shape, and the inner diameter is the coil C.
The outer diameter is equal to or slightly smaller than the inner diameter of coil C.
Equal to or slightly larger than the outer diameter. A cooling gas flow path 42 is provided along the circumference of Vcid inside the base grate 41 . A cooling gas supply pipe 45 is provided in the cooling gas flow path 42.
A cooling gas discharge pipe (indicated by reference numeral 46 in FIG. 3) located 180 degrees away from this in the circumferential direction communicates therewith. Both pipes 45 and 41J pass through the bottom member 14 of the bottom chamber 11, and are connected via a flexible pipe 47 to a cooling gas circulation device 51, which will be described below. In addition, both pipes 45
, 46 are attached to the portion of the bottom chamber 11 that penetrates the bottom member 14, and a dynamic bellows 48 is attached to the bottom chamber 11 to make the inside of the bottom chamber 11 airtight. A bellows 49 is also provided in the middle of both tubes 45 and 46 to absorb thermal expansion that occurs during operation of the device.

FIG. 3 is a system diagram of the cooling gas circulation device 51.

A cooling gas circulation device 51 connects a cooling gas reservoir 52 to a supply source valve 53.
A blower 55 is connected via a cutoff valve 54. The blower 55 is connected to the cooling gas supply pipe 45 via a temperature control valve 56. - 10,000, the cooling gas discharge pipe 46 is connected to the blower 55 side via the cooler 57. The base grate 41 is supported by a support column 67 via an annular heat insulating material 61 and an intermediate member 63.

In order to absorb thermal expansion, the intermediate member 63 and the support column 67 are connected through a pin 65 inserted into a bottle hole 64 provided in the intermediate member 63 and a bottle hole (not shown) provided at the top of the support column 67. has been done. The lower part of the column 67 passes through the bottom member 14 of the bottom chamber 11. This penetrating portion [U dynamic bellows 69 is attached to keep the inside of the bottom chamber 11 airtight.

The base of the support column 67 is connected to a lifting drive device 71. The lifting drive device 71 includes a motor 72 with a speed reducer and a screw jack 73 driven by the motor 72. A screw jack 73 is connected to a guide bar 76 via a vertically extending connecting rod 74. Guide bar 7
6 is guided by guide posts 77 fixed to the floor. The base of the support column 67 is supported on the guide bar 76.

Note that a purge gas supply pipe 81 and a purge gas exhaust pipe 82 are attached to the bottom member 14 of the bottom chamber 11.

Next, a method for secondary recrystallization annealing of a silicon steel sheet coil using the batch annealing apparatus configured as described above will be described.

First, the base grate 41 is set at the upper limit position shown in FIG. 2 with the furnace body 1 and inner cover 2 removed. Then, the silicon steel plate coil C that has undergone primary recrystallization annealing is placed on the base plate 41. Subsequently, the coil C is covered with the inner cover 2, and the inch cover 2 is further covered with the furnace body 1. The inside of the furnace body 1 is supplied with N from the cooling gas blowing pipe 7, and the inside of the inch cover 2 is supplied with N from the atmospheric gas supply hole 32.
2 gas is supplied to purge the inside of these. Nipurge gas supply pipe 81 and exhaust pipe 8 in the bottom chamber 11
2, it is purged by supplying and exhausting N2 gas.

After the above purge is completed, the electric heater 5 attached to the inside of the furnace body 1 heats, for example, 10 to bN2. At this time, the first electric heater 36 of the fixed base 31 may be used in combination. The temperature of the atmospheric gas inside the inch cover 2 is at room temperature T as shown in FIG.

Once the temperature has risen to a predetermined temperature T (600 to 650°C), the inside of the furnace is kept soaked for a period A (10 to 20 hours). At the start of soaking in the furnace, the atmospheric gas N2 is switched to bagasse. Due to this soaking in the furnace, the atmospheric gas reaches a predetermined dew point (-
5 to −1θ° C.), and moisture released from the annealing separator applied to the coil C does not form condensation when the coil C is cooled.

When the soaking in the furnace is completed, the coil C is lowered to the lower limit by the lifting drive device 71 and stored in the bottom chamber 11. At this time, the upper end of the coil C is connected to the bottom chamber 11.
It is lined up at the same height as the upper end and the upper end of the partition part 33 of the fixed base 31. The coil C is then kept on standby within the bottom chamber 11 for a period B until the temperature at its upper end reaches 930° C. or higher. During this time, the temperature inside the furnace and the temperature at the upper end of the coil C rise, but the bottom chamber 1 which is partitioned from the inner cover 2 by the coil C and the partition part 33
Since the temperature inside coil C is low, the temperature at the bottom of coil C drops slightly.

When the temperature at the upper end of the coil C reaches 930°C or higher after the standby period B has elapsed, the lifting drive device 7] is driven again.
Coil C is raised at a speed of 0011 m/H.

The coil C is gradually sent out from the bottom chamber 11 into the inner cover 2, and a temperature gradient is generated in the boundary area between the portion of the coil C exposed inside the inner cover 2 and the portion located inside the bottom chamber 11. The heating rate in the furnace and the coil rising rate are adjusted so that the temperature gradient is 2° C. or more. When the coil C enters the inner cover 2 to some extent, the temperature of the portion of the coil C inside the bottom chamber 11 also rises considerably, making it impossible to maintain a predetermined temperature gradient. Cooling of the base plate 41 is started at time a, which is slightly before this time.

