JP2015055002A - Steel sheet cooling device and steel sheet cooling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet cooling device and a steel sheet cooling method enabling the occurrence of defects such as a stretcher strain to be more effectively prevented than conventional ones upon hot dip galvanizing the steel sheet in hot dip galvanizing equipment.SOLUTION: The steel sheet cooling device includes: a box which has openings in upper and lower portions thereof respectively and inside which a steel sheet runs upward and downward; one or more exhaust part which is formed in a side face of the box and vents inside of the box; a nozzle header which is arranged between the exhaust part and the steel sheet and has a plurality of nozzles for spraying water mist to the running steel sheet and extends in a width direction of the steel sheet; a seal mechanism for preventing water leak from lower opening of the box; a pressure measurement part for measuring pressure in a plurality of measurement locations having different position in the width direction of the steel sheet in the box; and an exhaust amount controlling part for controlling exhaust amount from the exhaust part based on pressure measured by the pressure measurement part.

Description

  The present invention relates to a steel plate cooling apparatus and a steel plate cooling method using water mist. In particular, the present invention is a steel plate cooling device and a steel plate cooling method capable of uniformly controlling the cooling state in cooling in the region where the steel plate temperature is 300 to 500 ° C. during the production of a hot dip galvanized steel plate.

  In continuous hot dip galvanizing equipment, when manufacturing hot dip galvanized steel sheet using a steel plate with yield point elongation such as BH steel sheet (baking hardening type steel sheet) as a plating base plate, there are defects such as stretcher strain and hip folding. May occur.

  As a technique for preventing hip breakage, Patent Document 1 discloses a technique for applying distortion in advance before hip breakage occurs. In addition, as techniques for preventing the occurrence of stretcher strain when forming a hot-dip galvanized steel sheet, for example, many techniques relating to temper rolling after plating and material design have been disclosed.

  In the above hot dip galvanizing equipment, the steel sheet is pulled up after being immersed in a hot dip galvanizing bath, and after the amount of adhesion is controlled by gas wiping, it is cooled as it is or after it is heated and alloyed. As a cooling method after plating, water mist cooling or gas cooling is generally used. In order to efficiently cool with a short equipment length, water mist cooling with a high cooling capacity is often selected. Generally, the hot dip galvanized steel sheet manufactured has a plate width exceeding 1000 mm, and the maximum plate width may approach 1900 mm. Such a hot dip galvanized steel sheet is required to have quality uniformity in the width direction. Usually, in a steel plate, a change in material and shape often occurs due to a temperature change such as heating and cooling as described above. The uniformity of heating and cooling in the plate width direction is an important requirement, but its control is not easy. In particular, in steel sheets that yield at a yield point below 500 ° C, such as 340BH steel sheets, there is a high possibility that stretcher strain will occur in the cooling process after hot dip galvanizing, and temperature control in the sheet width direction is particularly important. It is.

  Patent Document 2 relates to a technique for uniformly cooling a steel sheet by increasing the amount of water. For the purpose of preventing water droplet leakage from the lower part of the mist cooling box, the lowermost air supply pad of the mist cooling box is provided with a high pressure and a low pressure 2. A cooling method is disclosed in which the types are adjacent to each other, the water receiving pan is arranged at a predetermined position, and the wind speed of the rising air flow from the air supply pad is set to 20 m / s or more.

JP 2004-107682 A JP 2000-73125 A

  In the conventional technology as disclosed in Patent Document 2 and the like, in the hot dip galvanizing facility, when the hot dip galvanizing is performed on the steel sheet, the occurrence of stretcher strain in the cooling process after plating cannot be prevented appropriately There is.

  The present invention has been made in order to solve the above-mentioned problems. The purpose of the present invention is to more effectively generate defects such as stretcher strain when hot-dip galvanized steel sheets are used in hot-dip galvanizing equipment. It is providing the steel plate cooling device and steel plate cooling method which can be prevented.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, in the conventional method disclosed in Patent Document 2 and the like, since the liquid is uniformly exhausted from the exhaust part installed on the back of the nozzle header, droplets formed by aggregation of water mist adhere to the central part of the steel plate. It was found that local supercooling occurred. And the present inventors have found that this supercooling is the cause of the occurrence of defects such as stretcher strain, and further, if the internal pressure in the steel sheet cooling device is adjusted, the above problem due to supercooling will be solved. As a result, the present invention has been completed. More specifically, the present invention provides the following.

