JP2002282928A - Cooling apparatus and cooling method for plate-like material to be cooled - Google Patents

Abstract

(57) A cooling method for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-shaped cooling target conveyed in a horizontal direction. The present invention provides a cooling device and a cooling method capable of equalizing the temperature distribution after cooling at the leading end in the transport direction. SOLUTION: In the cooling method for cooling the cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-shaped cooling target conveyed in a horizontal direction, the cooling method includes: Including a plurality of cooling steps for cooling the cooled material in a cooling zone having a predetermined length in the transport direction, the plurality of cooling steps, after the tip of the cooled material enters the cooling zone A plurality of cooling steps for starting the injection of the cooling liquid in the cooling zone, and a cooling step for starting the injection of the cooling liquid in the cooling zone before the tip end of the material to be cooled enters the cooling zone. Including.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device and a cooling method for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-like cooling target conveyed in a horizontal direction. For example, the present invention relates to a cooling device and a cooling method for cooling a high-temperature metal plate by injecting cooling water onto a high-temperature metal plate such as a high-temperature steel plate being conveyed. More specifically, the present invention relates to a cooling device and a cooling method that make it possible to make the temperature distribution in the conveyance direction after cooling more uniform at the tip of a plate-shaped material to be conveyed.

[0002]

2. Description of the Related Art In recent years, in a manufacturing process of steel materials such as thick steel plates, a technology (controlled cooling) for increasing the strength and toughness by cooling a rolled steel material with water within a predetermined temperature range has been developed. It is becoming widely practiced. Normally, controlled cooling is performed by injecting cooling water from a cooling nozzle onto the surface of a conveyed 200-900 ° C. high-temperature steel material. By injecting water into the high-temperature steel material, a boiling heat transfer phenomenon occurs on the surface of the steel material, and cooling can be performed at a cooling rate several tens to several hundreds times higher than air cooling. As a result, a steel material having a finer crystal structure can be obtained, and a steel material having high strength and high toughness characteristics can be manufactured.

[0003] With the development of such controlled cooling technology, high strength and high toughness conventionally performed by adding a specific element can be realized by combining controlled rolling and controlled cooling. It has become possible to reduce manufacturing costs by reducing the amount of added elements and to improve various properties such as weldability. For this reason, the number of target materials for controlled cooling is steadily increasing.

[0004] By applying the controlled cooling technique in this way, it has become possible to produce steel materials having excellent characteristics at lower cost, but on the other hand, the need for higher quality is increasing. Several new problems have arisen with this.

[0005] Among them, a particularly important problem is that the tip of the steel material in the transport direction (hereinafter, also referred to as "steel tip") is supercooled, and the temperature distribution in the transport direction of the steel material after cooling is poor. There is a problem of uniformity.

The target temperature range of the steel material after cooling is determined in advance from the chemical composition of the steel material and required mechanical properties such as strength and toughness, and is set so as to fall within the target temperature range over the entire steel material. It is important to control the cooling.

[0007] If there is a portion of the steel material that has deviated from the target temperature range, it is necessary to confirm the mechanical characteristics of the portion again, and furthermore, the mechanical characteristic value of the portion does not satisfy the expected mechanical characteristics. In such a case, the entire steel material may be degraded and cause a decrease in yield. Further, when the end of the steel material is overcooled, a defective shape portion, for example, a warp is easily generated in the portion, and it is necessary to correct the defective shape portion, which may increase the manufacturing cost.

[0008] As described above, the following three points can be cited as the main causes of supercooling at the tip of the steel material. Primarily,
In the case of injecting the cooling water to the lower surface of the steel material, a part of the cooling water to be injected to the lower surface of the steel material falls to the upper surface side of the tip of the steel material. This is because if the cooling device previously injects cooling water upward from the lower surface side of the steel material before the steel material tip portion of the conveyed steel material enters the cooling device, the steel material tip portion reaches the cooling device. As a result, the cooling water that rises above the steel material is shut off, but the cooling water that is injected just before reaching and located above the steel material falls on the upper surface of the tip of the steel material. For this reason, excessive cooling water is supplied to the steel material tip compared with the central part of the steel material, and the steel material tip is supercooled.