To cool the base plate 41, the same gas as the atmospheric gas inside the inner cover 2 is supplied from the cooling gas circulation device 51 to the cooling gas passage 42 inside the base plate 41 via the cooling gas supply pipe 45. (N2 gas may also be used.) The gas sent to the cooling gas passage 42 cools the base grate 41 and rises in temperature, passes through the cooling gas discharge pipe 46, and reaches the cooler 57.

The cooling gas cooled by the cooler 57 is sent under pressure to the base grate 41 again by the blower 55. The cooling gas flow rate is adjusted by a temperature control valve 56 according to the temperature gradient.

In this way, the coil C is heated gradually from the upper end to the lower end, and the lower end of the coil C is heated to the bottom chamber 1.
1, the base plate 41 stops rising. At this time, the upper end of the coil C is at approximately the predetermined temperature T2 (1
150-1200°C). Furthermore, cooling of the base grate 41 is continued until the temperature at the lower end of the coil C reaches 930° C. or higher (period C). Note that when the temperature inside the furnace reaches a predetermined temperature T2, the atmospheric gas in the inner cover 2 is switched from bagasse to H2 gas.

The coil C is uniformly heated until the lower end reaches 1150° C. or higher. When this soaking is completed (time point C), cooling gas is blown into the furnace body 1 from the cooling gas blowing pipe 7 to cool the coil C together with the inner cover 2. When the temperature of the coil C drops to a predetermined temperature, the furnace body 1 is removed, and the inner cover 2 and the coil C are further cooled in the atmosphere. After cooling is completed, the inch cover 2 is removed and a series of annealing operations are completed.

In addition, when the dimensions of the coil C are large, the portion of the coil C that has entered the inner cover 2 cannot be sufficiently heated with only the electric heater 5 provided inside the furnace body 1, and the required temperature gradient cannot be obtained. Sometimes. In this case, fixed base 3
Auxiliary heating is performed by the first electric heater 36 of No. 1. Further, when the entire coil C is kept uniformly heated at a temperature of 1150° C. or higher, heat is dissipated from the lower end of the coil C by lightly touching the base plate 41. At this time, the base grate 41 is not cooled, and the heat insulating material 61 prevents heat from dissipating.

However, depending on the size of the coil C, it may be difficult to maintain the temperature at the lower end of the coil C due to heat dissipation. In this case, auxiliary heating is performed by the second electric heater 38 of the fixed base 31.

This invention is not limited to the above embodiments.

For example, a direct burner may be used instead of the electric heater 5 as the heating means, and the heating means may be provided not only on the peripheral wall of the furnace body 1 but also on the ceiling.

The cooling gas flow path 4 serves as a cooling means for the base grate 41.
2 may be replaced by a cooling pipe disposed on the upper surface of the heat insulating material 61. Insulating materials 16 and 34.4 are attached to the bottom chamber 11 and the fixed base 31, respectively.
0 or is not essential for the electric heater 36 or 38 attached to the fixed base 31. Insulation material 16.34
If not provided, the gap between the inner circumferential surface of the bottom chamber 11 and the outer circumferential surface of the coil C and the gap between the outer circumferential surface of the partition part 33 and the inner circumferential surface of the coil C are 1 inch. The temperature is set to such an extent (for example, 1 to 5 m) that the gas does not flow into the bottom chamber 11 and cause the temperature inside the bottom chamber 11 to exceed the FF temperature. Furthermore, a hydraulic jack may be used in place of the reduction gear motor 72 and the screw jack 73Vc of the lifting drive device 71.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an example of a conventional batch annealing device;
FIG. 2 is a longitudinal sectional view showing an example of the batch annealing apparatus of the present invention, FIG. 3 is a system diagram of a cooling gas circulation device used in the apparatus shown in FIG. 2, and FIG. 4 shows the temperature inside the furnace, coil temperature,
FIG. 3 is a diagram showing changes in coil position over time. DESCRIPTION OF SYMBOLS 1... Furnace body, 2... Inner cover, 3... Base plate), 11... Bottom chamber, 12... Chamber peripheral wall, 14... Chamber bottom member, 31...
- Fixed base, 33... Partition part, 41... Base grate, 42... Cooling gas flow path, 51... Cooling gas circulation device, 71... Lifting drive device. Patent applicant Representative patent attorney Tomoyuki Yafuki (and 1 other person) Figure 2 Figure 4

Claims (1)

[Claims] Equipped with a removable bell-shaped furnace body equipped with a 11Vc heating means, a base plate provided inside the furnace body, and a removable inner cover that covers a metal coil placed on the base plate with the coil axis perpendicular. In this apparatus, a bottom chamber is provided below the furnace body, which opens upward, has an inner diameter slightly larger than the outer diameter J of the metal coil, and can accommodate the metal coil. A columnar fixed base is provided coaxially with the bottom chamber and extends upward from the bottom of the bottom chamber, and the fixed base has an outer diameter slightly smaller than the inner diameter of the metal coil and has a partition located at the opening of the bottom chamber. Base plate) H has an annular shape, is equipped with a cooling means, and is supported by a support member that passes through the bottom of the bottom chamber and can be raised and lowered freely, and the lower end of the support member is connected to a lifting drive device. Characteristic batch annealing equipment.