JPH0368720A - Method and device for cooling in air opened vertical type annealing furnace - Google Patents

Abstract

PURPOSE:To prevent the development of warp, fold, scratch, etc., and to execute cooling of a steel strip by restraining side-run of the steel strip passing through heating zone at slowly cooling zone, slowly cooling and arranging a cooling mechanism so that temp. distribution becomes uniform in the cooling zone. CONSTITUTION:The steel strip 10 heated in the heating zone 9 is introduced into the slow cooling zone X at lower part, and air for shielding from a nozzle 4 and high pressure air for buffering from a nozzle 6 are blown to the steel strip 10, respectively to execute the slow cooling having uniform temp. distribution in the width direction of steel strip 10. Then, air curtain is formed with the blowing air and also air cushion is formed between recessed part 6a in injection hole of the nozzle 6 and the steel strip 10 to restrain the side-run of steel strip 10. Successively, at the time of executing cooling by blowing the air for cooling to the steel strip 10 from plural slit-state nozzles 1a in divided chambers 1 in the cooling zone Y, the pressure of blowing air for cooling is made higher with blasting rate adjusting means 2a according to coming from center chamber 1ea to end part chamber 1ec to uniformize the temp. distribution in the width direction of steel strip 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides continuous annealing of steel strips such as stainless steel strips in an open-air vertical annealing facility (hereinafter simply referred to as an open-air vertical annealing furnace). When the steel strip heated in the heating furnace of the heating zone is forcibly cooled to almost room temperature, the steel strip warps in a C-shape or W-shape in the width direction, which is called canoeing, which occurs as a result of the cooling. The present invention relates to a cooling method in an open-air vertical annealing furnace that can prevent cooling wrinkles, etc., as well as the occurrence of scratches, and a cooling device for an open-air vertical annealing furnace suitable for carrying out this method. .

[Conventional technology]

Continuous annealing of steel strips such as cold-rolled stainless steel strips is carried out using an annealing equipment equipped with a heating furnace and a cooling zone (
Annealing furnace), but in particular, the heating zone and the cooling zone are arranged in the vertical direction, and the heat is heated in the heating zone.
Vertical annealing furnaces, in which the I-strip is cooled by passing it through a vertically downward cooling zone, are more efficient than annealing furnaces in which the steel strip is passed horizontally through the cooling zone, such as a guide roll. Since there is no need to provide anything to abut, scratches are less likely to occur, and the sheet passing speed can be increased, which improves productivity, so it has come to be widely used.

However, if a steel strip that has been heated during annealing is rapidly cooled, thermal distortion occurs and wrinkles such as streaks occur, and if the temperature distribution in the width direction of the steel strip becomes uneven during cooling, uneven thermal stress can occur. occurs and the steel strip warps due to low temperatures, resulting in C-type and W-shaped
If a phenomenon of deformation into the mold occurs, and if such deformation occurs, the convex part of the deformed steel strip and the cooling zone or the slow cooling zone placed between the heating zone and the cooling zone. When the distance between the inner wall surface and the steel strip narrows, and when air or water mist is sprayed to cool the steel strip in the cooling zone or slow cooling zone, the force becomes uneven, causing the steel strip to have a rough surface. There is a problem in that the steel strip comes into contact with the inner wall surface of the cooling zone or the slow cooling zone, causing scratches on the surface due to the occurrence of lateral vibration in the vertical direction and the combination of these causes.

A cooling method and apparatus for a conventional vertical annealing furnace open to the atmosphere will be explained with reference to FIGS. 7 and 8.

