JP7601128B2 - Method for cooling coiled steel sheet, method for manufacturing coiled steel sheet, and cooling equipment for coiled steel sheet - Google Patents

Description

Embodiments of the present invention relate to a method for cooling coiled steel sheets, a method for manufacturing coiled steel sheets, and equipment for cooling coiled steel sheets.

When manufacturing coiled steel sheet, hot rolling or cold rolling is carried out. For example, when manufacturing hot-rolled steel sheet, a slab is first heated to a predetermined temperature in a heating furnace, and the heated slab is rolled in a rough rolling mill to form a rough bar. This rough bar is then passed through a continuous hot finishing rolling mill consisting of multiple rolling stands to form a hot-rolled steel sheet of a predetermined thickness.

The hot-rolled steel sheet that leaves the continuous hot finishing rolling mill is cooled with cooling water supplied from above and below the cooling device installed on the run-out table, and then wound up by a winding machine to become a coiled hot-rolled steel sheet. It is then stored in this state.

On the other hand, in the case of cold-rolled steel sheets, the hot-rolled steel sheets coming out of the continuous hot finishing mill go through various processes such as pickling, annealing, and cold rolling to become cold-rolled steel sheets. The cold-rolled steel sheets are then wound up on a winding machine to become coiled cold-rolled steel sheets. Such coiled cold-rolled steel sheets are also stored in this state.

In this way, various steel sheets are wound up into coils for storage. Incidentally, the temperature of various steel sheets in this wound state is, for example, 500-650°C in the case of coiled hot-rolled steel sheets, and below this temperature in the case of coiled cold-rolled steel sheets. However, they cannot be shipped or sent to the next process in this temperature state. Therefore, they are cooled to room temperature in the coil storage area where these coiled steel sheets are kept (hereinafter, such storage areas will be referred to as "cooling beds" as appropriate) before being transported and shipped.

A large amount of coiled steel plates are placed on the cooling bed and cooled. This means that other coiled steel plates at similarly high temperatures are placed around the hot coiled steel plates. In this case, the temperature around each coiled steel plate is therefore high. This reduces the cooling efficiency of the coiled steel plates, and it may take, for example, 3 to 5 days to complete the cooling of the coiled steel plates.

As a result, the area required to store the coiled steel sheets as a cooling bed must be large. In addition, because it takes time to cool, the time it takes to ship the coiled steel sheets increases. Furthermore, the time it takes to cool leads to problems such as a lack of space to store the coils in the cooling bed and an increase in coil inventory.

In order to shorten the cooling time of coiled steel sheets, various methods have been proposed for spraying cooling water onto the coiled steel sheets. However, when cooling water is sprayed onto the coiled steel sheets when the surface temperature of the coiled steel sheets is below 100°C, such as in the case of coiled cold-rolled steel sheets, the cooling water does not evaporate easily. As a result, the surface of the coiled steel sheets becomes wet with water, and if left as is, rust may form on the surface.

If rust occurs on the coiled steel plate, it will impair its appearance and the coiled steel plate will not be able to be shipped as a product. Even if cooling water is not sprayed, condensation may form on the coiled steel plate, especially during the cold seasons from winter to early spring, which may lead to rust.

The following Patent Documents 1 to 4 disclose various methods for cooling steel sheets. For example, as in the technology described in Patent Document 1, a water-cooling method for hot-rolled coils is proposed in which the temperature and humidity around the coil are measured and the amount of cooling water sprayed to cool the coil is controlled to prevent the surface of the hot-rolled steel sheet that constitutes the coil from getting wet.

Meanwhile, the technology described in Patent Document 2 also proposes a method of cooling hot-rolled coils in which cooling nozzles are placed on both end faces of each coil in the width direction, and cooling is performed from both sides using the respective cooling nozzles.

Furthermore, as in the technology described in Patent Document 3, a method for cooling a coiled hot-rolled steel sheet has also been proposed in which cooling is performed by intermittently spraying cooling mist onto both widthwise ends of the coiled steel sheet after it has been wound by a winding machine installed in a hot rolling line.

The technology described in Patent Document 4 involves cooling a metal coil after it has been wound by a winding machine installed on a hot rolling line, in which mist is sprayed from a mist nozzle onto a filter installed at the inlet of a duct. In this case, the filter prevents the mist from entering the duct, and a blower mixes the mist with outside air and blows the moist air onto the coil to cool it.

Japanese Unexamined Patent Publication No. 57-134207 Japanese Patent Application Publication No. 5-177240 JP 2013-188753 A JP 2011-167736 A

However, the water-cooling method for hot-rolled coils described in Patent Document 1 sprays cooling water onto the coils from the ceiling of the coil storage area, which is far away from the coils. This reduces the coil cooling capacity, and there is a problem in that the coils cannot be cooled efficiently.

In addition, the water-cooling method for hot-rolled coils described in Patent Document 2 only uses one cooling nozzle on each of the widthwise end faces of a single hot-rolled coil. As a result, the minute droplets coming out of the cooling nozzles (hereinafter, such "minute droplets" will be referred to as "mist" as appropriate) do not spread sufficiently over both widthwise end faces of the hot-rolled coil. In other words, since the cooling area is small, it is difficult to cool the entire hot-rolled coil. As a result, the water-cooling method for hot-rolled coils described in Patent Document 2 has the problem of reduced coil cooling efficiency.

Here, in order to improve the cooling capacity for the coiled steel plate, it is important to increase the mist spray flow rate per unit area (hereinafter referred to as "water volume density" where appropriate). However, if the water volume density is increased, the mist becomes difficult to evaporate due to factors such as an increase in humidity around the coiled steel plate and a decrease in the temperature of the coil surface.