  (1) A box having an opening at the top and bottom, in which the steel plate runs upward or downward, and in the box, the box is formed on a surface facing the surface of the steel plate, and one or more for exhausting in the box An exhaust section, a nozzle header installed between the exhaust section and the steel plate and having a plurality of nozzles for injecting water mist onto the traveling steel plate, extending from the steel plate width direction, and from the lower opening of the box Based on a seal mechanism that prevents water leakage, a pressure measurement unit that performs pressure measurement at a plurality of measurement locations having different positions in the steel plate width direction, and a plurality of pressure values measured by the pressure measurement unit in the box. A steel plate cooling apparatus comprising: an exhaust amount control unit that controls an exhaust amount from the exhaust unit.

  (2) The steel sheet cooling device according to (1), wherein the one or more exhaust parts are three or more exhaust parts arranged in the width direction of the steel sheet.

  (3) The exhaust amount control unit controls the exhaust amount from the exhaust unit so that a pressure deviation calculated from a plurality of pressure values measured by the pressure measurement unit is 40% or less. The steel plate cooling device according to (1) or (2).

  (4) The steel sheet cooling device according to any one of (1) to (3), wherein the one or more exhaust parts include two or more exhaust parts arranged in a longitudinal direction of the steel plate. .

  (5) A steel plate cooling method for cooling a steel plate by injecting water mist onto a traveling steel plate while exhausting the cooling device, and measuring pressures at a plurality of measurement points at different positions in the steel plate width direction. And cooling the steel sheet while adjusting the displacement of the exhaust gas so that the pressure deviation is reduced based on the measurement result.

  (6) The steel sheet cooling method according to (5), wherein the displacement is adjusted so that the pressure deviation is 40% or less.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a stretcher strain can be prevented more effectively than before, when hot-dip galvanizing a steel plate in a continuous hot-dip galvanization equipment.

It is a figure which shows typically the steel plate cooling device periphery in hot dip galvanization equipment. It is a figure which shows typically the inside of the steel plate cooling device of this invention. It is sectional drawing (AA cross section) which shows the steel plate cooling device of this invention typically. It is a figure which shows typically a mode that water mist cools a steel plate. It is a figure which shows typically the inside of the conventional steel plate cooling device. It is a figure which shows the cooling characteristic of water mist by the relationship between steel plate temperature and cooling capacity. It is a figure which shows the temperature nonuniformity of the width direction of the steel plate after leaving a steel plate cooling device. It is a figure which shows an example of the relationship between the width direction pressure deviation and a steel plate width direction temperature difference. It is a figure which shows arrangement | positioning of the nozzle injection hole in an Example.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment.

  First, a hot dip galvanizing facility to which the steel sheet cooling device of the present invention can be preferably applied will be described. FIG. 1 is a diagram schematically showing the periphery of a steel sheet cooling device in a hot dip galvanizing facility. The hot dip galvanizing equipment 1 includes a steel plate cooling device 10, a hot dip galvanizing bath 11, a sink roll 12, an alloying treatment zone 13, a gas wiping nozzle 14, and a support roll 15 in the bath around the steel plate cooling device. And a support roll 16 on the bath and a scanning radiation thermometer 17.

  The operation of the hot dip galvanizing equipment 1 around the steel plate cooling device is as follows. The steel sheet S exiting from the annealing furnace (not shown) travels in the hot dip galvanizing bath 11 and is moved upward by the sink roll 12. The steel sheet S traveling upward in the hot dip galvanizing bath 11 passes between the rolls of the support roll 15 in the bath, and therefore can travel without greatly vibrating. The steel plate S that has passed through the support roll 15 in the bath travels further upward and exits the hot dip galvanizing bath 11. A hot dip galvanizing solution adheres to the surface of the steel sheet S coming out of the hot dip galvanizing bath 11. Thereafter, the steel sheet S coming out of the hot dip galvanizing bath 11 travels further upward, passes through the gas wiping nozzle 14, and the amount of hot dip galvanizing solution adhering to the surface of the steel sheet S is adjusted. After the adhesion amount is adjusted, the steel sheet S further moves upward. At this time, since the steel sheet S passes between the rolls of the on-bath support roll 16, it can run smoothly without greatly vibrating. The steel plate S that has passed through the bath support roll 16 travels further upward, passes through the alloying zone 13 and is alloyed. The alloyed steel plate S exits from the alloying zone 13, travels further upward, and is cooled in the steel plate cooling device 10.