As shown in FIG. 7, in a conventional vertical annealing furnace open to the atmosphere, the steel strip 10 is first heated in a heating furnace 9 (hereinafter, this heating furnace may be referred to as a heating zone), and then a steel strip 10 is placed in an annealing zone in a vertically downward direction. The plate will be passed through. In order to block the influence of radiant heat from this slow cooling zone or the heating zone 9 that is open to the atmosphere, a lynchill 8 that has a built-in water cooling pipe and shielding air heated to about 200 to 300 degrees Celsius are blown onto the steel strip IO. The steel strip 10 is heated to a temperature of 700 to 900°C while forming an air curtain and cutting off the cooling zone Y, which will be described later.
A steel strip 10 that is threaded vertically downward is provided with a shielding air nozzle 4 that is slowly cooled to about 0°C and an intake port 4a that sucks the air that is injected from the shielding air nozzle 4 to form an air curtain. It had a structure in which they were arranged sequentially in the sheet threading direction. The steel strip 10 that has passed through this slow cooling * It consists of a divided chamber 1 in which a plurality of horizontal slit-shaped nozzles Ia are vertically arranged in a chamber body divided by a plurality of partition plates provided symmetrically and parallel to this line. In order to control the amount of cooling air supplied to the chamber body, each chamber 1 is divided vertically.
A damper is provided that adjusts every ea, leb, and 1ec, and the steel strip 10 that has been annealed in the annealing zone X is passed through this cooling zone Y and cooled air is blown from each divided chamber. Make all the amounts equal or steel strip 1
Since the ends of the steel strip IO are cooled relatively faster than the center, the temperature distribution in the width direction of the steel strip IO can be made uniform by adjusting the amount in the center chamber 1ea to be larger than that in the end chambers lec. It was an attempt to achieve this.

However, when the steel strip 10 heated in the heating zone 9 open to the atmosphere is cooled by such a cooling method, the steel strip 10
Since the distribution of the amount of cooling air blown from the divided chamber 1 in the cooling zone Y in the width direction is always equal from the upper end to the lower end of the cooling zone Y, the upper end side is where the temperature of the steel strip 10 is high and it is easily deformed. The steel strip 10 is cooled with the same cooling capacity as the lower end side, which has been cooled to a relatively low temperature and is difficult to deform. For this reason, the whole must be cooled while reducing the cooling capacity to such an extent that the steel strip IO does not deform at the upper end of the cooling zone Y, that is, to the extent that large thermal distortions do not occur.This becomes a bottleneck for the overall cooling. The drawback was that the threading speed was slow and the production efficiency was low. Furthermore, if the amount of cooling air blown is adjusted as described above in order to make the temperature distribution of the steel strip 10 uniform in the width direction, the total amount of cooling air blown onto the steel strip 10 in the cooling zone Y will be As a result, the cooling rate differs greatly in the width direction of the steel strip 10, and as a result, the portion where the total amount of cooling air blown in the width direction of the steel strip 10 is small has a slow cooling rate, so this portion forms a vertical stripe. It has the disadvantage that it stretches and wrinkles occur. Furthermore, since the cooling air blown onto the steel strip 1O convects on the surface of the steel strip 10 without directionality, the temperature distribution on the threaded surface of the steel strip 10 cannot be uniform. Therefore, uneven thermal stress is generated on both sides of the steel strip 10, causing the steel strip to warp toward the lower temperature side and deform into a C-shape or W-shape.

Furthermore, the steel strip 10 is blown with shielding air in the slow cooling zone X and cooling air in the cooling zone Y, but the pressure of these air is relatively low, and the steel strip 10 is The steel strip 10 cannot be completely restrained, and as a result, lateral vibration occurs in the steel strip 10 in a direction perpendicular to the strip passing surface, causing damage not only to the aforementioned inner wall surfaces but also to the shielding air nozzles of the divided chamber 1 of the cooling zone Y and the air nozzle of the slow cooling zone X. It also had the disadvantage of causing scratches when it came into contact with the 4th grade.

[Problem to be solved by the invention]

The present invention eliminates the drawbacks of the prior art, and reduces the difference in cooling rate in the width direction of the steel strip heated in the heating zone of a vertical annealing furnace open to the atmosphere, thereby making the temperature distribution uniform. To provide a cooling method in an open-air vertical annealing furnace that can produce excellent annealed products free of W-shaped or W-shaped deformations, wrinkles, and even scratches, and that has excellent production efficiency, and a cooling device suitable for carrying out the method. The challenge is to provide.

