JP2011167740A - Apparatus for cooling hot steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for cooling hot steel plates which has straight tube type nozzles and provides stable flow of cooling water which is jetted onto the upper surface of a steel plate from the plurality of nozzles connected to a header. <P>SOLUTION: The apparatus for cooling the hot steel plates includes the header and the plurality of straight tube type nozzles which are connected with the header at a predetermined interval in the width direction of the hot steel plate and which supply the cooling water to the upper surface of the hot steel plate. In the apparatus, a sleeve having the inside diameter of 20-80% of the inside diameter of the nozzle and a straightening member which is arranged at the lower end of the sleeve and includes a straightening plate dividing the flow passage of the cooling water from the sleeve into at least three or more passages are attached to the upper end of the straight tube type nozzle, thereby the cooling water which is jetted to the upper surface of the steel plate from the nozzles is stabilized. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cooling device for cooling a hot steel sheet, which is a heated steel sheet such as a hot rolled steel strip or a thick plate, from above.

  As shown in FIG. 1, for example, in order to manufacture a hot-rolled steel strip as one of the hot steel plates, the slab is heated to a predetermined temperature in a heating furnace 1, and the heated slab is rolled by a roughing mill 2. A rough bar is formed, and then this hot bar is formed into a hot rolled steel strip 6 having a predetermined thickness in a continuous hot finishing rolling mill 3 composed of a plurality of rolling stands. And after cooling a hot-rolled steel strip by supplying cooling water from the upper part and lower part of a hot-rolled steel strip from the cooling device 4 installed in the run-out table, it manufactures by winding with the winder 5. FIG.

  The quality of the steel sheet is greatly changed by the cooling by the cooling device. If the cooling capacity varies in the longitudinal and width directions of the steel sheet, the material will vary. Normally, in a cooling device that cools a hot steel plate from the upper surface, cooling water is poured onto the hot steel plate from a circular cooling nozzle connected to the header, but if the flow ejected from the nozzle is unstable, The flow after jetting is twisted, and variation in cooling capacity is generated for each nozzle, thereby causing variation in material in the longitudinal and width directions of the steel sheet. Therefore, attempts have been made to stabilize the flow ejected from the nozzle.

  In general, it is known that the flow of cooling water ejected from a nozzle becomes stable as the inner diameter of the nozzle increases and the nozzle length increases. However, as the inner diameter of the nozzle increases, the pressure loss decreases. Therefore, the cooling water must be injected with the pressure in the header being low. If so, a stable laminar flow cannot be obtained with some of the plurality of nozzles in the steel plate width direction. Therefore, when a nozzle having a large inner diameter is used, a device for increasing the pressure loss, such as providing a throttle portion, is necessary.

By the way, the cooling nozzle of the cooling device which is conventionally used and cools by pouring cooling water on the upper surface of the hot steel sheet is as shown in FIGS.
FIG. 2 shows a cooling nozzle that is one of the types frequently used for cooling hot steel sheets in a hot rolling line. This nozzle is called a hairpin type, one end is connected to the upper part of the header 7, and the other end that ejects cooling water from the header hangs down to a position adjacent to the left and right side surfaces of the header 7. It has an inverted U shape. A plurality of such nozzles are connected to the header at predetermined intervals in the plate width direction of the steel plate. Patent Document 1 discloses this hairpin type nozzle (see FIG. 1 of the same document).

  Moreover, as shown in FIG. 3, a cooling device having a straight tube type nozzle different from the hairpin type is also used. In the cooling device shown in FIG. 3, a mountain-shaped roof plate 9 is overlapped and crowned on the lower header 7, and an upper header 10 is formed in a chamber formed by the upper wall of the lower header 7 and the roof plate 9. The cooling water can be supplied from the lower header 7 to the upper header 10, and the nozzle 8 hangs down from the upper header 10 through the lower header 7. The cooling water supplied to the lower header 7 reaches the upper header 10, flows into the nozzle 8 from the upper end of the straight tubular nozzle 8, and is ejected from the lower end of the nozzle. A plurality of such nozzles 8 are connected to a header composed of an upper header and a lower header at a predetermined interval in the plate width direction of the steel plate. Patent Document 2 discloses this straight pipe type nozzle.

In the hairpin type nozzle shown in FIG. 2 described above, as a technique for stabilizing the flow ejected from the nozzle, Patent Document 1 provides a wide area by providing a throttle portion between the bent portion of the nozzle and the connecting portion of the header. An invention of a nozzle capable of maintaining a laminar flow over a water amount range is described (see FIG. 2 of the same document).
However, since this hairpin type nozzle has a bent portion and a narrowed portion, water stains are likely to adhere and accumulate on the inner surface, and it is necessary to clean frequently, and that cleaning is difficult. .

