JP3482338B2 - Uniform cooling method for rolled steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for uniformly cooling the temperature distribution of a steel sheet in the width direction when cooling the steel sheet with a water jet following hot rolling.

[0002]

2. Description of the Related Art Steel sheets manufactured by hot rolling are manufactured to obtain predetermined material properties or to improve production efficiency.
Usually, hot rolling is followed by forced cooling. As a forced cooling method, in many cases, water is used as a cooling medium to form a jet flow, which is collided with a steel sheet, and strong cooling accompanied by a boiling phenomenon is performed. At that time, it is important to make the temperature distribution of the steel sheet uniform in order to obtain uniform mechanical properties and shapes.

In order to make the temperature distribution of the steel plate in the plate width direction uniform, the distribution of the jet flow rate in the plate width direction is usually made uniform, but with only that, the steel plate temperature at the end in the plate width direction is as shown in FIG. As shown in FIG. Therefore, conventionally, some proposals have been made on cooling methods for preventing the decrease of the end temperature.

For example, in Japanese Unexamined Patent Publication No. 57-165114 and Japanese Unexamined Patent Publication No. 58-32511, when cooling a steel sheet, a gutter or the like is provided to block collision of a water jet with the steel sheet. Reducing cooling is disclosed. Further, Japanese Patent Laid-Open No. 6-71328 discloses a device in which a plurality of divided cooling headers are provided in a part of the cooling section in the plate width direction to control the amount of jet water in the plate width direction.

Further, in Japanese Patent Laid-Open No. 58-86904, a cooling water chamber is provided between the steel sheet conveying rolls, and the water jet injected into the cooling water chamber is only in the conveying direction of the steel sheet or in the opposite direction. By providing a guide plate in the cooling water chamber so that it does not flow in the plate width direction and by providing a drainage part in the cooling water chamber in the immediate vicinity of the roll, collision of water jets and subsequent water flow There is disclosed a method of making the above state uniform in the plate width direction.

[0006]

Among these conventional proposals, JP-A-57-165114 and JP-A-58-
In any of the methods disclosed in Japanese Patent No. 32511, the average temperature of the steel plate at the end increases due to the interruption of the water jet at the end in the plate width direction, but after the cooling water in the center part in the plate width direction collides with the steel plate,
Since it passes through the edge in the plate width direction and is drained from the end in the plate width direction, the drained running water does not change the cooling of the edge in the plate width direction. It is inevitable that it will drop towards the edges.

In the apparatus disclosed in Japanese Patent Laid-Open No. 6-71328, a plurality of divided cooling headers are provided in the plate width direction, which is advantageous in controlling the jet water amount distribution in the plate width direction. After all, after the cooling water collides with the steel plate, it passes through the plate width direction end part and is drained from the plate width direction most end part, and the problem that the plate width direction end part is cooled cannot be solved.
In addition, equipment costs such as control of the divided cooling header are high.

Further, in the method disclosed in Japanese Patent Laid-Open No. 58-86904, after the cooling water collides with the steel sheet, it passes through the edge portion in the sheet width direction and is discharged from the edge portion in the sheet width direction. The purpose is to solve the problem of cooling the edges in the strip width direction, but this method makes equipment complicated and expensive, and increases the striping speed as in the hot rolling of thin strips. In this case, it is particularly difficult to adopt due to the plateability. An object of the present invention is to solve such a problem and to provide a method for uniformly cooling the temperature distribution in the plate width direction of the steel plate when cooling the steel plate with a water jet following hot rolling.

[0009]

One of the methods of the present invention for achieving the above object is to provide a method for cooling a steel sheet with a jet flow using water as a cooling medium in the sheet width direction of the steel sheet after hot rolling. A water flow control plate that forms a gap of 30 mm or less between the plate and the upper surface of the steel plate is arranged at the end position, and
A part of the cooling water discharged from
Thus, the method for cooling a rolled steel sheet is characterized in that it is cooled.

Further, one of the methods of the present invention for achieving the above-mentioned object is to position the ends of the steel sheet in the plate width direction when the steel sheet is cooled by a jet flow using water as a cooling medium after hot rolling. A water flow control plate that forms a gap of 30 mm on average between the upper surface of the steel plate and the
So that a part of the cooling water discharged from the
In the cooling method for a rolled steel sheet, the gap between the water flow control plate and the upper surface of the steel sheet is made narrower in the sheet width direction end portion than in the sheet width direction central portion.

