JP2012012692A - Annealing furnace and cooling method in annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an annealing furnace improving a cooling capacity in cooling a metal strip by a gas jet cooling system.SOLUTION: The annealing furnace 1 is used to cool a continuously conveyed metal strip 3 in the cooling zone 15 of a furnace body 10, and is equipped with gas jet coolers 21 that cool the metal strip 3 by blowing a coolant gas thereto in the cooling zone 15; seal means 31 provided on the inlet and outlet sides of a scope S1 including the cooling zone 15 in the furnace body 10; and a pressurization means 41 for pressurizing the scope S1 including the cooling zone 15. In this way, it is possible to improve the cooling capacity of the coolant gas because the coolant gas used for cooling is pressurized and increases its density, which increases the weight of the coolant gas blown per unit time.

Description

  The present invention relates to an annealing furnace for cooling a continuously conveyed metal strip in a cooling zone of a furnace body, and a cooling method in the annealing furnace, and in particular, a cooling capacity when cooling a metal strip by a gas jet cooling device. The present invention relates to an annealing furnace suitable for improving the temperature and a cooling method in the annealing furnace.

  Conventionally, in an annealing furnace that performs an annealing treatment on a continuously conveyed metal strip, a water cooling method, a roll cooling method, a gas jet cooling method, and the like are known as methods for cooling the metal strip in the cooling zone. Yes.

  For example, as shown in Patent Document 1, the water cooling method is a method of cooling a metal strip by spraying a mist mixed with liquid or gas-liquid on a metal strip that is continuously transported in the furnace body. is there. When the water cooling method is used, there is a merit that it is possible to stably cool while obtaining a high cooling capacity, but an oxide film is generated by spraying a liquid on the surface of a high-temperature metal strip, There is a demerit that an additional post-treatment of the oxide film is required. Further, since an oxide film needs to be post-processed, it is used in a continuous galvanizing line (CGL) in which a metal strip annealed by an annealing furnace is continuously subjected to hot dip plating without being carried out of the furnace. The disadvantage of not being able to do so arises.

  For example, as shown in Patent Document 2, the roll cooling system is a system that cools a metal band by flowing a coolant through the transport roll to cool the coolant, and guiding the metal band with the cooled transport roll. . When the roll cooling method is used, an oxide film is not generated in the metal band due to the cooling, so that there is an advantage that a high cooling capacity can be obtained while the post-treatment of the oxide film is unnecessary. On the other hand, when the roll cooling method is used, only the portion where the metal band contacts the transport roll is mainly cooled, and therefore the temperature distribution in the width direction of the metal band during cooling is unstable. As a result, there is a demerit that the shape defect of the metal band is likely to occur. In particular, when the metal strip is cooled from a high temperature region, the tendency of the temperature distribution to become unstable becomes strong, so that the roll cooling method has a demerit that there is a limitation on the applicable objects.

  A gas jet cooling system is a system which cools a metal strip by spraying refrigerant gas with respect to the metal strip conveyed, for example, as shown in patent document 3. FIG. When the gas jet cooling method is used, no oxide film is formed on the metal band due to cooling, and the temperature distribution in the width direction of the metal band during cooling is stabilized, so that post-treatment of the oxide film is unnecessary. There is an advantage that cooling can be performed stably. On the other hand, when the gas jet cooling method is used, since the cooling medium is a gas, there is a demerit that the cooling capacity is inferior to the water cooling method or the roll cooling method.

JP 58-61236 A JP 51-104417 A JP 62-116724 A JP 09-235626 A

  As described above, when the gas jet cooling method is used, although it is inferior to other cooling methods in terms of cooling capacity, it is superior to other cooling methods in other points. For this reason, if the cooling capacity in the gas jet cooling system can be increased, it is possible to reduce the size of the cooling zone by reducing the size of the cooling zone while receiving the above-mentioned advantages, It is possible to receive a further merit that it is possible to suppress the amount of alloying element added during the manufacture of the (tensile steel plate).