Secondly, when spraying the cooling water onto the upper or lower surface of the steel material, the front surface in the transport direction of the tip of the steel material collides with the cooling water flow injected onto the upper or lower surface of the steel material. This is because if the cooling device injects cooling water in advance from the upper surface side or downward from the lower surface side in the cooling device before the steel material tip of the conveyed steel material enters the cooling device, the steel material tip becomes In order to rush in the flow of the cooling water, the front surface in the transport direction of the steel material tip collides with the flow of the cooling water, and excessive cooling water is supplied to the steel material tip compared to the central part of the steel material. And the tip of the steel material is supercooled.

Third, when the two-way valve or the three-way valve is used to perform ON / OFF control for supplying the cooling water injected to the upper surface or the lower surface of the steel material, immediately after the valve is turned to the open state. (Hereinafter, turning a valve to an open state is also referred to as "valve opening.") A pressure fluctuation occurs in a pipe (hereinafter, also simply referred to as "pipe") for supplying cooling water to an injection unit. However, it takes time until the amount of cooling water injected onto the lower surface of the conveyed steel material is stabilized, and during this time, cooling unevenness occurs in the conveying direction at the portion of the cooled steel material.

Here, the two-way valve is a valve that shuts off the flow of cooling water from the inlet pipe to the outlet pipe by closing it, and the three-way valve is closed. By switching the flow of cooling water from the inlet pipe to the outlet pipe to another pipe (relief pipe),
This valve stops the supply to the outlet pipe. Since the flow of the cooling water flowing through the valve section is instantaneously shut off when the three-way valve is opened, the pressure fluctuation in the piping is smaller than that of the two-way valve, and the degree of the above-mentioned uneven cooling can be suppressed. For this reason,
It is suitable as ON / OFF control means for supplying cooling water injected to the lower surface of the steel material.

However, even when a three-way valve is applied, the flow path is shut off when the valve is opened, albeit momentarily, so that the pressure in the pipe for supplying the cooling water to the cooling water injection unit fluctuates. Therefore, immediately after the valve is opened, the flow rate of the cooling water supplied to the cooling water injection unit fluctuates.

FIG. 1 is a graph showing an example of the relationship between the flow rate of cooling water immediately after valve opening and the elapsed time when a three-way valve is applied. As shown in the figure, the flow rate of the cooling water increases immediately after the valve is opened, and exceeds the set flow rate after about 0.5 seconds.
After seconds, the flow rate is maximum. After that, the flow rate decreases,
After a second, the flow rate stabilizes and reaches the set flow rate. In this example, the maximum value of the flow rate of the cooling water has reached about 1.7 times the set value.

Under the conditions shown in this example, when the leading end of the conveyed steel material reaches the cooling zone and the valve is opened to start spraying cooling water to the upper or lower surface of the steel material, The part of the steel material where the flow rate of water is maximum is slightly cooled from the tip to the center. For example, when the conveying speed of the steel material is 1 m / s, the part on the center side about 1 m from the tip of the steel material is supercooled.

[0015] Such a fluctuation in the flow rate immediately after the valve is opened depends on the speed at which the valve is rotated when the valve is opened (hereinafter referred to as "rotation speed"). When the rotation speed is reduced, the maximum value of the flow rate of the cooling water immediately after the valve is opened is reduced. Therefore, the temperature difference in the transport direction of the steel material due to uneven cooling can be reduced by reducing the rotation speed. However, on the other hand, if the rotation speed is reduced, the time until the flow rate of the cooling water immediately after the valve is opened becomes longer, and the range of the cooling unevenness in the transport direction of the steel material increases. Therefore, it is not preferable to excessively reduce the rotation speed.

Hitherto, several techniques have been proposed which attempt to suppress the supercooling occurring at the tip of the steel material described above. Japanese Patent Application Laid-Open No. 61-76624 discloses that when cooling by spraying pressurized cooling water onto the upper and lower surfaces of a hot steel sheet while moving the hot steel sheet, the leading end of the steel sheet to be cooled goes out from the cooling device outlet side. A cooling method is disclosed in which the steel sheet is temporarily stopped in a state where the cooling is performed, and the cooling is continued until the cooling state of a portion other than the distal end is substantially equal to the cooling state of the distal end.

Further, Japanese Patent No. 2941878 discloses that
In cooling the thick steel plate with the automatic cooling device, the cooling device is divided into a plurality of zones in the transport direction of the thick steel plate, and the zone from the time when the non-cooling offset portion at the tip of the thick steel plate is sequentially charged into each of the zones. A cooling method for initiating the cooling of the cooling device is disclosed.