[Means to solve the problem]

As a result of various studies, the inventors of the present invention have found that an air cushion is formed in which warmed, high-pressure buffer air is blown into the slow cooling zone between the heating zone and the cooling zone to suppress the lateral vibration of the steel strip being annealed. The cooling air blown onto the steel strip in the cooling zone is forced to convect in the width direction, and the conditions of this cooling air blowing are adjusted sequentially from the top to the bottom of the cooling zone, thereby controlling the cooling rate of the steel strip. The present invention was completed by discovering that the above problem can be solved by reducing the difference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a cooling method and apparatus for an open-air vertical annealing furnace according to the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory side view showing an embodiment of a device for carrying out the cooling method in an open-air vertical annealing furnace according to the present invention, FIG. 2 is an explanatory enlarged cross-sectional view taken along the line A-A in FIG. 1, FIG. 3 is a front explanatory view showing the divided chamber shown in FIG. 2;
Fig. 4 is an explanatory diagram showing an example of the buffer air nozzle shown in Fig. 1, and Fig. 5 is an explanatory diagram showing the circulation path of air sucked from the intake port in the slow cooling zone shown in Fig. 1. , FIG. 6 is a diagram showing the distribution of the amount of cooling air blown onto the steel strip in the method of the present invention.

First, a cooling method in an open-air vertical annealing furnace according to the present invention will be explained.

In the method of the present invention, a steel strip heated in an open-air heating furnace (heating zone) of an open-air vertical annealing furnace is cooled by passing it sequentially through an annealing zone and a cooling zone toward the downstream side. be.

That is, in the slow cooling zone, the heating zone and the cooling zone are separated by an air curtain formed by blowing shielding air warmed to about 200 to 300 degrees Celsius onto the steel strip. The air cushion, which is formed by blowing high-pressure buffer air warmed to around 300°C onto the steel strip, suppresses the lateral deflection of the steel strip in the direction perpendicular to the steel strip threading surface and maintains the strip threading surface. At the same time, air is taken in at least both above and below the heating zone side of the air curtain and the downstream side of the air cushion to reliably isolate the heating zone and the cooling zone. At this time, it is preferable to prevent outside air, that is, unheated air, from mixing with the intake air, causing the steel strip to cool rapidly and significantly disturbing the uniformity of the temperature distribution in the width direction of the steel strip. Gradual cooling is performed using only shielding air and buffer air.

Next, in the cooling zone, the cooling air to be blown onto the steel strip is taken in from both sides in the width direction of the steel strip with the steel strip in between, and the chamber body for supplying the cooling air to be blown onto the steel strip is installed in an ALS. A horizontal slit-shaped nozzle that is divided into an odd number of symmetrical chambers each having at least a central chamber and an end chamber by a partition plate provided in a V-shape symmetrically along a vertical line corresponding to the center in the width direction. are formed in a plurality in the vertical direction, and a sixth
As shown in the figure, the cooling air is blown from the central chamber to the end chambers so that the difference in cooling rate in the width direction of the steel strip is reduced and the temperature distribution in the width direction of the steel strip is made as uniform as possible. It is cooled to do so. At this time, cooling may be performed by spraying a mist of cooling water at the same time as blowing cold ready air.In this case, the amount of spraying of the mist of cooling water depends on the thickness of the steel strip to be threaded and the threading speed. It is preferable to adjust the amount, and spray the amount more toward the lower end of the chamber. However, the steel strip has a wall thickness of 0.
In the case of an ultra-thin steel strip of 4 m or less, it is preferable to cool it only with cooling air.

Next, a cooling device for an atmospherically open vertical annealing furnace according to the present invention, which is suitable for implementing the cooling method for an atmospherically open vertical annealing furnace according to the present invention, will be described.

In the drawings, FIGS. 1 to 3, reference numeral 1 denotes a central partition plate 1da provided in a V-shape symmetrically with respect to a vertical line corresponding to the center in the width direction of the steel strip 10 that is threaded vertically downward. This central chamber 1ea is further divided by a central partition plate 1d.
It is a divided chamber divided into an odd number of left-right symmetrical chambers having at least an end chamber 1ec divided by an outer partition plate 1db, and the divided chamber 1 is divided into an odd number of left-right symmetrical chambers. A plurality of horizontal slit-shaped nozzles 1a are formed in the vertical direction.