In order to increase the cooling capacity when using the gas jet method, the capacity of the blower for blowing the refrigerant gas is increased to increase the blowing amount of the refrigerant gas (m ³ / (min · m ² )). As shown in Patent Document 4, means for increasing the hydrogen concentration in the refrigerant gas is known. However, in recent years when technological innovation is required, it has been desired to propose a technique that can enhance the cooling capacity by a method different from these means.

  Therefore, the present invention has been devised in view of the above-described problems, and an object thereof is an annealing furnace capable of improving the cooling capacity when cooling a metal strip by a gas jet cooling method. And it is providing the cooling method in an annealing furnace.

  In order to solve the above-described problems, the present inventors have invented the following annealing furnace and a cooling method in the annealing furnace after intensive studies.

  An annealing furnace according to a first aspect of the present invention is an annealing furnace that cools a continuously transported metal strip in a cooling zone of a furnace body, and a gas jet cooling device that cools the metal strip by spraying a refrigerant gas in the cooling zone; The furnace body includes sealing means provided on the entry side and the exit side of the range including the cooling zone, and a pressurizing means for pressurizing the range including the cooling zone.

  An annealing furnace according to a second invention is characterized in that, in the first invention, the pressurizing means pressurizes the cooling zone so that a pressure difference between the inside and outside of the furnace becomes 9.8 kPa or more.

  An annealing furnace according to a third invention is the first invention or the second invention, wherein the pressurizing means pressurizes the atmosphere in the furnace sucked in from the low pressure side in the furnace body with the sealing means sandwiched therebetween, and the high pressure side It is the blower or compressor which discharges toward

  An annealing furnace according to a fourth invention is the annealing furnace according to any one of the first to third inventions, wherein the pressurizing means supplies the atmospheric gas within a range including the cooling zone and includes the cooling zone. It is an atmospheric gas supply device that pressurizes the inside.

  The annealing furnace according to a fifth aspect of the present invention is the annealing furnace according to any one of the first to fourth aspects, wherein the sealing means is sealed by a sealing member disposed close to or in contact with the metal plate. It is characterized by.

  An annealing furnace according to a sixth invention is any one of the first to fifth inventions, wherein the furnace body is partially immersed in a liquid bath, and the sealing means is the furnace body. The liquid bath is hermetically sealed inside.

  An annealing furnace according to a seventh invention is the annealing furnace according to any one of the first to sixth inventions, wherein the sealing means is provided on the inlet side and the outlet side of the cooling zone in the furnace body, and the pressurizing means. Is characterized in that only the cooling zone is pressurized.

  In the cooling method in the annealing furnace according to the eighth aspect of the present invention, in the furnace body in which sealing means are provided on the entry side and the exit side of the range including the cooling zone in the furnace body, the range including the cooling zone is pressurized. In this state, the metal band is cooled by spraying a refrigerant gas in the cooling band.

  According to the first to eighth inventions, it is possible to cool the metal strip with the refrigerant gas in a state where the cooling zone is pressurized to a predetermined pressure or higher. As a result, the refrigerant gas used for cooling is also pressurized and its density is increased, so that the weight of the refrigerant gas blown per unit time increases, and the cooling capacity by the refrigerant gas is improved. . For this reason, it is possible to improve the cooling capacity as compared with the conventional one while receiving the merit of the gas jet cooling method in which the post-treatment of the oxide film is not required and can be stably cooled. Further, since the size of the cooling zone can be reduced, the furnace body can be made compact.

  According to the third invention, it is possible to pressurize the range including the cooling zone while suppressing an increase in the weight of the atmospheric gas supplied into the furnace.

It is a side view which shows roughly the structure of the annealing furnace which concerns on 1st Embodiment. It is an enlarged side view which expands and shows the structure of the cooling zone of an annealing furnace. (A) is an expanded side view which expands and shows the structure of the sealing device used in 1st Embodiment, (b) is the rear view. It is a side view which shows roughly the structure of the annealing furnace which concerns on 2nd Embodiment. It is a side view which shows roughly the structure of the annealing furnace which concerns on 3rd Embodiment. It is a side view which shows roughly the structure of the annealing furnace which concerns on 4th Embodiment. It is a side view which shows the structure of the box used in the present Example.