[0018]

According to the cooling method disclosed in the above publication, the degree of supercooling at the tip of the steel sheet can be suppressed to some extent, but there are still the following problems.

In the cooling method disclosed in Japanese Patent Application Laid-Open No. 61-76624, the movement of the steel sheet is temporarily stopped in a state in which the tip of the steel sheet to be cooled is out of the cooling device exit side, and the steel sheet other than the tip is stopped. Since it is necessary to continue cooling until the cooling state of the part is substantially equal to the cooling state of the tip, the length of the steel plate to be cooled in the transport direction is the sum of the length of the cooling device and the length of the tip. Must be shorter than length. Therefore, the elongation of the rolling in the rolling step of manufacturing the steel plate to be cooled by rolling is restricted, and the rolling efficiency in the rolling step is reduced. In order to prevent such a reduction in the rolling efficiency, it is necessary to increase the length of the cooling equipment so as not to cause a reduction in the rolling efficiency, but not only does the equipment cost become enormous, but also the maintenance cost increases. It is not practical.

In the cooling method disclosed in Japanese Patent No. 2941878, when cooling a thick steel plate with an automatic cooling device, the cooling device is divided into a plurality of zones in the conveying direction of the thick steel plate, and the leading end of the thick steel plate is not cooled. By starting the cooling of the zone from the time when the offset portion is sequentially loaded in each zone, the supercooling of the leading end portion is suppressed.
There is no problem that the length of the cooling equipment is increased unlike the cooling method disclosed in JP-A-76624. However, as described in the embodiment of Japanese Patent No. 2941878, when the same offset length is set uniformly for each zone, the offset length can be made shorter than the conventional offset length. However, it is not possible to reduce the temperature difference in the transport direction of the steel sheet due to uneven cooling caused by the fluctuation of the flow rate of the cooling water immediately after the valve is opened.

As a technique for suppressing the degree of uneven cooling caused by the fluctuation of the flow rate of the cooling water immediately after the valve is opened, an ON / OFF method for supplying the cooling water to be injected to the upper and lower surfaces of the steel material is used.
As a control means, a cooling method that applies opening and closing of a shielding plate instead of opening and closing of a valve can be considered. Actually, there is a case where a shielding plate is applied as an ON / OFF control unit for supplying cooling water injected to the upper surface of a steel material. However, in general, the nozzle that injects cooling water to the lower surface of the steel material increases the collision pressure of the cooling water that is injected to the lower surface of the steel material to ensure a high cooling capacity, so that it is close to the lower surface of the conveyed steel material. Be placed. For this reason, it is difficult to secure the opening / closing mechanism using the shielding plate at the disposition position. In addition, the temperature of the steel material to be cooled is a high temperature close to 800 ° C., and it is difficult to maintain such a mechanism soundly under a severe environment in which such high-temperature radiant heat is directly received and the cooling water falls. Not practical.

Also, as for the nozzle for injecting the cooling water to the upper surface of the steel material, similarly to the nozzle for injecting the cooling water to the lower surface of the steel material, the collision pressure of the cooling water injected to the upper surface of the steel material is increased to increase the cooling performance. In order to secure it, it may be arranged so as to be close to the upper surface of the conveyed steel material. In such a case, similarly to the above, it is difficult to secure the opening / closing mechanism using the shielding plate at the disposition position.

In view of the above problems, the present invention provides a cooling device and a cooling method for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-shaped cooling target conveyed in a horizontal direction. It is an object of the present invention to provide a practical cooling device and a practical cooling method capable of making the temperature distribution in the transport direction after cooling of the front end of the cooled material more uniform.

[0024]

Means for Solving the Problems The present inventors have proposed a method for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-like cooling target conveyed in a horizontal direction. As a method for making the temperature distribution in the transport direction of the tip end of the cooled material after cooling more uniform, a case of controlled cooling of a high-temperature steel sheet was examined in detail as an example. As a result, the following findings were obtained.

In general, the controlled cooling of the high-temperature steel sheet is performed by injecting cooling water onto the surface of the high-temperature steel sheet by using a cooling device having a plurality of cooling zones in the conveyance direction while conveying the high-temperature steel sheet horizontally by a roller table. Done. Here, the cooling zone includes a nozzle group including a plurality of nozzles that inject cooling water to an upper surface and / or a lower surface of the high-temperature steel plate, and supplies cooling water to the nozzle group.
The control is performed by a three-way valve or the like. The injection start timing of each cooling zone is configured to be independently controllable.

