JP2016193446A - Method for cooling hot rolled steel sheet and cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a fine temperature control by removing on-sheet residual cooling water with respect to a hot rolled steel sheet after strong cooling.SOLUTION: A method for cooling a hot rolled steel sheet includes: a step where a hot rolled steel sheet 10 after finish rolling of continuous hot rolling process is subjected to strong cooling by a cooling water nozzle 20 and then is dewatered by a dewatering device 30; and a step where the hot rolled steel sheet 10 is sprayed with cooling water obliquely from above to the top face thereof by a spray nozzle 41 of a side spray device 40. Thus, fine temperature control at a core boiling region is enabled while discharging the on-sheet residual cooling water of the hot rolled steel sheet 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method and apparatus for cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process.

  The hot-rolled steel sheet after finish rolling in the continuous hot rolling process is a run-out table installed between the finish rolling mill and the winding device. For example, the hot-rolled steel plate has a predetermined temperature by a cooling device provided above and below the run-out table. Then, it is wound up by a winding device. In hot rolling of hot-rolled steel sheets, the cooling capacity after finish rolling is an important factor that determines the mechanical properties, workability, weldability, etc. of the hot-rolled steel sheets. It is important to cool to a temperature of

  In this regard, conventionally, there is provided a cooling device for a hot-rolled steel strip that cools a hot-rolled steel strip after finish rolling that is transported on a run-out table, and is provided on the upper surface side of the steel strip from the upstream side of the table roll. Heat arranged so as to oppose a cooling nozzle that injects bar-shaped cooling water inclined directly above the roll and a cooling nozzle that injects bar-shaped cooling water inclined from the downstream side of the table roll directly above the table roll A steel strip cooling device (Patent Document 1), a hot-rolled steel strip cooling device that cools a hot-rolled steel strip after finish rolling conveyed on a run-out table. Cooling nozzle that injects rod-shaped cooling water inclined from the upstream side directly above the position where the cooling water injected from the nozzle collides with the steel strip, and cooling water injected from the bottom cooling nozzle collides with the steel strip Right next to As a cooling nozzle for injecting the rod-like cooling water are inclined from the downstream side, the cooling device of hot-rolled steel strip disposed the to face (Patent Document 2) have been proposed toward.

JP 2008-73765 A JP 2008-73766 A

By the way, inventors aim at cooling to about 200 degreeC in the step before winding the steel plate after cooling with a winding device. When a steel sheet having a predetermined component is cooled to about 200 ° C., tempered martensite is generated while the steel sheet taken up by the winding device is allowed to cool, so that the deformability is improved and the TS-λ balance (tensile strength) is improved. -Stretch flangeability λ balance) is improved. Further, the stretch flangeability λ is improved by the martensite tempering effect during the cooling of the steel sheet, and the low carbon tempered martensite structure is generated, whereby the stretch flangeability λ can be secured. In addition, there is an effect that scales can be suppressed from being formed on the steel plate.
In this regard, the techniques disclosed in Patent Documents 1 and 2 are both cooling at about 400 ° C., and cannot be directly applied to cooling to about 200 ° C.
Moreover, even if it is going to cool to about 200 degreeC using the technique disclosed by patent document 1, 2, the technique disclosed by patent document 1, 2 performs normal cooling (what is called strong cooling) after finish rolling, After that, rod-shaped cooling water is sprayed onto the steel sheet. With such a configuration, the water on the plate stays on the steel plate, making it difficult to control the temperature.

  This invention is made | formed in view of this point, and it aims at enabling fine temperature adjustment with respect to the steel plate after what is called strong cooling.

  In order to achieve the above object, the present invention is a method for cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process, and cools the steel sheet immediately after finish rolling by injecting cooling water, Then, draining is performed, and the steel sheet is further cooled in the nucleate boiling region by spraying cooling water obliquely from above on the upper surface of the steel sheet after draining using a side spray device.

  According to the present invention, the residual cooling water on the plate (also simply referred to as plate water) is removed from the steel plate after so-called strong cooling by draining, and then the upper surface of the steel plate after draining is cooled from the side spray device. Because water is injected, cooling by nucleate boiling can be performed, and cooling water is injected obliquely from the side spray device to the steel sheet, so the cooling temperature of the steel sheet can be controlled while suppressing the generation of new stagnant water. It can be cooled slowly. Therefore, the temperature control of the steel sheet is easy.