  Hereinafter, the form for implementing the annealing furnace which concerns on this invention is demonstrated in detail, referring drawings.

  First, the annealing furnace according to the first embodiment will be described. FIG. 1 is a side view schematically showing a configuration of an annealing furnace 1 according to the first embodiment, and FIG. 2 is an enlarged side view showing an enlarged configuration of a cooling zone 15 of the annealing furnace 1.

An annealing furnace 1 according to the first embodiment includes a heating zone 11 that heats a metal strip 3 made of a steel material, a soaking zone 13 that holds the heated metal strip 3 in a temperature range within a predetermined range, and a gas jet cooling device. 21 is provided with a cooling zone 15 for cooling the metal zone 3. The metal strip 3 continuously transported from the entrance 10a on the furnace body 10 entrance side is guided through the strips 11, 13, and 15 by the transport roll 17 installed in the furnace, and in each strip 11, 13, 15 After annealing by performing heat treatment under a predetermined condition, it is unloaded from the unillustrated unloading port on the exit side of the furnace body 10, and post-treatment such as temper rolling and winding as necessary. Applied. In each of the zones 11, 13, and 15 of the annealing furnace 1, for example, a reducing atmosphere gas in which less than 10% by volume is H ₂ and the balance is N ₂ or other inert gas is an atmosphere gas supply device. 18 is supplied.

  The annealing furnace 1 according to the first embodiment includes a gas jet cooling device 21 that blows a refrigerant gas in the cooling zone 15 to cool the metal zone 3, and an inlet side and an outlet side in a range S 1 that includes the cooling zone 15 in the furnace body 10. And a pressurizing device 41 as a means for pressurizing the range S1 including the cooling zone 15.

  In the first embodiment, as shown in FIG. 2, the gas jet cooling device 21 includes a cooling box 23 installed on both sides of the metal strip 3 in the conveyance direction of the metal strip 3, and a cooling box 23. The nozzle 25 is provided so as to protrude from the surface on the metal band 3 side toward the metal band 3.

Refrigerant gas is supplied into the cooling box 23, and the refrigerant gas supplied into the cooling box 23 is blown from the nozzle 25 toward the metal band 3, thereby cooling the metal band 3. . As the refrigerant gas, for example, the above-described reducing atmosphere gas supplied into the annealing furnace 1 in which less than 10% by volume is H ₂ and the balance is N ₂ or other inert gas is used. It is done.

  The refrigerant gas used in the gas jet cooling device 21 is configured to be circulated through the ducts 26 and 29 by the circulation blower 28. Specifically, the gas jet cooling device 21 includes a suction side duct 26 that communicates a gas suction port formed in the furnace body 10 and a suction port of the circulation blower 28, a discharge port of the circulation blower 28, and a cooling box 23. And a heat exchanger 27 for cooling the refrigerant gas is installed in the middle of the suction duct 26. The refrigerant gas blown to the metal strip 3 is sucked into the circulation blower 28 from the gas suction port of the furnace body 10 through the suction side duct 26 and the heat exchanger 27 and then is discharged in a pressurized state. 29 is supplied again to the cooling box 23 via 29, and is used so as to circulate.

  Fig.3 (a) is an enlarged side view which expands and shows the structure of the sealing device 31 used in 1st Embodiment, FIG.3 (b) is the rear view.

  The sealing device 31 prevents the atmosphere in the pressurizing range S1 of the furnace body 10 to be pressurized by the pressurizing device 41 from leaking outside the range, and the pressure of the atmosphere in the pressurizing range S1 is predetermined. It is provided so that it may be maintained above the pressure. In the first embodiment, the sealing device 31 is provided on the inlet side and the outlet side of the cooling zone 15 so that the pressurizing range S1 is only the cooling zone 15.