  Moreover, when applying the steel plate cooling device 10 of the present invention to the hot dip galvanizing equipment 1, the temperature of the surface of the steel plate S exiting the steel plate cooling device 10 is measured by a temperature measuring unit such as a scanning radiation thermometer 17. It is preferable that it can be measured.

  When the steel sheet S can run smoothly in the hot dip galvanizing facility. The support roll 15 in the bath and the support roll 16 on the bath may be omitted. Further, when the alloying treatment is not performed, the alloying treatment zone 13 may not be provided.

  The steel plate cooling device of the present invention is disposed in the hot dip galvanizing facility as described above. FIG. 2 is a diagram schematically showing the inside of the steel sheet cooling device of the present invention. FIG. 3 is a sectional view (AA section) schematically showing the steel sheet cooling device of the present invention. Hereinafter, the steel sheet cooling device of the present invention will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the steel sheet cooling device 10 of the present invention includes a box 100, an exhaust unit 101, a nozzle header 102, a seal mechanism 103, a pressure measurement unit 104, an exhaust amount control unit 105, It has an exhaust fan 106 and an exhaust part partition plate 107 (FIGS. 2 and 3 are symmetrical, so the left half of the exhaust part 101, pressure measuring part 104, exhaust amount control part 105, etc. is omitted).

  The box 100 has openings at the top and bottom, and forms the outer shape of the steel sheet cooling device 10. Although the arrangement | positioning method of the box 100 is not specifically limited, Usually, the steel plate cooling apparatus 10 is arrange | positioned at a hot dip galvanization installation so that the steel plate S may approach from a lower opening, and may come out from an upper opening.

  The exhaust unit 101 exhausts the inside of the box 100. The exhaust unit 101 only needs to be capable of exhausting. For example, in the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, the exhaust unit 101 is an exhaust port, and each exhaust port is exhausted via a connecting unit such as a pipe. It is connected to the fan 106. The exhaust amount of the exhaust unit 101 can be adjusted by an exhaust amount control unit 105 described later.

  In the present invention, the position and number of the exhaust portions 101 are not particularly limited, but in the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, a plurality of exhaust portions 101 are formed on the side surface of the box 100 facing one surface of the steel plate S. The Although not shown, the exhaust portion 101 is also formed on the side surface of the box 100 facing the other surface of the steel plate S.

  Moreover, in the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, a plurality of exhaust portions 101 are provided so as to be aligned in the width direction and the longitudinal direction of the steel plate S. In particular, in the steel sheet cooling apparatus 10 shown in FIGS. 2 and 3, in the width direction of the steel sheet S, the exhaust portion 101 is positioned opposite the center of the steel sheet width direction, positioned opposite one end in the steel sheet width direction, and other positions in the steel plate width direction. Three are arranged side by side at positions facing the ends. In the longitudinal direction of the steel plate, a plurality of three exhaust parts 101 arranged in the steel plate width direction are formed so as to be arranged vertically.

  The nozzle header 102 is installed between the steel plate S and the exhaust part 101. In the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, a plurality of nozzle headers 102 extending in the steel plate width direction are provided so as to be aligned in the vertical direction (steel plate traveling direction). The interval between the nozzle headers 102 arranged in the vertical direction is 50 to 300 mm.

  The nozzle header 102 has a nozzle 1020 that ejects water mist. A plurality of nozzles 1020 are provided on the nozzle header 102 side by side in the steel plate width direction. The injection port of the nozzle 1020 faces the surface of the steel sheet S.

  The seal mechanism 103 is provided in the lower opening of the box 100 and prevents water leakage. A conventionally known seal mechanism 103 can be used. For example, a static pressure pad that forms a pressure pool on the surface of the steel plate, a gas nozzle that forms an upward flow near the steel plate, and the like can be used. Further, a water pan (not shown) may be provided at the lower opening of the box 100 to collect the droplets that adhere to the inner wall of the box 100 and flow downward.