  On the other hand, Patent Document 2 discloses a technique in which a sleeve (throttle portion) for reducing the inner diameter of a nozzle is installed at the upper end opening of a straight tube type nozzle as shown in FIG. However, as shown in FIG. 4, the cooling water is injected at the sleeve outlet with the sleeve inner diameter being thick, and the entire nozzle interior is not filled with the cooling water. There was a problem that it could not be maintained. Also, if the inner diameter difference between the sleeve and nozzle is increased, the pressure loss increases and the pressure in the cooling header increases, resulting in the uniform flow distribution of each nozzle installed in the width direction of the steel plate. In order to achieve more uniform cooling in the width direction of the steel sheet, it is important to eliminate this flow instability.

Japanese Patent Publication No.53-36809 Japanese Utility Model Publication No. 63-44168

  In view of the above circumstances, an object of the present invention is to provide a thermal steel sheet cooling device having a straight pipe type nozzle in which the flow of cooling water injected from the nozzle onto the upper surface of the steel sheet is stable.

  As a result of diligent investigations, the present inventors have attached a sleeve having an inner diameter of 20 to 80% of the inner diameter of the nozzle to the upper end of the straight tubular nozzle in a cooling device having a straight tubular nozzle, and the lower end of the sleeve. Further, it has been found that the flow of cooling water injected from the lower end of the nozzle can be stabilized by connecting a flow regulating member that divides the cooling water flow path from the sleeve into at least three or more flow paths.

Therefore, the present invention employs the following means in order to solve the above problems.
(1) In a thermal steel sheet cooling apparatus comprising a plurality of straight tubular nozzles connected to the header at a predetermined interval in the width direction of the header and the thermal steel sheet and supplying cooling water to the upper surface of the thermal steel sheet, A sleeve having an inner diameter of 20 to 80% of the inner diameter of the nozzle, and a rectifying member that is disposed at the lower end of the sleeve and includes a rectifying plate that divides the cooling water flow path from the sleeve into at least three; and Heating steel sheet cooling device.
(2) The thermal steel plate cooling device according to (1), wherein the flow straightening member including the flow straightening plate has a cross-shaped cross section and divides the cooling water flow path from the sleeve into four.
(3) The rectifying member including the rectifying plate has a Y-shaped cross section and divides the cooling water flow path from the sleeve into three, and the thermal steel sheet cooling device according to (1) .
(4) The flow straightening plate of the flow straightening member is inclined with respect to the nozzle axis direction so as to give the flow of cooling water a circumferential speed in the nozzle cross section. 3)
The thermal steel sheet cooling device according to any one of the above.

  By using the thermal steel sheet cooling device of the present invention, the flow of cooling water sprayed from the nozzle is stabilized, and as a result, the hot steel sheet can be cooled with high cooling uniformity in the longitudinal and width directions of the steel sheet. It is possible to manufacture a high quality steel sheet with a small variation in the thickness.

It is a figure which shows the outline of the rolling line of a hot-rolled steel strip. It is a side view of a general upper surface cooling device (hairpin type). It is a side view of a general upper surface cooling device (straight tube type). It is a figure showing the state of the cooling water injected from a sleeve exit. (A) is a figure which shows the upper part of the straight tube | pipe type nozzle with which the rectification | straightening member which divides a sleeve and a flow path into 4 was mounted | worn, (b) is the perspective view. (A) is a figure which shows the upper part of the straight tube | pipe type nozzle with which the rectification | straightening member which divides a sleeve and a flow path into 3 was mounted | worn, (b) is the perspective view. It is a figure which shows the upper part of the straight tube | pipe type nozzle with which the rectification | straightening member inclined in the sleeve and the nozzle axial direction was mounted | worn. It is a figure showing the change of the stability of the flow by d (sleeve inner diameter) / D (nozzle inner diameter) and flow volume. (A) is the side view of one Example of the cooling device of this invention, (b) shows the front view.

The thermal steel sheet cooling device of the present invention includes a header and a plurality of straight tubular nozzles connected to the header at a predetermined interval in the width direction of the hot steel sheet. A member is mounted. The flow regulating member is provided continuously at the lower end of the straight tubular sleeve.
The sleeve has an inner diameter of 20 to 80% of the inner diameter of the nozzle, and forms a throttle portion for cooling water at the upper end of the nozzle. The rectifying member includes a rectifying plate, The cooling water flow path is divided into at least three or more.

