JP6569843B1 - Thick steel plate cooling device and cooling method, and thick steel plate manufacturing equipment and manufacturing method - Google Patents

Abstract

The ratio P / D between the constraining roll pitch P and the constraining roll diameter D is set to 2.5 or less, a plurality of cooling headers are arranged between the constraining rolls, and each cooling header is connected to one of two or more cooling water supply systems. Connected, each cooling water supply system has an adjustment valve that can independently control on / off of water supply and flow control, each cooling header has a plurality of cooling spray nozzles in the steel plate width direction, and is adjacent to the steel plate width direction The cooling spray nozzles are connected to the cooling headers of different cooling water supply systems, and the cooling water flow densities injected from the cooling spray nozzles adjacent in the width direction of the steel sheet are different from each other with respect to the same injection pressure. The cooling spray nozzle that injects cooling water with the maximum flow density can inject cooling water with a flow density more than three times that from the cooling spray nozzle that injects cooling water with the minimum flow density. Comprising a control mechanism for controlling using the adjustment valve so that 却水 supply system individually select and injects cooling water from the cooling spray nozzles, the steel plate cooling apparatus.

Description

  In the production line of the thick steel plate, the present invention provides a cooling rate higher than that of the conventional one while controlling the shape when the steel plate cooled to room temperature after hot rolling or controlled cooling after hot rolling is cooled by reheating quenching. Further, the present invention relates to a cooling device and a cooling method that can be adjusted in a wide range. Moreover, this invention relates to the manufacturing method of the thick steel plate using this cooling device, and the manufacturing method of the thick steel plate using this cooling method.

  In particular, in the production of a thick steel plate (sometimes simply referred to as a steel plate), it is necessary to ensure mechanical properties required for the steel plate, particularly strength and toughness. In order to achieve this, an operation of cooling the high-temperature thick steel plate after rolling as it is, or once air-cooling to room temperature and reheating and quenching offline is performed. In this cooling operation, cooling is often performed at a high cooling rate in view of the material properties required for the steel sheet, particularly in terms of high strength.

  On the other hand, with the recent advancement of material control, not only the need for higher strength but also the need to combine soft and hard transformation structures has increased. For example, this is a method of obtaining a composite structure such as ferrite + bainite or ferrite + martensite by setting the cooling rate to a relatively slow condition in the early or late stages of cooling. With this composite structure, for example, the yield ratio, which is the ratio of the yield strength to the tensile strength, can be lowered, and a steel plate having excellent earthquake resistance may be manufactured.

  Conventionally, in order to realize such a composite structure with a thick steel plate, multistage heat treatment in which reheating and quenching is performed a plurality of times has been performed, but in terms of process saving, it is optional at the time of one quenching. There is a need for a cooling technique capable of changing the cooling rate at the timing. In particular, in order to promote the formation of ferrite, it is necessary to cool over a long time at an extremely slow cooling rate (for example, about 2 to 20 ° C./s). For this reason, it is required to adjust the cooling rate to a very low speed compared with the cooling rate of a general online control cooling device or a quenching device during heat treatment (approximately 30 to 60 ° C./s at a plate thickness of 20 mm). Yes.

  As a technique for changing the cooling rate at an arbitrary timing during cooling of a thick steel plate, there are the following patent documents.

  Patent Document 1 discloses a technique for changing a cooling capacity over a wide range by disposing a water tank and a spray nozzle installed in the water tank and changing the liquid surface height of the water tank with respect to the cooling header on the lower surface. . In Patent Document 1, in order to increase the cooling capacity, the liquid level of the water tank is increased to submerge the nozzle tip, and the water in the water tank is accompanied by the spray water in addition to the spray cooling water. The amount of water larger than the injection flow rate can be flooded onto the steel plate. In addition, when lowering the cooling capacity, the water level of the water tank should be lowered so that the tip of the spray nozzle is not submerged, and a small amount of water is allowed to flood the steel plate by not generating the accompanying flow described above. Can do. On the other hand, in such a technique, since it is necessary to arrange | position a water tank between table rolls, cooling is limited to the lower surface of a steel plate, and cannot be used for cooling of an upper surface. Further, in a facility where the distance between table rolls is narrow, such as a thick plate quenching apparatus, a water tank cannot be installed between rolls in the first place.

  Patent Document 2 is a technique for adjusting the flow rate by supplying water from an independent system to adjacent nozzles of a plurality of nozzles attached in the width direction and injecting only one of them when the flow rate is lowered. On the other hand, even with such a technique, the adjustment amount of the flow rate can only be adjusted by about 50% with respect to the maximum cooling rate.

  Therefore, in Patent Document 3, in order to improve the above points, a rapid cooling device and a slow cooling device having rod-shaped cooling water nozzles having different flow rate characteristics are arranged at the front and rear, and the rapid cooling device is provided in one cooling area. And a technique for adjusting the cooling rate in a wide range by switching the slow cooling device and spraying.

JP 59-47010 A JP 2014-124634 A JP 2011-167759 A

  In the cooling of thick steel plates, particularly offline heat treatment, so-called roller quench is often employed in which the steel plates are cooled while being constrained by a roll. This type is widely used because the steel plate is cooled while being constrained by a roll so that the flatness of the steel plate after cooling is good and the subsequent shape correction treatment can be reduced. On the other hand, roller quench uses a relatively large diameter roll and constrains the steel sheet with a narrow roll pitch in order to improve the cooling shape, thus ensuring a wide space for the cooling device installed between the rolls. I can't. For this reason, it is difficult to apply the technique of Patent Document 3 to a roller quench type cooling device.