  The pressure measurement unit 104 measures the pressure at a plurality of measurement points at different positions in the steel plate width direction. Measurement can be performed at a plurality of pressure measurement locations, and at least two of the plurality of pressure measurement locations may be measurement locations having different positions in the steel plate width direction. In addition, what is necessary is just to be two or more places.

  Moreover, the pressure measurement part 104 should just be a thing which can measure the pressure of the said measurement location, for example, is comprised from the pressure hole 1040 and the pressure gauge 1041 as shown in FIG. In the steel plate cooling apparatus 10 shown in FIG. 2, a pressure gauge 1041 measures the pressure at a measurement location represented by a double circle (◎) through a pressure measurement tube or the like through the pressure hole 1040.

  In the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, a plurality of pressure measuring units 104 are provided so as to be aligned in the width direction and the longitudinal direction of the steel plate. In particular, in the steel sheet cooling apparatus 10 shown in FIGS. 2 and 3, in the width direction of the steel sheet, the pressure measuring unit 104 is opposed to the center in the width direction of the steel sheet, is opposed to one end of the steel sheet, and is opposed to the other end of the steel sheet. Are provided in three places. Then, the three pressure measuring units 104 arranged in the steel plate width direction are formed so as to be arranged vertically in the steel plate longitudinal direction.

  Moreover, in the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, the position of the pressure measuring unit 104 in the longitudinal direction of the steel plate is between two nozzle headers 102 arranged vertically.

  The exhaust amount control unit 105 controls the exhaust amount in the exhaust unit 101 based on the pressure value measured by the pressure measuring unit 104. For example, the exhaust amount control unit 105 receives the pressure value measured by the pressure measuring unit 104 so that the pressure unevenness in the steel plate cooling device 10 is reduced. Control the amount of exhaust. Control of the exhaust amount that can reduce the pressure unevenness in the steel plate cooling device 10 may be performed based on information obtained through experiments and simulations.

  In the present invention, it is preferable that the displacement control unit 105 can control the displacement so as to reduce the pressure deviation between the center and the end of the steel sheet in the width direction. Moreover, it is preferable that the exhaust amount control unit 105 performs control so that the high pressure portion is set to a lower pressure with respect to the pressure unevenness in the steel plate cooling device 10. Further, it is preferable that the exhaust amount control unit 105 can control the exhaust amount on the lower side in the longitudinal direction of the steel plate (the side on which the steel plate S enters) and on the upper side (the side on which the steel plate S exits).

  2 has a damper 1050 and an intermediate damper 1051 between each exhaust part 101 and the exhaust fan 106, and adjusts the exhaust amount in each exhaust part 101 using these. Specifically, the exhaust amount at each exhaust unit 101 is controlled using the damper 1050, and the total exhaust amount assigned to each of the plurality of dampers 1050 connected to each intermediate damper 1051 using the intermediate damper 1051. Adjust the displacement rate. When the exhaust unit 101 includes a plurality of exhaust ports and exhaust fans provided at the respective exhaust ports, the operation of each exhaust fan may be adjusted by a method of controlling based on the pressure value. Good.

  Further, when adjusting the exhaust amount by the exhaust amount control unit 105, the exhaust amount is set to a sufficient exhaust amount (1.5 times or more) with respect to the air amount ejected from the nozzle in order to improve the discharge property of the mist droplets. It is desirable. However, if the exhaust amount is increased more than necessary, the mist droplets and gas escape are improved, but the cooling capacity is lowered, so that the equipment length is increased. For this reason, it is necessary to determine the displacement so that the equipment length does not become too long.

  The exhaust part partition plate 107 is a plate provided between the exhaust parts 101 arranged in the steel plate width direction as shown in FIG. The exhaust part partition plate 107 extends in the longitudinal direction of the steel plate, and the width direction of the exhaust part partition plate 107 is substantially perpendicular to the steel plate width direction (vertical direction in FIG. 3). And the exhaust part partition plate 107 is arrange | positioned in the steel plate cooling device 10 so that the space between the nozzle header 102 arranged in a steel plate longitudinal direction and the side surface of the box 100 in which the exhaust part 101 was formed may be partitioned. Although the exhaust part partition plate 107 is not shown in FIG. 2, it is preferable that all the exhaust parts 101 arranged in the longitudinal direction of the steel plate are partitioned by the exhaust part 101 adjacent in the steel plate width direction and the exhaust partition plate 107.