In order to make it easy to attach the sleeve to the upper end of the nozzle, it is desirable that a flange is formed on the outer periphery of the upper end of the sleeve and the flange is locked to the upper end of the nozzle.
The sleeve and the rectifying member may be integrated with each other by welding or screws, or may be separable.
In order to facilitate maintenance, it is desirable that the sleeve and the rectifying member be detachable from the nozzle.

5 to 7 show examples of the rectifying member of the present invention attached to the upper end portion of the sleeve together with the sleeve.
The rectifying member 15 shown in FIG. 5 includes four rectifying plates 16, has a cross-shaped cross section, and divides the flow path into four. Moreover, the rectifying member 15 shown in FIG. 6 has three rectifying plates 16, has a Y-shaped cross section, and divides the flow path into three.
When the rectifying member is installed as shown in FIGS. 5 and 6, the flow of the cooling water is divided and diffused by the rectifying member, and the entire inside of the nozzle is filled with the cooling water to obtain a stable laminar flow. Further, the flow straightening member 15 shown in FIG. 7 has the flow straightening plate 16 inclined with respect to the axial direction of the nozzle, and the flow diffusion effect is increased by giving the cooling water a circumferential speed in the nozzle cross section. The flow of cooling water can be stabilized more effectively.

The nozzle inner diameter is D, the sleeve inner diameter is d, and the relationship between d / D and the lower limit of the flow rate at which the flow is stable FIG. 8 shows the results of investigation on the three cases, when the sleeve is attached and when the sleeve and the lower end thereof are attached with the rectifying member provided with the rectifying plate having an inclination with respect to the nozzle axis direction.
In FIG. 8, the solid line has no rectifying member, only the sleeve, the broken line has the sleeve and the lower end connected with the rectifying member, and the alternate long and short dash line is the sleeve and its lower end with respect to the nozzle axis direction. The case where what connected the rectification | straightening member provided with the rectification | straightening board which has an inclination is each shown.

The condition that the flow was stable was that the fluctuation range of the value measured by the pressure sensor installed at the position where the cooling water landed on the steel plate was within 10%. This agrees well with the visual judgment result.
As shown in FIG. 8, the flow rate at which the flow stabilizes increases as d / D decreases in any case. Therefore, if the nozzle inner diameter is constant, when using a sleeve with a small inner diameter, the flow will not be stable unless a larger flow rate is applied than when using a sleeve with a large inner diameter. However, the flow is more stable in the case where there is no rectifying member, and the flow rate to be stabilized is reduced by about 10 L / min (L is liter). It can also be seen that when the rectifying member is inclined with respect to the nozzle axis direction, the flow rate to be further stabilized is small and the flow is more stable.

  The inner diameter d of the sleeve in the cooling device of the present invention is in the range of 20 to 80% of the nozzle inner diameter D. If it is less than 20%, foreign matter is likely to be clogged in the sleeve, the cooling water may not flow, and there will be a problem that the pressure loss becomes larger than necessary. In addition, when the nozzle is larger than 80%, a sufficient pressure loss cannot be given, and a stable laminar flow cannot be obtained with some of the plurality of nozzles in the steel plate width direction.

FIG. 9 shows a schematic diagram of an example of the embodiment of the cooling device of the present invention.
In the cooling device in FIG. 9, a mountain-shaped roof plate 9 is overlapped on the lower header 7, and the upper header 10 is formed in a chamber formed by the upper wall of the lower header 7 and the roof plate 9. Cooling water can be supplied from the lower header 7 to the upper header 10 through holes (not shown) formed in several places on the upper wall of the header 7, and a plurality of pieces attached at predetermined intervals in the width direction of the steel plate. A straight tubular nozzle 8 is penetrating from the upper header 10 through the lower header 7. The cooling water supplied from the water supply pipe 13 to the lower header 7 reaches the upper header 10 through the hole, flows into the nozzle from the upper end of the nozzle 8, and is ejected from the lower end of the nozzle. Reference numeral 11 denotes cooling water, and 12 denotes a table roller.
A sleeve 14 and a rectifying member 15 are mounted inside the upper end portion of the nozzle 8.

  In the cooling device shown in FIG. 9, the header is composed of an upper header and a lower header, but the present invention can also be applied to a cooling device in which a straight pipe type nozzle is connected to a single header made of a hollow tube. As long as the nozzle connected to the header is a straight pipe type, any cooling device of the present invention can be applied.

