JPS6252019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a batch annealing furnace for metal coils, particularly a batch annealing furnace for heating metal coils such that each part of the metal coil in the width or length direction passes through a specific temperature range with a specific temperature gradient. Regarding annealing furnace.

Conventionally, in a commonly used annealing furnace for metal coils, the metal coil is placed on a base plate, and the metal coil is held stationary while being annealed by applying a predetermined heat pattern. For example, in the manufacturing process of unidirectional electrical steel sheets, final 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 perpendicular to the coil axis, 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 N ₂ is supplied into the inner cover 2 through the air supply pipe 4.
Supply atmospheric gas such as AX, _H2 gas. Then, an electric heater 5 installed inside the furnace body 1
An electric heater 6 disposed below the base plate 3 heats and raises the temperature of the entire coil C at the same time and relatively uniformly. Coil C to the required temperature (1150
After raising the temperature to 1200°C) and maintaining the temperature, a cooling gas blowing pipe 7 connected to the top of the furnace body 1 is inserted into the furnace body 1.
Cooling gas is blown into the tank to cool it to a specified temperature.
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 electromagnetic steel sheets has recently become an important issue. In order to reduce the core weight of these electrical devices, unidirectional electrical steel sheets with further improved excitation characteristics ( _B8 characteristics) and iron loss characteristics have become necessary.

The heat treatment method previously filed by the applicant (Japanese Patent Application No. 1983)
−75033, 56−20154, 56−198443, 56−96740)
The secondary recrystallization proceeds while applying a predetermined temperature gradient to the electromagnetic steel sheet coil in the boundary region between the primary recrystallization region and the secondary crystallization region. That is, heating is continued from one end of the electromagnetic steel sheet coil that has undergone primary recrystallization annealing toward the other end to cause secondary recrystallization over the entire width of the coil. At this time, heating is performed within a temperature range of 930 to 1050°C so as to give a temperature gradient of 0.5°C/cm or more to the boundary area between the primary recrystallization region and the secondary recrystallization region. According to this method, it has become possible to produce an electrical steel sheet with groundbreakingly excellent _B8 properties and iron loss properties, which were previously unobtainable.

However, in the 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide a batch annealing furnace that can heat and raise the temperature of a metal coil while applying a predetermined temperature gradient to a specific region during annealing of the metal coil.

The batch annealing furnace of the present invention is equipped with a bell-shaped furnace body, a base plate, and an inner cover, and has a bottom chamber that opens upward, has an inner diameter slightly larger than the outer diameter of the metal coil, and can accommodate the metal coil. It is located below the furnace 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. A heater is provided within the bottom chamber and above the partition of the fixed base. Further, the base plate has an annular shape and is provided with cooling means. The base plate is supported by a support member that passes 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 furnace configured as described above, in order to heat the metal coil while giving a predetermined temperature gradient in a specific area, first lower the base plate on which the metal coil is placed, and move the metal coil into the bottom chamber. Store inside. Then, the base plate is gradually raised. 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 progresses. The portion within the bottom chamber of the metal coil remains in the state of primary recrystallization. The heating means, the rising speed of the metal coil, and In addition to these, adjust the cooling means for the base plate.

The batch annealing furnace of the present invention has a bottom chamber as described above, the inner diameter of the bottom chamber is slightly larger than the outer diameter of the metal coil, and a cylindrical shape having a partition portion whose outer diameter is slightly smaller than the inner diameter of the metal coil. A fixed base is provided within the bottom chamber. Therefore, the bottom chamber is separated from the high-temperature inner cover by the metal coil and fixed base partition, so it is possible to maintain the inside of the bottom chamber at a much lower temperature than the inside of the inner cover. I can do it. Thereby, when the metal coil is sent out from the bottom chamber into the inner cover, a desired temperature gradient can be given to the boundary area.

Furthermore, since the furnace of the present invention is provided with cooling means on the base plate, the portion of the metal coil that remains within 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, the temperature gradient can also be adjusted to the desired value by controlling the cooling.

Furthermore, since the heater is provided in the bottom chamber, heat dissipation from the base plate is suppressed when the coil is heated to a required temperature and kept uniformly heated. This heater then dries the moisture contained in the lining material (refractory material) inside the bottom chamber. Further, the heater provided above the partition of the fixed base heats the coil from the inner circumferential surface in relation to the furnace temperature when heating the coil. Therefore, since the coil can be heated uniformly in the radial direction of the coil, even if the coil is large, for example, 10 tons or more, it is possible to obtain a coil of uniform quality throughout. Summer.

Examples of the present invention will be described below.

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

The bottom chamber 11 consists of a cylindrical body 12 having a flange 13 at the upper end and a bottom member 14, and is constructed of firebrick. fuselage 12
is placed on the top of the support structure 21 so as to be supported by the flange 13. As shown in FIG. 2, the bottom member 14 is placed below the support structure 21. A sand seal 15 is provided between the body 12 and the bottom member 14. The inner peripheral surface of the body 12 is lined with a flexible and resilient heat insulating material 16 (eg, ceramic fiber block). The inner diameter of the body 12 lined with a heat insulating material 16 is slightly smaller than the outer diameter of the metal coil C, so that the outer peripheral surface of the coil C slides on the heat insulating material 16.

