JPH09316547A - Device for uniformly cooling width direction of steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly cool a steel plate by arranging a dewatering roll at a specific position in the vertical lower part from a cooling nozzle for spouting coolant. SOLUTION: The steel plate 1 is cooled by spraying the coolant 3 to the steel plate 1 from the cooling nozzle 2. The coolant 3 after spraying becomes the flow-down coolant 4 and drops along the steel plate 1. The dewatering roll 5 comes in contact with the steel plate 1 to remove the flow-down coolant 4 from the steel plate surface. In order to make the steel plate quality a specific performance, it is necessary that cooling error is made to be <=10%. The cooling error becomes <=10% by positioning a shaft 7 of the dewatering roll 5 at the range of 1.2m vertical lower part from the cooling nozzle 2. The dewatering roll 5 is desirable to be shiftable in the vertical direction to the steel plate 1. The flow-down distance of the flow-down coolant 4 is made short and the uneven cooling caused by unstable fluid can be reduced. Surface flaw caused by stretched strain is not developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for uniform cooling in the width direction of a steel sheet in a vertical pass using a liquid as a cooling medium in a continuous steel sheet heat treatment step, for example, a continuous annealing step.

[0002]

2. Description of the Related Art In the cooling zone in the continuous type steel plate heat treatment process, the steel plate material is built up by controlling the cooling rate and the cooling start and end temperatures. Therefore, it is easy to control the cooling capacity as a cooling method. In addition, a method with a wide control range is adopted.

The method of directly spraying a cooling medium using a simple substance of water or a liquid such as mist on a steel sheet is widely used as a steel sheet cooling method because the control range of the cooling capacity is wide. When the method is selected, a phenomenon occurs in which a part of the refrigerant after spraying falls along the steel plate due to gravity. (Hereinafter, the refrigerant falling along this steel plate is referred to as "downflow refrigerant")

The flowing-down refrigerant itself has a cooling capacity according to its flow state, and if the flow state is non-uniform on the steel sheet, the steel sheet is accordingly non-uniformly cooled. Since the flowing-down refrigerant is in the process of falling due to gravity, the flow state is very unstable, and as a result, the cooling of the steel sheet tends to be uneven in the width and longitudinal directions.

FIG. 1 shows an example of the temperature distribution in the width direction of the steel plate when water is sprayed onto the steel plate to cool it in a vertical pass. If the cooling is non-uniform, the material to be built in will vary, and in the case of temperature variations in the width direction, thermal stress will be generated, and in addition, surface defects due to stretcher strain will be generated.

Therefore, in order to stabilize the quality, it is necessary to remove the flowing-down refrigerant, and as a method therefor, for example, as shown in JP-B-61-1494, the refrigerant is jetted from a slit nozzle. A method is disclosed in which the flowing-down refrigerant is collided from below and removed from the surface of the steel sheet.

[0007]

In the conventional method, a part of the refrigerant injected for removing the flowing-down refrigerant comes into contact with the steel sheet to cool the steel sheet, and it is necessary to consider this cooling capacity in controlling the end point temperature. Therefore, complicated control was required for the end temperature of cooling.

Further, in this method, when the collision strength of the refrigerant against the flowing-down refrigerant is too strong, vibration of the steel sheet occurs, causing trouble due to contact with the internal structure of the cooling zone. Will not be removed. Therefore, it is necessary to control the refrigerant collision strength according to the state of the flowing-down refrigerant, but since the flowing state of the flowing-down refrigerant is extremely unstable as described above, such control is very complicated and costly. Will also be higher.

The present invention provides a widthwise uniform cooling device for a steel sheet and a method thereof, which does not affect the controllability of the cooling end point temperature and is capable of stably removing the flowing-down refrigerant regardless of its state. .

[0010]

[Means for Solving the Problems]

(1) The cooling device of the present invention, in the continuous type steel plate heat treatment step, in a cooling device for a steel plate in a vertical path using a liquid as a cooling medium, the roll axis of which vertically extends from a cooling nozzle for discharging the cooling medium. A uniform cooling device in the width direction of a steel plate (hereinafter referred to as a cooling device A), characterized in that a draining roll that comes into contact with the steel plate is installed so as to be located within a range of 1.2 m below.