An embodiment of the present invention will be described in the case where the hot-rolled steel strip is cooled by the cooling device shown in FIG. 9 in the hot-rolled steel strip rolling line shown in FIG.
In FIG. 9, the inner diameter D of the nozzle 8 is 25 mm, the flow rate per nozzle is 35 L / min, the nozzle pitch in the width direction of the hot-rolled steel strip is 50 mm, and the number of nozzles connected to the header is 48.

Then, under the conditions that the length of the sleeve is 30 mm, the inner diameter d of the sleeve is 8.3 mm, and d / D = about ３, the first embodiment of the present invention has a rectifying member (divided into four channels, long length). 30 mm) is a cooling device in which a rectifying member (divided into four channels, 30 mm in length, inclined at 10 ° with respect to the nozzle axis direction) shown in FIG. Was cooled.
In Comparative Example 1, cooling was performed with a conventional cooling device having only a sleeve (length 30 mm) that does not have a current plate member.

Using the cooling devices of Invention Example 1, Invention Example 2 and Comparative Example 1 described above, a hot-rolled steel strip having a finished sheet thickness of 3.0 mm and a tensile strength of 550 MPa was produced. The conveying speed on the delivery side of the finish rolling mill was 650 mpm at the steel strip tip, and after the steel strip tip reached the winder, the speed was gradually increased to a maximum of 800 mpm. The temperature at the delivery side of the finishing strip of the steel strip was 860 ° C., and the cooling zone was used to control the length of the cooling zone so that the instruction of the thermometer before the winder was 500 ° C.
About each, the pressure value fluctuation | variation on the steel strip of the cooling water ejected from a nozzle, the dispersion | variation in the winding temperature of a steel strip, and the dispersion | variation in the tensile strength of a steel strip were measured. The results are shown in Table 1.

In Comparative Example 1, the shape of the cooling water jetted from the nozzle is unstable, the pressure sensor value variation is 30%, and the winding temperature variation ΔT is ± 45 ° C. relative to the target value. Thus, the tensile strength variation ΔTS was ± 43 MPa with respect to the target 550 MPa. Because the variation in tensile strength was large, the portion with large temperature variation was discarded, and the product yield was low.
On the other hand, in Example 1 of the present invention, the cooling water sprayed from the nozzle has a stable shape, the variation in the pressure measurement value by the pressure sensor is 5%, and the variation in winding temperature ΔT is: The target value was ± 7 ° C., and the tensile strength variation ΔTS was ± 6 MPa with respect to the target 550 MPa. Also in Example 2 of the present invention, the cooling water sprayed from the nozzle has a stable shape, the variation in the pressure measurement value by the pressure sensor is 4%, and the variation ΔT in the coiling temperature is As shown in FIG. 2, the target value was ± 6 ° C., and the tensile strength variation ΔTS was ± 5 MPa with respect to the target 550 MPa.

As described above, the cooling device of the present invention can reduce the variation in the winding temperature in the longitudinal and width directions of the steel strip, and can improve the material uniformity.
In the embodiment of the present invention, the hot-rolled steel strip cooling device has been described. However, the present invention is not limited to this, and is applied to the case where other hot steel plates such as thick plates are cooled with cooling water. It is also possible.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Coarse rolling mill 3 Finish rolling mill 4 Cooling device 5 Winding machine 6 Hot steel plate, hot-rolled steel strip 7 Header, lower header 8 Nozzle 9 Roof plate 10 Upper header 11 Cooling water 12 Table roller 13 Water supply pipe 14 Sleeve 15 Rectification member 16 Rectification plate

Claims (4)

  In a thermal steel sheet cooling apparatus comprising a plurality of straight tubular nozzles connected to the header at a predetermined interval in the width direction of the header and the thermal steel sheet, and supplying cooling water to the upper surface of the thermal steel sheet, A thermal steel sheet comprising: a sleeve having an inner diameter of 20 to 80%; and a rectifying member that is disposed at a lower end of the sleeve and includes a rectifying plate that divides a cooling water flow path from the sleeve into at least three or more. Cooling system.   The apparatus for cooling a hot steel sheet according to claim 1, wherein the rectifying member including the rectifying plate has a cross-shaped cross section and divides the cooling water flow path from the sleeve into four.   The apparatus for cooling a hot steel sheet according to claim 1, wherein the rectifying member including the rectifying plate has a Y-shaped cross section and divides the cooling water flow path from the sleeve into three. The rectifying plate of the rectifying member is inclined with respect to the nozzle axial direction so that a circumferential velocity is given to the flow of the cooling water within the nozzle cross section. The thermal steel sheet cooling device according to Item.