  In the first embodiment, the seal device 31 includes seal members 33 and 35 such as a seal roll 33 and a seal plate 35 that are installed close to the metal strip 3. Specifically, the sealing device 31 includes a pair of seal rolls 33 installed on both sides of the metal strip 3 and a pair of atmospheres that prevent leakage of the atmosphere between the seal roll 33 and the furnace body 10. And a seal plate 35. The seal roll 33 and the metal strip 3, or the seal roll 33 and the seal plate 35 are in contact with each other or provided close to each other with a slight gap therebetween, and the pair of seal rolls 33 and the pair of seal plates 35 are provided. And a set of the sealing device 31 so that the atmosphere in the pressurization range S1 can be prevented from leaking outside the range. The smaller the gap between the seal roll 33 and the metal strip 3 is, the more efficiently the differential pressure can be maintained, and the performance of the pressurizing device 41 described later can be suppressed. Is better, for example, it may be 10 mm to 50 mm.

  In the first embodiment, the seal device 31 has been described as including the seal roll 33 and the seal plate 35. In addition, the seal device 31 is configured only from the seal plate 35 by omitting the seal roll 33. Also good. Further, in the first embodiment, the sealing device 31 has been described for sealing using the sealing members 33 and 35 such as the sealing roll 33, but the atmosphere in the pressurization range S1 is out of the range by the sealing device 31. As long as the differential pressure across the sealing device 31 can be maintained by preventing leakage, the configuration is not particularly limited. For this reason, as the sealing device 31, for example, a known sealing device such as a member that presses and seals a flexible sealing member against the metal strip 3 may be used. In addition, the sealing device 31 may be constituted by a liquid bath such as a hot dipping bath 53 described later.

  In the case where the sealing device 31 is configured from what is sealed using the sealing members 33 and 35 such as the sealing roll 33, the sealing device 31 according to the sealing capability required to make the pressure within the pressurizing range S1 equal to or higher than the predetermined pressure. Then, as in the first embodiment, a plurality of sealing devices 32 may be configured by providing a plurality in the conveying direction at intervals.

  In the first embodiment, the pressurizing device 41 is configured by a blower that pressurizes the atmosphere in the furnace sucked from the low pressure side in the furnace body 10 with the seal device group 32 interposed therebetween and discharges the atmosphere toward the high pressure side. . Thereby, a differential pressure is generated in the furnace atmosphere before and after the sealing device group 32. In the first embodiment, two pressurizing devices 41 are provided so that a differential pressure is generated before and after the inlet side sealing device group 32 and the outlet side sealing device group 32 of the cooling zone 15. Thereby, the range between the inlet side sealing device group 32 and the outlet side sealing device group 32 provided with the cooling zone 15 in between is held in a state where the pressure device 41 is pressurized. become.

  Note that the atmosphere outside the pressurization range S1 is reduced in pressure by the operation of the pressurization device 41, so that the atmospheric gas is supplied from an unillustrated atmospheric gas supply source so that the pressure is maintained before and after the pressurization device 41 is operated. Is preferably supplied. In addition to this, the pressurizing device 41 may be constituted by a compressor and an atmospheric gas supply device 31 described later.

  Next, the effect of the annealing furnace 1 according to the present invention will be described.

  The annealing furnace 1 according to the present invention is configured such that the atmosphere within the range including the cooling zone 15 is pressurized, and the metal zone 3 made of refrigerant gas in a state where the cooling zone 15 is pressurized to a predetermined pressure or higher. Can be cooled. As a result, the refrigerant gas used for cooling is also pressurized and its density increases, so that the weight of the refrigerant gas sprayed per unit time increases, and the cooling capacity by the refrigerant gas increases. . For this reason, according to the annealing furnace 1 according to the present invention, the cooling capability is improved as compared with the conventional one while receiving the merit of the gas jet cooling method that enables stable cooling while eliminating the post-treatment of the oxide film. It is possible to make it. Moreover, since the size of the cooling zone 15 can be reduced by this, the furnace body 10 can be made compact. Further, when the annealing furnace 1 according to the present invention is used, the cooling capacity can be improved without greatly improving the performance of the gas jet cooling device 21.