It is preferable that this slit-shaped nozzle la is formed in such a manner that the jetting port protrudes toward the steel strip 10 side, and that a groove-shaped recess IC is formed between the jetting ports arranged vertically at a position avoiding this jetting port. . The divided chamber 1 further includes one or more intermediate chambers l between the central chamber 1ea and the end chambers 1ec.
eb may be provided, and this intermediate chamber leb
If the central partition plate 1da is provided with an outer partition plate 1db substantially parallel to the central partition plate 1da, an outer partition plate 1db is provided on each end chamber 1ec side of the central partition plate 1da. Furthermore, as shown in FIG. 3, water spray nozzles lb for cooling are provided in the divided chamber 1 at predetermined intervals in the vertical and horizontal directions at positions in the upper and lower groove-shaped recesses 1c, avoiding the horizontal slit-shaped nozzles 1a. is desirable. Reference numeral 2 denotes a cooling air supply pipe that supplies cooling air to the divided chamber 1, and the cooling air supply pipe 2 supplies cooling air to the central chamber 1ea and the end chamber l.
Air volume adjusting means 2a for adjusting the amount of cooling air to be supplied to ec and, if an intermediate chamber leb is provided, to the intermediate chamber lab is provided for each chamber, and this air volume adjusting means 2a For this purpose, a damper may be used. In this case, independent cooling air supply sources may be used as the supply sources to the cooling air supply pipe 2 that supplies cooling air to the air volume adjusting means 2a.
As shown in FIG. 2, one cooling air supply source (not shown) supplies its supply pipe 2 to each chamber 1ea, 1ec,
1ec and 1ec are connected to each other via the air volume g1m means 2a, which is a simple structure and preferred from the viewpoint of air volume adjustment control. Reference numeral 3 denotes an exhaust duct having intake ports arranged on both sides of the divided chamber 1 with the steel strip 10 to be cooled in between, and this exhaust duct 3 corresponds to the groove-shaped recess 1c formed in the divided chamber 1. However, it is preferable to have an intake port corresponding to the entire vertical length of the divided chamber 1, and furthermore, an adjustment means is provided to equalize the suction force on both sides. This is desirable. For example, this adjusting means may include providing an exhaust volume adjusting means (not shown) in the exhaust outlet path from the exhaust duct 3, or controlling the rotation speed of an exhaust blower (not shown) on both sides. All you have to do is adjust the exhaust volume and suction power. 4 is installed between the heating zone 9 and the cooling zone Y, which are open to the atmosphere, and directs the shielding air heated to about 200 to 300 degrees Celsius toward the steel strip IO. The shielding air nozzle 4 is a shielding air nozzle that blows air out to shut off the heating zone 9 and its downstream side with an air curtain. It is preferable that the groove be formed, and it is further preferable that the width corresponds to the entire width of the steel strip 10 to be threaded. As shown in Figures 1 and 5, 5
is a shielding air circulation duct which is provided with an intake port 5c at least closer to the heating zone 9 than the shielding air nozzle 4, and supplies the shielding air sucked from the intake port 5c to the shielding air nozzle 4; A blower 5a is provided in the middle of the shielding air circulation duct 5, and a damper 5b is preferably provided for introducing outside air into the circulation duct 5 to adjust the temperature of the circulating air. Figure 1,
As shown in FIGS. 4 and 5, 6 is a shielding air nozzle 4.
Buffer air heated to about 200 to 300°C with high pressure is blown toward the steel strip 10 between the cooling zone Y and the cooling zone Y to form an air cushion, which causes the steel strip to pass in a direction perpendicular to the threading surface. This is a buffering air nozzle for suppressing the lateral vibration of the steel strip 10 and maintaining and restraining the steel strip passing surface as much as possible, and this buffering air nozzle 6 is compatible with the entire width of the steel strip IO as shown in Fig. 4. A recess 6 is provided between the spout ports at a slight angle inward with an interval such that the spout ports are vertically spaced apart from each other.
It is desirable that a is formed. 7, as shown in FIGS. 1 and 5, an intake port 7c is provided at least on the cooling zone Y side from the buffer air nozzle 6, and buffer air taken in from this intake port 7c is supplied to the buffer air nozzle 6. This buffer air circulation duct 7 is provided with a blower 7a in the middle like the shielding air circulation duct 5.
It is preferable that a damper 7b is provided to adjust the temperature of the circulating air by introducing outside air into the air. Reference numeral 8 is a lynchill having a built-in water cooling pipe. The heating zone 9 is provided between the heating zone 9 that is open to the atmosphere and the shielding air nozzle 4 and closer to the heating zone 9 than the intake port 5c of the shielding air circulation duct 5.