As a result, the mist that does not evaporate is likely to adhere to the coil. In particular, when the surface temperature of the coiled steel sheet is below 100°C, the mist that adheres to the coil is unlikely to evaporate, and the coil surface is likely to remain wet, which may induce rust.

To prevent the coil surface from getting wet during water cooling, it is believed that using mist with a small particle size is effective. This is because mist with a smaller particle size requires less heat to evaporate, making it easier to evaporate.

On the other hand, if the particle size of the mist is reduced, it is possible that the mist will be dispersed by the influence of the wind around the coiled steel sheet, and the mist will be more likely to miss the coiled steel sheet that is the target for cooling. In addition, the spray distance from the mist nozzle to the coil will be shortened, which raises the problem that the sprayed mist may not even reach the coiled steel sheet in the first place.

The cooling method for coiled hot-rolled steel sheet described in Patent Document 3 constantly sprays cooling mist from a mist nozzle onto the coiled steel sheet. At the same time, the method also uses an oscillating blower to carry the cooling mist on an air current and intermittently blow it onto the widthwise ends of the coiled steel sheet.

However, even with this method, there is a possibility that the coiled hot-rolled steel sheet may not be cooled properly due to the problems mentioned above. Moreover, this may actually lead to an increase in the humidity in the surrounding area other than the coiled steel sheet being cooled. In particular, condensation occurs in the coil once cooling is complete using the above-mentioned method for cooling the coiled hot-rolled steel sheet, increasing the risk of rust occurring in the coil.

In addition, in the metal coil cooling method described in Patent Document 4, the mist reaches the metal coil through a filter, but depending on the particle size of the mist, the mist does not evaporate sufficiently and water or the like adheres to and condenses on the filter, leaving it wet. In addition, the cooling bed may be humidified by passing air through a wet filter.

Furthermore, the heat of vaporization of the mist lowers the air temperature, making it humid and cold, increasing the risk of condensation inside the duct and on the coil surface. It is true that humidity and temperature measurements are taken and the mist nozzle is controlled on and off based on those measurements, but the filter may get wet even after mist spray from the mist nozzle has stopped, so the control response is poor and the risk of condensation cannot be sufficiently suppressed.

In addition, if the duct is long and the route is complicated, humidity distribution will occur within the duct, making humidity control complicated. For this reason, ducts through which moist air passes require anti-rust treatment, which requires a high level of installation and maintenance work.

The present invention has been made with a focus on the above-mentioned points, and aims to provide a method for cooling coiled steel plate, a manufacturing method for coiled steel plate, and a cooling equipment for coiled steel plate that can simultaneously suppress wetting of the surface of the coiled steel plate and improve the cooling capacity of the coiled steel plate, prevent rust from forming on the coiled steel plate, and allow the coiled steel plate to be cooled with high efficiency.

A method for cooling a coiled steel plate in an embodiment of the present invention comprises: (1) a step of spraying cooling mist using a cooling mist generator arranged indoors; and a step of a cooling fan sucking in air cooled by evaporation of the cooling mist sprayed by the cooling mist generator and blowing it onto the coiled steel plate placed on the cooling bed, the cooling mist generator being arranged behind the direction of air blown by the cooling fan at a distance corresponding to the particle diameter of the cooling mist .

In addition, in the above-mentioned (1) coiled steel sheet cooling method in the embodiment of the present invention, (2) the particle diameter of the cooling mist sprayed by the cooling mist generator is 40 μm or less.

Furthermore, in the above-mentioned (1) or (2) coiled steel sheet cooling method in the embodiment of the present invention, (3) after the step of the cooling fan blowing air onto the coiled steel sheet, the step of exhausting the air around the coiled steel sheet, including the gas blown onto the coiled steel sheet by the cooling fan, to the outside of the cooling bed is provided.

The coiled steel sheet cooling method according to the above (1) to (3) in the embodiment of the present invention also includes a step of (4) providing a measuring device that detects the state of both or either of the coiled steel sheet and the cooling bed, and controlling both or either of the cooling mist generator and the cooling fan based on the conditions measured by the measuring device.

The coiled steel sheet manufacturing method according to the above (1) to (4) in the embodiment of the present invention includes (5) a step of spraying cooling mist by a cooling mist generator, and a step of sucking in air cooled by evaporation of the cooling mist sprayed by the cooling mist generator and blowing the air to the coiled steel sheet placed on the cooling bed by a cooling fan, and the cooling mist generator has a method of cooling the coiled steel sheet arranged behind the direction of air blown by the cooling fan to the coiled steel sheet.

The manufacturing method of coiled steel sheet (5) in the embodiment of the present invention is characterized by manufacturing (6) hot-rolled steel sheet or cold-rolled steel sheet.

The cooling equipment for the coiled steel plate in the embodiment of the present invention (7) is arranged indoors and comprises a cooling mist generator which sprays cooling mist, and a cooling fan which sucks in air cooled by the evaporation of the cooling mist sprayed by the cooling mist generator and blows it onto the coiled steel plate placed on the cooling bed, and the cooling mist generator is arranged behind the direction of air blown by the cooling fan towards the coiled steel plate at a distance according to the particle diameter of the cooling mist .

In addition, in the coil steel sheet cooling equipment of the embodiment of the present invention described above in (7), the particle diameter of the cooling mist sprayed by the cooling mist generator (8) is 40 μm or less.