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 a sand seal 25 and a liquid seal 26. Further, the inner cover 2 is also placed on the flange 13 and sealed with a sand seal 28.

As shown in FIG. 3, a cylindrical fixed base 31 is provided within the bottom chamber 11 so as to be coaxial with the body 12 and project upward from the bottom member 14. The fixed base 31 is made of firebrick, and has an atmospheric gas supply hole 32 penetrating 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 34, which is the same as the heat insulating material 16 lined on the inner circumferential surface of the body 12, is attached to the outer circumferential surface of the partition portion 33. The outer diameter of the partition part 33 is slightly larger 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. Also,
The upper end of the partition part 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 34 and a second heating part 36, respectively. Each heating part 34, 36 is provided with a large number of grooves 38 along the circumference, and the electric heaters 35, 37 are provided here.
It is installed so that it is embedded.
A base portion 39 is located between the lower end of the second heating portion 36 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 equal to or slightly smaller than the inner diameter of the coil C.
The outer diameter is equal to or slightly larger than the outer diameter of coil C. A cooling gas flow path 42 is provided inside the base plate 41 along the circumference. The cooling gas flow path 42 communicates with a cooling gas supply pipe 45 and a cooling gas discharge pipe (indicated by reference numeral 46 in FIG. 4) located 180 degrees away from the cooling gas supply pipe in the circumferential direction. Both tubes 45 and 46 pass through the bottom member 14 of the bottom chamber 11 and are connected via a flexible tube 47 to a cooling gas circulation device 51, which will be described below. A dynamic bellows 48 is attached to the portion where both the tubes 45 and 46 pass through the bottom member 14 of the bottom chamber 11 to ensure airtightness within the bottom chamber 11. Also, both pipes 45, 4
A bellows 49 is provided in the middle of 6 to absorb thermal expansion that occurs during operation of the device.

FIG. 4 is a system diagram of the cooling gas circulation device 51.

A cooling gas circulation device 51 supplies a cooling gas reservoir 52 with a blower 55 via a supply source valve 53 and a cutoff valve 54.
is connected. Blower 55 is temperature control valve 5
6 to the cooling gas supply pipe 45. On the other hand, the cooling gas exhaust pipe 46 is connected to the inlet side of the blower 55 via a cooler 57.

The base plate 41 is supported by a support 67 via an annular heat insulator 61 and an intermediate member 63. Intermediate member 6 to absorb thermal expansion
The intermediate member 63 and the support column 67 are connected through a pin 64 provided at the top of the support support 67 and a pin 65 inserted into a pin hole (not shown) provided at the top of the support support 67. The lower part of the column 67 is the bottom chamber 1
It penetrates through the bottom member 14 of 1. A dynamic bellows 69 is attached to this penetrating portion 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 elevating drive device 71 includes a motor 72 with a speed reducer and a screw jack 73 driven by the motor 72. Screw Jyatsuki 73
is connected to a guide plate 76 via a vertically extending connecting rod 74. Both ends of the guide plate 76 are guided by guide posts 77 fixed to the floor 23. The guide plate 76 supports the base of the support column 67.

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

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

First, with the furnace body 1 and inner cover 2 removed, the base plate 41 is set at the upper limit position shown in FIG. And base plate 41
An electromagnetic steel sheet coil C that has undergone primary recrystallization annealing is placed on top. Subsequently, the coil C is covered with an inner cover 2, and the inner cover 2 is further covered with the furnace body 1. _N2 is supplied to the inside of the furnace body 1 from the cooling gas blowing pipe 7, and to the inside of the inner cover 2 from the atmospheric gas supply hole 32.
Supply gas and purge these insides. The inside of the bottom chamber 11 is purged by supplying and exhausting N ₂ gas through a purge gas supply pipe 81 and an exhaust pipe 82 .

After the above purge is completed, the electric heater 5 attached to the inside of the furnace body 1 will cause a
The atmospheric gas N ₂ inside the inner cover 2 is heated at a heating rate of °C/H. At this time, the first electric heater 35 of the fixed base 31 may also be used. When the temperature of the atmospheric gas inside the inner cover 2 rises from the room temperature T ₀ to the predetermined temperature T ₁ (600 to 650°C) as shown in Fig. Keep the temperature uniform. Atmospheric gas at the start of soaking in the furnace
Switch _N2 to AX gas. This soaking in the furnace keeps the atmospheric gas at a predetermined dew point (below -5 to -10°C), and the moisture released from the annealing separator applied to coil C does not condense when 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 housed in the bottom chamber 11. At this time, the upper end of the coil C is connected to the upper end of the bottom chamber 11 and the fixed base 3.
They are lined up at the same height as the upper end of the partition section 33 of No. 1.
And the temperature of the upper end of coil C is 930℃
Until the above conditions are reached, the device is kept on standby within the bottom chamber 11 for a period B. During this time, the temperature inside the furnace and the coil C
Although the temperature at the upper end increases, the coil C and partition 3
Since the temperature inside the bottom chamber 11, which is partitioned from the inner cover 2 by 3, is low, the temperature at the bottom of the coil C drops slightly.