In the present invention, the position and length of the water flow control plate arranged in the steel plate passing direction are not particularly limited. These are determined according to a desired cooling pattern, cooling conditions, and steel plate temperature uniformity. For example, when the water flow control plate is arranged at discontinuous positions in the steel plate passing direction, a desired uniform cooling effect can be obtained at each position. Further, in the present invention, a jet flow refers to a jet flow referred to as a spray or the like, or a columnar continuous flow referred to as a laminar flow or the like, if necessary, a flow that collides with a steel sheet with a certain momentum. It is a generic term.

In the present invention, the plate width direction end part means a part within approximately 200 mm from the most end part of the steel plate in the plate width direction toward the center in the plate width direction, and the plate width direction center part means It means the other parts of the steel plate. In one method of the present invention, in cooling the steel sheet, on the steel sheet upper surface that governs the cooling effect and the temperature distribution in the sheet width direction of the steel sheet, the water flow control plate is located at the end of the sheet width direction and the gap between the upper surface of the steel sheet. Is arranged within 30 mm, preferably within 10 mm, and a part of the cooling water discharged from the end of the steel plate is allowed to flow through this gap, thereby You can reduce the turbulence of the water flow,
As a result, the heat transfer strength at the widthwise ends of the steel sheet can be reduced and supercooling can be prevented.

Further, in one method of the present invention, the water flow control plate is placed at the end of the steel plate in the width direction on the upper surface of the steel plate that controls the cooling effect and the temperature distribution in the width direction of the steel plate when cooling the steel plate. The gap between the upper surface and the upper surface of the water flow control plate should be 30 mm or less, preferably 10 mm or less. By narrowing and allowing a part of the cooling water discharged from the end of the steel plate to flow through this gap, it is possible to reduce the turbulence of the water flow on the upper surface of the end of the steel plate, and By making the effect larger at the end in the width direction than at the center in the width direction,
When the heat transfer strength decrease is increased toward the widthwise outermost end of the steel sheet, and the supercooling of the widthwise end portion of the steel sheet is large, that is,
Even when the temperature distribution in the width direction of the steel sheet due to supercooling tends to decrease as it is located at the outermost end, supercooling can be prevented and a uniform temperature distribution can be obtained.

The principle of operation of the water flow control plate will be described below with reference to the drawings. FIG. 3 is an explanatory view showing the flow of cooling water at the upper end width direction end of the steel plate of one method of the present invention, and FIG. 4 is the upper surface width end of the steel plate of one method of the present invention. 5 is an explanatory view showing the flow of cooling water in FIG.
FIG. 6 is an explanatory view showing a flow of cooling water at an end portion in a width direction of an upper surface portion of a steel plate according to a conventional method. In FIG. 5, all the water used for cooling flows toward the outermost end of the steel sheet and drops from the outermost end. At this time, the temperature distribution at the edge of the steel sheet in the sheet width direction decreases toward the outermost portion in the sheet width direction as shown in FIG. As a cause for this, the inventors have found that the water flow increases toward the end in the plate width direction and the influence of the water flow drop from the end in the plate width direction causes the turbulence of the water flow to be maximized on the steel plate upper surface. Assuming an increase in heat transfer intensity.

Therefore, the inventors have devised a method of arranging the water flow control plate in order to eliminate these heat transfer strength increasing factors. One method will be described with reference to FIG. That is, in FIG. 3, the water flow 10 traveling from the plate width direction central portion of the steel plate 1 toward the plate width direction most end part is divided by the water flow control plate 2 between the water flow control plate 2 and the steel plate upper surface at the plate width direction end. It is split into a water flow 11 passing through the gap and a water flow 12 discharged above the water flow control plate 2. At this time, the water flow 11 flowing on the upper surface of the plate width direction end portion of the steel plate 1 has a smaller amount of water than the original water flow 10, and the water channel between the water flow control plate 2 and the steel plate upper surface is narrow. Disturbance also becomes small. Further, since the water flow 11 is guided to the water flow control plate 2 and the upper surface of the steel plate to the end in the plate width direction, the water flow 11 does not have a free surface and is disturbed by the influence of the drop of the water flow from the end in the plate width direction. Hard to happen. That is, the heat transfer strength increasing factor can be eliminated by an extremely simple and inexpensive method.