Furthermore, the coiled steel plate cooling equipment of (7) or (8) in the embodiment of the present invention includes (9) an exhaust device that exhausts the air around the coiled steel plate, including the gas blown to the coiled steel plate by the cooling fan, out of the cooling bed.

The coiled steel sheet cooling equipment described in any one of (7) to (9) above in the embodiment of the present invention (10) further includes a measuring device that detects the state of both the coiled steel sheet and the cooling bed, or either one of them.

The coiled steel sheet cooling equipment described in any one of (7) to (10) above in the embodiment of the present invention is characterized in that it is equipped with a control device that controls both the cooling mist generator and the cooling fan, or either one of them, based on the conditions measured by the measuring device (11).

The coiled steel sheet cooling method, coiled steel sheet manufacturing method, and coiled steel sheet cooling equipment according to the embodiments of the present invention make it possible to simultaneously suppress wetting of the surface of the coiled steel sheet and improve the cooling capacity of the coiled steel sheet, preventing rust from forming on the coiled steel sheet and enabling the coiled steel sheet to be cooled with high efficiency.

FIG. 2 is a perspective view showing an entire building in which the coiled steel plate is cooled in the embodiment of the present invention. FIG. 2 is an explanatory front view of a building in which the coiled steel plate is cooled in an embodiment of the present invention. 1 is a table showing examples of a cooling method for a coiled steel sheet in an embodiment of the present invention.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the contents described below are not limited to the coiled steel sheet to be cooled, and may be either a hot-rolled steel sheet or a cold-rolled steel sheet. Therefore, in the following description, no particular distinction will be made and the term "coiled steel sheet" will be used.

The coiled steel sheet cooling method in the embodiment of the present invention described below is used when the coiled steel sheet S is formed by winding a coiling machine attached to or installed in a hot rolling line, cold rolling line, or other pickling or annealing equipment, and is placed on a cooling bed to be cooled.

Fig. 1 is a perspective view showing an entire building B in which a coiled steel sheet S is cooled in an embodiment of the present invention. In Fig. 1, in order to clarify the inside of the building B, the building B itself is shown by a dashed line _.

On the other hand, FIG. 2 is an explanatory diagram showing the front view of the building B in which the coiled steel plate S is cooled in an embodiment of the present invention. Note that in FIG. 2, unlike FIG. 1, the building B is shown in solid lines. Also, the flow of air sent from a cooling fan, which will be described later, toward the coiled steel plate S is shown in dashed lines.

In addition, in the embodiment of the present invention, building B is formed in a rectangular shape as shown in Figures 1 and 2. However, the structure of building B may be any type and is not limited to the structure shown in Figure 1 etc.

As shown in FIG. 1, the building B is composed of a cooling bed CF on which the coiled steel sheet S to be cooled is placed, walls surrounding the cooling bed CF on all four sides, and a ceiling R located opposite the cooling bed CF. Note that in FIG. 1 and other figures, structures that are not necessary for explaining the method for cooling the coiled steel sheet S in the embodiment of the present invention are omitted.

In addition, in FIG. 1 etc., the entire floor surface of building B is used as a cooling bed CF for cooling the coiled steel plate S. However, the extent to which an area of building B is used as a cooling bed CF can be set arbitrarily. Furthermore, building B itself does not have to be a building dedicated to cooling the coiled steel plate S.

Coiled steel plates S are placed on the cooling bed CF. This is placed inside the building B in order to cool the coiled steel plates S to the desired temperature. In FIG. 1, three rows of five coiled steel plates S are placed on the cooling bed CF. However, the number of coiled steel plates S placed on the cooling bed CF can be set arbitrarily depending on the operation.

When multiple coiled steel sheets S are arranged between cooling equipment C, such as the cooling mist generator 1 and cooling fan 2 described below, it is preferable to place the coiled steel sheets S, for example, 1 to 2 m apart.

The cooling bed CF shown in Figure 1 is shown placed so that the direction of the rotation axis when winding the coiled steel sheet S, i.e., the central axis of the coil, is in the left-right direction in the drawing. On the other hand, the cooling bed CF shown in Figure 2 is shown so that the central axis is in a direction perpendicular to the left-right direction in the drawing. In other words, the coiled steel sheet S may be placed in either direction on the cooling bed CF.

For the purpose of drawing the drawings, the size of each coiled steel sheet S placed on the cooling bed CF is the same, but the size of the coiled steel sheet S to be cooled may be any size. As described above, the coiled steel sheet S may be a coiled hot-rolled steel sheet or a coiled cold-rolled steel sheet.

In FIG. 1, cooling equipment C for cooling the coiled steel plate S is provided at a position parallel to the central axis of the coiled steel plate S, i.e., on both sides of the row in which the coiled steel plate S is arranged. The cooling equipment C is composed of at least a cooling mist generator 1 and a cooling fan 2.

First, the cooling mist generator 1 generates the cooling mist used to cool the coiled steel sheet S. Any liquid may be used as the cooling mist, but water is preferably used due to its ease of operation in the cooling bed CF, cost, and availability.

The method for generating the cooling mist in the cooling mist generator 1 can be either a one-fluid method or a two-fluid method. For example, when using a two-fluid method, the volume ratio of the gas that makes up the cooling mist to the cooling liquid (i.e., the "air-water ratio") can be set in the range of 10 to 1000, taking into account certain conditions.

The cooling fan 2 draws in air that has been cooled by the evaporation of the cooling mist sprayed from the cooling mist generator 1, as described below, and sends it to the coiled steel plate S placed on the cooling bed CF. Therefore, the cooling fan 2 is positioned in front of the cooling mist generator 1, i.e., downwind, so that the air from the cooling fan 2 is sent to the coiled steel plate S.