  The cooling by the side spray device may be performed by injecting cooling water onto the upper surface of the steel plate from both sides or one side of the steel plate by a plurality of side spray devices arranged at positions shifted in the conveying direction of the steel plate. .

  The draining may be performed by injecting a fluid from both sides or one side of the steel plate to the upper surface of the steel plate with a side spray device. The side spray device in this case may have the same configuration as the spray device that performs the slow cooling described above.

  According to another aspect, the present invention is an apparatus for cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process, and cools the steel sheet immediately after finish rolling by injecting cooling water. And installed on the downstream side in the steel plate conveyance direction of the cooling device, draining the cooling water, and installed along the conveyance direction on the downstream side in the steel plate conveyance direction of the drainage device, on the upper surface of the steel plate after draining On the other hand, it has a plurality of nucleate boiling region cooling side spray devices for injecting cooling water obliquely from above from one side or both sides of the steel sheet.

  According to the present invention, it is possible to finely adjust the temperature of a steel plate after so-called strong cooling.

It is explanatory drawing which shows the outline of a structure of the continuous hot rolling equipment provided with the cooling device in this Embodiment. It is a side view which shows the outline of a structure of the cooling device concerning embodiment. It is a top view which shows the outline of a structure of the cooling device concerning embodiment. It is explanatory drawing seen from the conveyance direction front which shows arrangement | positioning of the spray nozzle in the case of both-sides arrangement | positioning. It is plane explanatory drawing which shows arrangement | positioning of the spray nozzle in the case of both-side arrangement | positioning. It is explanatory drawing seen from the conveyance direction front which shows arrangement | positioning of the spray nozzle in the case of one side arrangement | positioning. It is plane explanatory drawing which shows arrangement | positioning of the spray nozzle in the case of one side arrangement | positioning. It is a top view which shows the outline of a structure of the cooling device at the time of abolishing a dedicated draining device.

  Embodiments of the present invention will be described below. Drawing 1 is an explanatory view showing the outline of the composition of continuous hot rolling equipment 1 provided with the cooling device in this embodiment.

  In the continuous hot rolling facility 1, the heated slab 5 is continuously rolled up and down with rolls, and the hot rolled steel sheet 10 is wound up with a minimum thickness of 1 mm. The continuous hot rolling facility 1 has a heating furnace 11 for heating the slab 5, a width direction rolling machine 12 for rolling the slab 5 heated in the heating furnace 11 in the width direction, and the width in the width direction. A rough rolling machine 13 that rolls the slab 5 from the upper and lower directions to form a rough bar, a finish rolling machine 14 that continuously performs hot finish rolling of the rough bar to a predetermined thickness, and the finish rolling machine 14 A cooling device 15 that cools the hot-rolled steel plate 10 that has been finish-rolled with cooling water, and a winding device 16 that winds the hot-rolled steel plate 10 cooled by the cooling device 15 into a coil shape are provided. The above is a general configuration and is not limited to this.

  In the heating furnace 11, the process which heats the slab 5 carried in from the outside through a loading port to predetermined temperature is performed. When the heat treatment in the heating furnace 11 is completed, the slab 5 is transferred to the outside of the heating furnace 11, and the process proceeds to a rolling process by the roughing mill 13.

  The slab 5 that has been conveyed is rolled to a plate thickness of about 30 to 60 mm by the rough rolling mill 13 and conveyed to the finishing mill 14.

  In the finish rolling mill 14, the conveyed hot-rolled steel sheet 10 is rolled to a thickness of about several millimeters. The rolled hot-rolled steel sheet 10 is transported by the transport roll 17 and sent to the cooling device 15. The hot-rolled steel sheet 10 is cooled by the cooling device 15 and wound in a coil shape by the winding device 16.

  Next, the detail of the cooling device 15 concerning embodiment is demonstrated. FIG. 2 schematically shows a side surface of the cooling device 15, and FIG. 3 schematically shows a plane of the cooling device 15. As shown in FIG. 2, an upper cooling device 15 a arranged above the hot-rolled steel plate 10 conveyed on the conveyance roll 17 of the run-out table, and a lower cooling device (under the hot-rolled steel plate 10) (Not shown).

