JP5181752B2 - Steel cooling method and cooling device - Google Patents

Description

  The present invention relates to a cooling method and a cooling device for steel materials such as thick steel plates, thin steel plates, and shaped steels, and in particular, quickly injects / stops cooling water, accurately controls cooling temperature, and reduces temperature unevenness after cooling. Is intended.

  In the process of manufacturing steel materials (thick steel plates, thin steel plates, shaped steels, etc.) by hot rolling, in recent years, the steel materials are cooled to adjust the rolling temperature, or the steel materials immediately after rolling are rapidly cooled to Development of techniques for increasing the strength and workability of steel materials by increasing the size and controlling transformation structures such as pearlite, bainite and martensite has been extensive.

  In this regard, for example, when the steel plate immediately after rolling is passed through the cooling device and cooled, the time at which the leading end and the tail end of the steel plate enter the cooling device is different. Thus, a temperature distribution is generated in the longitudinal direction of the steel plate. That is, the maximum temperature of the steel sheet is in the vicinity of its front end (for example, about 860 ° C.), and the minimum temperature of the steel sheet is in the vicinity of its rear end (for example, about 820 ° C.). In order to obtain a uniform material in the steel sheet, it is important to make the cooling stop temperature uniform in the steel sheet, but for that purpose, during cooling, so as to cancel the temperature difference on the inlet side of the cooling device, It is necessary to control the cooling in the longitudinal direction of the steel sheet. Further, when the temperature after cooling is higher or lower than the target temperature, it is necessary to take a measure for correcting this.

  With respect to this problem, a method of changing the cooling capacity by changing the flow rate of the cooling water from the cooling device is usually employed. On the other hand, since a change in the flow rate of the cooling water cannot cope with a large temperature change, a method of adjusting the length of the cooling water injection zone is adopted in, for example, a hot-roll runout table. The cooling water injection zone length is adjusted by injecting / stopping the supply of cooling water from the cooling nozzle.

  For such cooling control, the excellent responsiveness of the cooling device is important, and the time from when the cooling water supply command is issued until the cooling water is actually supplied to the steel sheet (cooling water start delay time) In addition, the time (cooling water stop delay time) from when the cooling water supply stop command is issued until the cooling water supply to the steel plate is actually stopped must be short. In particular, it is most important that the cooling water stop delay time is short.

  However, with a normal nozzle header, particularly with a nozzle header that cools the upper surface side, a problem arises particularly when the cooling water is stopped.

  The nozzle on the upper surface of the steel plate has a vertically downward nozzle hole and the nozzle on the lower surface of the steel plate has a vertically upward nozzle hole. On the side, the water including the water accumulated in the cooling water supply pipe between the main valve and the nozzle comes out of the nozzle, so even if the main valve is closed rapidly, the water does not stop suddenly.

  In contrast, various studies have been made, and for example, the following techniques have been proposed (Patent Documents 1 to 8).

  Patent Document 1 discloses a method of stopping a jet of cooling water from a nozzle by providing a mechanism capable of sealing from a nozzle outlet inside a water tank that supplies cooling water to a slit nozzle (FIG. 10). .

  Patent Document 2 discloses a method of opening or closing the gap of the nozzle injection hole with respect to the slit nozzle and opening or closing the gap according to the injection / stop of the cooling water (FIG. 11).

  Patent Document 3 avoids unnecessary cooling water from the nozzle outlet by providing a movable frame at the downstream portion of the slit nozzle and providing a shutter capable of shielding the nozzle outlet. A method for improving on-off characteristics is disclosed (FIG. 12).

  Patent Document 4 discloses a method of draining water from a nozzle hole at high speed by connecting a high-pressure air pipe to a nozzle header and closing a cooling water source valve at the same time with respect to a slit nozzle. (FIG. 13).

  Patent Document 5 relates to a spray nozzle and attaches a spray nozzle to a pipe provided with a U-shaped bent portion from the nozzle header, connects a high-pressure air introduction pipe to the apex of the bent portion, and closes the cooling water source valve. , A method of discharging air at high speed by blowing air is disclosed (FIG. 14).