The cooling fan 2 is installed at a distance of, for example, about 1 m from the coiled steel plate S. If the cooling fan 2 and the coiled steel plate S are placed too close to each other, there is a risk that the cooling fan 2 will be damaged by the heat of the coiled steel plate S that is being cooled.

On the other hand, it is desirable that the distance between the cooling fan 2 and the cooling mist generator 1 be sufficient to allow the cooling mist to evaporate and avoid the cooling mist diffusing and not being sucked in by the cooling fan 2.

In other words, if the mist is sucked into the fan before it evaporates and reaches the coiled steel sheet S, the risk of condensation on the coiled steel sheet S increases. On the other hand, if the distance between the cooling fan 2 and the cooling mist generator 1 is too great, some of the evaporated mist will not be sucked into the cooling fan 2 and will spread to the surrounding area, making it impossible to effectively utilize the evaporation effect of the mist. Therefore, the suitable distance varies depending on the mist particle size, and the smaller the particle size, the closer the distance is. Therefore, it is important to control the mist particle size according to the distance between the cooling fan 2 and the cooling mist generator 1. This point will be discussed later.

Furthermore, the cooling mist sprayed from the cooling mist generator 1 is designed to evaporate before being sucked into the cooling fan 2. In other words, the cooling fan 2 blows a gas consisting of air cooled by the evaporation of the cooling mist and the surrounding air or gas onto the coiled steel plate S, which is the object to be cooled.

This is because if the cooling mist sprayed from the cooling mist generator 1 is sent to the coiled steel plate S via the cooling fan 2 without evaporating, the cooling mist adhering to the coiled steel plate S increases the risk of rust occurring, especially at low temperatures.

Here, heat removal from the coiled steel plate S, i.e., cooling, is achieved by two types of heat transfer: radiation and convection. Of these, radiation is expressed as the product of the emissivity and the difference between the fourth power of the absolute temperature of the surface of the coiled steel plate S and the fourth power of the absolute temperature of the surroundings. On the other hand, convection is expressed as the product of the convection heat transfer coefficient and the difference between the surface temperature of the coiled steel plate S and the surrounding air temperature. Therefore, the effect of radiation is greater when cooling high-temperature objects, and the effect of convection is greater at low temperatures.

In addition, when looking at the time required to cool the coiled steel sheet S, there is a tendency for the time taken to complete cooling, i.e., to be longer at low temperatures, particularly from below 100°C, to reach the desired temperature. Therefore, it is important to improve the cooling capacity by convection, which has a large impact on cooling at low temperatures as described above.

Of the above mentioned conditions, improving the convection heat transfer coefficient and lowering the surrounding air temperature are effective in improving the cooling capacity of convection. Furthermore, installing a cooling fan is effective in improving the convection heat transfer coefficient, while spraying cooling mist is effective in lowering the surrounding air temperature.

In this way, by increasing the convection heat transfer coefficient of the cooling fan, the evaporation rate of the condensed water can be increased, so that even if condensation occurs on the coiled steel plate S, the occurrence of rust can be suppressed.

On the other hand, experiments have shown that when the cooling mist evaporates, the latent heat of vaporization causes the air temperature to drop by around 5°C. In this way, spraying cooling mist from a cooling mist generator contributes to improving the cooling capacity of convection, especially at low temperatures.

From the above viewpoints, the coiled steel sheet cooling method in the embodiment of the present invention uses at least a cooling mist generator 1 and a cooling fan 2 as the cooling equipment C. Furthermore, based on the cooling concept described above, the cooling mist sprayed by the cooling mist generator 1 is not sent directly to the coiled steel sheet S, but is evaporated once and the cooled air is sent to the coiled steel sheet S via the cooling fan 2.

By using this cooling method, it is possible to reduce the occurrence of rust caused by the cooling mist adhering to the coiled steel plate S. In addition, even if condensation occurs on the coiled steel plate S, the surface of the coiled steel plate S can be prevented from becoming wet because air is blown from the cooling fan 2. In addition, because the air at a lower temperature is blown to the coiled steel plate S via the cooling fan 2, the coiled steel plate S can be cooled more effectively.

Therefore, the flow rate of the cooling mist sprayed from the cooling mist generator 1 is limited to the amount at which the cooling mist can evaporate before reaching the cooling fan 2. If the flow rate of the cooling mist is too high, the relative humidity around the coiled steel plate S increases, and when the relative humidity reaches 100%, the cooling mist sprayed from the cooling mist generator 1 cannot evaporate completely.

On the other hand, if the flow rate of the cooling mist is small, the cooling capacity will be insufficient because the air will not be cooled sufficiently by the latent heat of vaporization caused by the evaporation of the cooling mist. Therefore, it is necessary to adjust the balance between the air flow rate of the cooling fan 2 and the amount of cooling mist sprayed by the cooling mist generator 1 to control the relative humidity in the cooling bed CF.

In this way, the method for cooling the coiled steel sheet in the embodiment of the present invention cools the coiled steel sheet S by sending the air cooled by the evaporation of the cooling mist sprayed from the cooling mist generating device 1 to the coiled steel sheet S via the cooling fan 2. Therefore, as described above, it is preferable to adopt a distance between the cooling mist generating device 1 and the cooling fan 2 according to the particle diameter of the cooling mist.