One method will be described with reference to FIG. In FIG. 4, the gap between the water flow control plate 2 and the upper surface of the steel plate is not constant as compared with FIG. 3, and the end portion in the plate width direction is narrower than the central portion in the plate width direction. Therefore, the effect described with reference to FIG. 3 increases as it is located at the outermost end of the steel sheet in the width direction.
This method makes it possible to eliminate the heat transfer strength increasing factor by an extremely simple and inexpensive method even when the temperature distribution in the width direction of the steel sheet due to overcooling tends to decrease as it is located at the outermost end. .

The inventors conducted an experiment to verify the effect of the method of the present invention, and obtained the results shown in FIG. Figure 8
Is a diagram for explaining the heat transfer strength reduction effect of the water flow control plate,
A graph in which the horizontal axis represents the gap distance between the steel plate and the water flow control plate (unit: mm), and the vertical axis represents the heat transfer strength index when the heat transfer coefficient of the steel plate surface when there is no water flow control plate is 1. Is. Here, the thickness (depth) of the water flow in this experiment is
It is set to 50 mm.

From FIG. 8, it can be seen that when the gap distance is set to 10 mm or less, the heat transfer strength is almost halved, and there is a remarkable heat transfer strength reduction effect. Further, it is understood that when the gap distance is 30 mm or less, the heat transfer strength can be 80% or less. However, when the gap distance is set to 40 mm, the heat transfer strength is almost the same as that without the water flow control plate, and no effect can be seen. As described above, according to the method of the present invention, it is possible to eliminate the heat transfer strength increasing factor at the sheet width direction end portion of the steel sheet, thereby preventing the temperature decrease at the sheet width direction end portion of the steel sheet, and the steel sheet temperature distribution. Is flattened and a uniform cooling action is obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic cross-sectional view in the steel plate width direction of equipment for explaining an embodiment of one method of the present invention. In FIG. 1, 1 is a steel plate, 2 is a water flow control plate, 3 is a water flow control plate position adjusting mechanism, 4 is a transport roll,
5 is an upper surface cooling water header, 6 is an upper surface cooling nozzle, 7 is a lower surface cooling water header, and 8 is a lower surface cooling nozzle.

In FIG. 1, the steel sheet 1 is hot-rolled and then conveyed by rolls 4 for conveyance while being cooled by the collision of water jets from above and below and the flowing water after the collision. Below, steel plate 1
The effect of cooling the will be described in detail. Steel plate 1
At the central portion in the plate width direction of the plate, the water jet 9 injected from the upper surface cooling nozzle 6 through the upper surface cooling water header 5 and the water jet 1
After the collision, the flowing water 10 is cooled along the plate surface by the running water 10 drained from the end of the plate width. At this time, since the amount of the running water 10 is not so large, the cooling capacity is almost determined by the water jet flow 9, and the steel plate temperature distribution in the central part in the plate width direction is
As shown in FIG. 9, it becomes relatively uniform even in normal cooling.

Regarding the action of cooling the end portion in the plate width direction, the case where the present invention is not applied and cooling is performed only by making the distribution of the jet flow amount in the plate width direction uniform will be described. It is cooled by the water jet 10 and the water jet 9 jetted from the upper surface cooling nozzle 6 through the upper surface cooling water header 5. Since the flowing water 10 at the end portion in the plate width direction is also added to the flowing water at the central portion in the plate width direction, the amount of water increases, and the cooling capacity is affected. Therefore, the temperature distribution of the steel plate at the end in the plate width direction is shown in FIG.
As shown in, it decreases toward the end of the plate width direction. This is because, as described in the previous section, the heat transfer strength at the plate width direction end increases.

