JP2003236607A - Method for cooling hot-rolled steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cooling a hot-rolled steel strip by which the accuracy of the coiling temperature in the length direction of the hot-rolled steel strip is suppressed from lowering and temperature deviation in the width direction of the hot-rolled steel strip is reduced even in the case that the steel strip is wide and the coiling temperature is low. <P>SOLUTION: Side sprays which are arranged closely to the downstream side of the water cooling banks located on the most downstream side among the side sprays installed in a plurality of places in the length direction of cooling equipment in accordance with the number of the water cooling banks are jetted, and the jetting of the side sprays arranged on the upstream side of the water cooling bank located on the most downstream side and in a water-injecting cooling zone is stopped. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention increases or decreases the number of water injection cooling banks of cooling equipment provided downstream of a finish rolling mill,
The present invention relates to a method for cooling a hot rolled steel strip when controlling a winding temperature.

[0002]

2. Description of the Related Art A finish-rolled hot-rolled steel strip is cooled to a desired winding temperature by a cooling facility between a finish rolling machine and a winding machine, and is wound on the winding machine. The cooling equipment provided downstream of the finish rolling mill is generally composed of a plurality of upper and lower cooling banks, and each cooling bank includes:
For example, a plurality of headers 2a and 3a each having a plurality of cooling nozzles 2 and 3 attached in the width direction as shown in FIG. 8 are installed.

Also, side spray nozzles 5 are installed at a plurality of locations in the length direction of the cooling equipment. The side spray nozzle 5 is located on one side of the line, generally the operating side (O
It is installed at an upper position (also called the p side) and is connected to a jet water supply device (not shown) via a pipe 5a. In such a cooling facility, the winding temperature is controlled in the longitudinal position of the hot rolled steel strip by increasing or decreasing the number of water injection cooling banks. Specifically, the temperature (FDT) and target coiling temperature (CT) at the final stand of the hot-rolled steel strip finish rolling machine, various physical properties of the hot-rolled steel strip, and the final stand output of the hot-rolled steel strip finish rolling machine. Increase or decrease the number of water injection cooling banks according to the required cooling water amount in the longitudinal position of the hot-rolled steel strip, which is determined by the rolling conditions such as the lateral speed (also called the transport speed of the hot-rolled steel strip) and the finishing rolling speed acceleration rate. However, the winding temperature is controlled.

At this time, as shown in FIG. 8, the cooling water 1 supplied from the cooling nozzle 2 of the cooling bank is transferred to the upper surface of the hot-rolled steel strip S being conveyed on the conveying roller 4 in the direction shown by the arrow 10. After reaching, it rides on the hot-rolled steel strip S and is carried to the downstream side of the line to be used as riding water. It is well known that this ride water causes a large disturbance to the cooling capacity of the water injection cooling bank on the downstream side. Therefore, it is common practice to inject the cooling water from the side spray nozzle 5 described above to purge the riding water.

Reference numeral 6 in FIG. 8 indicates Dr of the hot rolled steel strip S.
The accumulated water is temporarily accumulated on the upper surface of the side. Accumulated water 6
Means that the water sprayed from the side spray nozzle 5 hits the wall 7 (also called the splash guard 7) of the cooling table and bounces off. Especially, when the plate width W is wide, the splash guard 7 and the heat spreader suspended on the Dr side of the cooling table Since the space between the steel strip S and the steel strip S is narrow, the jet water after use does not immediately flow out and temporarily stays on the upper surface of the hot-rolled steel strip on the Dr side or is carried on the hot-rolled steel strip S. Depending on the cooling conditions and the rolling conditions, the incoming water is collected by the water sprayed from the side spray nozzle 5 on the Dr side of the hot-rolled steel strip, and is the temporarily used used cooling water.