First, it is desirable that the particle diameter of the cooling mist, i.e., the diameter of the droplets sprayed from the cooling mist generator 1, is 40 μm or less. If the particle diameter of the cooling mist is 40 μm or less, the cooling mist evaporates in approximately one second. And if the particle diameter of the cooling mist is 40 μm, it is desirable that the distance between the cooling mist generator 1 and the cooling fan 2 is approximately 1.5 m ± 0.5 m.

On the other hand, the larger the particle diameter of the cooling mist, the longer it takes for the cooling mist to evaporate. Therefore, if the particle diameter of the cooling mist is larger than 40 μm, the efficiency of evaporation of the cooling mist is poor, and the cooling of the air by the heat of vaporization is insufficient. If the cooling mist is sucked into the cooling fan 2 without evaporating, there is a high possibility that the cooling mist will adhere to the coiled steel plate S without evaporating, increasing the risk of rust.

In contrast, for example, if the particle diameter of the cooling mist is 20 μm, it is desirable to set the distance between the cooling mist generator 1 and the cooling fan 2 to approximately 1 m ± 0.5 m. Of course, the particle diameter of the cooling mist may be 20 μm or less, in which case the distance between the cooling mist generator 1 and the cooling fan 2 will be closer than when the particle diameter of the cooling mist is 20 μm.

As such, there is a correlation between the particle diameter of the cooling mist and the distance between the cooling mist generator 1 and the cooling fan 2. Therefore, when the particle diameter of the cooling mist is 20 μm to 40 μm, the distance between the cooling mist generator 1 and the cooling fan 2 is approximately 0.5 m to 2 m.

It is desirable for the particle size of the cooling mist to be as large as described above, but if the ease of evaporation is taken into too much consideration, the amount of cooling mist sprayed will be small, which will inevitably result in a small amount of evaporation. Therefore, in such cases, it is desirable to spray a large amount of cooling mist with a small particle size.

Furthermore, in the method for cooling the coiled steel sheet S according to the embodiment of the present invention, the cooling mist generator 1 intermittently sprays the cooling mist and stops spraying the cooling mist, and the spraying is controlled to be repeated alternately for a certain period of time. The spray interval can then be set according to the target cooling time for the coiled steel sheet S.

In this way, by alternately repeating the spraying and stopping of spraying of cooling mist for a certain period of time, it is possible to suppress an increase in humidity around the coil-shaped steel sheet S compared to when spraying is continuous. More preferably, since the risk of condensation increases as the temperature of the coil-shaped steel sheet S decreases, it is possible to more easily suppress rust by setting the spray interval of cooling mist to be longer.

In addition, when the coiled steel sheet S has cooled sufficiently and cooling is complete, it is preferable to stop spraying the cooling mist from the cooling mist generator 1 from the standpoint of running costs and the risk of condensation.

Here, when the cooling mist evaporates, the humidity increases, particularly around the coiled steel sheet S. If the humidity increases, condensation will form, especially when the coiled steel sheet S is at a low temperature, making it more likely to rust. For this reason, an increase in humidity is undesirable.

Since warm air rises, it is possible to prevent an increase in humidity by installing an exhaust fan on the ceiling R of the cooling floor CF and actively exhausting the air from the cooling floor CF, for example, outside the building B.

For example, if the temperature of the cooling bed CF is 40°C, the relative humidity is 90%, and the dew point is 38°C, the coiled steel plate S will condense at or below 38°C. Therefore, when cooling causes the surface temperature of the coiled steel plate S to drop by 2°C relative to the temperature around the coiled steel plate S, or when the relative humidity reaches 100%, condensation will form on the surface of the coiled steel plate S, so it is necessary to exhaust the air around the cooling bed CF to reduce the humidity.

Therefore, in the cooling equipment C for the coiled steel plate S in the embodiment of the present invention, roof fans RF are provided on the ceiling R of the building B. That is, as shown in Figures 1 and 2, for example, three roof fans RF are provided in the building B. The number of roof fans RF to be provided can be freely set. Also, as shown in Figure 1, the roof fans RF are installed in a row on the ceiling R, but the position of the roof fans RF can also be freely set.

In addition, as described above, considering that the heated air rises above the coiled steel plate S when the coiled steel plate S is cooled, the embodiment of the present invention will not describe exhaust, and it is not necessary to use the roof fan RF installed on the ceiling R1. In other words, it is sufficient that the exhaust device is installed above the upper end of the coiled steel plate S arranged on the cooling bed CF.

In Figure 2, the dashed lines show the movement of air when the cooling equipment C, consisting of the cooling mist generator 1, the cooling fan 2, and the roof fan RF, is in operation. As shown in Figure 2, the cooling mist generator 1 and the cooling fan 2 are arranged on both sides of the coiled steel plate S placed in a row.

The cooling mist sprayed from the cooling mist generator 1 evaporates between the cooling mist generator 1 and the cooling fan 2, thereby cooling the surrounding air. The cooling fan 2 sucks in this cooled air and blows it out together with the surrounding gas toward the coiled steel plate S. The gas sent from the cooling fan 2 toward the coiled steel plate S is exhausted from the roof fan RF to the outside of the building B, including the air around the cooling bed CF, as shown by the dashed arrows in Figure 2.

Furthermore, the cooling mist generator 1 and cooling fan 2 described above can be controlled based on information obtained by grasping the conditions inside building B using a measuring device 3. Figures 1 and 2 show a thermometer and hygrometer installed on the wall of building B as an example of the measuring device 3.