Here, if the injection amount of the cooling water injected to the lower surface of the high-temperature steel sheet is constant before the high-temperature steel sheet enters the cooling device until the high-temperature steel sheet is completely passed, as described above, When a part of the cooling water injected to the lower surface of the steel plate falls to the upper surface side of the steel material tip portion, the tip portion in the transport direction of the steel sheet (hereinafter, also referred to as “steel plate tip portion”) is supercooled. In addition, when the cooling water is injected at a constant injection amount on the upper surface or the lower surface of the high-temperature steel sheet before the high-temperature steel sheet enters the cooling device and before the high-temperature steel sheet passes through the cooling device, the injection of the cooling water is constant. When the front surface in the transport direction collides with the flow of the cooling water injected downward from the upper surface side or upward from the lower surface side, the front end portion of the steel plate is supercooled. In order to suppress this, it is necessary to start cooling after the tip of the steel sheet enters the cooling zone.

Hereinafter, starting the cooling after the leading end of the cooled material such as the leading end of the steel sheet in the transport direction of the cooled material (hereinafter also referred to as the "cooled material leading end") enters the cooling zone, "masking". The length at which the tip of the coolant enters the cooling zone at that time is referred to as the "masking amount", and the time when cooling in the cooling zone starts after the coolant enters the cooling zone to secure the masking amount. The time up to is referred to as “masking time”. Here, the “cooling zone” refers to a region where the cooling liquid can be jetted onto the lower surface of the material to be cooled, and the “entered length” refers to a case where the tip of the material to be cooled is located in the cooling zone. The length of the tip end of the cooling material existing inside the cooling zone, and when the tip end of the cooling material passes through the cooling zone and is located outside the cooling zone, the cooling zone inlet To the tip of the material to be cooled.

However, as described in the embodiment of Japanese Patent No. 2941878, when masking is uniformly performed with the same masking amount in all the cooling zones, the leading end of the steel sheet in the transport direction ( Hereinafter, also referred to as a “steel plate front end portion”), the supercooling suppression effect by masking becomes excessive, and becomes higher than the target temperature. In addition, in a portion slightly closer to the center than the portion, the influence of uneven cooling caused by a change in the flow rate of the cooling water immediately after the valve is opened appears remarkably.

As a method for preventing such a phenomenon, the masking amount is reduced in some cooling zones and the masking amount in other cooling zones is increased to perform masking with a different masking amount for each cooling zone. By dispersing the influence of uneven cooling due to the fluctuation of the flow rate of the cooling water immediately after the valve is opened in the transport direction of the steel sheet, the top end of the steel sheet is suppressed from becoming hot, It is conceivable to mitigate the effect of uneven cooling due to fluctuations in the flow rate of cooling water immediately after the valve is opened.

However, by setting a different masking amount for each cooling zone in this manner, even if the temperature distribution in the transport direction of the steel sheet at the tip end portion of the steel sheet is made uniform, the effect is not sufficient. In addition, since the area affected by the uneven cooling caused by the fluctuation of the flow rate of the cooling water immediately after the valve is opened increases, the method for cooling the high-temperature steel sheet is insufficient.

As described above, if the masking is performed in all the cooling zones, the temperature distribution at the tip of the steel sheet cannot be sufficiently made uniform. Therefore, the present inventors combine a plurality of cooling zones for performing masking and a cooling zone for which masking is not performed, thereby suppressing the masking effect from being excessive at the forefront of the steel sheet, and controlling the tip of the steel sheet after cooling. The idea was to make the temperature distribution uniform.

With respect to a plurality of cooling zones for performing masking, by providing cooling zones having different masking amounts, fluctuations in the flow rate of the cooling water immediately after the valve is opened at a portion slightly closer to the center than the foremost portion of the steel plate. The idea was to disperse the effects of the uneven cooling and make the temperature distribution at the tip of the steel sheet even more uniform after cooling.

In the cooling zone where masking is not performed, the cooling water injection is started at the timing when the injection flow rate of the cooling water at the time when the steel sheet enters the cooling zone is stabilized, so that the cooling immediately after the valve is opened. The idea was to make the temperature distribution at the tip of the steel sheet after cooling more uniform by avoiding the effects of uneven cooling caused by fluctuations in the flow rate of water and performing cooling control more stably.

