JPS62112733A - Cooling method for hot rolled steel sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a controlled cooling method for hot rolled steel sheets.

[Prior art] In the controlled cooling of underground rolled steel plates, the temperature distribution along the width direction of the Shape defects occur.

In order to prevent the occurrence of such shape defects, Japanese Patent Application Laid-Open No. 57-165114 discloses that the injection of cooling water is blocked in areas adjacent to the side edges of the steel plate, so that the area adjacent to the side edges in the width direction of the steel plate is located at the center in the width direction. This paper proposes a method to prevent overcooling compared to other parts.

Furthermore, Japanese Patent Laid-Open No. 60-87914 specifically proposes a control method on the premise that it is possible to control the amount of cooling water injected along the width direction.

In other words, the temperature of the steel plate is actually measured before the start of water cooling, and the conditions for setting the water injection amount in the width direction are determined so that the temperature difference in the width direction of the steel plate at the end of water cooling is within the allowable value. This is a method of modifying the amount of coolant injected in the width direction.

The applicant of the present application previously proposed Japanese Patent Application No. 59-28666 as an improvement on the above-mentioned prior art.

In this proposed method, physical properties such as the coefficient of linear expansion and specific heat of the steel plate change drastically during the Ar3 transformation during the cooling process, and when the progress of the Ar transformation differs depending on the location in the width direction of the steel plate, the internal It was devised by focusing on the fact that stress or plastic strain occurs, causing shape defects such as wave 1 warping in steel plates at room temperature. so that they proceed at the same time or with a delay,
This controls the amount of water flowing in the width direction during the cooling process.

[Problems to be Solved by the Invention] The above-mentioned Japanese Unexamined Patent Publication No. 60-87914 discloses controlling the amount of perspiration in the width direction so that the temperature difference in the width direction of the steel plate is within an allowable value at the end of water cooling. However, the inventors of the present invention have discovered that even if the temperature distribution in the width direction at the end of water cooling is simply uniform, shape defects such as wave 8 warpage may occur in the steel sheet.

Japanese Patent Application No. 59-28666 discloses a method of controlling the amount of water injected in the width direction so that the progress of Ar3 transformation at the side edges of the steel plate is simultaneous or delayed from the progress of Ar3 transformation at the central part. .

The present invention is similar to Japanese Patent Application No. 59-28666 in recognizing that it is necessary to control the temperature distribution in the width direction during water cooling, but the temperature during water cooling is actually measured, and the temperature distribution in the width direction during water cooling is measured. The present invention provides a cooling power method that further enhances the effect of preventing the occurrence of shape defects in steel plates by directly controlling the aqua regia fountain.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention cools a hot-rolled steel plate by supplying cooling water (j) to the plate from nozzles arranged above and below while transferring the steel plate in the longitudinal direction In this method, the temperature difference in the width direction of the steel plate is detected for each unit length of the steel plate at the entrance side of each cooling zone for each length in which the amount of cooling water injected in the width direction can be controlled along the longitudinal direction of the cooling device, The method is to control the amount of water injected in the width direction to the unit length of the steel plate in the cooling zone based on the detected temperature difference in the width direction.

[Operation] In the present invention, for example, it is assumed that the cooling zone is divided into N parts along the longitudinal direction of the cooling device.

At this time, the temperature difference in the width direction of each unit length of the steel plate to be cooled is detected N times during the entire water cooling process. The amount of sweat water in the width direction in the cooling zones No. 1 to No. N is based on the actual measurement results of the temperature difference in the width direction by the thermometer at the entrance of each cooling zone, and the temperature difference in the width direction becomes zero at the exit side of each cooling zone. controlled as follows.

For example, the specified cooling condition is water cooling start temperature 750℃.
, the temperature rise F meter due to water cooling is 75 at the end temperature of water cooling of 450℃.
When 0-450 = 300°C, the temperature drop per 1 cooling zone according to the present invention is approximately (30°/N)'
It becomes C. Here, if N=10, (1) the amount of temperature drop per cooling zone will be 30°C.

This amount of temperature drop per cooling zone can be further reduced by increasing N. The smaller the amount of temperature drop in the l cooling zone, the smaller the widthwise temperature difference that occurs in the l cooling zone.

In the present invention, the temperature difference in the width direction is detected for each cooling zone and the amount of water injected in the width direction of the next cooling zone is adjusted. Therefore, as a result, the temperature difference in the width direction during the entire water cooling process can be reduced to f5.Furthermore, as described above, the present invention reduces the temperature difference in the width direction of the steel plate during the entire water cooling process for each steel plate by water cooling. Since the process is directly controlled, it is possible to prevent shape defects from occurring in the steel plate from the first grain of the coolant treatment lot.

C Embodiment) The present invention will be described in detail below based on the illustrated embodiment.

FIG. 1 is a diagram showing the overall configuration of an apparatus in an embodiment of the present invention. In FIG. 1, 1 is a finishing rolling machine for thick steel plates, 2 is a hot straightening machine, 3 is a measuring roll, 4 is a steel plate position detection sensor, 5 is a cooling device, 61 to 612 are upper and lower water injection headers, 7. ~7° is the thermometer.