  Patent Document 6 describes a hairpin laminator in which a small hole is made in the U-shaped portion of the hairpin nozzle, and when the cooling water source is closed, air enters from the small hole and the cooling water is quickly drained from the nozzle. Is disclosed (FIG. 15).

  In Patent Document 7, the hairpin laminator is installed at a position where the U-shaped portion of the hairpin nozzle is higher than the piping that supplies the cooling water, and even if the cooling water source valve is closed, it is closer to the water supply piping than the U-shaped portion. A method for preventing water from leaving the nozzle holes is disclosed (FIG. 16).

In Patent Document 8, the header has a double structure of an inner tube and an outer tube, and a gap of 4 mm or less is formed above the header inner tube, where cooling water is held and remains in the gap between the header outer tube and the inner tube. Disclosed is a method in which only water to be discharged is discharged to the outside through a nozzle (FIG. 17).
JP-A-53-30912 JP-A-9-19711 JP-A-55-54210 JP-A-10-192945 JP 2001-79608 A JP 49-129609 A JP 49-129608 A JP 2001-321821 A

  In patent documents 1-8, it is devised according to each nozzle type, and there exists a big effect. However, in recent years, the cooling rate tends to be extremely high from the viewpoint of material control, and a cooling nozzle capable of injecting a large amount of water has been developed to achieve this, and for this cooling nozzle capable of injecting a large amount of water, In many cases, the techniques of Patent Documents 1 to 8 cannot be used.

  For example, as in Patent Document 1 and Patent Document 2, in the method of shutting down the cooling water at the outlet of the slit nozzle or inside the water tank, the slit nozzle itself is a cooling system that can inject a large amount of water, The use damages the seal part that provides cooling water shielding, resulting in an incomplete sealing and inadequate shielding effectiveness. In particular, in a wide slit nozzle having a plate width as long as 5 m, such as a thick steel plate, the shielding mechanism is structurally difficult and not practical.

  In addition, in the method of providing a shutter that can be opened and closed at the exit of the slit nozzle as in Patent Document 3, the effect is certain, but a large space is required to install the shutter. For this reason, when it is necessary to install a plurality of rows of slit nozzles in the longitudinal direction and increase the cooling rate, it is impossible to arrange the nozzles densely from the viewpoint of securing the retracting space of the shutter. There are limits.

  Further, in the methods described in Patent Document 4 and Patent Document 5, when the cooling water is stopped and air is enclosed at the same time, the water in the header is ejected from the nozzle by the air pressure, but the nozzle capable of ejecting a large amount of water The header has a large header capacity in the first place, and it is necessary to replace the inside of the header with a large amount of air. Further, since the water escape port is a nozzle hole, water is ejected from the nozzle while being replaced with air, and the water is stopped with a certain time constant from the cooling water stop command.

  In the methods described in Patent Document 6 and Patent Document 7, only a structure in which a nozzle is attached to a U-shaped pipe such as a hairpin laminator can be employed. On the other hand, the hairpin laminar is not a very compact header because of the attachment of the U-shaped tube, and is not very suitable for large flow rate injection. Like the slit laminator of Patent Document 1 and Patent Document 2, it cannot be densely arranged in the longitudinal direction, and the cooling rate cannot be increased.

  In addition, the method described in Patent Document 8 has been studied especially for a header capable of ejecting a large amount of water, and has high practicality. However, even if the cooling water source valve is closed, water is discharged for the capacity of the header outer pipe, but especially after the cooling water stops, cooling water comes out due to the head difference between the cooling inlet to the nozzle and the liquid level in the header. . In particular, in the region where the head difference is small, there is a problem because the state in which water leaks from the nozzle hole continues for a long time.

The present invention has been made in view of the circumstances as described above, and has a large amount of water cooled, in particular, a large amount of water is injected by a cooling device having a relatively wide equipment width for cooling steel materials such as thick steel plates, thin steel plates, and shaped steels. In the case (especially when the cooling water density is injected at 1500 L / min · m ² or more), it has excellent responsiveness, and in particular, the cooling water stop delay time (after issuing the cooling water supply stop command, onto the steel material) The cooling water supply from the nozzle outlet is reduced even if it is used for a long period of time. To provide a cooling method and a cooling device for steel that can prevent cooling unevenness without leakage, that is, a cooling method and a cooling device for steel that can cool steel uniformly and stably at a high cooling rate. It is intended.