  Therefore, the present invention has been made in view of the circumstances as described above, and in cooling the thick steel plate, the cooling rate can be adjusted in a wide range by adjusting the amount of cooling water in a wide range while controlling the shape, In particular, in a roller quench type cooling device in which a cooling device is installed between rolls for restraining thick steel plates, an object is to provide a cooling device and a cooling method effective for a narrow cooling space. Moreover, an object of this invention is to provide the manufacturing equipment of the thick steel plate using this cooling device, and the manufacturing method of the thick steel plate using this cooling method.

  As a result of intensive studies, the present inventors controlled the shape of the steel sheet by setting the ratio P / D of the constraining roll pitch P and the constraining roll diameter D to a predetermined range, and used cooling spray nozzles having different flow density. It was found that the cooling rate can be adjusted in a wide range.

The gist of the present invention is as follows.
[1] In a cooling device in which a plurality of restraining rolls are installed in the steel plate conveyance direction and a plurality of cooling headers are arranged between the restraining rolls,
The ratio P / D between the constraint roll pitch P and the constraint roll diameter D is 2.5 or less,
Each cooling header is connected to one of two or more cooling water supply systems,
Each cooling water supply system is equipped with a regulating valve so that water supply can be turned on and off independently and the flow rate can be controlled independently.
Each cooling header is equipped with multiple cooling spray nozzles in the steel plate width direction,
The cooling spray nozzles adjacent in the steel plate width direction are connected to cooling headers of different cooling water supply systems,
The cooling water flow density injected from the cooling spray nozzles adjacent to each other in the width direction of the steel sheet is different from the flow density of the cooling water. Cooling water with a flow rate density more than 3 times that of the cooling spray nozzle that injects cooling water with a flow rate density of
A cooling apparatus for a thick steel plate, comprising a control mechanism that controls each cooling water supply system by using an adjustment valve so as to individually select cooling water supply systems and inject cooling water from cooling spray nozzles.
[2] The cooling of the thick steel plate according to [1], wherein the distance from the tip of each cooling spray nozzle to the steel plate is set to be within a range of ± 50 mm or less with respect to the height of the central axis of the restraint roll. apparatus.
[3] Each cooling spray nozzle is one or more of a flat spray nozzle, a full cone spray nozzle, a square spray nozzle, and an elliptical spray nozzle, and cooling when cooling water is jetted from each cooling spray nozzle The cooling apparatus for thick steel plates according to [1] or [2], wherein the water injection angle is in the range of 60 to 120 °.
[4] In a cooling method for a thick steel plate using a cooling device in which a plurality of restraining rolls are installed in the steel plate conveyance direction and a plurality of cooling headers are arranged between the restraining rolls,
The ratio P / D between the constraint roll pitch P and the constraint roll diameter D is 2.5 or less,
Each cooling header is connected to one of two or more cooling water supply systems,
Each cooling water supply system is equipped with a regulating valve so that water supply can be turned on and off independently and the flow rate can be controlled independently.
Each cooling header is equipped with multiple cooling spray nozzles in the steel plate width direction,
The cooling spray nozzles adjacent in the steel plate width direction are connected to cooling headers of different cooling water supply systems,
The cooling water flow density injected from the cooling spray nozzles adjacent to each other in the width direction of the steel sheet is different from the flow density of the cooling water. Cooling water with a flow rate density more than 3 times that of the cooling spray nozzle that injects cooling water with a flow rate density of
A method for cooling a thick steel plate, wherein each cooling water supply system is individually selected and controlled using an adjustment valve so as to inject cooling water from a cooling spray nozzle.
[5] The distance from the tip of each cooling spray nozzle to the steel plate is set so that the distance from the central axis height of the restraining roll is within a range of ± 50 mm or less. Cooling method.
[6] Each cooling spray nozzle is at least one of a flat spray nozzle, a full cone spray nozzle, a square spray nozzle, and an elliptical spray nozzle, and cooling when cooling water is jetted from each cooling spray nozzle The method for cooling a thick steel plate according to [4] or [5], wherein the water injection angle is in a range of 60 to 120 °.
[7] A thick steel plate manufacturing facility comprising the cooling device according to any one of [1] to [3].
[8] A method for producing a thick steel plate having a step of cooling by the cooling method according to any one of [4] to [6].

  ADVANTAGE OF THE INVENTION According to this invention, in cooling of a thick steel plate, adjustment of a cooling rate is possible in a wide range, controlling a shape, and manufacture of the thick steel plate with various intensity | strength is attained. In particular, this is an effective technique for a narrow cooling space in which a cooling device is installed between restraining rolls installed at a narrow pitch in the transport direction.

FIG. 1 is a schematic diagram of an off-line heat treatment facility for thick steel plates using the cooling device of the present invention. FIG. 2 is a schematic view showing an embodiment of the cooling device of the present invention. FIG. 3 is a view for explaining the positional relationship between the cooling spray nozzle and the restraining roll of the present invention. FIG. 4 is a diagram illustrating an injection angle of cooling water (spray water) injected from the cooling spray nozzle. FIG. 5 is a schematic view of the cooling device of the present invention as viewed from above, FIG. 5 (a) is a diagram showing the configuration of the cooling header, and FIGS. 5 (b) and 5 (c) are sprays injected from the cooling spray nozzle. It is a figure which shows the mode of water. FIG. 6 is a diagram showing the arrangement of cooling headers and cooling spray nozzles when the number of cooling header systems is increased (four systems). FIG. 7 is a top view of a state in which spray water from a small flow rate cooling spray nozzle collides with a thick steel plate when cooling water is injected from two cooling headers. FIG. 7 (a) is a flat spray. When a nozzle is used, FIG. 7B shows a case where an oval spray nozzle is used, FIG. 7C shows a case where a full cone spray nozzle is used, and FIG. 7D shows a case where a square blow spray nozzle is used. is there. FIG. 8 is a schematic view of the large flow cooling spray nozzle and the small flow cooling spray nozzle when the nozzle pitch is different. FIG. 8 (a) is a diagram showing the configuration of the cooling header, and FIG. 8 (b). Fig. 8 is a view showing the state of water sprayed by a large flow rate cooling spray nozzle, and Fig. 8 (c) is a view showing the state of water sprayed by a small flow rate cooling spray nozzle. FIG. 9 is a schematic view of a cooling treatment facility for thick steel plates using the cooling device of the present invention. FIG. 10 is a graph showing the relationship between the injection pressure and the flow density in the large flow cooling spray nozzle and the small flow cooling spray nozzle. FIG. 11 is a graph showing the relationship between the cooling rate and the flow density until the temperature reaches 800 ° C. to 400 ° C. at the center in the thickness direction when the steel plate is cooled.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a case where the cooling device of the present invention is applied to offline heat treatment of a thick steel plate. The thick steel plate S is previously processed into a predetermined thickness (for example, 40 mm) and width (for example, 2500 mm) by a rolling facility, and is transported to the main heat treatment line and then heated to a predetermined temperature (for example, 920 ° C.) in the heating furnace 1. After that, it is cooled by the cooling device 2 installed on the exit side of the heating furnace 1. The cooling device 2 includes a table roll 3 that conveys the thick steel plate S, a restraining roll 4 that restrains the thick steel plate S, and a cooling header 5 that is provided on the upper and lower surfaces of the thick steel plate S.