  Next, the operation and effect of the steel sheet cooling device of the present invention will be described.

  The operation of the steel sheet cooling device 10 of the present invention is as follows. First, the steel plate S enters the steel plate cooling device 10 from the lower opening of the box 100 and travels upward. The traveling steel sheet S is cooled by being in contact with water mist sprayed from the nozzle 1020. Specifically, the water mist cools the steel sheet S as follows.

  Water mist is sprayed from the nozzle 1020 toward the surface of the steel sheet S. Since a plurality of nozzles 1020 are provided side by side in the steel plate width direction, the water mist contacts the entire steel plate S without unevenness. By this contact, the water mist that has contacted the steel sheet S absorbs the heat of the steel sheet S and evaporates, or absorbs the heat of the steel sheet S and bounces without evaporating (broken arrows in FIG. 4). In this way, the water mist cools the steel sheet S. The bounced water mist is discharged from the exhaust unit 101 to the outside of the box 100 together with the gas in the box 100. At this time, the exhaust amount from each exhaust unit 101 is adjusted based on the pressure value measured by the pressure measuring unit 104.

  Before describing the effects of the present invention, problems of the conventional steel sheet cooling apparatus will be described. FIG. 5 is a diagram schematically showing the inside of a conventional steel plate cooling apparatus. The apparatus shown in FIG. 5 is different from the steel sheet cooling apparatus of the present invention in that it does not include a pressure measurement unit or an exhaust amount control unit. Moreover, the apparatus shown in FIG. 5 differs from the steel plate cooling apparatus shown in FIGS. In the apparatus shown in FIG. 5, the two exhaust parts 101 facing each other with the steel plate S interposed therebetween exhausts air. Other configurations are the same as those of the apparatus shown in FIGS. In the conventional steel plate cooling device 10, exhaust is performed from the exhaust unit 101 without considering the pressure in the steel plate cooling device 10. Conventional steel plate cooling devices have the following problems.

  The water boiling phenomenon as shown in FIG. 6 is related as the cooling characteristic of water mist cooling (FIG. 6 is a diagram showing the cooling characteristic of water mist in relation to the steel sheet temperature and the cooling capacity). As shown in FIG. 6, if the water mist cooling is within the film boiling region, the cooling ability is almost constant regardless of the steel plate temperature. However, when the steel plate temperature is lowered to the transition boiling region, the cooling capability is increased as the steel plate temperature is lower, and the temperature difference in the plate width direction is easily increased. In particular, if there is uneven heating in the steel plate before cooling, the temperature deviation in the plate width direction before cooling will increase several times after cooling. Therefore, it is desirable to perform water mist cooling within the film boiling region. The transition temperature at which transition boiling transitions varies with the amount of water. In the case of water mist, the transition temperature is 200 to 500 ° C., and this temperature range overlaps the temperature range of the temperature of the steel plate to be cooled. For this reason, water quantity control becomes very important in cooling with water mist. Specifically, the ratio of the amount of water sprayed from the nozzles (the ratio when the set water amount of each nozzle is 100%) should be within ± 10% in the steel plate width direction. In this way, by controlling the ratio of the amount of water in the width direction to within ± 10% to eliminate temperature unevenness, it is intended to suppress defects called stretcher strains that are caused by temperature unevenness caused by variations in the amount of water.

  Conventionally, it was thought that quality adjustments such as stretcher strain would not occur if the amount of water was adjusted. However, even though the amount of water sprayed from the nozzle 1020 can be adjusted within a range of ± 10% in the width direction of the steel plate, the temperature unevenness in the width direction of the steel plate after leaving the steel plate cooling device is radiated temperature. When monitored by a meter, non-uniformity (approximately a temperature difference of 50 ° C. or more) occurs in the width direction as shown in FIG. This temperature unevenness may cause quality defects such as stretcher strain.

  As a result of intensive studies on the cause of temperature deviation in the width direction (cause of the above-mentioned temperature unevenness), the cause of this is that the droplets ejected from the nozzles do not quickly discharge but stay in the box and partly aggregate. It was found that the amount of water increased, and transitional boiling occurred and local supercooling occurred. Further investigation of the location where water droplets are likely to accumulate reveals that there is a correlation between the internal pressure between the nozzle header and the steel sheet and the supercooling position (70 Pa at the center in the width direction in FIG. 7 and 21 Pa at the end from the center). .

