JPH0833915A - Cooling equipment for hot rolled steel sheet - Google Patents

Abstract

PURPOSE:To obtain a runout table that is capable of gaining a high heat transfer coefficient and to obtain a high quality thin steel sheet without making an interval between a steel sheet and a cooler so small as to raise a problem at the time of passing. CONSTITUTION:The equipment is constituted of a regulating equipment for the vertical motion of a steel sheet 2; group 5, 6 of cooling water jetting headers consisting of a cooling water distribution pipe connected to a cooling water supply piping and of a jetting nozzle which is attached to the pipe and which is faced opposite to a hot rolled steel sheet 2; group of compressed air jetting headers provided with a large number of compressed air jetting nozzles which are faced opposite to the hot rolled steel sheet 2 and which are connected to a compressed air supply pipe; or group of cooling water sucking headers 10 provided with a large number of opening holes oppositely facing the hot rolled steel sheet 2; and additionally, in these cooling water jetting headers, a large member of spray nozzles for jetting water screens are arranged in the direction of spreading the water screens so that the screens are superimposed one another.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin steel plate manufacturing facility, and more particularly, to a quenching technique in an outlet cooling facility of a hot rolling facility.

[0002]

2. Description of the Related Art Conventionally, a lamina cooling system has been favorably used for a delivery facility (runout table; hereinafter abbreviated as ROT) of a rolling mill. The lamina cooling system uses 1 to 1 cooling water.
10 from a straight pipe of 10 to 30 mm installed at a height of 2 m
A water column ejected at a flow velocity of ~ 20 m / s collides with a steel plate, and a new water can directly contact the steel plate by penetrating a retained water layer and a vapor film formed on the surface of the steel plate, so that a high cooling capacity is achieved. In addition, the hot rolled steel sheet does not interfere with the straight pipe at the time of passing the steel sheet.
However, in recent years, as the requirements for rolled steel sheets have become more sophisticated, tempering cooling for producing materials has been actively attempted in ROT, and further improvement in cooling capacity of ROT has been required.

Generally, it is most effective to increase the amount of cooling water in order to improve the cooling capacity, not limited to the lamina cooling method, but the heat which does not contribute to cooling by merely increasing the amount of cooling water is used. The thickness of the accumulated water layer on the rolled steel sheet becomes thick, and it becomes difficult to penetrate the accumulated water and its vapor film even with the lamina water column. Therefore, there is a limit to improving the cooling performance by increasing the amount of cooling water.

Therefore, there have been some proposals for improving the cooling capacity without increasing the amount of cooling water. For example, Proceedings of the Japan Society of Mechanical Engineers, Vol. 58, 556.
No. 3710, there has been proposed a method of cooling by forcibly flowing cooling water into a narrow gap between a high temperature surface and a cooling pad opposed to the high temperature surface at an interval of about several mm. This method can obtain an extremely high cooling capacity because it is possible to break the vapor film on the hot surface by the turbulence of the flow of forced convection and increase the probability of direct contact between the cooling water and the hot surface.

Further, as disclosed in JP-A-5-69029, electrodes are arranged on the front and back sides or around the steel sheet via cooling water, and an electric field is applied to the electrodes and the steel sheet to destroy the vapor film and cool the steel sheet. Methods such as increasing the probability of direct contact with water have also been proposed. In this method, the vapor film on the high temperature surface is destroyed by an electric field, and high cooling performance can be expected as in the above method.

[0006]

However, while both of them can be expected to have a high cooling capacity, a great difficulty occurs when trying to realize both types. The former method is for cooling steel plate,
It is extremely difficult to keep the cooling pad and the steel plate, which constantly move up and down, due to the warp of the steel plate at such a narrow interval. It is also difficult for the ROT passing plate itself. In order to alleviate this point, if the distance between the two is increased, the cooling performance drops sharply, and there is not much difference from the lamina cooling method. In the latter case, there is a problem that a large-capacity high-voltage generating facility for applying a high voltage to the electrodes arranged over the entire ROT is newly required. In addition, it is necessary to pay close attention to accidents such as device breakdown and electric shock. Therefore, both are extremely difficult to realize, and neither mentions any countermeasures against them.

An object of the present invention is to obtain a well-balanced ROT which has a high cooling capacity and is easily realized by hardware.

[0008]

In order to achieve the above object, the present invention is directed to a vertical motion regulating facility for steel plates, a cooling water pipe connected to a cooling water supply pipe, and the hot rolled steel plate attached to the cooling water pipe. And a cooling air jet header group consisting of jet ports facing each other, and a compressed air jet header group having a large number of compressed air jet ports facing the hot rolled steel plate and connected to a compressed air supply pipe, or the hot rolled steel plate, This can be realized by arranging cooling water suction header groups having a large number of facing opening holes alternately in the steel plate moving direction, and also arranging a large number of spray nozzles for injecting water films in the water film spreading direction so that the water films overlap each other. A cooling water jet outlet is provided.