  Details of the cooling device 2 according to an embodiment of the present invention are shown in FIG. As shown in FIG. 2, there are a plurality of table rolls 3 for conveying the thick steel plates S and a plurality of restraining rolls 4 for restraining the thick steel plates S, and a large flow rate cooling is performed on the upper surface and the lower surface (between the table rolls 3) between the restraining rolls 4 A plurality of headers 51 and small flow rate cooling headers 52 are installed. In each cooling header, the flow rate adjustment valve 7 is installed so that the flow rate of the cooling water supplied to the cooling header is measured by the flow meter 6 and can be adjusted to a predetermined flow rate based on the measurement result. Further, the flow rate adjusting valve 7 is connected to a control mechanism (not shown) so that the cooling water can be individually turned on / off (water supply / shutoff). A plurality of cooling spray nozzles 53 (54) are attached to each cooling header. Details of the cooling spray nozzle 53 (54) will be described later.

  Hereinafter, the positional relationship between the cooling header (cooling spray nozzle) and the restraining roll 4 on the upper surface of the thick steel plate will be described. In addition, the pitch of the table roll 3 and the restraint roll 4 is the same. Therefore, the positional relationship between the cooling header (cooling spray nozzle) and the table roll 3 on the lower surface of the thick steel plate is the same as the positional relationship between the cooling header (cooling spray nozzle) and the restraining roll 4 on the upper surface of the thick steel plate.

  FIG. 3 is a view for explaining the positional relationship between the cooling spray nozzle and the restraining roll of the present invention. In the present invention, application to thick steel plates is mainly considered, and it is an important issue to prevent out-of-plane deformation that occurs when cooling thick steel plates. Therefore, from the viewpoint of preventing out-of-plane deformation, a cooling method is adopted in which the thick steel plate S is restrained by the restraining roll 4 and the table roll 3. At that time, the narrowest possible installation pitch (constraint roll pitch P) with respect to the conveying direction of the restraint roll 4 is advantageous from the viewpoint of preventing out-of-plane deformation of the steel sheet. Further, in order to appropriately prevent the out-of-plane deformation of the constraining roll 4, it is preferable that the constraining roll diameter D is as large as possible in order to reduce the deflection of the constraining roll 4 even when a large load is applied. On the other hand, as the constraining roll pitch P of the constraining roll 4 is arranged narrower, the gap G between the rolls becomes narrower, so the space for installing the cooling device 2 becomes smaller. For this reason, it is impossible to install the cooling device as in the present invention in a nozzle that requires a large cooling header as described in Patent Document 3, in particular. Moreover, in order to cool to the contact point vicinity of the restraint roll 4 and the thick steel plate S from the viewpoint of uniform cooling, the spray length L when the cooling spray nozzle 53 (or the cooling spray nozzle 54) is viewed from the side is determined between the rolls. It is preferable that the cooling water is wetted by the thick steel plate S up to an area below the constraining roll 4 wider than the gap G. From this point of view, a method that can spray the cooling water over a wide range such as spray cooling is preferable.

  As a result of intensive studies by the present inventors based on these, the ratio P / D between the restraint roll pitch P and the restraint roll diameter D of the restraint roll 4 is set to a range of 2.5 or less from the viewpoint of shape control of the steel sheet. . When P / D is 1.0, the restraint roll pitch and the restraint roll diameter are the same, there is no gap between the front and rear restraint rolls, and the cooling spray nozzle cannot be installed. Therefore, P / D is preferably greater than 1.0, and the clearance (P-D) between the front and rear restraint rolls is ensured to be at least 50 mm. Therefore, from the viewpoint of operation, it is more preferable that P / D is 1.17 or more. Moreover, since P / D should be as small as possible from the point of shape control, P / D is preferably 2.0 or less.

  Note that the roll diameter of the table roll 3 and the constraining roll diameter D are not necessarily the same. Even when the roll diameter of the table roll 3 and the restraint roll diameter D are the same on the upper and lower surfaces of the thick steel plate, the ratio P / D may satisfy 2.5 or less as described above. Further, the ratio of the roll pitch and the table roll diameter of the table roll 3 on the lower surface of the thick steel plate only needs to satisfy 2.5 or less.