Here, the "timing at which the injection flow rate is stabilized" is defined as the area after about 2 seconds shown in FIG. 1 where the flow rate change immediately after the valve is opened is completed and the actual flow rate becomes the set flow rate. This is the timing at which the state becomes calm, and the two-way valve is similarly defined.

The present invention has been completed based on the above findings, and the gist thereof is as follows.

(1) In a cooling device that cools the cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-like cooling target conveyed in a horizontal direction, the cooling device includes the cooling target. A plurality of cooling zones arranged in the direction of transport of the coolant, wherein the plurality of cooling zones start injecting the cooling liquid in the cooling zone after a leading end of the material to be cooled enters the cooling zone. And a cooling zone for starting injection of the cooling liquid in the cooling zone before the leading end of the material to be cooled enters the cooling zone.

(2) The plurality of cooling zones in which the injection of the cooling liquid is started in the cooling zone after the leading end of the material to be cooled has entered the cooling zone are transferred to the cooling zone at the start of the injection of the cooling liquid. The cooling device according to the above item (1), further comprising a cooling zone having a different approach distance of a tip of the material to be cooled.

(3) In the cooling zone in which the injection of the cooling liquid is started in the cooling zone before the leading end of the cooling material enters the cooling zone, the leading end of the cooling material enters the cooling zone. The cooling device according to the above (1) or (2), wherein the cooling zone is a cooling zone in which the injection of the cooling liquid is started at a timing when the injection flow rate of the cooling liquid at the time is stabilized.

(4) In the cooling method for cooling the cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-shaped cooling target conveyed in a horizontal direction, the cooling method includes: The method further includes a plurality of cooling steps for cooling the material to be cooled in a cooling zone having a predetermined length in a transport direction of the coolant, wherein the plurality of cooling steps include a step in which a tip of the material to be cooled enters the cooling zone. A plurality of cooling steps to start the injection of the cooling liquid in the cooling zone after the
A cooling step of starting injection of the cooling liquid in the cooling zone before the leading end of the coolant enters the cooling zone.

(5) The plurality of cooling steps for starting the injection of the cooling liquid in the cooling zone after the leading end of the material to be cooled has entered the cooling zone include the cooling zone at the start of the injection of the cooling liquid. The cooling method according to the above mode (4), further comprising a cooling step in which the distance of the leading end of the material to be cooled into the cooling medium is different.

(6) In the cooling step of starting the injection of the cooling liquid in the cooling zone before the leading end of the cooled material enters the cooling zone, the leading end of the cooled material is moved to the cooling zone. The cooling method according to the above (4) or (5), wherein the cooling step is a step of starting the injection of the cooling liquid at a timing at which the injection flow rate of the cooling liquid at the time of entry is stabilized.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail below with reference to the drawings, together with the results of studies conducted in creating the present invention.

FIG. 2 is an explanatory view schematically showing the configuration of the cooling facility studied above. As shown in the figure, the cooling equipment used in this study is a roller (not shown) that is disposed downstream of the hot finishing mill 1 and that horizontally transports a hot-rolled steel plate 2 that is a plate-like material to be cooled. A table, and a cooling device 3 for cooling the hot-rolled steel sheet by injecting cooling water as a cooling liquid onto the upper and lower surfaces of the conveyed hot-rolled steel sheet,
In order to prevent the cooling water on the upper surface of the steel plate from flowing out of the cooling device, there are provided drainage nozzles 4 and 4 disposed on the inlet side and the outlet side of the cooling device. The cooling device 3 includes an upper surface cooling device 5 that injects cooling water onto the upper surface of the conveyed steel plate to cool it, and a lower surface cooling device 6 that injects cooling water onto the lower surface of the conveyed steel plate to cool it. Prepare.

Here, the lower surface cooling device 6 includes eight cooling zones (# 1 to # 8) arranged at intervals of 0.75 m in the conveying direction of the steel sheet.
Equipped with two spray nozzle headers arranged at intervals,
The spray nozzle header includes spray nozzles arranged at a pitch of 200 mm in a direction perpendicular to the conveying direction of the steel sheet.