If the temperature and humidity can be grasped in this way, the dew point can be estimated. This makes it possible to grasp the risk of condensation occurring on the coiled steel sheet S, and to control the cooling equipment C, such as the cooling mist generator 1 and the cooling fan 2, for example, using a control device (not shown). In addition, based on information such as temperature grasped by the thermometer and hygrometer, it is also possible to remove the coiled steel sheet S from the cooling bed CF before condensation occurs.

Since many coiled steel plates S are placed on the cooling bed CF, it is preferable to use, for example, a radiation thermometer as the measuring device 3 used for measuring the temperature. Also, a two-dimensional radiation thermometer may be used to measure the temperature of multiple coiled steel plates S with one device. The measurement position is preferably a surface perpendicular to the central axis of the coiled steel plate S, i.e., the surface formed by its width ends.

This is because the surface of the coiled steel sheet S that is made up of the width ends has poor thermal conductivity because the steel sheets are stacked in the radial direction. In addition, the outermost and innermost circumferences may be loosely wound, which may further worsen thermal conductivity. When thermal conductivity is poor in this way, the temperature is not easily transmitted from the inside, making it necessary to underestimate the temperature and making accurate measurement difficult. Therefore, the surface made up of the width ends is measured, which allows the temperature of the coiled steel sheet S to be measured reliably without such problems.

Here, a thermometer and hygrometer are given as an example of the measuring device 3. However, for example, in regard to the occurrence of condensation, a video camera may be installed as the measuring device 3 and the coiled steel plate S may be directly observed to determine whether condensation has occurred.

Next, an example of a method for cooling a coiled steel sheet S using cooling equipment C such as the cooling mist generator 1 described above will be described. Figure 3 is a table showing an example of a method for cooling a coiled steel sheet S in an embodiment of the present invention.

As shown in the table in Figure 3, eight working examples are listed vertically, and five comparative examples are listed for comparison with these working examples. Twelve conditions are listed horizontally: "Cooling method," "Number of fans (units/row)," "Number of coils (pieces/row)," "Use of roof fan," "Mist particle diameter (μm)," "Filter (presence/absence)," "Intermittent pattern," "Installation of radiation thermometer," "Installation of cooling bed thermometer/hygrometer," "Average cooling bed temperature (°C)," "Average relative humidity (%)," and "Coil recovery temperature (°C)." Meanwhile, the two items "Cooling time" and "Rust" show the results of the implementation.

First, there are two types of "cooling methods," and in all of the examples, a cooling method using a cooling mist generator 1 and a cooling fan 2 is adopted. On the other hand, in the comparative examples, cooling is basically performed by leaving it in the air, and the cooling mist generator 1 and cooling fan 2 are not used. However, comparative example 5 is an example in which a cooling mist generator 1 and a cooling fan 2 are used with a filter between them.

Therefore, the condition "Number of fans (units/row)" applies to all examples and Comparative Example 5. This condition indicates how many cooling fans 2 are arranged in one row when multiple coil-shaped steel plates S are lined up. In most cases, the number is "2 units," but in Example 2, it is "1 unit," and in Example 8, it is "4 units."

"Roof fan used" indicates whether or not a roof fan RF installed on the ceiling R was used to cool the coiled steel sheet S. Among the comparative examples, Comparative Example 4 uses a roof fan RF, and Comparative Example 5 does not use a roof fan RF. On the other hand, among the examples, only Example 5 does not use a roof fan RF, and the other examples use a roof fan RF.

"Mist particle diameter (μm)" is a condition that is set for the particle diameter of the cooling mist sprayed from the cooling mist generator 1. As is clear from the table in Figure 3, the particle diameter was set to "20 μm" in most cases, but it was set to "40 μm" for Comparative Example 5 and Example 3, and "50 μm" for Example 4.

"Filter (with or without)" indicates whether or not a filter is placed between the cooling mist generator 1 and the cooling fan 2. Here, a filter is placed only in Comparative Example 5, and no filter is placed in the other Comparative Examples and all Examples.

The "intermittent pattern" refers to a pattern in which spraying and stopping are repeated alternately when spraying cooling mist from the cooling mist generator 1, and an "spray time (s)" and a "stop time (s)" are set in Comparative Example 5 and each Example. That is, except for Example 7, the "spray time" is "20 s" and the "stop time" is "10 s". On the other hand, for Example 7, both the "spray time" and the "stop time" are "20 s", and the "stop time" is set longer than the other Examples.

In addition, the conditions of "mist particle diameter (μm)", "intermittent pattern", "radiation thermometer installation", and "cooling bed temperature and humidity meter installation" described below are not shown in Comparative Examples 1 to 4 except Comparative Example 5, where cooling is performed by air cooling, and the cooling mist generator 1 and cooling fan 2 are not used.

"Radiation thermometer installed" indicates whether or not a radiation thermometer was installed in building B as the measuring device 3 described above. In the comparative examples, a radiation thermometer was not installed in any of them except for Comparative Example 5. In contrast, in the examples, a radiation thermometer was installed in all of them except for Example 6.

"Cooling bed thermometer/hygrometer installation" indicates whether or not a thermometer/hygrometer was installed on the cooling bed CF. It was installed in all examples except for Example 7. On the other hand, in the comparative examples, a cooling bed thermometer/hygrometer was installed in Comparative Example 4 and Comparative Example 5, but not in the other comparative examples.

The conditions for "average cooling bed temperature (°C)," "average relative humidity (%)," and "coil recovery temperature (°C)" indicate the basic conditions for conducting the experiments in each embodiment and comparative example. The following conditions were set when conducting these experiments.