  Further, the spray length L in the conveying direction of the cooling spray nozzle 53 (54) between the restraint rolls 4 is as close to the restraint roll pitch P as possible, so that the number of non-cooling portions between the restraint rolls 4 is reduced, and the efficiency is increased. Cooling is possible. For this reason, it is preferable that at least the spray length L is larger than the gap G between rolls. On the other hand, in order to increase the spray length L, it is necessary to increase the injection angle θ of the cooling spray nozzle 53 (54) shown in FIG. At that time, the spray angle θ of the cooling spray nozzle 53 (54) is excessively increased, or the nozzle central axis of the cooling spray nozzle 53 (54) is moved in the transport direction (left and right in the drawing) from the central position between the restraining rolls 4. When the cooling spray nozzle 53 (54) is installed in a state shifted in the direction), the spray water 55 (56) from the cooling spray nozzle 53 (54) collides with the restraining roll 4 before colliding with the thick steel plate S. The thick steel plate S may not be cooled efficiently. Therefore, an appropriate injection angle θ is selected, and the nozzle central axis of the cooling spray nozzle 53 (54) is within ± 10 mm from the central position between the restraining rolls 4 with respect to the transport direction (left and right direction in the drawing). It is preferable to arrange the nozzle central axis of the cooling spray nozzle 53 (54), and the substantially central position between the restraining rolls 4 is most preferable.

  Next, the cooling header of the cooling device 2 will be described. Fig.5 (a) is the schematic diagram which looked at the cooling device 2 of this invention from the top, and is a figure explaining the structure of a cooling header. A plurality of large-flow-rate cooling spray nozzles 53 are attached to the large-flow-rate cooling header 51 in the steel plate width direction. On the other hand, a plurality of small flow rate cooling spray nozzles 54 are attached to the small flow rate cooling header 52 in the steel plate width direction.

In the present invention, the cooling spray nozzles are arranged so that the flow rates per unit area and unit time are different. Here, the unit area and the unit time are the flow rate of the cooling water injected into the range of the interval P ′ between the adjacent cooling spray nozzles. Hereinafter, the flow rate per unit area and unit time is referred to as a flow rate density (unit: L / (min · m ² )).

  That is, as shown in FIG. 5A, a large flow density cooling spray nozzle is attached to the large flow rate cooling header 51 and a small flow density cooling spray nozzle is attached to the small flow rate cooling header 52. The cooling spray nozzles adjacent to each other are connected to cooling headers of different systems.

  In the present invention, the cooling spray nozzles having different flow densities are arranged adjacent to each other in the width direction. The large flow rate cooling spray nozzle 53 and the small flow rate cooling spray nozzle 54 may be arranged in a row in the width direction of the thick steel plate S at a predetermined pitch.

  In the present invention, when the cooling rate of the steel plate is increased, the water supply to the small flow rate cooling header 52 is shut off by the flow rate adjusting valve 7 so that the cooling water is not jetted from the small flow rate cooling spray nozzle 54, and the large flow rate cooling spray. Cooling water is jetted from the nozzle 53. On the other hand, when slowing down the cooling rate, the flow rate adjusting valve 7 shuts off the water supply to the large flow rate cooling header 51 so that the cooling water is not jetted from the large flow rate cooling spray nozzle 53 by the flow rate adjusting valve 7. Cooling water is sprayed from the cooling spray nozzle 54. That is, in the present invention, the flow rate can be adjusted in a wide range by individually selecting each cooling water supply system and injecting the cooling water, and the cooling rate can be adjusted in a wide range.

  Generally, when a nozzle having a certain characteristic is selected and cooling water is injected from the nozzle, the flow rate of the cooling water is proportional to the 0.5th power of the injection pressure. It is very difficult to change the cooling rate greatly. In general, it is said that the cooling rate is proportional to about 0.7 of the flow density. Therefore, the cooling rate is proportional to about 0.35 of the injection pressure.

  For this reason, for example, when the cooling rate is about half, the injection pressure needs to be lowered to about 1/7. In a general flow rate adjusting valve, the injection pressure can be adjusted to a range of about 10 to 100% of the rated value, so that the adjustment of the cooling capacity is about 50 to 100% at most. Moreover, since the injection flow rate is proportional to the 0.5th power of the injection pressure, the injection flow rate is 31.6 to 100% when it is considered that the injection pressure can be adjusted in the range of about 10 to 100% as described above. Adjustment within this range is the limit. Therefore, in the present invention, a cooling spray nozzle having a different flow density is disposed between the restraining rolls 4 to enable adjustment of a wide range of cooling rates.

  In the present invention, the flow density of the cooling water sprayed from the cooling spray nozzles adjacent to each other in the width direction of the steel sheet is different from the flow density, and the cooling spray nozzle that sprays the cooling water having the maximum flow density with respect to the same spray pressure. From the above, it is possible to inject cooling water having a flow rate density of three times or more from the cooling spray nozzle that injects cooling water having the minimum flow rate density. In FIG. 5A, the flow rate density of the large flow rate cooling spray nozzles 53 arranged at intervals of the pitch P ′ is at least three times the flow rate of the same injection pressure as compared to the small flow rate cooling spray nozzles 54. It becomes density.

  Next, a specific method for selecting the cooling spray nozzle will be described with reference to an example in which cooling water is injected from two cooling headers.

When the nozzle flow in the steel sheet width direction of the large flow cooling spray nozzle 53 and the small flow cooling spray nozzle 54 is the same, and cooling water is injected at a pressure of 0.4 MPa, the flow density of the large flow cooling spray nozzle 53 is 1500 L / (min. M ² ), and the flow density of the small flow rate cooling spray nozzle 54 is selected to be 500 L / (min · m ² ). With such a configuration, by controlling the flow rate using the flow rate adjusting valve 7, the flow rate density of the large flow rate cooling spray nozzle 53 is 500 L / (min · m ² ) (1/3 of the rating), and the small flow rate cooling spray nozzle. The flow density of 54 can be adjusted to 167 L / (min · m ² ) (1/3 of the rating). Therefore, by switching the cooling spray nozzles and flow control, continuously from the large flow cooling maximum flow density of the spray nozzle 1500L / (min · ^{m 2)} to a small flow cooling minimum flow density of the spray nozzle 167L / (min · ^{m 2)} The flow rate can be adjusted. In addition, in the manufacture of the steel sheet, as described above, when it is not necessary to adjust the flow density in the large flow cooling spray and the small flow cooling spray nozzle 54 continuously, the maximum of the small flow cooling spray nozzle 54 is used. The flow density need not be the same as the minimum flow density of the large flow cooling spray nozzle 53. For example, the maximum flow density of the large flow cooling spray nozzle 53 is 1500 L / (min · m ² ), and the small flow cooling spray nozzle is used. The maximum flow density of 54 may be selected as 50 L / (min · m ² ).