By the way, in the conventional cooling method, the entire side spray is sprayed regardless of the number of water-cooling banks, so that the accumulated water 6 causes a heat having a particularly wide width and a low winding temperature. In the case of a rolled steel strip, the width side end of the hot rolled steel strip on the Dr side may be overcooled, and the temperature deviation in the width direction of the hot rolled steel strip may increase. However, if the injection of all of the side sprays installed at a plurality of positions in the length direction of the cooling equipment is stopped, there is a problem that the winding temperature accuracy at the position in the length direction of the hot-rolled steel strip deteriorates.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention is to eliminate the above-mentioned problems of the prior art. Even in the case of a hot-rolled steel strip having a wide width and a low coiling temperature, the length of the hot-rolled steel strip is long. An object of the present invention is to provide a method for cooling a hot-rolled steel strip, which can suppress a decrease in the accuracy of the winding temperature in the depth direction and can reduce a temperature deviation in the width direction of the hot-rolled steel strip.

[0008]

Means for Solving the Problems The inventors of the present invention basically stop the injection of a side spray installed beside the water injection cooling bank on the upstream side of the water injection cooling bank located at the most downstream side. The present invention has been completed based on the finding that it is possible to suppress a decrease in the winding temperature accuracy in the length direction of the hot-rolled steel strip.

The present invention is as follows. 1. When increasing or decreasing the number of water injection cooling banks of the cooling equipment installed on the downstream side of the finishing rolling mill to control the winding temperature in the longitudinal position of the hot-rolled steel strip, the downstream side of the water injection cooling bank located on the most downstream side. A method for cooling a hot-rolled steel strip, comprising injecting a side spray in the vicinity of the water injection side, and stopping the injection of the side spray upstream of the water injection cooling bank located at the most downstream side and next to the water injection cooling bank. 2. An air cooling zone is provided in the cooling facility, an intermediate thermometer for detecting the temperature of the hot rolled steel strip online is arranged in the air cooling zone, and a side spray is injected from one or more locations upstream of the intermediate thermometer. The above 1. The method for cooling a hot rolled steel strip according to.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the case where the present invention is applied to the cooling equipment shown in FIG. 1 will be described in detail. Figure 1
[Fig. 4] is a schematic layout diagram of cooling equipment installed between a final stand 8 of a finish rolling mill and a winding machine 9. The cooling equipment has a plurality of upper cooling banks 11, a plurality of lower cooling banks (not shown), and a plurality of side sprays 51 to 59.

In the figure, reference numerals # 1 to # 20 are numbers of upper cooling banks sequentially added from the upstream side. This cooling facility includes cooling zones A1, A2, A3 that consist of multiple cooling banks in series.
Further, an air cooling zone B1 is provided between the cooling zones A1 and A2, and an air cooling zone B2 having an intermediate thermometer is provided between the cooling zones A2 and A3. In addition, between the finishing stand 8 of the finishing rolling mill and the # 1 cooling bank, a thermometer for detecting the exit side temperature (FDT) of the finishing stand of the finishing rolling mill of the hot-rolled steel strip S and the thickness of the hot-rolled steel strip S are installed. This is an air-cooled area where detectors such as a thickness gauge for detection are installed.

In the figure, the final stand 8 of the finishing rolling mill is shown.
The hot-rolled steel strip S sent from is conveyed in the direction of arrow 10 and cooled to a desired winding temperature by cooling water supplied from the upper cooling bank 11 and a lower cooling bank (not shown), and the winding machine 9 To be wound up. At that time, the winding temperature of the hot rolled steel strip S is controlled by the finish stand temperature (FDT) of the finish rolling mill of the hot rolled steel strip and the target winding temperature, various physical properties of the hot rolled steel strip, the hot rolled steel strip. Finishing rolling mill final stand exit side speed (simply called finishing rolling speed) and finishing rolling speed Acceleration rate, etc. The number of cooling banks is increasing or decreasing.

In the case of this cooling equipment, a winding thermometer (CT) installed on the downstream side of the # 20 cooling bank is used, and based on the detected winding temperature of the hot-rolled steel strip S, a winding not shown is shown. The temperature control device is configured to be able to perform feedback temperature control for changing the number of water injection cooling banks. Further, the temperature of the hot-rolled steel strip S detected by the intermediate thermometer is detected online, and the above-described operation is performed based on the intermediate temperature. It is also possible to change the number of water injection cooling banks by the winding temperature control device.