That is, the cooling start temperature of the coiled steel plate S was 600°C, and the unit weight of the coiled steel plate S was 20 tons per piece. Furthermore, there were five coiled steel plates S per row, the temperature of the cooling bed CF was 30°C, and the relative humidity was 80%. Water was used as the raw material for the cooling mist, and its temperature was 30°C. Finally, the cooling of the coiled steel plate S was stopped when the surface temperature of the coiled steel plate S reached 50°C.

Therefore, among the various conditions mentioned above, the values of "average cooling bed temperature (°C)," "average relative humidity (%)," and "coil recovery temperature (°C) (cooling stop temperature)" were appropriately changed in the examples and comparative examples to understand the changes.

The above conditions were set for each example and comparative example, and the results of the experiment are shown in the "cooling time" and "rust" sections. The former shows the "effect of shortening the cooling time," _and the effect is shown in four types: double circle, circle, triangle, and cross.

Among these, the effect indicated by a double circle is "when the cooling time is shortened by more than two days compared to the cooling time required by leaving the coiled steel sheet to cool in the air." A circle indicates "when the cooling time is shortened by more than 1.5 days to 2 days compared to the cooling time required by leaving the coiled steel sheet to cool in the air."

On the other hand, a triangle indicates "cases where the cooling time has been shortened by more than 1 day to 1.5 days compared to the cooling time required by leaving the coiled steel plate to cool in the air." A cross indicates "cases where the cooling time has been shortened by 1 day or less compared to the cooling time required by leaving the coiled steel plate to cool in the air."

Next, the effect shown as "rust" indicates the result of "evaluation based on rust generation after cooling." As with the above-mentioned "cooling time," this effect is also shown in four types _: double circle, circle, triangle, and cross.

First, the effect indicated by the double circle indicates that "no rust has occurred along the entire length and width of the coiled steel plate." The circle indicates that "rust has occurred over an area less than 5% of the entire length and width of the coiled steel plate."

On the other hand, a triangle indicates that "rust has occurred over an area less than 10% of the total length and width of the coiled steel plate," and a cross indicates that "rust has occurred over an area more than 10% of the total length and width of the coiled steel plate."

Looking at the above conditions and results, the comparative examples received a double circle for rust occurrence, meaning that there were cases where no rust occurred on the coiled steel plate S. However, in all of Comparative Examples 1 to 4, cooling was done in the atmosphere without using a cooling mist generator 1 or the like, and cooling took a long time. As a result, all of these comparative examples received a "X" for cooling time.

As mentioned above, Comparative Example 5 is the only one of the Comparative Examples and Examples that is equipped with a filter. Looking at the results of Comparative Example 5, as with the Examples, cooling was performed using the cooling mist generator 1, etc., and therefore a double circle was obtained for the "cooling time".

However, as with Comparative Example 2, the result for "rust" was a "X", which indicates that "rust has occurred over an area of 10% or more of the total length and width of the coiled steel plate." This is thought to be due to a decrease in the responsiveness of humidity control due to the installation of the filter.

In addition, in Comparative Example 5, the roof fan RF was not used, and proper exhaust was not achieved, which led to an increase in humidity in the cooling bed CF (the average relative humidity in the table in Figure 3 is 90%), which is also thought to be one of the factors that caused rust to form over a wide area of the coiled steel plate S.

In contrast, looking at the eight examples, cooling was performed using a cooling mist generator 1, etc. As a result, at the very least, the results showed that "the cooling time was shortened by more than 1.5 to 2 days compared to the cooling time required by cooling the coiled steel plate in the air (circle)."

That is, first, four examples obtained a double circle result. On the other hand, the remaining four examples did not obtain a double circle result, but only a circle result. Of the examples that obtained a circle result, it is believed that this result was due to the number of cooling fans 2 being one per row in example 2, and the particle diameter of the cooling mist sprayed from the cooling mist generator 1 being set to "40 μm" in example 3. Also, it is believed that the particle diameter of the cooling mist in example 4 was too large, just like example 3.

On the other hand, in Example 6, a radiation thermometer was not installed. In this case, the temperature of the coiled steel sheet S was unknown, which is thought to be the reason for the delay in recovering the coiled steel sheet S from the cooling bed CF.

On the other hand, with regard to rust occurrence, four of the eight examples were marked with double circles, but two were marked with triangles. The triangles were in examples 4 and 5. In example 4, the particle diameter of the cooling mist sprayed from the cooling mist generator 1 was larger than in the other examples, and was larger than the preferred particle diameter mentioned above.

In other words, in the case of Example 4, the particle diameter of the cooling mist was large at 50 μm, and it is believed that after being sprayed from the cooling mist generator 1, some of the mist did not evaporate before being sucked into the cooling fan 2 and instead adhered to the coiled steel plate S as it was.

In the case of Example 5, among the above-mentioned conditions, the roof fan RF was not used. Therefore, it is believed that the humidity of the cooling bed CF increased due to insufficient exhaust (the average relative humidity in the table of Figure 3 is 90%), causing rust to form on the coiled steel plate S.

Example 7 received a perfect score for rust occurrence. In Example 7, a thermometer and hygrometer were not installed on the cooling bed CF. As a result, it was not possible to optimize the control of the intermittent pattern of the roof fan RF and the cooling mist, which led to an increase in humidity in the cooling bed CF, which is thought to have resulted in rust occurring on the coiled steel plate S.

On the other hand, both Example 1 and Example 8 were able to obtain double circles for the cooling time and rust effects. As a result, it was possible to ship high-quality coiled steel sheets in a short time. In addition, by installing a radiation thermometer and a thermometer/hygrometer on the cooling bed, it was possible to grasp the surface temperature of the coiled steel sheets and the temperature and humidity of the cooling bed, which allowed for the optimization of the shipping timing of the coiled steel sheets and accurate prediction of condensation, thereby achieving further benefits.