  In order to solve the above problems, the present invention has the following features.

[1] A nozzle header connected to a cooling water supply source via a cooling water supply pipe, a cooling water supply control means provided in the cooling water supply pipe, and a nozzle group attached to the nozzle header. When supplying the cooling water to the upper surface of the steel with a water density of 1500 L / min · m ² or more using the steel cooling device, each nozzle of the nozzle group is penetrated into the nozzle header, and the horizontal plane position of the cooling water inlet of each nozzle When the supply of cooling water to the top surface of the steel material is stopped, the cooling to the nozzle header is cooled by the cooling water supply control means. At the same time as the supply of water is stopped, the negative pressure generating mechanism cancels the head pressure of the cooling water acting on the nozzle cooling water inlet, and the cooling water drops from the nozzle. The steel material is cooled by a negative pressure sufficient to stop the operation .

  [2] The steel material cooling method according to [1], wherein an ejector is used as the negative pressure generating mechanism.

[3] A nozzle header connected to a cooling water supply source via a cooling water supply pipe, cooling water supply control means provided in the cooling water supply pipe, and a nozzle group attached to the nozzle header. In the steel material cooling apparatus for supplying cooling water to the steel upper surface at a water density of 1500 L / min · m ² or more, each nozzle of the nozzle group penetrates into the nozzle header, and the horizontal plane position of the cooling water inlet of each nozzle is When the supply of cooling water to the steel material upper surface is stopped, the cooling water supply control means supplies the nozzle header to the nozzle header. At the same time as the cooling water supply is stopped, the negative pressure generation mechanism cancels the cooling water head pressure acting on the cooling water inlet of the nozzle in the nozzle header to stop the cooling water from dropping from the nozzle. A steel cooling device characterized by a negative pressure that can be stopped.

  [4] The steel material cooling device according to [3], wherein an ejector is used as the negative pressure generating mechanism.

  By using the present invention, the cooling water stop delay time (the time from when the cooling water supply stop command is issued until the cooling water supply actually stops on the steel material) is extremely shortened, and the delay from the nozzle outlet is reduced. The required cooling water can be avoided and the controllability of steel cooling can be greatly improved. As a result, it is possible to cool the steel material uniformly and stably at a high cooling rate, prevent the occurrence of material defects due to temperature unevenness in the longitudinal direction of the steel material, reduce the deviation of the material, and high quality Steel can be manufactured.

  Embodiments of the present invention will be described with reference to the drawings. In addition, although it describes here about a steel plate, it can apply similarly to other steel materials, such as a shape steel.

  1 and 2 are schematic explanatory views showing a steel sheet cooling device according to an embodiment of the present invention, and FIG. 1 is a view (front view) seen from the longitudinal direction (conveying direction) of the steel sheet (not shown). 2 is a view (side view) seen from the width direction of a steel plate (not shown).

  As shown in FIG. 1 and FIG. 2, the steel sheet cooling device according to one embodiment of the present invention is configured to inject cooling water onto the upper surface of the steel sheet, and a cooling water supply source 1 through a cooling water supply pipe 1. And the nozzle header 2 connected to each other, the cooling water supply control means 6 provided in the cooling water supply pipe 1, and the nozzle (nozzle group) 4 attached to the nozzle header 2.

  Here, in this embodiment, since a large amount of water is injected, a plurality of spray nozzles or circular tube nozzles are attached to the rectangular nozzle header in the width direction and the longitudinal direction, so that more nozzles than the hairpin laminator can be used. The cooling water can be injected.

  Further, the nozzle header 2 has a double pipe structure including an inner pipe 2a and an outer pipe 2b, the nozzle installation surface of the nozzle header 2 is horizontal, and the nozzle 4 penetrates to the inside of the nozzle header outer pipe 2b. The height of the cooling water inlet (upper end of the nozzle 4) 4a of each nozzle 4 is aligned in the horizontal direction.