  Incidentally, when the cooling capacity of the gas jet cooling device 21 is improved according to the present invention, a cooling method using a method of improving the cooling capacity by increasing the hydrogen concentration in the cooling gas as shown in Patent Document 4 is used. There is a merit that the effect of increasing the capacity is amplified like multiplication. For example, a cooling rate obtained by adjusting the hydrogen concentration with respect to the original cooling rate after increasing the cooling rate obtained by applying the present invention to 1.5 times the original cooling rate. The actual cooling rate can be increased to 2.25 times 1.5 × 1.5 of the original cooling rate by increasing the value to 1.5 times. .

  In addition, when pressurizing the cooling zone 15 of the furnace body 10 by the pressurizing device 41, the pressure in the cooling zone 15 is increased so that the pressure difference between the inside and outside of the furnace is larger than 0. In order to obtain an excellent effect of increasing the cooling rate by applying the above, it is preferable to pressurize so that the differential pressure between the inside and outside of the furnace is 9.8 kPa or more, and further about the effect of increasing the cooling rate. In order to obtain an excellent product, it is more preferable to pressurize so that the differential pressure between the inside and outside of the furnace is 19 kPa or more. Further, the upper limit value of the pressure of the cooling zone 15 for pressurization by the pressurizing device 41 is not particularly limited. For example, it may be set to less than 1 MPa from the viewpoint of avoiding application as a high-pressure gas. Good.

  Next, an annealing furnace 1 according to the second embodiment will be described. FIG. 4 is a side view schematically showing the configuration of the annealing furnace 1 according to the second embodiment. In addition, about the component same as the component mentioned above, the description below is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The annealing furnace 1 which concerns on 2nd Embodiment is comprised as what is used for a continuous hot dip plating line (CGL: Continuous Galvanizing Line). An annealing furnace 1 is provided with a hot dipping bath 51 on the outlet side. In the annealing furnace 1, a cylindrical snout 19 is provided on the outlet side of the furnace body 10, and the outlet side end portion 10 b of the furnace body 10, which is the end portion of the snout 19, is a hot dipping bath 53 of the hot dipping bath 51. Soaked in.

  When the annealing furnace 1 is used for CGL as in the second embodiment, the exit end 10b of the furnace body 10 is immersed in a liquid bath such as a hot dipping bath 53, so the exit side of the furnace body 10 is used. Without sealing, the exit side of the pressurization range S1 is hermetically sealed, and the airtightness of the exit side of the pressurization range S1 is maintained. Thus, in the present invention, when a part of the furnace body 10 is immersed in a liquid bath such as the hot dipping bath 53, the liquid that the sealing device 31 seals the inside of the furnace body 10 in an airtight manner. It may consist of a bath. As another example of the liquid bath for hermetically sealing a part of the furnace body 10, for example, when the metal strip 3 is water-quenched by a continuous annealing line (CAPL), the metal strip 3 is immersed and cooled. A coolant to be used.

  Next, an annealing furnace 1 according to the third embodiment will be described. FIG. 5 is a side view schematically showing the configuration of the annealing furnace 1 according to the third embodiment.

  The annealing furnace 1 according to the third embodiment is configured such that the pressurizing range S1 to be pressurized by the pressurizing device 41 includes other bands 11 and 13 other than the cooling band 15 of the furnace body 10. . Specifically, it is set as the structure which abbreviate | omitted the sealing apparatus 31 and the pressurization apparatus 41 which were provided in the entrance side of the cooling zone 15 in the annealing furnace 1 which concerns on 1st Embodiment, Instead, the annealing furnace 1 is used. A sealing device group 32 including a plurality of sealing devices 31 is provided on the entrance side of the heating zone 11. In this case, it is needless to say that the sealing device 31 and the pressurizing device 41 may be provided on the entry side of the cooling zone 15 without being omitted.

  Like the annealing furnace 1 according to the third embodiment, the range S1 to be pressurized by the pressurizing device 41 in the present invention is configured to be substantially the entire range of the furnace body 10 including the cooling zone 15. In this case, however, the entire furnace body 10 needs to have a pressure-resistant structure, which causes a significant cost increase. For this reason, like the annealing furnace 1 according to the first embodiment, it is preferable that only the cooling zone 15 is within the pressurizing range S1.

  Next, an annealing furnace 1 according to the fourth embodiment will be described. FIG. 6 is a side view schematically showing the configuration of the annealing furnace 1 according to the fourth embodiment.