Here, the side sprays 51 to 59 are installed at nine locations in the length direction of the cooling equipment shown in FIG. That is, the side sprays 51, 52, 53 are in the downstream air cooling zone B1 following the cooling zone A1, the side sprays 54, 55 are between cooling banks in the cooling zone A2, and the side sprays 56 are downstream air cooling in the cooling zone A2. Zone B2, side spray 57,
58 is a side spray between cooling banks in cooling zone A3
59 are installed in the downstream air-cooling areas following the cooling zone A3, respectively.

These side sprays 51 to 59 are installed above the cooling table on the Op side, and as shown in FIG. 2, spray from the Op side of the upper surface of the hot rolled steel strip S toward the Dr side, or It is connected to a cooling water supply device (not shown) via a pipe 5a so that the injection can be stopped. In such cooling equipment, the finish rolling speed is gradually increased, and the injection method of the side spray when the number of water injection cooling banks is increased according to the required cooling water amount determined by the rolling conditions is sequentially shown in FIGS. 3 to 6. It was Note that the number of upper cooling banks for water injection is 12 banks in FIG. 3, 14 banks in FIG.
There are 17 banks, and in Figure 6, there are 20 banks.

Explaining the injection method of the side spray, in the state of FIG. 3, the # 12 cooling bank is the water injection cooling bank located at the most downstream side, and the side spray 56 adjacent to the downstream side of the # 12 cooling bank is injected. , # 12 Side spray 54 upstream of the water cooling bank and in cooling zone A2,
55 injection is stopped. In addition, the side spray 57 installed in the cooling zone A3 on the downstream side of the # 12 cooling bank,
No. 58 has stopped jetting.

In the state shown in FIG. 4, the # 14 cooling bank is the water injection cooling bank located at the most downstream side, and the side spray 57 which is close to the downstream side of the # 14 cooling bank is injected to the upstream side of the # 14 cooling bank. Side spray in cooling zone A2 54, 55
Has stopped injection. In addition, the side spray 58 installed in the cooling zone A3 on the downstream side of the # 14 cooling bank is stopped.

Further, in the state of FIG. 5, the # 17 cooling bank is the water injection cooling bank located at the most downstream side, and the side spray 58 adjacent to the downstream side of the # 17 cooling bank is injected to the upstream side of the # 17 cooling bank. And side spray in cooling zone A3
57 and the side sprays 54 and 55 in the cooling zone A2 are stopped. Further, in the state of FIG. 6, all the cooling banks # 1 to # 20 are water-injection cooling banks, and the side spray 59 close to the downstream side of the # 20 cooling bank is injected to
Side sprays 54, 55 upstream of the cooling bank and in cooling zone A2 and side sprays 5 in cooling zone A3
The injection of 7 and 58 is stopped.

In the present invention, as described above, the side spray on the upstream side of the water injection cooling bank located on the most downstream side and in the cooling zone A2 is stopped, so that the width end of the hot rolled steel strip on the Dr side is stopped. It is possible to prevent overcooling in the portion and reduce the temperature deviation in the width direction of the hot-rolled steel strip. In addition, in the present invention, since the side spray that is close to the downstream side of the water injection cooling bank located on the most downstream side is injected, it is possible to suppress a decrease in the winding temperature accuracy in the length direction of the hot-rolled steel strip. it can.

At this time, in the present invention, an air cooling zone is provided between the cooling banks, and an intermediate thermometer for detecting the temperature of the hot rolled steel strip online is arranged in this air cooling zone, and the intermediate thermometer is provided upstream of the intermediate thermometer. It is possible to detect the temperature of the hot-rolled steel strip S with high accuracy by installing side sprays at one or more locations and injecting side sprays installed at one or more locations upstream of the intermediate thermometer. This is preferable because the winding temperature accuracy can be further improved.