  The cooling water supply control means 6 is composed of an open / close valve (for example, an electromagnetic valve) that opens and closes in response to an electrical signal. The cooling water supply control means 6 (cooling water supply open / close valve) 6 is sent by sending a signal. If opened, the cooling water from the cooling water supply source is supplied to the inner pipe 2 a of the nozzle header through the cooling water supply pipe 1. The cooling water supplied into the inner pipe 2a in this way is supplied into the nozzle header outer pipe 2b through the through hole 2c formed in the upper portion thereof, and the cooling water outlet of the nozzle 4 with a uniform pressure. (Lower end of nozzle) 4b is ejected and cooling water is supplied to the upper surface of the steel plate. If the cooling water supply control means (cooling water supply opening / closing valve) 6 is closed, the supply of cooling water into the nozzle header 1 is shut off, and the cooling water flows into the drainage groove 9 outside.

  However, at that time, due to the inner diameter and length of the cooling water supply pipe 1, the cooling water supply pipe 1 between the cooling water supply opening / closing valve 6 and the nozzle header inner pipe 2 a and the nozzle header 2 The amount of accumulated cooling water is large. Therefore, in the case of only the basic structure described above, when the supply of the cooling water to the upper surface of the steel plate is stopped, the cooling water supply opening / closing valve 6 is closed and the cooling water from the cooling water supply source to the nozzle header 2 is closed. Even if the supply is stopped, the cooling water remaining in the cooling water supply pipe 1 and the nozzle header 2 (the shaded area in FIG. 1) moves downward due to gravity, passes through the nozzle 4 and the upper surface of the steel plate. Will be discharged.

  Therefore, in this embodiment, as shown in FIG. 1, a negative pressure generating mechanism that makes the inside of the nozzle header 2 a negative pressure is provided, and the inside of the nozzle header 2 is made a negative pressure by the negative pressure generating mechanism. The cooling water remaining in the cooling water supply pipe 1 and the nozzle header 2 is prevented from flowing out from the nozzle 4 to the outside.

  As shown in FIG. 1, the negative pressure generating mechanism 10 includes a suction machine 13, a suction pipe 11 branched from the cooling water supply pipe 1 and connected to the suction machine 13, and a suction provided in the middle of the suction pipe 11. Control means (for example, electromagnetic valve) 12 is provided.

  The suction control means (suction control electromagnetic valve) 12 is closed when the cooling water supply control means (cooling water supply opening / closing valve) 6 is opened, and the cooling water supply control means (cooling water supply opening / closing). The valve 6 is opened when it is closed. That is, the opening / closing operations of the cooling water supply opening / closing valve 6 and the suction control solenoid valve 12 are performed in reverse to each other.

  Thus, when the cooling water supply opening / closing valve 6 is closed and the supply of the cooling water from the cooling water supply source to the nozzle header 2 is stopped, the cooling water remaining in the cooling water supply pipe 6 or the nozzle header 2 is stopped. The water can be prevented from being drained from the nozzle 4 by the generation of the negative pressure by the negative pressure generating mechanism 10.

  In this embodiment, the suction pipe 11 is connected to the cooling water supply pipe 1, but the suction pipe 11 is connected to either one or both of the cooling water supply pipe 1 and the nozzle header outer pipe 2b. Good. Further, when a necessary suction force cannot be obtained, the suction pipes 11 may be attached to a plurality of locations of the nozzle header outer pipe 2b, for example.

  By the way, the height position of the cooling water inlet 4a of each nozzle 4 needs to be aligned horizontally. In the nozzle 4, the cooling water stops at a balance between the atmospheric pressure from the outside air and the water pressure applied to the cooling water inlet 4 a of the nozzle 4. And as the water pressure in the cooling water inlet 4a of the nozzle 4, since the head pressure of the remaining cooling water which fills the cooling water supply pipe 1 and the nozzle header 2 is applied, the height position of the cooling water inlet 4a of the nozzle 4 is In the case where the pressure is different, the pressure applied to the cooling water inlet 4a of each nozzle 4 varies for each nozzle 4, the water is discharged from the place where the pressure of the cooling water inlet 4a is high, and the pressure of the cooling water inlet 4a is low. Will get air. If air enters, the header cannot be stably made to have a negative pressure, so it is impossible to stop the cooling water from leaking out of the nozzle.