(2) Further, in the cooling device A, the water draining roll is installed so that the water draining roll can move in the vertical direction with respect to the steel plate and the moving amount can be freely changed. It is a uniform cooling device (hereinafter referred to as cooling device B).

(3) In the cooling device A or B,
A uniform widthwise cooling device for a steel plate (hereinafter, referred to as a cooling device C), characterized in that two roll shafts of the draining rolls are vertically shifted so as not to interfere with each other and sandwiched between the steel plates.

(4) The cooling method of the present invention comprises the cooling device A,
A steel sheet is cooled to 400 ° C. or lower by using B or C, which is a widthwise uniform cooling method for steel sheet (hereinafter, referred to as cooling method A).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 2 shows a side view of the schematic structure of the cooling device A according to the present invention. Steel plate 1 is liquid refrigerant 3 from cooling nozzle 2.
Although it is cooled by being sprayed, the refrigerant after spraying becomes the flowing-down refrigerant 4 and falls along the steel plate. This downflowing refrigerant 4
Is removed from the surface of the steel sheet by a draining roll 5 installed in contact with the steel sheet 1.

Since the down-flowing refrigerant 4 cools the steel sheet 1 in the process of down-flowing, it is possible to reduce the degree of uneven cooling due to the unstable flow of the down-flowing refrigerant 4 by making the down-flow distance 6 as small as possible. Is.

As a result of the investigation by the inventor, the ratio of the maximum temperature difference ΔT in the width direction of the steel plate to the temperature difference between the entrance and exit of the cooling zone (hereinafter referred to as cooling margin) (hereinafter referred to as cooling error) is as follows. It is known that the flow-down distance 6 has a relationship as shown in FIG. 3 (however, the removal rate of the flow-down refrigerant is 100%). Allowable cooling error is 10 when incorporating steel plate material.
% Or less, and from this requirement, the roll shaft 7 must be positioned within 1.2 m vertically below the cooling nozzle.

FIG. 4 shows a schematic structure of the cooling device B according to the present invention. The downflowing refrigerant 4 can be almost removed by the water draining roll 5, but when the steel sheet passing speed is high, a part of it leaks out from the gap between the steel sheet 1 and the water draining roll 5, and the leaking refrigerant 8 is also nonuniformly cooled. Cause.

FIG. 5 shows the relationship between the contact length 9 between the steel plate 1 and the draining roll 5 and the leakage rate of the downflowing refrigerant 4. As seen from this, by increasing the contact length 9, the amount of the leaked refrigerant 8 can be reduced, and a preferable result for uniform cooling can be obtained.

Therefore, in the continuous steel plate heat treatment step of passing the steel plate at a high speed, as shown in FIG. 4, the draining roll 5 is movable in the vertical direction of the steel plate 1 and the moving amount can be freely changed. If the contact length 9 can be changed by providing a different roll moving mechanism 10, more uniform cooling becomes possible.

FIG. 6 shows a schematic structure of the cooling device C according to the present invention. When the cooling nozzles 2 are arranged on both sides of the steel plate 1, it is also necessary to install draining rolls 5 on both sides as shown in FIG. In this case, as described above, it is necessary to allow the draining rolls 5 to move vertically with respect to the steel plate 1 and to position the roll shafts 7 in the vertical direction so that the opposing draining rolls 5 do not interfere with each other. is there. Usually, two rolls do not interfere with each other if the roll axis is displaced by 50 mm or more.

Although the above has described the so-called continuous annealing process such as heat treatment of steel sheet, it goes without saying that the present invention can be applied to equipment involving heat treatment of steel strip such as hot dip galvanizing.

When water is used as a cooling medium for spray cooling or mist cooling, although the surface temperature of the steel strip at which transition boiling occurs is slightly changed depending on the cooling water temperature and the cooling water amount,
It was revealed in the course of the research leading to the present invention that the temperature was approximately 300 to 400 ° C.