In this case, between the side sprays 51, 52, 53 installed in the air cooling zone B1 and the side sprays 56 and # 20 cooling banks installed in the air cooling zone B2 and the winding thermometer CT. The side spray 59 installed in the air cooling area is always sprayed when the hot-rolled steel strip S is cooled. However, in the above description, the case where the air cooling zones B1 and B2 are provided has been described, but the present invention can also be applied to cooling equipment in which the air cooling zones B1 and B2 are not provided. Also,
In the above description, the upper cooling bank has been described, but it can be applied to the lower cooling bank because water flows from the lower cooling bank.

[0022]

EXAMPLE A finish rolling mill consisting of 7 stands and FIG.
In the hot rolling line having the cooling equipment shown in 2, a hot rolled steel strip having a width of 2000 mm, a thickness of 3.20 mm and a target coiling temperature of 500 ° C was manufactured. At that time, in the invention example, as described in FIGS. 3 to 6, the side spray was injected or stopped depending on the number of the water injection cooling banks. On the other hand, in the conventional example, in the same hot rolling line as the invention example, the same dimensions as the invention example,
Hot-rolled steel strips made of a material and having a target coiling temperature were jetted from all of the side sprays installed at a plurality of locations, and other cooling conditions were the same as those of the invention example.

As a result, in the case of the conventional example, the temperature deviation ΔT in the width direction of the hot rolled steel strip was 50 ° C. as shown in FIG. The temperature deviation could be reduced to about 1/3 of the conventional example. In addition, the winding temperature accuracy in the length direction of the hot rolled steel strip was the same in the invention example and the conventional example.

[0024]

EFFECTS OF THE INVENTION According to the present invention, it is possible to suppress a decrease in the winding temperature accuracy in the lengthwise direction of a hot-rolled steel strip, prevent overcooling at the width end of the hot-rolled steel strip, and The widthwise temperature deviation of the steel strip can be reduced. As a result, in particular, even in the case of a hot rolled steel strip having a wide width and a low winding temperature, it is possible to prevent the width end portion on the Dr side from extending into the edge.

[Brief description of drawings]

FIG. 1 is a schematic layout of cooling equipment to which the present invention is applied.

FIG. 2 is a schematic plan view showing a spray direction of the side spray installed in FIG.

FIG. 3 is an explanatory diagram of an injection state of side sprays corresponding to the number of water injection cooling banks.

FIG. 4 is an explanatory diagram of a side spray injection state when the number of water injection cooling banks is different from that in FIG.

FIG. 5 is an explanatory diagram of a side spray injection state when the number of water injection cooling banks is different from that in FIG. 3.

6 is an explanatory diagram of a side spray injection state when the number of water injection cooling banks is different from that in FIG. 3. FIG.

FIG. 7 is a graph illustrating the effect of the present invention.

FIG. 8 is a schematic perspective view showing positions of accumulated water.

[Explanation of symbols]

S Hot-rolled steel strip (hot-rolled steel plate) W Plate width 1 Cooling water 2 Upper cooling nozzle 3 Lower cooling nozzle 2a, 3a Header 4 Conveying rollers 5, 51, 52, 53, 54, 55, 56, 57, 58, 59 Side spray 6 Retained water 7 Cooling table wall 8 Finishing mill Final stand 9 Winder 10 Arrow 11 Upper cooling bank CT Winding thermometer A1, A2, A3 Cooling zone B1, B2 Air cooling zone

Claims (2)

[Claims] 1. The water injection located at the most downstream side in controlling the winding temperature in the longitudinal position of the hot-rolled steel strip by increasing or decreasing the number of water injection cooling banks of the cooling equipment provided on the downstream side of the finish rolling mill. A method for cooling a hot-rolled steel strip, characterized by injecting a side spray close to the downstream side of the cooling bank and stopping the injection of the side spray upstream of the water injection cooling bank located at the most downstream side and next to the water injection cooling bank. . 2. An air cooling zone is provided in the cooling equipment, and an intermediate thermometer for detecting the temperature of the hot rolled steel strip online is arranged in the air cooling zone.
The method for cooling a hot-rolled steel strip according to claim 1, wherein the side spray is injected from more than one place.