  Next, the negative pressure generating mechanism 10 will be described. In order to generate the negative pressure, it is conceivable to use a turbo pump or a suction machine using the ejector principle. In the present invention, it is sufficient to generate a negative pressure that stops the cooling water from dropping. The pressure applied to the cooling water inlet 4 a of the nozzle 4 is determined by the head pressure (liquid level height) of the cooling water that fills the cooling water supply pipe 1 and the nozzle header 2. For this reason, the piping design must first reduce the head pressure. The suction force by the suction device 8 may be such that the head pressure is canceled. For example, if the liquid surface height from the tip 4b of the nozzle 4 is about 400 mm, a negative pressure of about −400 mmAq (−0.04 atm) is required. The ejector method is particularly preferable. FIG. 3 shows a general structure of the ejector 14. When the working fluid is injected into the suction chamber 14 b by the nozzle 14 a, the pressure of the suction chamber 14 b becomes a negative pressure from Bernoulli's theorem, and the fluid is sucked from the suction port 14 c. And is discharged from the discharge port 14d. The working fluid includes air, water, steam, etc., but air and water are preferable from the viewpoint of operating cost. In addition, since the ejector has no mechanical operation part, it can be easily maintained. Moreover, since it is difficult for the turbo pump to stably suck in the mixed fluid of water and air, an ejector is also preferable from this viewpoint.

  And when installing the cooling device which concerns on this embodiment as mentioned above in the hot rolling line of a steel plate, what is necessary is just to arrange | position the cooling device side by side by the desired number in the steel plate conveyance direction.

  In the cooling device according to this embodiment, since the suction pipe 11 can be installed on the side of the cooling water supply pipe 1 or the nozzle header 2 in the steel plate traveling direction, the nozzles 4 can be densely arranged in the steel plate traveling direction. Therefore, compared with a shutter mechanism like patent document 3, an installation becomes compact and shows the predominance of this invention.

The present invention is particularly useful when the amount of cooling water per unit area in which the capacity of the residual cooling water in the nozzle header is large is 1500 L / min · m ² or more. By applying the present invention, the cooling water is stopped. The delay time can be 3 sec or less.

  Next, the operation of the steel sheet cooling device according to this embodiment will be described below.

  First, when cooling water is supplied to the upper surface of the steel plate in order to cool the steel plate, an electric signal (cooling water start command) is sent to open the cooling water supply opening / closing valve 6. At the same time, an electrical signal is sent to close the suction control solenoid valve 7. Thereby, the cooling water from the cooling water supply source passes through the cooling water supply pipe 1 and is supplied to the nozzle header inner pipe 2a, and the cooling water supplied into the inner pipe 2a passes through the through hole 2c and passes through the nozzle. After being supplied into the header outer pipe 3b, it is ejected from the cooling water outlet 4b of the nozzle 4 with a uniform pressure to cool the entire upper surface of the steel plate.

  Next, when the supply of the cooling water to the upper surface of the steel plate is stopped, an electric signal (cooling water stop command) is sent to close the cooling water supply opening / closing valve 6. At the same time, the suction control electromagnetic valve 7 is opened. As a result, the cooling water remaining in the cooling water supply pipe 1 and the nozzle header 2 is pulled by the suction device 13, and the cooling water does not come out from the tip 4 b of the nozzle 4.

  Thus, in this embodiment, the time (cooling water stop delay time) from when the cooling water supply stop command is issued until the cooling water supply to the steel plate is actually stopped is extremely short. Unnecessary cooling water pouring from the tip is avoided, an excellent cooling water stop characteristic (off characteristic) is obtained, and the controllability of cooling of the steel sheet can be greatly improved. As a result, it is possible to cool the steel plate uniformly and stably at a high cooling rate, prevent the occurrence of material defects due to temperature unevenness in the longitudinal direction of the steel plate, reduce the material deviation, and high quality Steel sheets can be manufactured.