Therefore, the temperature of the steel strip on the outlet side of the cooling zone is 400 ° C.
The effects of the present invention can be obtained in the following processing. However, even a slight temperature variation does not lead to problematic material variations and surface flaws, so that the effect of the present invention can be more remarkably obtained when the temperature of the steel strip on the cooling strip exit side is 320 ° C. or less. .

[0025]

EXAMPLE An example of the present invention is shown in the schematic side view of FIG.

Steel plate 1 having a plate thickness of 1 mm and a plate width of 1200 mm
Was passed at a line speed of 320 mpm, and water was sprayed from both sides of the steel plate in a vertical pass to cool it from 700 ° C to 300 ° C.

In this case, the cooling nozzle 2 has a height of 10
Two stages of water-draining rolls 5 having a diameter of 200 mm, one of which has a shaft 7 at a point 0.5 m vertically below the nozzle 2,
One was installed for each nozzle 2 such that its axis 7 was located at a point of 0.6 m. The shaft 7 and the pass line were moved so that the distance between them was 80 mm.

As a result, the temperature difference in the width direction at the end of cooling is
As shown in FIG. 8, it was stably obtained at an extremely low temperature of 5 ° C. or lower.

[0029]

As described above, according to the present invention, it is possible to reduce the downflow distance of the downflow refrigerant as much as possible by a simple means to reduce the degree of uneven cooling due to the unstable flow of the downflow refrigerant. In this way, the steel plate cooling in the vertical pass using the liquid as the cooling medium in the continuous annealing process can be made uniform in the steel plate width and the longitudinal direction. It is possible to prevent the occurrence of surface defects due to strain and improve the quality of the steel sheet produced.

[Brief description of drawings]

FIG. 1 is a drawing showing a plate temperature distribution on a cooling zone outlet side when no measure is taken for a flowing-down refrigerant.

FIG. 2 is a side view showing a schematic structure of a cooling device A according to the present invention.

FIG. 3 is a diagram showing a relationship between a flow-down distance of a cooling medium and a cooling error.

FIG. 4 is a side view showing a schematic structure of a cooling device B according to the present invention.

FIG. 5 is a diagram showing a relationship between a contact length of a steel plate with a draining roll and a leakage rate of a flowing-down refrigerant.

FIG. 6 is a side view showing a schematic structure of a cooling device C according to the present invention.

FIG. 7 is a schematic side view showing an embodiment of the present invention.

FIG. 8 is a drawing showing the plate temperature distribution on the cooling zone outlet side when cooled under the conditions shown in the example of the present invention.

[Explanation of symbols]

 1 Steel Plate 2 Cooling Nozzle 3 Liquid Refrigerant 4 Downflowing Refrigerant 5 Draining Roll 6 Downflow Distance 7 Roll Axis 8 Leaked Refrigerant 9 Contact Length 10 Roll Moving Mechanism 11 Pass Line

Claims (4)

[Claims] 1. A cooling device for a steel plate in a vertical path using a liquid as a cooling medium in a continuous type steel plate heat treatment process, wherein a roll axis of which is 1.2 m vertically below a cooling nozzle for discharging the cooling medium. A widthwise uniform cooling device for a steel plate, wherein a draining roll that comes into contact with the steel plate is installed so as to be located within the range. 2. The uniform cooling in the width direction of the steel sheet according to claim 1, wherein the water draining roll is movable in a direction perpendicular to the steel sheet, and the water draining roll is installed so that the moving amount can be freely changed. apparatus. 3. A uniform cooling device for a width direction of a steel sheet according to claim 1 or 2, wherein the roll axes of two draining rolls are vertically shifted so as not to interfere with each other and sandwiched between the steel sheets. . 4. A method for uniformly cooling a steel sheet in the width direction using the apparatus for uniformly cooling the steel sheet in the width direction according to claim 1, wherein the steel sheet is cooled to 400 ° C. or less.