  The upper cooling device 15 a includes a plurality of cooling water nozzles 20 that inject cooling water vertically downward from above the hot rolled steel sheet 10 toward the upper surface of the hot rolled steel sheet 10. As the cooling water nozzle 20, for example, a slit laminar nozzle or a pipe laminar nozzle is used. A plurality of cooling water nozzles 20 are arranged side by side along the conveying direction of the hot-rolled steel sheet 10 (thick arrow direction in the figure). The cooling water nozzle 20 is not limited to these nozzles, and other nozzles may be used.

  On the downstream side in the transport direction of the upper cooling device 15a, a draining device 30 is provided for draining the on-plate residual cooling water 21 in which the cooling water sprayed from the upper cooling device 15a flows along with the steel plate. . As shown in FIG. 3, the drainer 30 of this embodiment uses a plurality of drainer spray devices 31, and the drainer fluid from each sprayer 31 toward the upstream in the transport direction, for example, Water is jetted.

  A side spray device 40 is provided downstream of the drainer 30 in the conveyance direction. In this embodiment, a plurality of spray nozzles 41 are installed along both sides of the hot-rolled steel sheet 10 in the conveying direction. For convenience of illustration, FIG. 3 shows a total of four spray nozzles 41, two on each side, but of course this is not limiting, and the number of installations can be selected as appropriate.

  In the present embodiment, the spray nozzle 41 is arranged as shown in FIGS. That is, the height h from the upper surface of the hot-rolled steel plate 10 to the jet nozzle 41a of the spray nozzle 41 is 500 mm, the jet angle θ1 from the jet nozzle 41a, and the jet range are jetted from the center P in the width direction of the hot-rolled steel plate 10. This is a range that covers at least the end portion (distant end portion) of the hot-rolled steel sheet 10. Of course, although these numerical values differ depending on the width of the hot-rolled steel sheet 10, the height h is 0 mm to 1000 mm. The height h is the mounting height of the spray nozzle 41, and the jet impingement pressure to the hot-rolled steel sheet 10 changes depending on the height h. That is, when the same nozzle is used, if the height h is small, the collision pressure is high and the heat transfer coefficient is large. If the height h is large, the jet flow is attenuated and the collision pressure is lowered and the heat transfer coefficient is small. Then, from the viewpoint of finely adjusting the temperature of the hot-rolled steel sheet 10, it is desirable that the height h is small. Also, from the viewpoint of discharging the on-plate residual cooling water 21 on the hot-rolled steel sheet 10 from the end side to the outside of the steel sheet, 0 to 45 degrees is appropriate for θ1, and 45 to 90 degrees is appropriate for θ2. It is. That is, with respect to θ1, it is necessary to cover at least the region beyond the center P in the width direction of the hot-rolled steel sheet 10 from the end (distant end) of the ejection destination. You may set so that it may cover about the width direction edge part (near edge part). Further, the spray spread angle θ3 from the spray nozzle 41a of the spray nozzle 41 is preferably 0 to 15 degrees.

The spray flow rate from the spray nozzle 41 is about 100 L / min, and 1200 m ^{2 to} 1300 m ² of water per minute per unit area is sprayed onto the region S sprayed onto the hot-rolled steel sheet 10. It is good.
Furthermore, as for the angle formed between the hot-rolled steel sheet 10 and the spray inclination angle, when the case where the steel sheet and the spray are parallel is defined as 0 degrees, the spray inclination is preferably 30 degrees to 60 degrees toward the upstream side. As shown in FIG. 3, the regions S ejected from the spray nozzles 41 onto the hot-rolled steel sheet 10 should not overlap each other. When the spray angle is less than 30 degrees, the water sprayed from the spray nozzle 41 may get over the draining fluid from the spray device 31 or the cooling region by the upper cooling device 15a. On the other hand, when the spray angle exceeds 60 degrees, the effect of so-called return water, in which the water sprayed from the spray nozzle 41 collides with the hot-rolled steel sheet 10 and returns to the spray nozzle 41 side becomes remarkable.

  A draining device 50 is provided on the downstream side of the side spray device 40 in the conveying direction. As shown in FIG. 3, the drainer 50 of this embodiment uses a plurality of drainer spray devices 51, and the drainer fluid from each sprayer 51 toward the upstream in the transport direction, for example, Water is jetted.