Next, when the present invention is applied, as described in the preceding paragraph, the water flow 10 traveling from the central part in the plate width direction to the most end part in the plate width direction is the water flow control plate at the end part in the plate width direction. Due to 2, the water flow 11 is divided into a water flow 11 passing through the gap between the water flow control plate 2 and the upper surface of the steel plate, and a water flow 12 discharged above the water flow control plate 2. The water flow control plate 2 can adjust the gap distance from the upper surface of the steel plate by the water flow control plate position adjusting mechanism 3 so as to cope with the case where the required heat transfer strengths are different. As a result, the water flow 11 flowing on the upper surface of the end of the steel plate in the plate width direction is adjusted so as to properly receive the action and effect described in the preceding paragraph, and a flat temperature distribution in the plate width direction of the steel plate is obtained as shown in FIG. You can Here, in FIG. 6, the temperature at the end in the plate width direction is lowered, but this is due to heat removal from the side surface of the end of the steel plate, and depending on the thickness of the steel plate, It is affected in the distance range from the extreme of 2 to 10 times the thickness of the steel sheet. However, there is no problem because this distance range is usually trimmed for another purpose and discarded.

It should be noted that the water flow control plate position adjusting mechanism 3 may have any structure as long as it can adjust the gap distance between the steel plate 1 and the water flow control plate 2 to a constant state, and a known mechanism is used. For example, a configuration is used in which the water flow control plate 2 is moved up and down by a cylinder, or the rotational force of a motor is moved up and down via an appropriate transmission means such as a gear. 2 shows a schematic cross-sectional view in the steel plate width direction of equipment for explaining an embodiment of one method of the present invention. The difference from the embodiment shown in FIG. That is, the gap adjusting mechanism 13 is provided so as to operate. With this gap adjusting mechanism 13, the gap between the water flow control plate 2 and the upper surface of the steel plate 1 is not constant, and the end portion in the plate width direction can be made narrower than the central portion in the plate width direction. This allows
The water flow 11 flowing on the upper surface of the end portion of the steel plate in the width direction is adjusted so as to receive the above-described action and effect to a greater extent as it is located closer to the end portion of the width of the plate, and as shown in FIG. It is possible to further prevent the temperature decrease of the steel plate toward which the temperature is directed, and obtain a uniform temperature distribution. In this method, the gap adjusting mechanism 13 does not necessarily have to be provided, and the gap between the water flow control plate 2 and the upper surface of the steel plate 1 is set to the center in the plate width direction when the temperature reduction condition of the steel plate is relatively constant. The end portion in the plate width direction may be narrower than the end portion and fixedly provided.

Further, in any of the methods of the present invention,
The water flow control plate position adjusting mechanism 3 may be fixed in position if the cooling conditions are relatively unchanged and the required heat transfer strength is constant, and is not always necessary. Further, the water flow control plate position adjusting mechanism 3 may be provided as necessary in order to use the water flow control plate 2 for withdrawal from the position where the water flow control plate 2 is used in view of problems with passage of steel plates, maintenance, and facility maintenance.

Further, the water flow control plate position adjusting mechanism 3 may be provided as necessary as a mechanism for adjusting to follow the meandering of the steel plate in the plate width direction. The gap adjusting mechanism 13 may have a configuration capable of adjusting the gap distance between the steel plate 1 and the water flow control plate 2, and a known mechanism is used. For example, the water flow control plate 2
Is moved up and down by a cylinder, or the rotational force of the screw motor is moved up and down via an appropriate transmission means such as a gear.

[0026]

EXAMPLES Examples of the present invention will be described below. Figure 1
Table 1 shows the results of Examples in which a steel sheet having a width of 1.5 m and a thickness of 1.2 mm was cooled with water from 800 ° C. to 550 ° C. using the apparatus shown in FIG.

[0027]

[Table 1]

In the embodiment shown in the third row above the method of the present invention in Table 1, the gap distance between the water flow control plate 2 and the steel plate 1 is the same on the end side and the center side in the plate width direction, 5m each
m, 10 mm and 30 mm, and the examples shown in the third row under the method of the present invention are, as shown in the table,
This is an example in which the gap distance on the end side is made smaller than that on the center side. In addition, the comparative example is an example in which the other conditions are the same and the water flow control plate is not arranged.

From Table 1, when the gap distance between the water flow control plate 2 and the steel plate 1 of the method of the present invention is 5 mm on both the end side and the center side in the width direction, the surface temperature at the end in the plate width direction is the plate width. It can be seen that the cooling is rather slow compared to the surface temperature at the center of the direction. Further, when the gap distance is 10 mm on both the end side and the center side in the width direction, the surface temperature at the end portion in the plate width direction is almost the same as the surface temperature at the center portion in the plate width direction, and extremely good uniform cooling is achieved. Has been achieved. In addition, when the gap distance is 30 mm on both the end side and the center side in the width direction, the surface temperature at the edge part in the plate width direction is lower than the surface temperature at the center part in the plate width direction. Cold is weak and shows remarkable improvement.