  As Example 1 of the present invention, based on the above-described embodiment of the present invention, the nozzle header and nozzle having the following specifications are used to stop the cooling water supply on / off valve 6 by the cooling water stop command, and then the nozzle The time (cooling water stop delay time) until no cooling water comes out from 4 was investigated.

  Here, as shown in FIGS. 1 and 2, the structure of the nozzle header 2 is such that the cooling water flows from the cooling water supply pipe 1 into the nozzle header inner pipe 2a, where the pressure is equalized, and the nozzle header inner pipe 2a The coolant flows into the nozzle header outer pipe 2b from the upper through-hole 2c, and the cooling water is jetted from the tip 4b of the nozzle 4. The geometric dimensions are as shown in the front view of FIG. 4 and the side view of FIG. The inner volume discharged from the nozzle 4 is V1, the nozzle header outer tube 2b is rectangular, the width is w, the length is L, the height above the nozzle upper end 4a is h, and the volume is V2b. The specifications of the nozzle header 2 when the header inner pipe 2a is cylindrical, its capacity is V2a, and the nozzle 4 is a φd circular nozzle are shown below.

(A) Cooling water supply pipe: length 10 m, pipe diameter φ280 mm, capacity V1 = 0.24 m ³
(A) Nozzle header outer tube: width w = 2400 mm, height h = 600 mm,
Length L = 900mm, volume V2b = 1.38m ³
(C) Nozzle header inner tube: Volume V2a = 0.6 m ³
(D) Nozzles (nozzle group): diameter d = φ6 mm, number 120
Total cross-sectional area of the nozzle channel A1 = 0.0034 m ³
(E) Cooling water: amount of cooling water 2500 L / mm, water density 1600 L / min · m ²
And when the suction device 13 is operated based on one embodiment of the present invention and the cooling water is stopped, it is referred to as Invention Example 1, and when the cooling water is stopped without operating the suction device 13 (patent) Comparative example 1 was used as a comparative example 1 and the suction machine 13 was reversed to introduce high-pressure air into the nozzle header 2 to stop the cooling water (simulated in Patent Document 4). The target cooling water stop delay time was 1 sec.

  Table 1 shows the results of the investigation of the cooling water stop delay time described above.

  As shown in Table 1, the cooling water stop delay time was 0.6 sec in the invention example 1 and was within the target, but the cooling water stop delay time was 45 sec in the comparative example 1 and 4.5 sec in the comparative example 2. I have.

  As Example 2 of the present invention, a case where Example 1 of the present invention and Comparative Example 1 shown in Example 1 are applied to a thick steel plate production line will be described.

  In recent years, in order to produce high-strength steel, controlled rolling (CR) is performed in which a rolled material (thick steel plate) is cooled online to a predetermined temperature during rolling, and the subsequent rolling is performed at a low temperature. Here, in the thick steel plate production line as shown in FIG. 6, the case where the above-described cooling device of the present invention is employed as a cooling device for the upper surface of the steel plate in order to cool the thick steel plate online will be described.

  As shown in FIG. 6, after the raw material 21 is heated to about 1200 ° C. in a heating furnace 60, it is rolled while being reversed by a thick plate rolling machine 61, and is conveyed to the cooling device 50 of the present invention when a certain plate thickness is reached. Then, after cooling while oscillating, it is conveyed to the thick plate mill 61 and rolled again. After the completion of rolling, the temperature distribution of the steel plate 21 is measured by the surface thermometer 65 and the shape is corrected by the roller leveler 62.

  Here, the cooling device 50 according to the present invention is used. When the transported steel plate 21 comes directly under the cooling device 50 according to the present invention, the cooling water is injected, and after cooling for a predetermined time, the cooling water is stopped. Transport to thick plate mill 61.

  Specifically, a thick steel plate having a plate width of 2400 mm, a plate length of 15 m, and a plate thickness of 50 mm was conveyed to just below the cooling water, where it was cooled from 1000 ° C. to 900 ° C. by water cooling for 20 seconds. The temperature after cooling was measured with a surface thermometer 65. In addition, about the length of the cooling device 50, although the thing of 900 mm was employ | adopted in Example 1, since it is necessary to cool simultaneously the board length 15m thing, the cooling device of this invention is longitudinally arranged. 20 units 50 were attached to form a cooling device group 51.