  In plan view, a temperature sensor MT for measuring the temperature of the hot-rolled steel sheet 10 is disposed between the draining device 30 and the side spray device 40, and between the draining device 50 and the winding device 16, A temperature sensor CT for measuring the temperature of the rolled steel sheet 10 is disposed. The temperature signal from the temperature sensor MT is used, for example, for controlling the upper cooling device 15a (for example, feedback control), and the temperature signal from the temperature sensor CT is used for controlling, for example, the side spray device 40 (for example, feedback control). .

  The cooling device 15 according to the embodiment has the above-described configuration, and the hot-rolled steel sheet 10 rolled to a predetermined thickness by the finish rolling mill 14 is first cooled with cooling water from the cooling water nozzle of the upper cooling device 15a. (The illustration of the lower cooling device is omitted as described above). Then, draining is performed by the draining device 30. Next, the drained hot rolled steel sheet 10 is slowly cooled by the side spray device 40.

  At this time, as described above, the spray nozzle 41 of the side spray device 40 is sprayed obliquely from above with a predetermined spray angle with respect to the upper surface of the hot-rolled steel sheet 10, as shown in FIGS. Therefore, even if the on-plate residual cooling water 21 remains on the upper surface of the hot-rolled steel sheet 10, it is discharged to the end side (distant end) of the hot-rolled steel sheet 10. In addition, since the cooling water having the predetermined water flow density is sprayed, the control in the nucleate boiling region can be suitably performed, and the temperature of the hot-rolled steel sheet 10 can be finely controlled. Yes. Of course, it is possible to set the target winding temperature to 200 ° C.

  In the above-described embodiment, the spray nozzles 41 of the side spray device 40 are arranged on both sides of the hot-rolled steel sheet 10, and the spray nozzle 41 located on one side does not face the spray nozzle 41 located on the other side. However, as shown in FIGS. 6 and 7, the spray nozzle 41 is disposed only on one side of the hot-rolled steel sheet 10. You may make it do.

In such a one-sided arrangement, of course, these numerical values vary depending on the width of the hot-rolled steel sheet 10, but the height h from the upper surface of the hot-rolled steel sheet 10 to the jet nozzle 41a of the spray nozzle 41 is 0 mm to 1000 mm. From the viewpoint of discharging the on-plate residual cooling water 21 on the steel plate 10 from the end (distant end) of the spray nozzle 41 to the outside of the steel plate, θ1 is suitably 0 ° to 45 °, and θ2 is suitably 45 ° to 90 °. It is. That is, the end part (distant end part) of the ejection destination is covered from the end part (near end part) of the ejection source in the width direction of the hot-rolled steel sheet 10. Further, the spray spread angle θ3 from the spray nozzle 41a of the spray nozzle 41 is preferably 0 to 15 degrees. The spray flow rate from the spray nozzle 41 is 100 L / min, and 1200 m ^{2 to} 1300 m ² of water per minute per unit area is sprayed onto the region S sprayed onto the hot-rolled steel sheet 10. Is good. Furthermore, as for the angle formed between the hot-rolled steel sheet 10 and the spray inclination angle, when the case where the steel sheet and the spray are parallel is defined as 0 degrees, the spray inclination is preferably 30 degrees to 60 degrees toward the upstream side. As shown in FIG. 7, the regions S ejected from the spray nozzles 41 onto the hot-rolled steel sheet 10 should not overlap each other.

  4 and 5 is compared with the one side arrangement of the spray nozzle 41 shown in FIGS. 6 and 7, the cooling uniformity and the transport direction necessary for the nozzle arrangement are compared. From the viewpoint of securing the space of the side spray device along the side, it is preferable to arrange both sides. However, in any case, the present invention is superior to the conventional one in that the fine temperature of the hot-rolled steel sheet 10 is controlled.

  Furthermore, in the above-described embodiment, the dedicated draining device 30 is used for draining the on-plate residual cooling water 21 after the strong cooling. However, as shown in FIG. And the spray nozzle 41 of the side spray device 40 may be installed. That is, in addition to the spray nozzle 41 used for the original fine adjustment, the spray nozzle 41 may be installed on the upstream side in the transport direction for draining water.