The upper surface cooling device 5 has six slit nozzle headers arranged at intervals of 2 m in the direction of transport of the steel sheet, and the slit nozzle header has a slit exit gap of 10 mm. In addition, the slit nozzle header has an injection port of the nozzle positioned 1.5 m above the conveying surface of the roller table so that the nozzle does not collide with the steel plate even if the conveyed steel plate has a warp. It is arranged as follows.

Using the cooling equipment shown in FIG.
mm, plate width: 3200 mm, plate length: 25 m, 1 m
The cooling was performed from 750 ° C. to 500 ° C. while transporting at a transport speed of / s.

The cooling of the steel plate was performed by controlling the flow rate of the cooling water supplied to each nozzle header, and a three-way valve was used for ON / OFF control of the cooling water supply to each nozzle header. Here, the cooling by the upper surface cooling device 5 was performed by starting the injection of the cooling water at a timing such that the flow rate of the cooling water injected from the slit nozzle header was stabilized when the steel sheet entered the cooling device. On the other hand, the cooling by the lower surface cooling device 6 was performed by changing the masking conditions in each cooling zone in various ways and starting spraying the cooling water from the spray nozzle header.

At the outlet of the cooling device, the temperature in the transport direction of the front end portion of the steel sheet after cooling was measured, and the influence of the masking conditions of the lower surface cooling device 6 was investigated. In addition, ON / OFF of cooling water supply to each spray nozzle header of the lower surface cooling device 6
For the three-way valve used for the OFF control, the rotation time until the valve was opened was 0.3 seconds. The response of the flow rate in this case was as shown in FIG. Table 1 shows typical examples of the masking conditions studied.

[0049]

[Table 1]

In Table 1, for the cooling zones in which the masking was not performed, that is, the cooling zones in which the injection was started before the leading end of the steel sheet entered each cooling zone, the masking amount is shown as a minus for convenience. In other words, it indicates that the injection of the cooling water from the spray nozzle header was started before the tip of the steel sheet entered the cooling zone in the cooling zone. And the numerical value shows the distance between the cooling zone entrance side and the tip of the steel sheet at the time when the injection of the cooling water is started in the cooling zone.

As shown in Table 1, the test number (a) was determined as described in Examples of Japanese Patent No. 2941878.
Masking was performed with the same masking amount in all cooling zones. In test number (b), the masking amount was set to 0 in the cooling zone # 1, and masking was performed by increasing the masking amount by 0.5 m from the upstream to the downstream cooling zone. The number (c) indicates that the masking amount in the cooling zone # 1 was set to 0, and the masking amount was increased by 1.0 m from the upstream side to the downstream side in the cooling zone.
In the test number (d), no masking is performed in the cooling zones # 1 to # 4. In the cooling zones # 5 to # 8, the masking amount of the cooling zone # 5 is set to 0.5 m, and the cooling zone # 6 is set. The masking is performed by increasing the masking amount by 1.0 m from # 8 to # 8.

FIG. 3 shows test numbers (a) to (c) shown in Table 1.
3D is a graph showing the temperature in the transport direction of the steel sheet after cooling for each example of FIG. 3D, where FIG. 3A shows the test number (a), and FIG. 3B shows the test number (b). 3
FIG. 3C is a graph for test number (c), and FIG. 3D is a graph for test number (d).

As shown in FIG. 3 (a), when the masking is performed with the same masking amount in all the cooling zones, 1.5 mm, which is the foremost portion of the steel plate subjected to the masking, is used.
For the portion m, the supercooling suppression effect by the masking became excessive, and the temperature became about 60 ° C. higher than the target temperature.
In addition, as shown in FIG. 1, the injection flow rate of the cooling water from the spray nozzle header becomes maximum about 1 second after the valve is opened.
Significant undercooling occurred, as low as 0 ° C.

As shown in FIGS. 3B and 3C,
If masking is performed with a different masking amount for each cooling zone, the effect of uneven cooling due to fluctuations in the flow rate of cooling water immediately after opening the valve can be dispersed in the transport direction of the steel sheet. It was possible to reduce the degree of supercooling temperature that had occurred slightly on the center side. FIG. 3 (a)
3B, about 2/3 in the case of FIG.
In the case of FIG. 3C, the size was reduced to about 1/3.

However, the area in the transport direction of the steel sheet which is affected by the cooling unevenness caused by the fluctuation of the flow rate of the cooling water immediately after the valve is opened increases, and in the case of FIG.
3B, it increased to about 6.0 m in FIG. 3B and to about 9.5 m in FIG. 3C.