  In the annealing furnace 1 according to the fourth embodiment, one of the pair of seal rolls 33 of the sealing device 31 according to the first embodiment is constituted by a transport roll 17 that guides the metal strip 3. Specifically, the sealing device 31 according to the fourth embodiment is opposite to the transport roll 17 with the transport roll 17 installed in the upper and lower portions of the cooling zone 15 of the furnace body 10 and the metal strip 3 interposed therebetween. A seal roll 33 installed on the side, and a pair of seal plates 35 that prevent leakage of the atmosphere between the seal roll 33 or the transport roll 17 and the furnace body 10 are provided.

  As in the annealing furnace 1 according to the fourth embodiment, when one of the pair of seal rolls 33 is composed of the transport roll 17, the plurality of seal rolls are spaced apart in the circumferential direction of the single transport roll 17. 33 and the seal plate 35 can be installed. Thereby, there is an advantage that the number of the seal rolls 33 and the number of drive mechanisms required to raise and lower the seal rolls 33 can be suppressed.

  As mentioned above, although the example of embodiment of this invention was demonstrated in detail, all the embodiment mentioned above showed only the example of actualization in implementing this invention, and these are the technical aspects of this invention. The range should not be construed as limiting.

  For example, the means for pressurizing the atmosphere in the pressurizing range S1 includes the atmospheric gas supply device 18 that supplies the pressurized atmospheric gas to the bands 11, 13, and 15 such as the cooling band 15 in the furnace body 10. May be. As a means for pressurizing the atmosphere in the pressurizing range S1, as in the first embodiment, a high pressure is applied by pressurizing the furnace atmosphere sucked from the low pressure side in the furnace body 10 with the sealing device 31 interposed therebetween. It is preferable to use what is discharged to the side because it is possible to pressurize the atmosphere in the pressurizing range S1 while suppressing an increase in the weight of the atmosphere gas to be supplied into the furnace.

  Hereinafter, the effects of the present invention will be further described with reference to examples.

FIG. 7 is a side view showing the configuration of the box body 61 used in this embodiment. In this embodiment, the test plain steel 4 having a thickness of 2 mm × 50 cm × 50 cm is disposed in a hollow box 61 in which the internal airtightness is maintained, and the atmospheric gas in the box 61 is A gas jet cooling device 21 used to circulate was installed. The box 61 was filled with an atmospheric gas in which 5% by volume is H ₂ and 95% by volume is N ₂ . As described in the first embodiment, the gas jet cooling device 21 sucks the atmospheric gas in the box 61 by the circulation blower 28 and then supplies the atmospheric gas from the circulation blower 28 to the cooling box 23. What was comprised so that it might spray on the normal steel 4 for a test from the nozzle 25 of the cooling box 23 was used.

In this embodiment, the pressure difference between the pressure inside the box 61 and the pressure outside the box 61 (atmospheric pressure) was changed to various conditions as shown in Table 1 below. In the gas jet cooling device 21, the rotational speed of the circulation blower 28 is adjusted in advance so that the spraying amount per unit area from the nozzle 25 at each pressure difference becomes 200 (m ³ / (min · m ² )). What was done was used. Further, in this example, the test ordinary steel 4 was energized and heated to 600 ° C. under conditions where the pressure difference was varied, and then the test ordinary steel 4 was heated to 400 ° C. by the gas jet cooling device 21. The time for cooling and the temperature of the atmospheric gas sprayed from the nozzle 25 when the ordinary test steel 4 was 600 ° C. and 400 ° C. were measured. In this embodiment, the heat transfer coefficient (kcal / m ² ) is divided by the logarithm average temperature difference of the measured atmospheric gas and the time, and the heat transfer coefficient (kcal / m ² ). kcal / (m ² · hr · ° C.) was calculated. Since the calculated heat transfer coefficient in each example represents the degree of the cooling rate, in evaluating the test result of each example, there is a pressure difference between the inside and outside of the box 61. The values of the heat transfer coefficients at 11 to 18 are No. The value obtained by dividing by the value of the heat transfer coefficient at 1 was defined as the rate of increase of the cooling rate, and evaluation was made based on the rate of increase of the cooling rate. The temperature of the atmospheric gas when the ordinary test steel 4 was 600 ° C. was set to 40 ° C. by cooling the atmospheric gas sucked by the circulation blower 28 by the heat exchanger 27. Further, as the measured value of the temperature of the atmospheric gas blown from the nozzle 25, the measured value of the temperature of the atmospheric gas in the cooling box 23 was used. The data on the heat content of the steel sheet is also described in “Report of the Japan Steel Association Thermal Economic Technology Subcommittee Heating Furnace Subcommittee, Heat Transfer Experiment and Calculation Method in Continuous Steel Heating Furnace, p.82-83, 1971”. Yes.