Also, compared to Comparative Example 5, none of Examples 1 to 8 use a filter. Therefore, it is believed that it was possible to prevent the mist sprayed by the cooling mist generator 1 from adhering to the filter and leaving it wet, i.e., in a humid state. As a result, the humidity control was responsive and the risk of condensation was reduced, so that generally satisfactory results were obtained with regard to rust.

In the above-mentioned embodiments, the cooling start temperature of the coiled steel sheet S is set to 600°C, but the effect of the invention does not change significantly depending on the cooling start temperature. In addition, the temperature of the water supplied to the cooling mist generating device 1 is set to 30°C, but a lower temperature will provide a higher cooling effect. In addition, if the water temperature exceeds the cooling target temperature of 50°C, it will be difficult to cool to the cooling stop temperature, so in this case a water temperature of 40°C or less is preferable.

As described above, by using the coiled steel sheet cooling method, coiled steel sheet manufacturing method, and coiled steel sheet cooling equipment according to the embodiments of the present invention, it is possible to suppress wetting of the surface of the coiled steel sheet while improving the cooling capacity of the coiled steel sheet, and the coiled steel sheet can be cooled with high efficiency without causing rust on the coiled steel sheet.

Based on the above-mentioned embodiment, when starting to cool the coiled steel sheet S, more reliable cooling can be achieved by determining the amount of spray and airflow from the cooling equipment C, such as the cooling mist generator 1 and the cooling fan 2, and then performing cooling.

As mentioned above, the present invention can be applied to cold-rolled steel sheets, which have stricter surface quality requirements, by implementing stricter temperature and humidity control.

Furthermore, in the above-mentioned embodiment, the coiled steel sheets are arranged in a row of five sheets, and one or two cooling devices are installed per row. However, depending on the number of coiled steel sheets per row, the row may be divided and additional cooling devices may be installed between the divisions.

For example, although the cooling mist generating device 1 and the cooling fan 2 have been described as separate devices, they may have an integrated structure. Of course, even in this case, the gas blown from the fan to the coiled steel plate S is air that has been cooled by the evaporation of the cooling mist.

The embodiments of the present invention described so far are merely examples of the present invention. Various modifications or improvements can be made to each of these embodiments, and such modifications or improvements can also be included in the present invention. Each of these embodiments and their variations are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

1 Cooling mist generator 2 Cooling fan 3 Measuring device B Building CF Cooling floor RF Roof fan S Coiled steel plate

Claims (12)

A step of spraying cooling mist by a cooling mist generating device disposed indoors ;
a cooling fan sucking in air cooled by evaporation of the cooling mist sprayed by the cooling mist generating device and blowing the air onto the coil-shaped steel plate placed on the cooling bed;
Equipped with
A method for cooling a coiled steel plate, characterized in that the cooling mist generating device is arranged behind the direction of air blown by the cooling fan toward the coiled steel plate at a distance corresponding to the particle diameter of the cooling mist . The method for cooling coiled steel sheets according to claim 1, characterized in that the particle diameter of the cooling mist is 40 μm or less. After the step of blowing air onto the coiled steel sheet by the cooling fan,
2. The method for cooling a coiled steel plate according to claim 1, further comprising a step of exhausting the air around the coiled steel plate, including the gas blown to the coiled steel plate by the cooling fan, to the outside of the cooling bed. A measuring device is provided for detecting the state of both the coiled steel plate and the cooling bed, or one of the two,
2. The method for cooling a coiled steel sheet according to claim 1, further comprising a step of controlling either or both of the cooling mist generating device and the cooling fan based on the conditions measured by the measuring device. A method for manufacturing a coiled steel sheet, comprising the method for cooling a coiled steel sheet according to any one of claims 1 to 4. The method for manufacturing coiled steel sheet according to claim 5, characterized in that hot-rolled steel sheet or cold-rolled steel sheet is manufactured. A cooling mist generator that is disposed indoors and sprays cooling mist;
a cooling fan that sucks in air cooled by evaporation of the cooling mist sprayed by the cooling mist generator and sends the air to the coiled steel plate placed on the cooling bed;
Equipped with
A cooling equipment for a coiled steel plate, characterized in that the cooling mist generating device is arranged behind the direction of air blown by the cooling fan to the coiled steel plate at a distance corresponding to the particle diameter of the cooling mist . The coil steel sheet cooling equipment according to claim 7, characterized in that the particle diameter of the cooling mist sprayed by the cooling mist generating device is 40 μm or less. The cooling equipment for the coiled steel plate according to claim 7, characterized in that the cooling equipment for the coiled steel plate is provided with an exhaust device that exhausts the air around the coiled steel plate, including the gas blown to the coiled steel plate by the cooling fan, to the outside of the cooling bed. The cooling equipment for the coiled steel plate according to claim 8, characterized in that the cooling equipment for the coiled steel plate is provided with an exhaust device that exhausts the air around the coiled steel plate, including the gas blown to the coiled steel plate by the cooling fan, to the outside of the cooling bed. The cooling equipment for coiled steel sheets according to claim 7, further comprising a measuring device for detecting the condition of the coiled steel sheets and/or the cooling bed. The cooling equipment for coiled steel sheets according to any one of claims 7 to 11, characterized in that the cooling equipment for coiled steel sheets is equipped with a control device that controls both or either the cooling mist generating device and the cooling fan based on the conditions measured by the measuring device.

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