  And when the suction machine 13 is operated based on the above-described first invention example and the cooling water is stopped (invention example 2), the cooling is performed without operating the suction machine 13 based on the above-described comparative example 1. FIG. 7 shows the surface temperature measurement results in the plate width direction of the steel sheet after cooling with the cooling device 50 for the case where water was stopped (Comparative Example 3).

  As shown in FIG. 7, in Invention Example 2, the cooling water stopped immediately after the cooling water stop command, and thus the temperature distribution after cooling was good. In Comparative Example 3, 45 seconds after the cooling water stop command. Since cooling water continued to come out, it was supercooled locally just below the nozzle. Further, due to the continued cooling water, stagnant water was generated on the steel plate, and the steel plate temperature after cooling was lower than that of Invention Example 2.

  As Example 3 of the present invention, a case will be described in which Invention Example 1 and Comparative Example 1 shown in Example 1 are applied to a hot-rolled steel sheet (hot-rolled steel strip) production line.

  Here, in the hot-rolled steel strip production line as shown in FIG. 8, in order to cool the hot-rolled steel strip after finish rolling with a runout table, the above-described cooling device of the present invention is adopted as a cooling device for the upper surface of the steel strip. The case will be described.

  As shown in FIG. 8, after the raw material 22 having a thickness of 250 mm and a width of 1200 mm is heated to 1200 ° C. in the heating furnace 70, it is rolled to about 30 mm by reverse rolling in the rough rolling mill group 71, and from there 6 to 7 It is rolled to about 3.2 mm by a finish rolling mill 72 constituted by a rolling mill. Thereafter, the sample is cooled by the cooling device at the runout table 73, measured by the surface thermometers 76 and 77, and taken up by the coiler 74.

  In recent years, in order to manufacture high-strength steel, various controls are performed so that the winding temperature does not deviate from the target value. In particular, there is a high need for producing high-strength steel sheets by cooling with a large amount of water. Therefore, the cooling device 50 of the present invention is employed as a cooling device for the upper surface of the steel strip in the runout table 73. In Example 3, since the steel strip is cooled while passing through the plate, the length of the cooling device may be shorter than the length of the steel strip. Here, 15 cooling devices 50 of the present invention are installed in the longitudinal direction. Thus, the upper surface cooling device group 52 was obtained. On the other hand, as a cooling device for the steel strip lower surface in the run-out table 73, a lower surface cooling device group 75 including an existing spray cooling device was used.

  Here, although it is the usage of the cooling device group 52 of this invention, a cooling water is injected from the predetermined cooling device 50 in the cooling device group 52, the steel strip 22 is cooled, and the steel strip 22 after being cooled is used. After the temperature is measured by the surface thermometers 76 and 77, if the actual steel strip temperature is lower than the target temperature, the cooling water from some cooling devices 50 injecting the cooling water is used. If the injection is stopped and the actual steel strip temperature is higher than the target temperature, the cooling water is injected from the cooling device 50 that is not injecting the cooling water.

  As specific target temperatures, in Example 3, the target temperature on the delivery side of the finish rolling mill was controlled at 850 ° C., and the target winding temperature was controlled at 500 ° C.

  Then, when the suction device 13 is operated based on the above-described first invention example and the cooling water is stopped (invention example 3), cooling is performed without operating the suction device 13 based on the above-described comparative example 1. FIG. 9 shows the results of measuring the surface temperature in the longitudinal direction of the central portion of the width of the steel strip 22 measured with the surface thermometer 77 installed in front of the coiler 74 when water was stopped (Comparative Example 4). .

  As shown in FIG. 9, in Invention Example 3, the cooling water stopped immediately after the cooling water stop command, so the temperature distribution after cooling was good. In Comparative Example 4, 45 seconds after the cooling water stop command. Because the cooling water continued to come out, even if the cooling water stop command was issued after detecting that the steel strip temperature was not at the target temperature, the cooling water continued to come out, resulting in local overcooling and temperature variations. It was big.