  As described above, by selecting one system cooling header by the flow rate adjusting valve 7 and injecting the cooling water from the cooling spray nozzle, the amount of spray water in a wide range can be adjusted continuously.

  Further, in the present invention, the cooling spray nozzles having different flow densities are arranged so as to be adjacent to each other, and only one of them is sprayed. Therefore, the arrangement is sprayed in a fan shape as shown in FIGS. 5 (b) and 5 (c), for example. In the example of the flat spray shape, the injection angle θ such that the width end portion of the spray water 55 sprayed from the large-flow-rate cooling spray nozzle 53 in FIG. (See FIG. 4) and a twist angle α (see FIG. 5 (c)), when the steel sheet is cooled by passage, a portion where the cooling water does not collide with the steel sheet is generated across the width direction when viewed from the steel sheet side. The steel sheet can be uniformly cooled without any problem.

  Similarly, in the case of FIG. 5C, the spray angle θ (see FIG. 5) such that the width end portion of the spray water 56 sprayed from the small flow rate cooling spray nozzle 54 is substantially at the same position as the adjacent spray water 56. 4) and a torsion angle α (see FIG. 5C), when the steel sheet passes and is cooled, there is no portion where the cooling water does not collide with the steel sheet in the width direction when viewed from the steel sheet side. The steel sheet can be cooled uniformly.

  As the spray angle θ of the cooling spray nozzle (large flow cooling spray nozzle 53 or small flow cooling spray nozzle 54), a cooling spray nozzle is installed between the narrow restricting rolls 4 so that the sprayed cooling water does not collide with the restricting rolls 4. Since it is preferable that the steel plate is wetted, it is preferable that the steel plate can be sprayed at as wide an angle as possible. In the present invention, the spray angle θ of the cooling spray nozzle (see FIG. 4) is preferably at least 60 to 120 °. When the injection angle θ is less than 60 °, the cooling water is not sprayed over a wide area, so there is a concern about temperature unevenness due to the non-impact portion of the cooling water. On the other hand, when the spray angle is larger than 120 °, the flying distance to the steel plate of the spray water varies greatly depending on the flying distance to the nozzle and the flying distance to other places. This is because it is difficult to ensure the above.

  Moreover, the distance (nozzle height H) from the front-end | tip of a cooling spray nozzle to a steel plate is demonstrated using FIG. The distance between the cooling spray nozzle (large flow cooling spray nozzle 53 or small flow cooling spray nozzle 54) and the thick steel plate S is considered from the point of collision between the restraining roll 4 and the spray water, and the tip of the cooling spray nozzle is close to the steel plate. As such, the cooling water hardly collides with the restraining roll 4 even if it is injected at a wide injection angle θ. In particular, when the distance between the cooling spray nozzle and the thick steel plate S is larger than half of the restraining roll diameter D where the gap between the restraining rolls 4 is the narrowest, the minimum gap between the restraining rolls 4 is from the cooling spray nozzle. The spray water easily collides with the restraining roll 4. Therefore, it is preferable that the distance between the cooling spray nozzle and the thick steel plate S be as low as possible near the half (radius) of the constraining roll diameter D. On the other hand, when the distance between the cooling spray nozzle tip and the thick steel plate S is short, the spray water must be sprayed at a wide angle, and there is a risk that the spray angle θ shown above exceeds 120 °. There is also a risk that the tip of the steel plate in the plate will collide with the tip of the cooling spray nozzle. Considering practical use from both points, when cooling a thick steel plate, the distance H from the tip of each cooling spray nozzle to the steel plate is the center of the upstream and downstream restraint rolls in the steel plate conveying direction with respect to the spray nozzle. It is preferable to install the tip of the spray nozzle within ± 50 mm with respect to the height of the central axis of the restraint roll, which is the distance from the shaft to the steel plate.

  In the above description, the example in which the cooling rate is adjusted with the flow density of two systems of the large flow cooling spray nozzle 53 and the small flow cooling spray nozzle 54 has been described. However, the present invention can be applied to two or more systems. . For example, as shown in FIG. 6, the number of cooling header systems can be increased (four systems), and the cooling rate can be adjusted to a wider range.

  In FIG. 6, in addition to the large flow cooling header 51 in which a plurality of large flow cooling spray nozzles 53 are attached in the steel sheet width direction, and the small flow cooling header 52 in which a plurality of small flow cooling spray nozzles 54 are attached in the steel sheet width direction. In addition, medium flow cooling headers 57 and 58 are arranged. A plurality of medium flow cooling spray nozzles 59 and 60 are attached to the medium flow cooling headers 57 and 58 in the steel plate width direction, respectively.

As a specific cooling spray nozzle selection method in the case of FIG. 6, when the nozzle pitch in the width direction of each cooling spray nozzle is the same and spraying is performed at a pressure of 0.4 MPa, the flow density of the large flow cooling spray nozzle 53 is the ^{1500L / (min · m 2)} , the flow density of the medium flow cooling spray nozzles ^{59 150L / (min · m 2} ), the flow density of the medium flow cooling spray nozzles ^{60 40L / (min · m 2} ), a low flow rate The flow density of the cooling spray nozzle 54 is selected to be 10 L / (min · m ² ). By doing in this way, in the cooling spray nozzle of the largest flow density and the cooling spray nozzle of the smallest flow density, the difference of the flow density of at least 3 times is provided with respect to the same injection pressure. With such a configuration, the flow rate is further controlled by using the flow rate adjusting valve 7 to continuously adjust the cooling rate in a wide range.