  When the interval between the nozzle headers arranged above and below is very narrow (in the type of steel sheet cooling apparatus of the present invention, the interval between the nozzle headers arranged vertically is very narrow), mist and gas ejected from the nozzles Is unlikely to be discharged from between the nozzle headers, resulting in an increase in internal pressure. In particular, the pressure value tends to be higher at the center than at the end in the width direction. This is probably because the water mist from the nozzles in the center of the nozzle header is surrounded by the water mist from the surrounding nozzles, and there is no escape path other than between the nozzle headers. As described above, it has been found that the unevenness of the internal pressure in the steel sheet cooling apparatus causes the generation of quality defects, and the occurrence of defects such as stretcher strain can be suppressed by reducing the unevenness of the internal pressure.

  Here, reducing the pressure unevenness can determine the degree of “reducing” by the following method, for example. The difference between the pressure value at the high pressure location and the pressure value at the low pressure location is expressed as a ratio (width direction pressure deviation) when the average value of the pressure in the width direction is 100%. Create a graph with the temperature difference in the width direction (maximum temperature in the width direction of the steel sheet-minimum temperature in the width direction of the steel sheet) as the vertical axis, and pressure unevenness so that the temperature difference in the width direction does not rise rapidly Should be reduced. When the steel plate cooling device having a general interval between the nozzle headers is used under the condition of a normal steel plate temperature, it is as shown in FIG. In the case as shown in FIG. 8, the pressure deviation is preferably 40% or less.

  The present invention completed based on the above knowledge has the following effects.

  The steel sheet cooling device 10 of the present invention includes a pressure measurement unit 104 and an exhaust amount control unit 105. The pressure measurement unit 104 can measure the pressure at a plurality of measurement points having different positions in the steel plate width direction. If the exhaust amount control unit 105 is used, the exhaust amount from the exhaust unit 101 can be adjusted in accordance with the pressure value measured by the pressure measuring unit 104 so as to reduce the pressure unevenness in the steel sheet cooling device. For this reason, if adjustment as described above is performed, unevenness of the internal pressure in the steel sheet cooling device is reduced even during the cooling of the steel sheet S, and quality defects such as a rain property outside the stretcher are less likely to occur.

  Moreover, in the steel plate cooling apparatus 10 according to the present invention, the plurality of exhaust portions 101 are formed, so that the exhaust amount can be adjusted at a plurality of positions, and pressure adjustment at a plurality of locations in the steel plate cooling apparatus 10 is easy. become. As a result, it becomes easy to adjust so that the pressure non-uniformity in the steel plate cooling device 10 does not easily occur. In particular, if a plurality of exhaust portions 101 are provided on the side surface of the box 100 facing one surface of the steel plate S and the side surface of the box 100 facing the other surface of the steel plate S, the pressure unevenness is particularly easily reduced.

  In the present invention, it is preferable that a plurality of exhaust portions 101 are provided side by side in the width direction of the steel plate. As shown in FIG. 7, pressure unevenness is particularly likely to occur in the width direction of the steel sheet. By providing a plurality of the exhaust portions 101 in the width direction of the steel sheet, it is easy to adjust the exhaust amount at a location where the pressure is high and a location where the pressure is low, and it is easier to eliminate this pressure unevenness. In particular, as shown in FIGS. 2 and 3, in the width direction of the steel plate S, the exhaust portion 101 faces the center in the steel plate width direction, the position facing one end in the steel plate width direction, and the other end in the steel plate width direction. It is particularly preferable that three positions are provided at the positions where the above effects are to be achieved. Further, by arranging not only in the width direction of the steel sheet but also in the longitudinal direction, it becomes easy to finely adjust the pressure in the steel sheet cooling apparatus 10 and the pressure unevenness in the steel sheet cooling apparatus 10 can be further reduced.

  In the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, a plurality of pressure measuring units 104 are provided so as to be aligned in the width direction and the longitudinal direction of the steel plate. A large number of pressure measurement points is preferable because the state of pressure in the steel sheet cooling device can be grasped more accurately. Further, in the steel plate cooling apparatus 10 shown in FIGS. 2 and 3, each of the pressure measuring units 104 is provided substantially in parallel with each of the exhaust units 101, and therefore, in the vicinity of the measurement location measured by the pressure measuring unit 104. Pressure adjustment is easy. Since the pressure at the measurement location can be directly controlled, it is easy to perform adjustment to reduce the pressure unevenness in the steel plate cooling device 10.