  The test results for each example are as shown in Table 1 above.

  Those satisfying the requirements of the present invention are No. 11-No. 18 examples. These are all No. A heat transfer coefficient higher than the heat transfer coefficient of 1 is obtained. From these examples, it can be confirmed that the cooling capacity can be improved by applying the present invention.

  Of these examples, No. 12-No. No. 18 is pressurized so that the differential pressure at static pressure is 9.8 kPa or more, the increase rate of the cooling rate is 5% or more, and an excellent effect of increasing the cooling rate is obtained. It has been. Of these examples, No. 13-No. No. 18 is pressurized so that the differential pressure at static pressure is 19 kPa or more, and the rate of increase of the cooling rate is 10% or more, and a further excellent effect of increasing the cooling rate is obtained. ing.

1: Annealing furnace 3: Metal strip 10: Furnace 10a: Carry-in entrance 10b: Outlet end 11: Heating zone 13: Soaking zone 15: Cooling zone 17: Conveying roll 18: Atmospheric gas supply device 19: Snout 21: Gas Jet cooling device 23: Cooling box 25: Nozzle 26: Suction side duct 27: Heat exchanger 28: Circulation blower 29: Discharge side duct 31: Seal device 32: Seal device group 33: Seal roll 35: Seal plate 41: Pressurizing device 51: Hot dipping bath 53: Hot dipping bath S1: Pressure range

Claims (8)

In an annealing furnace that cools the metal strip that is continuously conveyed in the cooling zone of the furnace body,
A gas jet cooling device that cools the metal strip by blowing a refrigerant gas in the cooling zone;
Sealing means provided on the entry side and the exit side of the range including the cooling zone in the furnace body;
An annealing furnace comprising: a pressurizing means for pressurizing the inside of the range including the cooling zone. The annealing furnace according to claim 1, wherein the pressurizing unit pressurizes the cooling zone so that a pressure difference between the inside and outside of the furnace becomes 9.8 kPa or more. The pressurizing means is a blower or a compressor that pressurizes an atmosphere in a furnace sucked from a low pressure side in the furnace body with the sealing means interposed therebetween and discharges the atmosphere toward the high pressure side. Or the annealing furnace of 2 description. The said pressurization means is an atmospheric gas supply apparatus which supplies atmospheric gas within the range containing the said cooling zone, and pressurizes the inside of the range containing the said cooling zone. An annealing furnace according to item. The annealing furnace according to any one of claims 1 to 4, wherein the sealing means is configured by a sealing member that is installed close to or in contact with the metal strip. A part of the furnace body is immersed in a liquid bath,
The annealing furnace according to any one of claims 1 to 5, wherein the sealing means includes the liquid bath that hermetically seals the inside of the furnace body. The sealing means is provided on the inlet side and the outlet side of the cooling zone in the furnace body,
The annealing furnace according to any one of claims 1 to 6, wherein the pressurizing unit pressurizes only the cooling zone. In the cooling method in the annealing furnace that cools the continuously conveyed metal strip in the cooling zone of the furnace body,
With respect to the furnace body provided with sealing means on the inlet side and the outlet side in the range including the cooling zone in the furnace body, the refrigerant gas is blown in the cooling zone in a state where the range including the cooling zone is pressurized. A cooling method in an annealing furnace, characterized by cooling a metal strip.

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