  In the present invention, each cooling spray nozzle is preferably one or more of a flat spray nozzle, a full cone spray nozzle, a square spray nozzle, and an elliptical spray nozzle.

  The spray angle of each cooling spray nozzle means the angle at which the spray angle is the widest in each direction when the spray spray water is viewed from the side. FIG. 7 is a top view of the spray water 55 (56) of the cooling spray nozzle 53 (54) colliding with the thick steel plate. FIG. 7A shows an example of a flat spray nozzle having a substantially fan-shaped jet, a collision surface having a thin thickness (about 20 mm) and a wide width, and FIG. 7B an example of an oval spray nozzle having an elliptical collision surface. When the collision surface of the cooling water is elliptical like a flat spray nozzle or an oval spray nozzle, as shown in FIGS. 7 (a) and 7 (b), the angle extending in the major axis direction of the collision surface is the widest angle. Therefore, this angle may be set as the injection angle. In addition, in the full cone spray nozzle having a circular collision surface as shown in FIG. 7C, the injection angle is the same regardless of the direction in the side view. As shown in FIG. 7 (d), the angle spray nozzle or the like in which the collision surface is rectangular (square or rectangular) has the widest angle spreading in the diagonal direction of the collision surface. That's fine.

Further, as shown in FIG. 8, the nozzle pitches in the width direction of the large flow cooling spray nozzle 53 and the small flow cooling spray nozzle 54 may be different nozzle pitches. FIG. 8A is a diagram showing the configuration of the cooling header when the mounting pitch of the small flow cooling spray nozzle 54 is doubled with respect to the mounting pitch in the width direction of the large flow cooling spray nozzle 53, FIG. ) Is a view showing the state of spray water from the large flow rate spray nozzle 53, and FIG. 8C is a view showing the state of spray water from the small flow rate cooling spray nozzle 54. In FIGS. 8B and 8C, each spray nozzle is a flat spray nozzle. For example, as an example in which the flow rate density is larger than three times, when the flow rate density of the large flow rate cooling spray nozzle 53 is four times the flow rate density of the small flow rate cooling spray nozzle 54, spraying at a pressure of 0.4 MPa causes a large flow rate. minimum flow density of the cooling maximum flow density of the spray nozzle 53 ^{1500L / (min · m 2)} , low-flow cooling spray nozzles 54 are as ^{375L / (min · m 2)} .

  Note that the high flow cooling spray nozzle 53 and the small flow cooling spray nozzle 54 may have different spray formats.

  In the above, although the example of the offline heat treatment process of the thick steel plate has been described, as shown in FIG. 9, the slab is heated in the heating furnace 1 and then rolled to a predetermined size in the rolling mill 8, and then as in the present invention. You may cool with the cooling device 2 provided with the cooling header 5 between the restraint rolls 4. In order to smoothly convey the thick steel plate S immediately after rolling to the cooling device 2, it is preferable that the steel plate is flattened in advance by the hot straightening machine 9 and then conveyed to the cooling device 2.

  The cooling device of the present invention can be suitably used for a thick steel plate having a plate thickness of 4.0 mm or more and a plate width of 100 mm or more.

  Therefore, if the steel plate manufacturing equipment equipped with the cooling device of the present invention, the cooling rate can be adjusted over a wide range while controlling the shape of the steel plate, so that it is possible to manufacture steel plates with various strengths. It is. Further, according to the cooling method of the present invention, the thick steel plate can be cooled at a wide range of cooling rates while controlling the shape of the thick steel plate. Therefore, in the manufacturing method including the step of cooling the thick steel plate by the cooling method of the present invention. If it exists, thick steel plates with various strengths can be manufactured.

  As a first embodiment of the present invention, a thick steel plate was manufactured using the offline heat treatment facility for thick steel plate shown in FIG. After heating a steel plate having a room temperature (thickness 25 mm, plate width 3500 mm, steel plate length 7 m) to 920 ° C. in the heating furnace 1, the steel plate temperature is 100 in the cooling device 2 located 2.5 m behind the heating furnace 1. Cooling was carried out by adjusting the plate passing speed so that the temperature became 0 ° C. The configuration of the cooling device 2 is the same as in FIG. 2, the diameter of the table roll 3 and the restraining roll 4 is 300 mm, the roll pitch P of the table roll 3 and the restraining roll 4 is 600 mm, and the cooling spray nozzle 53 is placed between the restraining rolls 4. , 54 (P / D = 2.0). In addition, the cooling spray nozzles 53 and 54 and the restraint roll 4 were installed 15 units (cooling device 2 length 9.0 m) in the steel plate conveyance direction.

The arrangement of the cooling spray nozzles 53 and 54 is the same as that in FIG. 3, and the distance between the cooling spray nozzle and the steel plate is 200 mm. The large flow rate cooling spray nozzle 53 was a flat spray nozzle sprayed at 150 L / min at a spray pressure of 0.4 MPa. The injection angle θ of the large flow cooling spray nozzle 53 is 100 °, the pitch P ′ in the width direction of the adjacent large flow cooling spray nozzles 53 is 160 mm, and the twist angle α is 48 ° in the steel plate traveling direction. At this time, the flow density of the large flow cooling spray nozzle 53 when the injection pressure is 0.4 MPa is 1563 L / (min · m ² ). The small flow rate cooling spray nozzle 54 was a flat spray nozzle that was sprayed at 40 L / min at a spray pressure of 0.4 MPa. The injection angle θ of the small flow rate cooling spray nozzle 54 is 100 °, the pitch P ′ in the width direction of the adjacent small flow rate cooling spray nozzles 54 is 160 mm, and the twist angle α is 48 ° in the steel plate traveling direction. At this time, the flow rate density of the small flow rate cooling spray nozzle 54 when the injection pressure is 0.4 MPa is 417 L / (min · m ² ).