  In the present invention, as described above, pressure unevenness is likely to occur in the width direction of the steel sheet, and this pressure unevenness affects the occurrence of defects such as stretcher strain. Since the displacement control unit 105 can control the displacement so that the pressure deviation between the center and the end of the steel sheet in the width direction is reduced, the pressure unevenness generated in the width direction of the steel sheet can be easily suppressed.

  Further, in pressure unevenness, a high pressure state often leads to problems such as defects. Since the displacement control unit 105 can adjust the high pressure portion to a lower pressure with respect to the pressure unevenness in the steel sheet cooling device 10, problems caused in the high pressure portion can be easily suppressed.

  Further, in the completion process of the present invention, it has been found that the latter is larger in the water droplet diameter discharged from the upper side in the longitudinal direction of the steel sheet and the water droplet diameter discharged from the lower side. This is thought to be because water droplets that were not discharged at the exhaust port dropped and aggregated. Aggregated water droplets cause cooling unevenness and need to be discharged quickly. If the displacement control unit 105 can control the displacement according to the lower side in the longitudinal direction of the steel plate (the side where the steel plate S enters) and the upper side (the side where the steel plate S exits), the above-described cooling unevenness in the longitudinal direction of the steel plate. This problem can be easily suppressed.

  Moreover, when the steel plate cooling device 10 has the exhaust part partition plate 107, since the exhaust parts 101 arranged in the steel plate width direction are partitioned, it is preferable because the exhaust amount control can be controlled with higher accuracy. In particular, it is preferable that all the exhaust portions 101 arranged in the longitudinal direction of the steel plate are partitioned by the exhaust portions 101 adjacent to each other in the steel plate width direction and the exhaust portion partition plate 107, since the accuracy of exhaust amount control is further increased.

  If the steel sheet cooling device 10 of the present invention is applied to a hot dip galvanizing facility 1 equipped with a scanning radiation thermometer 17, the temperature unevenness of the steel sheet S can be evaluated, and the pressure unevenness in the steel sheet cooling device 10 can be determined from this temperature unevenness. I can confirm. Therefore, by manufacturing a hot-dip galvanized steel sheet while confirming the pressure unevenness in the steel sheet cooling device 10 using a scanning radiation thermometer or the like, more preferable manufacturing conditions (the pressure unevenness in the steel sheet cooling device 10 is small). Easy to adjust).

  In addition, as said steel plate size produced, the said effect of this invention is fully show | played in the range of width 2m or less. Further, the present invention can be preferably used even in the cooling in the region where the steel plate temperature is 300 to 500 ° C.

C: 0.0008-0.0040 mass%, Si: 0.2 mass% or less, Mn: 2.0 mass% or less, P: 0.070 mass% or less, S: 0.020 mass% or less, balance Fe 2 and 3 is a continuous hot dip galvanizing facility as shown in FIG. 1, which is made of a steel plate having a component composition consisting of inevitable impurities and a plate thickness of 0.65 mm and a tensile strength TS of 340 MPa. A hot-dip galvanized steel sheet was manufactured using such a steel sheet cooling apparatus. In continuous hot dip galvanizing equipment, steel plates are continuously annealed, then immersed in a hot dip galvanizing bath at a bath temperature of 470 ° C., and adjusted to a zinc adhesion amount of 45 g / m ² by gas wiping, up to 520 ° C. It heated and alloyed and then cooled to 300 ° C. in a water mist cooling zone. In the off-line cooling experiment, the amount of water is such that no transition boiling occurs.

The exhaust facility is provided with an exhaust port divided into three in the width direction, and further provided with a pressure measurement hole and a pressure gauge at each exhaust port, so that the opening degree of the damper installed at each exhaust port can be changed according to the pressure value. For the intermediate damper, the damper opening was manually adjusted according to the temperature deviation on the cooling zone exit side. One exhaust fan was provided at the connecting portion of the damper, and the air flow was operated at a constant output of 3600 m ³ / hr.