After waiting period B has elapsed, the temperature at the upper end of coil C has increased.
When the temperature reaches 930° C. or higher, the lifting drive device 71 is driven again to raise the coil C at a speed of 20 to 600 mm/H. The coil C is gradually fed out from the bottom chamber 11 into the inner cover 2, and a temperature gradient is generated in the boundary region between the portion of the coil C exposed inside the inner cover 2 and the portion 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./cm or more.
At this time, the first electric heater 3 of the fixed base 31
In step 5, the coil C is auxiliary heated from its inner peripheral surface.
Therefore, the portion of the coil C protruding into the inner cover 2 is heated from both the inner and outer circumferences, and is heated uniformly in the radial direction. 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.

The base plate 41 is cooled by the cooling gas supply pipe 4
The same gas as the atmospheric gas in the inner cover 2 is supplied from the cooling gas circulation device 51 to the cooling gas passage 42 in the base plate 41 via the cooling gas circulation device 51 . (N ₂ gas may also be used.) The gas sent to the cooling gas passage 42 cools the base plate 41 and rises in temperature, and reaches the cooler 57 via the cooling gas exhaust pipe 46 . Cooler 5
The cooling gas cooled in step 7 is again forced to be sent to the base plate 41 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 toward the lower end, and at the time b when the lower end of the coil C exits the bottom chamber 11, the raising of the base plate 41 is temporarily stopped. At this time, coil C
The upper end has almost reached the predetermined temperature T ₂ (1150 to 1200°C). Furthermore, cooling of the base plate 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 T ₂ , the atmospheric gas inside the inner cover 2 is switched from AX gas to H ₂ gas.

Coil C is kept uniformly heated until the lower end reaches 1150°C or higher. During uniform heating, heat is dissipated from the lower end of the coil C through the base plate 41. At this time, although the base plate 41 is not cooled and heat dissipation is suppressed by the heat insulating material 61, it is difficult to maintain the lower end of the coil C at a predetermined temperature. Therefore, auxiliary heating is performed by the second electric heater 37 of the fixed base 31.

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 inner cover 2 is removed and a series of annealing operations are completed.

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 inside of the bottom chamber 11 may be heated by a heater attached to the inner circumferential surface of the body 12, or both, instead of the heaters 35 and 37 attached to the fixed base 31.

The cooling means for the base plate 41 may be a cooling pipe arranged on the upper surface of the heat insulating material 61 instead of the cooling gas flow path 42. bottom chamber 11
Although the bottom member 14 was disk-shaped, it may be divided at the middle portion of the bottom chamber 11. In this case, the bottom member is bowl-shaped. Further, instead of the sand seal 15, a pressure sealing device using ceramic fiber or the like, a tightening sealing device using a gasket, or a combination of these and a liquid sealing device can also be used. Furthermore, the heat insulating materials 16, 34, and 40 attached to the bottom chamber 11 and the fixed base 31, respectively, are not essential. When the heat insulating materials 16 and 34 are 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 2
The temperature is set to such an extent (for example, 1 to 5 mm) that the high-temperature atmospheric gas inside the bottom chamber 11 does not flow into the bottom chamber 11 and cause the temperature inside the bottom chamber 11 to exceed an allowable temperature.
Furthermore, the motor 7 with a reduction gear of the lifting drive device 71
2 and screw jack 73 may be replaced with a hydraulic jack.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of a conventional batch annealing furnace, FIG. 2 is a longitudinal sectional view showing an example of a batch annealing furnace of the present invention, and FIG. 3 is a vertical sectional view showing an example of the batch annealing furnace of the present invention. FIG. 4 is a detailed sectional view, FIG. 4 is a system diagram of a cooling gas circulation system used in the furnace shown in FIG. 2, and FIG. 5 is a diagram showing changes in furnace temperature, coil temperature, and coil position over time. DESCRIPTION OF SYMBOLS 1...Furnace body, 2...Inner cover, 3...Base plate, 11...Bottom chamber, 12...
...Chamber body, 14...Chamber bottom member,
15... Sealing device, 31... Fixed base, 33
...Partition section, 34, 36...Heating section, 35, 37
...Electric heater, 41...Base plate, 4
2... Cooling gas flow path, 51... Cooling gas circulation device, 71... Lifting drive device.

Claims (1)

[Claims] 1 Equipped with a removable bell-shaped furnace body equipped with heating means inside, 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 the furnace, a bottom chamber that opens upward, has an inner diameter slightly larger than the outer diameter of the metal coil, and is capable of housing the metal coil is provided below the furnace body, and a bottom chamber is provided in the bottom chamber. Coaxially, a columnar fixed base is provided extending 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;
A heater is provided in the bottom chamber and above the partition of the fixed base, the base plate has an annular shape and is equipped with cooling means, and a support member that passes through the bottom of the bottom chamber and is movable up and down. What is claimed is: 1. A batch annealing furnace characterized in that the support member is supported by a support member, and a lower end portion of the support member is connected to an elevating drive device.