  FIG. 10 is a graph showing the relationship between the injection pressure and the flow density in the large flow cooling spray nozzle 53 and the small flow cooling spray nozzle 54.

First, water is passed through the large flow rate cooling header 51 and the injection pressure at the large flow rate cooling spray nozzle 53 is gradually reduced from 0.4 MPa. As a result, the flow rate adjustment valve 7 can adjust the pressure until the injection pressure reaches about 0.04 MPa. However, when the pressure was lower than this, the pressure fluctuated greatly due to a slight difference in the opening degree of the flow rate adjusting valve 7, so that the pressure could not be adjusted stably. Flow density of large flow cooling spray nozzles 53, 1563L / when the injection pressure 0.4MPa (min · ^m 2), when the injection pressure 0.04MPa was ^{494L / (min · m 2)} .

Next, water flow of the large flow rate cooling header 51 was stopped, and water flow of the small flow rate cooling header 52 was performed. The flow rate density when the injection pressure in the small flow rate cooling spray nozzle 54 is 0.4 MPa is 417 L / (min · m ² ), and cooling water having the same flow rate density as the lower limit water amount of the large flow rate cooling spray nozzle 53 can be injected. I understand. Further, when the injection pressure of the small flow rate cooling spray nozzle 54 was gradually reduced from 0.4 MPa, the pressure adjustment was possible with the flow rate adjustment valve 7 until the injection pressure was about 0.04 MPa. The pressure greatly fluctuated due to a slight difference in the opening degree of the flow rate adjusting valve 7, and the pressure could not be adjusted stably. The flow density of the small flow rate cooling spray nozzle 54 was 132 L / (min · m ² ) when the injection pressure was 0.04 MPa.

  From the result of FIG. 10, it was confirmed that a wide range of spray water amounts can be achieved by using cooling spray nozzles having different flow density.

  Next, FIG. 11 shows the relationship between the cooling rate and the flow density until the temperature reaches 800 ° C. to 400 ° C. at the center in the plate thickness direction when the steel plate is actually cooled. Each cooling spray nozzle has the same configuration as in FIG. Scanning radiation thermometers (not shown) are installed on the inlet side and the outlet side of the cooling device, and the surface temperature of the steel plate is measured in the plate width direction and the longitudinal direction. The average temperature in the thickness direction of the steel sheet was calculated by heat transfer calculation based on the information on the inlet and outlet thermometers, and the cooling rate during water cooling was calculated. For the cooling rate, the measurement result at the central part of the plate width and the central part in the longitudinal direction of the steel sheet was taken as the cooling rate at the center of the steel sheet.

  As shown in FIG. 11, the cooling rate can be adjusted in the range of about 20 to 30 ° C./s by cooling with the large-flow-rate cooling spray nozzle 53, and about 30% by cooling with the small-flow-rate cooling spray nozzle 54. It was found that the cooling rate can be adjusted in the range of 7 to 20 ° C./s, and the cooling rate can be adjusted in a wider range than when each cooling spray nozzle is used alone.

  As a second embodiment of the present invention, as in the first embodiment, after heating a steel plate of a room temperature state (thickness 25 mm, plate width 3500 mm, steel plate length 7 m) to 920 ° C. in the heating furnace 1, Cooling from 800 ° C. to 400 ° C. at the center in the plate thickness direction when cooling is performed by adjusting the plate passing speed so that the steel plate temperature becomes 100 ° C. in the cooling device 2 located 2.5 m behind the heating furnace 1. The speed and temperature deviation in the width direction of the steel sheet after cooling were examined. The temperature deviation in the width direction was measured with a scanning radiation thermometer at a pitch of 20 mm in the width direction and a pitch of 100 mm in the longitudinal direction, and the value at the central part in the longitudinal direction of the steel sheet was taken as the temperature deviation in the width direction.

  The configuration of the cooling device 2 is the same as in FIG. 2, and the diameters of the table roll 3 and the restraining roll 4 are as shown in Table 1. The large flow spray nozzle 53 and the small flow spray nozzle 54 are both flat spray nozzles, and the spray angle θ, the pitch P ′ in the width direction, and the twist angle α are set as shown in Table 1, respectively. The length of the cooling device 2 was 9.0 m, and the number of restraint rolls 4 and cooling spray nozzles 53 (54) installed was as shown in Table 1.

  For Examples 1 to 8, the cooling rate can be adjusted in the range of about 20 to 30 ° C./s by cooling with the large flow rate cooling spray nozzle 53, and the cooling rate with the small flow rate cooling spray nozzle 54 is about The cooling rate could be adjusted in the range of 7 to 20 ° C./s. The temperature deviation in the plate width direction at this time was less than 15 ° C. Later, the strength of the cooling material was measured, but the quality was not particularly problematic.

  For Examples 9 to 16, the cooling rate can be adjusted in the range of about 20 to 30 ° C./s by cooling with the large flow rate cooling spray nozzle 53, and the cooling rate with the small flow rate cooling spray nozzle 54 is about The cooling rate could be adjusted in the range of 7 to 20 ° C./s. In addition, the temperature deviation of the board width direction at this time was less than 20 degreeC. Although the temperature deviation was slightly larger than when P / D was 2.0, the strength of the cooling material was measured later, and the level was not particularly problematic.