[For production]

The cooling device suitable for carrying out the cooling method in the atmosphere-open vertical annealing furnace according to the present invention having the above-described structure operates as follows.

First, in the slow cooling zone X, shielding air from the shielding air nozzle 4 and high-pressure buffering air from the buffering air nozzle 6 are respectively blown onto the steel IIO to slowly cool it. That is, since both the shielding air and the buffer air are warmed, rapid cooling of the steel strip 10 can be prevented and gradual cooling can be performed without disturbing the uniformity of temperature distribution in the width direction of the steel strip 10. On the other hand, the former shielding air is blown slightly downward from the vertical direction of the steel strip 10 running surface to form an air curtain, thus shielding the air flowing from the downstream side to the upstream side. Since the buffer air forms an air cushion between the steel strip 10 and the concave portion 6a formed between the jet ports of the buffer air nozzle 6, the buffer air flows in a direction perpendicular to the threading surface of the steel strip 10. Lateral vibration of the steel strip 10 is suppressed. Inlet ports 5c and 7c are provided on the heating furnace 9 side of the shielding air nozzle 4 and on the cooling zone Y side of the buffering air nozzle 6.
This prevents outside air from entering the air curtain and cooling air from entering the air cushion.Furthermore, an intake port 5c or 7c is provided between the shielding air nozzle 4 and the buffering air nozzle 6. This prevents the air curtain and the air cushion from interfering with each other, and in particular, it is possible to prevent the air cushion from being affected by the shielding air that forms the air curtain. In this way, the intake port 5
The shielding air and buffer air sucked from c and 7c are passed through the shielding air circulation duct 5 and the buffering air circulation duct 7.
is provided, the dampers 5b and 7b provided in the middle of each circulation duct 5 and 7 supply outside air with an adjusted amount into each circulation duct 5 and 7, and the temperature is adjusted to a predetermined temperature. It is used again while being circulated as shielding air or buffering air.

The steel strip 10 that has been slowly cooled to about 700 to 900°C through the slow cooling zone X as described above is then blown with cooling air (cooling air and mist may be used together) in the cooling zone Y. and cooled to near room temperature.

That is, by sucking and exhausting the cooling air blown onto the steel strip 10 from the exhaust duct 3, the cooling air is transferred to the steel strip 1.
It is possible to maintain a state in which convection is forced in the width direction of 0. As shown in FIG. 6, in this state, the pressure of the cooling air blown from the slit-shaped nozzle Ia of the divided chamber 1 of the cooling zone Y is increased from the central chamber 1ea to the end chambers lec by the air volume adjusting means 2a. The slit-shaped nozzle 1a of the divided chamber 1
The amount of cooling air per unit area blown out from the jet ports increases from the central chamber 1ea to the end chambers 1ec. Therefore, in this type of blowing, a part of the cooling air blown from the end chamber lec, which has been adjusted in quantity, does not directly contribute to the cooling of the steel strip 10, but instead flows into the divided chambers with the steel strip 10 in between. In reality, the cooling air blown from the central chamber 1ea and a part of the cooling air blown from the end chambers 1ec. contributes to the cooling of the steel strip 10, so the amount of cooling air blown out from the divided chamber 1 is equal to the amount of cooling air blown from the central chamber 1ea that flows along the steel strip 10 above the cooling zone Y. The steel strip 1 is cooled slowly due to the small amount of
Rapid cooling is caused by the large amount of cooling air blown from the central chamber 1ea that flows along the central chamber 1ea.