Further, in the example in which the gap distance on the end side is made smaller than the center side in the plate width direction, the temperature difference of each of the distances on both sides of the center side and the end side is equal. The intermediate temperature difference is shown. In the example in which the gap distance on the end side is made smaller than the center side in the plate width direction, the surface temperature at the position of 50 mm from the end is determined from the temperature difference from the center of the surface temperature at the position of 100 mm from the end. The temperature difference from the center is on the positive value side, and it is clear that the effect of preventing the surface temperature decrease toward the outermost end is greater than when the gap distance is the same on the end side and the center side. is there.

The results of the examples shown in Table 1 are shown under the same other conditions in order to clearly explain the effect of each gap distance condition. In actual operation,
The conditions differ intricately, and the condition of the surface temperature drop at the edges also changes. Depending on the situation, if the condition of the gap distance is selected, a temperature difference smaller than the temperature difference shown in Table 1 can be obtained. From the above results, it is clear that the method of the present invention can prevent the supercooling of the sheet width direction end portion of the steel sheet, and that the purpose of uniform cooling of the steel sheet in the sheet width direction is achieved.

[0032]

As described above, according to the present invention,
Following the hot rolling, when cooling the steel sheet with a water jet,
Since the temperature distribution in the plate width direction of the steel sheet can be uniformly cooled, it is possible to provide a cooling method for obtaining uniform mechanical properties, shapes, etc., which can be expected to make a great contribution to the industrial field.

[Brief description of drawings]

FIG. 1 is a schematic sectional view in the width direction of a steel plate for explaining an apparatus of an embodiment of one method of the present invention.

FIG. 2 is a schematic sectional view in the width direction of a steel plate for explaining an apparatus of an embodiment of one method of the present invention.

FIG. 3 is a diagram illustrating a flow of cooling water at an end portion in a width direction of an upper surface portion of a steel plate according to one method of the present invention.

FIG. 4 is a view for explaining the flow of cooling water at the widthwise end of the upper surface of the steel sheet according to one of the methods of the present invention.

FIG. 5 is a diagram illustrating a flow of cooling water at an end portion in the width direction of an upper surface of a conventional steel plate.

FIG. 6 is a diagram illustrating distribution of steel plate temperature in a steel plate width direction according to one of the methods of the present invention.

FIG. 7 is a diagram for explaining distribution of steel plate temperature in the steel plate width direction according to one method of the present invention.

FIG. 8 is a diagram for explaining the heat transfer strength reduction effect of the water flow control plate of the method of the present invention.

FIG. 9 is a diagram illustrating a distribution of the steel plate temperature in the steel plate width direction according to the conventional method.

[Explanation of symbols]

1 Steel Plate 2 Water Flow Control Plate 3 Water Flow Control Plate Position Adjusting Mechanism 4 Transport Roll 5 Top Cooling Water Header 6 Top Cooling Nozzle 7 Bottom Cooling Water Header 8 Bottom Cooling Nozzle 9 Top Cooling Water Jet 10 Top Water Jet 10 Plate Width from Center Part of Plate Width Water flow toward the end in the direction 11 Water flow passing through the gap between the water flow control plate and the upper surface of the steel plate 12 Water flow discharged above the water flow control plate 13 Gap adjustment mechanism

Claims (2)

(57) [Claims] 1. A Following hot rolling, when cooling the steel plate at the jet where the water and the cooling medium, between gap within 30mm between the top surface of the steel plate to the position of the plate width direction end portion of the steel plate form
A plate for controlling water flow is formed and discharged from the end of the steel plate.
A method for cooling a rolled steel sheet, which comprises cooling a part of cooling water to be flowed through the gap . 2. When the steel sheet is cooled by a jet flow using water as a cooling medium subsequent to the hot rolling, an average value of 30 mm or less is provided between the steel sheet and the upper surface of the steel sheet at the end of the steel sheet in the sheet width direction. Place a water flow control plate that forms a gap, and
So that a part of the cooling water discharged from the
The method for cooling a rolled steel sheet is characterized in that the gap between the water flow control plate and the upper surface of the steel sheet is made narrower in the sheet width direction end portion than in the sheet width direction central portion.