It is a schematic explanatory drawing (front view) of one Embodiment of this invention. It is a schematic explanatory drawing (side view) of one Embodiment of this invention. It is a figure explaining the structure of the ejector which is a suction mechanism. It is explanatory drawing (front view) of the dimension and symbol of one Embodiment of this invention. It is explanatory drawing (side view) of the dimension and symbol of one Embodiment of this invention. It is a figure which shows the thick steel plate manufacturing line in Example 2 of this invention. It is the width direction temperature distribution of the thick steel plate after cooling in Example 2 of this invention. It is a figure which shows the hot rolled steel strip manufacturing line in Example 3 of this invention. It is a longitudinal direction temperature distribution of the hot-rolled steel strip after cooling in Example 3 of the present invention. It is a figure explaining prior art literature 1. It is a figure explaining prior art document 2. It is a figure explaining prior literature 3. It is a figure explaining prior literature 4. It is a figure explaining prior literature 5. It is a figure explaining prior literature 6. It is a figure explaining prior literature 7. It is a figure explaining prior literature 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooling water supply pipe 2 Nozzle header 2a Nozzle header inner pipe 2b Nozzle header outer pipe 2c Through-hole 4 Nozzle 4a Nozzle upper end (cooling water inlet)
4b Nozzle tip (cooling water outlet)
6 Cooling water supply control means (cooling water supply on / off valve)
9 Drain Groove 10 Negative Pressure Generation Mechanism 11 Suction Pipe 12 Suction Control Means (Suction Control Solenoid Valve)
13 Suction machine (ejector)
14 Ejector 14a Nozzle 14b Suction chamber 14c Suction port 14d Discharge port 21 Thick steel plate 22 Hot-rolled steel strip 50 Cooling device of the present invention 51 Cooling device group of the present invention applied to manufacture of thick steel plate 52 60 Heating furnace 61 Thick steel plate rolling machine 62 Straightening machine 65 Surface thermometer 70 Heating furnace 71 Coarse rolling mill group 72 Hot rolling strip finishing mill group 73 Runout table 74 Coiler 75 Heat Existing steel surface cooling device group for steel strip 76 Surface thermometer 77 Surface thermometer

Claims (4)

Cooling of a steel material comprising a nozzle header connected to a cooling water supply source via a cooling water supply pipe, cooling water supply control means provided in the cooling water supply pipe, and a nozzle group attached to the nozzle header. When supplying cooling water to the upper surface of the steel material at a water density of 1500 L / min · m ² or more using the apparatus, each nozzle of the nozzle group is passed through the nozzle header, and the horizontal plane position of the cooling water inlet of each nozzle is matched. In addition, in the case where a negative pressure generating mechanism for making the inside of the nozzle header negative is provided and the supply of cooling water to the upper surface of the steel material is stopped, the cooling water supply control means supplies cooling water to the nozzle header. At the same time, the negative pressure generating mechanism cancels the cooling water head pressure acting on the nozzle cooling water inlet, and stops the cooling water from dropping from the nozzle. A cooling method for steel, characterized by a negative pressure sufficient to allow   The steel material cooling method according to claim 1, wherein an ejector is used as the negative pressure generating mechanism. An upper surface of a steel material, comprising a nozzle header connected to a cooling water supply source via a cooling water supply pipe, cooling water supply control means provided in the cooling water supply pipe, and a nozzle group attached to the nozzle header. In the steel cooling device for supplying cooling water to the water density of 1500 L / min · m ² or more, each nozzle of the nozzle group penetrates into the nozzle header, and the horizontal plane position of the cooling water inlet of each nozzle matches. And a negative pressure generating mechanism for generating a negative pressure in the nozzle header, and when stopping the supply of cooling water to the upper surface of the steel material, the cooling water supply control means supplies the cooling water to the nozzle header. At the same time, the negative pressure generating mechanism cancels the cooling water head pressure acting on the cooling water inlet of the nozzle in the nozzle header to stop the cooling water from dropping from the nozzle. A steel material cooling device characterized by a negative pressure as much as possible .   The steel material cooling device according to claim 3, wherein an ejector is used as the negative pressure generating mechanism.

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