  In the example of this invention, the infrared thermography was installed in the exit position of the steel plate cooling device. Further, water mist mixed with water and air is used as a refrigerant, flat spray nozzles are provided at nine locations at intervals of 200 mm in the width direction of the steel sheet, and the amount of water mist injection from each refrigerant injection nozzle is determined by a cooling water flow rate adjustment valve. It can be controlled by adjusting the amount of cooling water. On the other hand, the cooling air for water mist was always injected at a constant pressure (200 kPa at each pipe header). The nozzles are arranged in 40 rows at intervals of 200 mm in the steel plate traveling direction, and 200 mm from the steel plate to the nozzle injection ports so that the adjacent refrigerant injection nozzles are shifted by 50 mm in the width direction. More specifically, it is as shown in FIG. 9 (in FIG. 9, four of nine nozzles arranged at intervals of 200 mm in the width direction are shown).

  If it is difficult to install a flow meter for each refrigerant injection nozzle, measure the amount of cooling water for each zone by dividing the refrigerant injection nozzle group into multiple zones in multiple rows in the direction of travel of the steel sheet. Can be managed under appropriate conditions by preliminarily grasping the relationship between the flow rate immediately before the refrigerant injection nozzle, the flow rate adjustment valve opening degree, and the pipe pressure, and constantly monitoring the flow rate adjustment valve opening degree and the pipe pressure. . Tables 1 and 2 describe the conditions such as the nozzle header arrangement, the number of divisions of the exhaust port, and the damper opening degree. Table 1 shows the case where the exhaust port is divided in the width direction, and Table 2 shows the case where the exhaust port is divided in the width direction and the longitudinal direction.

  In the comparative example, in order to confirm the effect of the conventional apparatus, the steel sheet cooling apparatus was used under the condition that the displacement control unit was not used. In the comparative example, local supercooling occurred due to poor discharge of mist droplets, and stretcher strain occurred during the subsequent press processing, whereas in the present example, an almost uniform temperature distribution was realized. As a result, it is possible to produce a steel plate that does not generate stretcher strain.

DESCRIPTION OF SYMBOLS 1 Hot dip galvanization equipment 10 Steel plate cooling device 100 Box 101 Exhaust part 102 Nozzle header 1020 Nozzle 103 Seal mechanism 104 Pressure measuring part 1040 Pressure hole 1041 Pressure gauge 105 Exhaust amount control part 1050 Damper 1051 Intermediate damper 106 Exhaust fan 11 Hot dip galvanizing bath 12 Sink Roll 13 Alloying Zone 14 Gas Wiping Nozzle 15 Support Roll in Bath 16 Support Roll on Bath 17 Scanning Radiation Thermometer

Claims (6)

A box having upper and lower openings, and a steel plate traveling upward or downward inside,
In the box, formed on a surface facing the steel plate surface, and one or more exhaust parts for exhausting the box,
A nozzle header installed between the exhaust part and the steel plate and having a plurality of nozzles for spraying water mist on the traveling steel plate, and extending in the steel plate width direction;
A sealing mechanism for preventing water leakage from the lower opening of the box;
In the box, a pressure measurement unit that performs pressure measurement at a plurality of measurement points at different positions in the steel plate width direction, and
A steel plate cooling apparatus comprising: an exhaust amount control unit that controls an exhaust amount from the exhaust unit based on a pressure value measured by the pressure measuring unit.   The steel plate cooling device according to claim 1, wherein the one or more exhaust parts are three or more exhaust parts arranged in the steel plate width direction.   The exhaust amount control unit controls an exhaust amount from the exhaust unit so that a pressure deviation calculated from a plurality of pressure values measured by the pressure measurement unit is 40% or less. The steel plate cooling apparatus according to 1 or 2.   The steel sheet cooling device according to any one of claims 1 to 3, wherein the one or more exhaust parts include two or more exhaust parts arranged in a longitudinal direction of the steel sheet. A steel plate cooling method for cooling a steel plate by injecting water mist onto a traveling steel plate while exhausting the cooling device,
The pressure measurement is performed at a plurality of measurement points having different positions in the steel plate width direction, and the steel plate is cooled while adjusting the exhaust amount of the exhaust gas so that the pressure deviation becomes small based on the measurement result. Steel plate cooling method to do.   The steel sheet cooling method according to claim 5, wherein the displacement is adjusted so that the pressure deviation is 40% or less.

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