  In such an example shown in FIG. 8, it is configured as a facility in which a plurality of spray nozzles 41 are installed on both downstream sides of the strong cooling zone, but the width and thickness of the hot-rolled steel sheet 10 to be cooled, the conveyance speed, the steel type Depending on the situation, the spray nozzle 41 used for draining water and the spray nozzle 41 used for fine adjustment of cooling are controlled by switching, or the number of sprays is controlled as necessary, so that a dedicated drainer device 30 is installed. There is no need to do so, and it is possible to make the equipment excellent in versatility.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

Examples of the present invention will be described below. The device configuration shown in FIGS. 2 and 3 is used. And the temperature of the cooling water sprayed from the spray nozzle 41 is 20 ° C., and the temperature of the hot rolled steel sheet 10 after draining by the draining device 30 is 550 ° C. (uniform in both the width direction and the thickness direction). The pressure of the cooling water jet is 0.3 MPa, the flow rate is 100 L / min, and the spread angle (θ3) is 10 degrees. Furthermore, the height h of the jet nozzle 41a of the spray nozzle 41 is 500 mm. And when the width | variety of the hot-rolled steel plate 10 is 1000 mm, the amount density of the cooling water from the spray nozzle 41 will be 1282 L / min / m < ² >.

The conveying speed of the hot-rolled steel sheet 10 is 10 m / sec, and one of the spray nozzles has the cooling ability as shown below. That is, the positions indicated by a, b, and c in FIG.
Position a: Initial side spray collision (near the edge on the side spray side)
Cooling position of hot-rolled steel sheet 10 at 8,000 W / K / m ² for 0.0087 seconds b: Cooling position of hot-rolled steel sheet 10 at 8,000 W / K / m ² in the width direction for 0.0098 seconds c: Side spray collision Last (near the opposite edge where the side spray is installed)
The hot-rolled steel sheet 10 is cooled for 0.0123 seconds at 8,000 W / K / m ² and has the above cooling capacity.
The cooling time at the positions a, b, and c is calculated in consideration of the conveying speed of the hot-rolled steel sheet 10 from the spread angle (θ3) of the cooling water jet from the spray nozzle 41.

Moreover, about the area | region width | variety (length along a conveyance direction) of the hot-rolled steel plate 10 in which the injected cooling water is, it is as follows.
Position a: 87 mm
Position b: 98 mm
Position c: 123 mm

  Under the above conditions, for the two cases of one-sided arrangement and two-sided arrangement, the side spray device 40 was subjected to slow cooling, and the surface temperature of the hot-rolled steel sheet 10 was measured by the temperature sensor CT. Results were obtained.

  As can be seen from these results, the target temperature of 200 ° C. could be achieved when 15 spray nozzles were used in either one-side arrangement or both-side arrangement. It was also confirmed that the temperature uniformity in the width direction was superior in the case of the both-side arrangement.

  The present invention is useful when cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process.

DESCRIPTION OF SYMBOLS 1 Continuous hot rolling equipment 5 Slab 10 Hot-rolled steel plate 11 Heating furnace 12 Width direction rolling mill 13 Coarse rolling mill 14 Finish rolling mill 15 Cooling device 15a Upper side cooling device 16 Winding device 17 Conveying roll 20 Cooling water nozzle 21 Residual on plate Cooling water 30, 50 Drainer 31, 51 Spray device 40 Side spray device 41 Spray nozzle 41a Spout

Claims (4)

A method of cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process,
Cooling is performed by injecting cooling water onto the steel sheet immediately after finish rolling, and then draining.
Cooling of the hot-rolled steel sheet, wherein the steel sheet is further cooled in the nucleate boiling region by spraying cooling water obliquely from above on the upper surface of the steel sheet after draining. Method. The cooling by the side spray device is performed by injecting cooling water onto the upper surface of the steel plate from both sides or one side of the steel plate by a plurality of side spray devices arranged at positions shifted in the conveying direction of the steel plate. The method for cooling a hot-rolled steel sheet according to claim 1. 3. The hot-rolled steel sheet according to claim 1, wherein the draining is performed by injecting a fluid from both sides or one side of the steel sheet to the upper surface of the steel sheet using a side spray device. Cooling method. An apparatus for cooling a hot-rolled steel sheet after finish rolling in a continuous hot rolling process,
A cooling device that cools the steel sheet immediately after finish rolling by injecting cooling water;
A draining device that is installed on the downstream side of the cooling device in the steel plate conveyance direction, and drains the cooling water;
A plurality of nucleate boiling regions that are installed along the conveying direction downstream of the draining device along the conveying direction and inject cooling water obliquely from above from one or both sides of the steel sheet with respect to the upper surface of the steel sheet after draining. A cooling device for a hot-rolled steel sheet, comprising: a side spray device for cooling.

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