[Effects of the Invention] As described in detail above, the cooling method and device for an open-air vertical annealing furnace according to the present invention has a divided chamber formed by a partition plate provided in a V-shape, so that steel strips can be cooled easily. In addition to making the cooling rate uniform in the width direction, the cooling rate gradually increases from the top to the bottom of the cooling zone after being slowly cooled in the slow cooling zone, making the steel strip thinner. Even when the sheet is cooled, the sheet can be cooled without causing any deformation or wrinkles, and as a result, the sheet threading speed can be increased, which improves production efficiency.

That is, the amount of cooling air blown out from the divided chambers of the cooling zone is adjusted to increase from the central chamber to the end chambers, and the @51 force on both sides is adjusted by exhaust ducts provided on both sides of the divided chambers. #RT in the width direction of the steel strip as it is suctioned and exhausted.
Since the temperature distribution of r can be made uniform, wrinkles due to uneven temperature distribution do not occur.

Furthermore, when the horizontal slit-shaped nozzle of one divided chamber is formed in a protruding state, the cooling air blown onto the steel strip does not convect in the vertical direction and the cooling air flows above and below the slit-shaped nozzle. It flows into the groove-shaped recess formed between the aligned spout ports, reduces the flow velocity, travels along the surface of the steel strip, and is forced to convect on both sides of the steel strip in the width direction, thereby increasing the temperature from the center to the ends of the strip in the width direction. Since the difference in cooling rate can be made smaller, the difference in cooling rate in the width direction of the steel strip can be made smaller, so C that occurs when the difference in cooling rate is large can be reduced.
This can prevent deformation of the shape or W shape.

By blowing high-pressure buffer air onto the steel strip in the slow cooling zone to form an air cushion, the lateral vibration of the steel strip can be suppressed and the occurrence of scratches can be prevented.

The cooling method and apparatus for an open-air U-type annealing furnace according to the present invention, which have various advantages as described above, will greatly contribute to the field of steel manufacturing.

[Brief explanation of drawings]

FIG. 1 is an explanatory side view showing one embodiment of a device for carrying out the cooling method in an open-air vertical annealing furnace according to the present invention, FIG. 2 is an explanatory enlarged cross-sectional view taken along the line A-A in FIG. 1, FIG. 3 is a front explanatory view showing the divided chamber shown in FIG. 2;
Fig. 4 is an explanatory diagram showing an example of the buffer air nozzle shown in Fig. 1, and Fig. 5 is an explanatory diagram showing the circulation path of air sucked from the intake port in the slow cooling zone shown in Fig. 1. , FIG. 6 is a diagram showing the distribution of the amount of cooling air blown onto the steel strip in the method of the present invention, FIG. 7 is an explanatory side view showing the conventional device, and FIG.
This figure is a front view showing the divided chamber shown in FIG. 7. In the drawings 1...Divided chamber 1a...Slit-shaped nozzle 1b...Water spray nozzle lc...Groove-shaped recess 1da...Central partition plate ldb...Outer partition plate 1ea... ... Central chamber leb ... Intermediate chamber 1ec ... End chamber 2 ... Cooling air supply pipe 2a ... Air volume 'IJRM means 3 ... Exhaust duct 4 ... -Shielding air nozzle 5...Shielding air circulation duct 5a...Blower 5b...Damper 5c...Intake port 6...Buffering air nozzle 6a...Recess 7 ...Buffer air circulation duct 7a ...Blower 7b ...Damper 7c ...Intake port 8 ...Lynchill 9 ...Heating furnace (heating zone) IO ... Steel strip

Claims (1)