In this example, for each upper and lower water injection header, the steel plate width direction/E
It is possible to control the water M, and the installation interval between water injection stations is 1 m. The steel plate to be cooled is designated by the symbol P.
and is transported in the direction of the arrow.

FIG. 2 is a diagram showing that in this embodiment, the temporary cooling of i'q, which is cooled at 5, and the shape of IJ1 are divided into unit lengths of the mouth plate.

Each of the thermometers 71 to 713 shown in FIG. 1 is a radiation thermometer using optical fibers. In this embodiment, each of the thermometers 71 to 713 is installed at the center and side edges of the steel plate P so that the pair of light-receiving ends thereof face the upper and lower surfaces of the steel plate P.

8 is a high-level arithmetic unit that calculates steel type, rolling conditions, steel plate dimensions,
The cooling conditions etc. are given to the computing unit 9. This calculator 9 determines the initial setting conditions for the amount of cooling water injected in the width direction.

In Figure 2! is the unit length of the steel plate, which is equal to both the length of each cooling zone and the longitudinal installation interval of each thermometer.

The initial setting conditions for the cooling water widthwise injection type in the computing unit 9 are set for each cooling zone using a known method with the aim of making the temperature difference in the widthwise direction of the steel plate zero during the entire cooling process.

10 is each thermometer 71-71. The temperature difference in the width direction is calculated by averaging the temperature at the central part and side edge part of the steel plate in the width direction detected by the method for a predetermined length of each block of rope unit length. . 11 is based on the temperature difference in the width direction detected by the thermometer on the entrance side of each cooling zone, and the amount of cooling water injected in the width direction is corrected so that the temperature difference in the width direction of each unit length of each steel plate becomes zero at the exit side of each cooling zone. It is a computing unit that calculates values.

The steel plates that have been hot rolled enter the cooling device 5 in order starting from the first block and are cooled. Immediately before the first block of copper plates enters the largest water injection header 61 in the cooling device 5, the temperature difference in the width direction of the first block of steel plates over a predetermined length has already been measured by the thermometer 71. There is. Based on the temperature difference in the width direction detected by the thermometer 71, the amount of water injected in the width direction of the water injection header 6I is corrected. Calculation of the correction amount regarding this water injection amount in the width direction is
．． The calculation is performed by the calculation unit 11 using a known calculation method, with the aim of making the temperature difference in the width direction of the first plate of the steel plate zero at the time when the cooling is completed.

Thereafter, the amount of water injected in the width direction of the water injection headers 6□, 63-6, 2 is sequentially corrected based on the temperature difference in the width direction of the first block of steel plates similarly detected by the thermometers 7□, 73-713.

Similar control is performed for the second to sixth blocks that are cooled following the first block of steel plates.

The water injection amount in the width direction of each water injection header is corrected when the tip of each block of steel plate arrives at the position of each water injection header. The timing is set using the steel plate position detection sensor 4 and the length measuring roll 3.

Table I compares the control results in this example with the conventional method.

In the control results of this embodiment, each thermometer 71 to 713
3 shows the results of the temperature difference detection in the width direction of the steel plate and the water injection amount control performance values in the width direction of each zone corrected based on the detection results of the temperature difference in the width direction.

As an example of the conventional method, the results of detecting the temperature difference in the width direction by each thermometer are shown when the equipment of this embodiment is used and the water injection amount in the width direction is fixed at the set condition of 1 J.

In Table 5, in the conventional example, since the amount of water injected in the width direction remains constant at the initial setting, the temperature difference in the width direction expands as cooling progresses, and at the end of water cooling, the temperature at the side edges in the width direction increases. The temperature is 60°C lower than the temperature at the center in the width direction, and the shape of the steel plate has an ear wave shape.

On the other hand, in the embodiment of the present invention, 12 water injections,
The initial setting conditions for the water injection amount in the width direction have been corrected for the 9 water injection headers in the center, and the temperature difference in the width direction of the steel plate during the entire cooling process is ±10℃.
As a result, a steel plate with a good shape was obtained.

〔Effect of the invention〕

As described above, according to the present invention, the temperature difference in the width direction of the steel sheet during the entire cooling process is substantially eliminated, and the occurrence of shape defects due to uneven temperature distribution in the temporary width direction can be prevented. Therefore, it becomes possible to produce a cooled steel sheet with a well-controlled shape.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a study in which the entire length of a steel plate is divided into blocks of unit length in a control 1111 according to the embodiment.

Claims (1)

[Claims] 1. In a method of cooling a hot rolled steel plate by supplying cooling water to the steel plate from nozzles arranged above and below while transferring the steel plate in the longitudinal direction of the steel plate, the cooling water is supplied in the width direction along the longitudinal direction of the cooling device. The temperature difference in the width direction of the steel plate is detected at the entrance side of each cooling zone for each length unit (hereinafter referred to as a cooling zone) in which the amount of water injection can be controlled, and the temperature difference in the width direction of the steel plate is determined based on the detected temperature difference in the width direction. A method for cooling a hot-rolled steel plate, characterized by controlling the amount of water injected in the width direction per unit length of the steel plate.