The temperature at the foremost part of the steel sheet is about 50 ° C. higher than the target temperature, which is better than that in FIG. 3A, but not satisfactory. FIG.
As shown in (c), when masking is performed in all the cooling zones, the temperature distribution at the tip of the steel sheet cannot be sufficiently uniformized.

As shown in FIG. 3 (d), when a plurality of cooling zones for performing masking and a cooling zone for not performing masking were combined, the temperature distribution at the front end portion of the steel plate could be made uniform.

The combination of the plurality of cooling zones for performing masking and the cooling zone for which no masking is performed as described above makes it possible to achieve a uniform temperature distribution at the tip of the steel sheet after cooling for the following reason.

First, in a plurality of cooling zones where masking is not performed, it is possible to prevent the maximum flow rate of cooling water from colliding with the steel plate in the flow rate fluctuation immediately after the valve is opened. This is because it is possible to suppress the cooling unevenness caused by the fluctuation in the flow rate. In the case shown in FIG. 3D, in the cooling zones # 1 to # 3, the flow rate of the cooling water is stabilized before the steel sheet enters each cooling zone. No unevenness in cooling due to fluctuations in the flow rate occurs. In the cooling zone where the masking is performed, it is impossible to prevent the maximum flow rate of the cooling water immediately after the valve is opened from colliding with the steel plate.

Secondly, supercooling of the steel plate tip caused by the cooling water jetted upward from the lower surface of the steel plate to the steel plate tip, which occurs in the cooling zone where masking is not performed, Combining multiple cooling zones for masking the supercooling of the tip of the sprayed steel sheet caused by the collision of the front face in the transport direction of the tip of the steel sheet with the flow of cooling water injected downward or upward from the bottom side This is because the temperature distribution at the front end portion of the steel sheet can be made uniform by compensating for the temperature.

The difference in the masking time between the cooling zones in which the masking is performed may be too short if the cooling water at the maximum flow rate immediately after the valve is opened collides with the steel plate, and if the cooling time is too long. The area in the transport direction of the steel sheet, which is affected by uneven cooling caused by the fluctuation of the flow rate of the cooling water immediately after the valve is opened, increases. Therefore, it is preferable that the time is 0.5 to 0.75 times the time required for the flow rate when the valve is opened to return to the set value (about 2 seconds in the example of FIG. 1).

The ratio of the number of the plurality of cooling zones for performing the masking to the number of the cooling zones for which the masking is not performed is determined by the amount of the supercooling caused by the cooling water from the lower surface cooling device falling on the upper surface of the steel plate. And the degree of supercooling caused by collision of the front surface of the front end of the steel sheet in the transport direction with the flow of cooling water from the upper surface cooling device or the lower surface cooling device. That is, since it depends on the nozzle shape and the like of the upper surface cooling device and the lower surface cooling device, it is preferable to determine after performing a test for each cooling facility.

In the description of the embodiment of the present invention, the case where the plate-shaped object to be cooled is a high-temperature steel plate is described as an example, but the present invention is not limited to this. Further, in the description of the embodiment of the present invention, the case where masking control is performed only for the lower surface cooling device has been described, but the present invention is not limited to this. Masking control may be performed only for the upper surface cooling device, or masking control may be performed for both the upper surface cooling device and the lower surface cooling device.

In the case of injecting the cooling water to the upper and lower surfaces of the steel material, the supercooling caused by the part of the cooling water injected to the lower surface of the steel material falling to the upper surface side of the tip of the steel material,
Masking control is preferably performed on at least the lower surface cooling device because the front surface of the steel material tip in the transport direction is larger than the supercooling caused by the collision with the cooling water jets jetted to the upper and lower surfaces of the steel material. When cooling water is sprayed onto the upper and lower surfaces of the steel material, masking control is performed on both the upper surface cooling device and the lower surface cooling device in order to make the temperature distribution in the transport direction after the cooling of the steel material uniform with higher accuracy. Is preferred.