[Scope of Claims] 1. Air that is formed by blowing shutoff air warmed below the heating zone onto a steel strip that is heated in a heating zone of an open-air annealing furnace and passed vertically downward. The heating zone and its downstream side are shut off by a curtain, and the steel strip is cooled by an annealing zone which gradually cools the steel strip, and a cooling zone which blows cooling air onto the slowly cooled steel strip to cool the steel strip. At this time, in the slow cooling zone, warmed buffer air with high pressure is blown onto the steel strip on the downstream side of the air curtain to form an air cushion while air is being taken in at least on both upper and lower sides of the slow cooling zone. to suppress the lateral deflection of the steel strip in a direction perpendicular to the steel strip passing surface, and in the cooling zone, the steel strip is formed in a V-shape symmetrically with respect to a vertical line corresponding to the center of the width direction of the steel strip. Both sides of a divided chamber that is divided by a partition plate into an odd number of symmetrical chambers each having at least a central chamber and an end chamber, and in which a plurality of horizontal slit-shaped nozzles are vertically formed. The difference in cooling rate in the width direction of the steel strip is reduced by increasing the amount of cooling air blown from the slit-shaped nozzle from the central chamber to the end chambers while taking in air. A cooling method in a vertical annealing furnace open to the atmosphere, characterized by cooling the steel strip with uniform temperature distribution in the width direction. 2. The cooling method in a vertical annealing furnace open to the atmosphere according to claim 1, wherein a mist of cooling water is sprayed in combination with cooling air in the cooling zone. 3. The cooling method in a vertical annealing furnace open to the atmosphere according to claim 1 or 2, wherein the slow cooling zone is slowly cooled in a state where low temperature outside air does not enter the slow cooling zone. 4 An atmosphere-open type slow cooling zone (X) that blows warmed blocking air onto a steel strip (10) heated in an atmosphere-open type heating furnace (9) and passed vertically downward, and said steel strip ( In a cooling device for an air-open vertical annealing furnace in which air-open cooling zones (Y) for blowing cooling air onto the steel strip (10) are sequentially arranged in the threading direction of the steel strip (10), X)
A shielding air nozzle (4) is provided for injecting warmed shielding air to form an air curtain, and a high pressure warmed buffer air is injected below the shielding air nozzle (4). A buffering air nozzle (6) for injecting air to form an air cushion is provided, and at least the heating furnace (9) of the shielding air nozzle (4) is provided.
) side and the cooling zone (Y) side of the buffer air nozzle (6), intake ports (5c, 7c) are arranged, and the cooling zone (Y)
At least a central chamber (1ea) and an end chamber (1ec) are separated by a partition plate (1da) provided in a V-shape symmetrically with respect to a vertical line corresponding to the center of the width direction of the steel strip (10). A plurality of horizontal slit-shaped nozzles (1a) are formed in the vertical direction to inject cooling air in the chambers toward the steel strip (10). a divided chamber (1), and an air volume adjustment means (2a) provided for each chamber of the divided chamber (1) for adjusting the amount of cooling air supplied from the cooling air supply pipe (2); Steel strip (1
1. A cooling device for a vertical annealing furnace open to the atmosphere, comprising: exhaust ducts (3) provided on both sides of the divided chamber (1) with the spacer (0) in between. 5 Shielding air nozzle (4) and buffering air nozzle (6)
5. The cooling device for an air-open vertical annealing furnace according to claim 4, wherein an air intake port (5c) or (7c) is provided between the cooling device and the air-opening vertical annealing furnace. 6 At least from the shielding air nozzle (4) to the heating furnace (9
) A shielding air circulation duct (5) is provided for supplying air drawn from the intake port (5c) provided on the side to the shielding air nozzle (4).
A cooling device for the atmospheric open vertical annealing furnace described in . 7 At least from the buffer air nozzle (6) to the cooling zone (Y
Claims 4 to 6, further comprising a buffer air circulation duct (7) for supplying air drawn from the intake port (7c) provided on the ) side to the buffer air nozzle (6).
A cooling device for an open-air vertical annealing furnace according to any one of the preceding items. 8. Claims 4 to 7, wherein water spray nozzles (1b) are provided at predetermined intervals vertically and horizontally at positions avoiding the slit-shaped nozzles (1a) formed in a plurality in the horizontal direction of the divided chamber (1). A cooling device for an open-air vertical annealing furnace according to any one of the above. 9 A plurality of slit-shaped nozzles (1a) formed in the horizontal direction of the divided chamber (1) are formed in a protruding state, and a groove-shaped recess (1c) is formed at a position avoiding the slit-shaped nozzles (1a). A cooling device for an atmospherically open vertical annealing furnace according to any one of claims 4 to 8.