  Comparative Examples 1 to 8 are examples in which the constraining roll pitch P is larger than those in Examples 1 to 8. P / D is 3.0, which is outside the scope of the present invention. The cooling rate can be adjusted in the range of about 20-30 ° C./s by cooling with the large flow rate cooling spray nozzle 53 and in the range of about 7-20 ° C./s by cooling with the small flow rate cooling spray nozzle 54. did it. On the other hand, the steel plate was deformed into a wave shape under all conditions. When the restraining roll 4 on the inlet side of the cooling device 2 was visually observed during the cooling operation, there was a gap between the restraining roll 4 and the steel sheet, and cooling water leaked from this gap to a part in the width direction, and the steel sheet was locally This is thought to be due to cooling. Moreover, the temperature deviation in the plate width direction after cooling varies in the range of 27 to 60 ° C. When the strength of the cooling material is measured later, the hardness of the steel plate where the leaked water has been placed becomes high, and the quality There was a problem above.

  Comparative Examples 9 to 16 are examples in which the roll diameter D is reduced with respect to Examples 1 to 8 of the present invention. P / D is 2.7, which is outside the scope of the present invention. The cooling rate can be adjusted in the range of about 20-30 ° C./s by cooling with the large flow rate cooling spray nozzle 53 and in the range of about 7-20 ° C./s by cooling with the small flow rate cooling spray nozzle 54. did it. On the other hand, the steel plate was deformed into a wave shape under all conditions. During the cooling work, when the restraint roll on the cooling device intrusion side was visually observed, there was a gap between the restraint roll and the steel sheet, and cooling water leaked to a part of the width direction from this gap, cooling the steel sheet. it is conceivable that. In addition, the temperature deviation in the plate width direction at this time varies in the range of 35 to 60 ° C., and when the strength of the cooling material is measured later, the hardness of the steel plate where the leaked water is placed increases, and the quality There was a problem above.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Cooling device 3 Table roll 4 Restraint roll 5 Cooling header 51 Large flow cooling header 52 Small flow cooling header 53 Large flow cooling spray nozzle 54 Small flow cooling spray nozzle 55 Spray water 56 Spray water 57 Medium flow cooling header 58 Medium Flow Cooling Header 59 Medium Flow Cooling Spray Nozzle 60 Medium Flow Cooling Spray Nozzle 6 Flow Meter 7 Flow Control Valve 8 Rolling Machine 9 Hot Straightening Machine S Thick Steel Plate P Constraining Roll Pitch D Constraining Roll Diameter G Gap Between Rolls L Spray Length H Nozzle height P ′ (width direction) pitch θ injection angle α twist angle

Claims (8)

In a cooling device in which a plurality of restraining rolls are installed in the steel plate conveyance direction and a plurality of cooling headers are arranged between the restraining rolls,
The ratio P / D between the constraint roll pitch P and the constraint roll diameter D is 2.5 or less,
Each cooling header is connected to one of two or more cooling water supply systems,
Each cooling water supply system is equipped with a regulating valve so that water supply can be turned on and off independently and the flow rate can be controlled independently.
Each cooling header is equipped with multiple cooling spray nozzles in the steel plate width direction,
The cooling spray nozzles adjacent in the steel plate width direction are connected to cooling headers of different cooling water supply systems,
The cooling water flow density injected from the cooling spray nozzles adjacent to each other in the width direction of the steel sheet is different from the flow density of the cooling water. Cooling water with a flow rate density more than 3 times that of the cooling spray nozzle that injects cooling water with a flow rate density of
A cooling apparatus for a thick steel plate, comprising a control mechanism that controls each cooling water supply system by using an adjustment valve so as to individually select cooling water supply systems and inject cooling water from cooling spray nozzles.   The apparatus for cooling a thick steel plate according to claim 1, wherein the cooling spray nozzle is installed such that the distance from the tip of each cooling spray nozzle to the steel plate is within a range of ± 50 mm or less with respect to the height of the central axis of the constraining roll.   Each cooling spray nozzle is at least one of a flat spray nozzle, a full cone spray nozzle, a square spray nozzle, and an elliptical spray nozzle, and the cooling water is sprayed when the cooling water is sprayed from each cooling spray nozzle. The cooling apparatus for a thick steel plate according to claim 1 or 2, wherein the angle is in a range of 60 to 120 °. In the cooling method of the thick steel plate using a cooling device in which a plurality of restraint rolls are installed in the steel plate conveyance direction and a plurality of cooling headers are arranged between the restraint rolls,
The ratio P / D between the constraint roll pitch P and the constraint roll diameter D is 2.5 or less,
Each cooling header is connected to one of two or more cooling water supply systems,
Each cooling water supply system is equipped with a regulating valve so that water supply can be turned on and off independently and the flow rate can be controlled independently.
Each cooling header is equipped with multiple cooling spray nozzles in the steel plate width direction,
The cooling spray nozzles adjacent in the steel plate width direction are connected to cooling headers of different cooling water supply systems,
The cooling water flow density injected from the cooling spray nozzles adjacent to each other in the width direction of the steel sheet is different from the flow density of the cooling water. Cooling water with a flow rate density more than 3 times that of the cooling spray nozzle that injects cooling water with a flow rate density of
A method for cooling a thick steel plate, wherein each cooling water supply system is individually selected and controlled using an adjustment valve so as to inject cooling water from a cooling spray nozzle.   The method for cooling a thick steel plate according to claim 4, wherein the distance from the tip of each cooling spray nozzle to the steel plate is set so as to be within a range of ± 50 mm or less with respect to the height of the central axis of the constraining roll.   Each cooling spray nozzle is at least one of a flat spray nozzle, a full cone spray nozzle, a square spray nozzle, and an elliptical spray nozzle, and the cooling water is sprayed when the cooling water is sprayed from each cooling spray nozzle. The method for cooling a thick steel plate according to claim 4 or 5, wherein the angle is in a range of 60 to 120 °.   A facility for manufacturing a thick steel plate, comprising the cooling device according to claim 1.   The manufacturing method of the thick steel plate which has the process cooled with the cooling method in any one of Claims 4-6.

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