When masking control is performed for both the upper cooling device and the lower cooling device, a combination of the upper nozzle and the lower nozzle is set as one cooling zone, and the same masking amount is set. Alternatively, separate cooling zones may be set for the upper nozzle and the lower nozzle, and the masking amounts may be set individually. Further, in the description of the embodiment of the present invention, the case where the masking control is performed by controlling the masking amount for each cooling zone has been described as an example, but the masking control is performed by controlling the masking time for each cooling zone. You may do so. Further, in the description of the embodiment of the present invention, the case where the number of cooling zones not performing masking is plural has been described, but the number of cooling zones not performing masking may be singular.

In the description of the embodiment of the present invention, two spray nozzle headers are used as one cooling zone, but the present invention is not limited to this. One spray nozzle header may be one cooling zone, or three or more spray nozzle headers may be one cooling zone. In order to perform the cooling control with higher precision, it is preferable that one or two spray nozzle headers be one cooling zone.

In the description of the embodiment of the present invention, the ON / OFF control of the supply of the cooling water to each nozzle header is performed by using the three-way valve. However, the control may be performed by using the two-way valve. It is preferable to use a three-way valve with small pressure fluctuations in the piping at the time of ON / OFF control, since the degree of uneven cooling caused by fluctuations in the flow rate of cooling water can be suppressed.

[0068]

According to the present invention, in the case where the cooling target is cooled by injecting cooling liquid and / or the upper surface of the plate-like cooling target conveyed in the horizontal direction, the conveying direction of the cooling target is , The temperature distribution in the transport direction after cooling can be made more uniform.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a relationship between a flow rate of cooling water and an elapsed time immediately after opening a valve when a three-way valve is applied.

FIG. 2 is an explanatory diagram schematically showing a configuration of a cooling facility under study.

FIG. 3 is a graph showing the temperature in the transport direction of a steel sheet after cooling for each example of test numbers (a) to (d) shown in Table 1.

[Explanation of symbols]

 1: Hot finishing mill 2: Hot-rolled steel plate 3: Cooling device 4: Drain nozzle 5: Upper surface cooling device 6: Lower surface cooling device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K034 AA02 BA05 CA01 DB03 FA05 FB03

Claims (6)

[Claims] 1. A cooling device for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-like cooling target conveyed in a horizontal direction, wherein the cooling device includes the cooling target. A plurality of cooling zones arranged in a conveying direction of the material, wherein the plurality of cooling zones start injecting the cooling liquid in the cooling zone after the leading end of the material to be cooled enters the cooling zone. A cooling device, comprising: a cooling zone; and a cooling zone which starts injection of the cooling liquid in the cooling zone before the leading end of the material to be cooled enters the cooling zone. 2. A plurality of cooling zones, which start injecting the cooling liquid in the cooling zone after the leading end portion of the material to be cooled has entered the cooling zone, include: 2. A cooling zone having a different approach distance of a tip end of a material to be cooled.
The cooling device according to claim 1. 3. The cooling zone in which the cooling liquid starts to be jetted in the cooling zone before the leading end of the material to be cooled enters the cooling zone is at the time when the leading end of the material to be cooled enters the cooling zone. 3. The cooling device according to claim 1, wherein the cooling zone is a cooling zone in which the injection of the cooling liquid is started at a timing at which the injection flow rate of the cooling liquid is stabilized. 4. A cooling method for cooling a cooling target by injecting a cooling liquid onto an upper surface and / or a lower surface of a plate-shaped cooling target conveyed in a horizontal direction, wherein the cooling method includes: The method includes a plurality of cooling steps of cooling the material to be cooled in a cooling zone having a predetermined length in a transport direction of the material, wherein the plurality of cooling steps include a leading end of the material to be cooled having entered the cooling zone. A plurality of cooling steps for starting the injection of the cooling liquid in the cooling zone later, and a cooling step for starting the injection of the cooling liquid in the cooling zone before the leading end of the material to be cooled enters the cooling zone. A cooling method comprising: 5. A plurality of cooling steps for starting the injection of the cooling liquid in the cooling zone after the leading end of the material to be cooled has entered the cooling zone, the cooling step includes: The cooling method according to claim 4, further comprising a cooling step in which the distances at which the leading ends of the cooled materials enter are different. 6. The cooling step of starting injection of the cooling liquid in the cooling zone before the leading end of the coolant enters the cooling zone, wherein the leading end of the coolant enters the cooling zone. 6. A cooling step of starting the injection of the cooling liquid at a timing when the injection flow rate of the cooling liquid at the time of performing the cooling is stabilized.
The cooling method described in the above item.