[0009]

The above-mentioned vertical motion regulating facility for steel plates acts so as to keep the range of vertical motion of the steel plates at a certain level or below during the passage of the steel plates or during steady rolling. The cooling water jet header group acts to cool the rolled hot rolled steel sheet. The compressed air jet header group and the cooling water suction header group steel plate remove the cooling water accumulated on the hot rolled steel plate. Further, the cooling water jet outlets in which a large number of spray nozzles for jetting the water film are arranged in the water film direction so that the water films overlap with each other serve to enhance the cooling capacity of the cooling water header. These can be easily realized by the current technology, and moreover, the cooling performance higher than the current one can be obtained. Further, since the distance between the hot-rolled steel sheet and the cooling water header, the compressed air jet header, or the cooling water suction header group can be kept relatively large, the ROT of the hot-rolled steel sheet can be achieved even in the strip passing apparatus based on the current technology. There is no concern about interference with the header group when passing through.

[0010]

The present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram of an embodiment using the present invention. Rolling machine 1
The steel plate 2 rolled by means of the restraining roller 3 restrains the steel plate 2 so that the steel plate 2 does not move vertically beyond a certain allowable value. The constraining roller 3 is necessary in order to set the height of the cooling water header and the compressed air header, which will be described later, from the steel plate to about 100 to 200 mm. The steel plate 2 moves on a roller 4 which constitutes a runout table. On the upper surface and the lower surface of the runout table, there are provided a cooling water header 5 and a cooling water header 6 facing a steel plate and having a large number of nozzles attached thereto. Cooling water is supplied to both cooling water headers from a pipe 8 and the cooling water is sprayed from a large number of nozzles onto the upper and lower surfaces of the steel sheet for cooling. At this time, the flow rate and the layout of the cooling water header must be considered so that the cooling performances of the upper surface and the lower surface of the steel sheet are equal. How to arrange the nozzles of the cooling water header will be described later. The compressed air jet header 7 is arranged between the cooling water headers 5 on the upper surface of the steel sheet, and jets the compressed air from the pipe 9 to the steel sheet. This is to quickly remove the cooling water accumulated between the cooling water headers 5. Without this,
Even if the amount of cooling water is increased to improve the cooling performance, the amount of cooling water staying on the steel plate also increases, which reduces the momentum when the cooling water injected from the nozzle collides with the steel plate. Cooling performance does not improve so much because the force penetrating through is weakened. The direction of the injection port is not vertical to the steel plate, but is preferably perpendicular to the traveling direction of the steel plate, that is, tilted in the plate width direction in order to remove the accumulated cooling water. The compressed air jet header is not necessary on the lower surface of the steel plate. This is because the cooling water is less likely to stay on the steel plate due to the action of gravity.

FIG. 2 shows an explanatory view of another embodiment using the present invention. In this embodiment, a cooling water suction header 10 is provided in place of the compressed air header 7 of the embodiment shown in FIG. 1, and this cooling water suction header is connected to a pipe 11 leading to a large capacity decompression device, The accumulated cooling water on the steel plate 2 is sucked and removed together with the surrounding air. This method has a higher effect of removing accumulated cooling water than the method shown in FIG. because,
According to the method of FIG. 1, the staying cooling water is only removed in the lateral direction of the steel plate, and it becomes difficult to remove it when the plate width of the steel plate 2 becomes large. Since the steel sheet 2 is cooled as much as possible, the edge portion of the steel sheet 2 having a higher probability of coming into contact with the cooling water is cooled better than the central portion, which makes it difficult to uniformly cool the steel sheet 2. On the other hand, in this method, since the accumulated cooling water is removed above the steel plate, it is quickly removed, and there is no difference in cooling characteristics between the end portion and the central portion of the steel sheet 2. However, this method requires a large capacity decompression device, and the effect becomes small unless the mounting height of the cooling water suction header 11 is made as low as possible. This height should be as low as the constraint range of the steel plate by the constraint roller 3 allows.

FIG. 3 shows an example of nozzle arrangement of the cooling water header. The nozzle 12 is the nozzle arrangement of the cooling water header 5 on the upper surface of the steel plate 2, and the nozzle 13 is the nozzle arrangement of the cooling water header 6 on the lower surface of the steel plate 2. Nozzles 12 and 1
For 3, a flat spray nozzle in which the jet liquid film 14 has a fan shape is used. Normally, a lamina pipe nozzle is used for cooling the run-out table, but it is difficult to raise the heat transfer coefficient to 1000 kcal / m ² h or more with this nozzle. A spray nozzle is required when trying to obtain. In the figure, elliptical lines 15 and 16 indicate regions of the jet liquid film 14 that collide with the steel plate 2.

Cooling performance is improved when the nozzles 12 are mounted so that the jet collision regions 15 overlap each other. That is, it is possible to increase the cooling water amount density in the overlapping portion of the jet flow collision regions and the momentum of the jet flow at the time of collision of the steel plate 2. For example, the spread angle of the jet liquid film is 50.
In the case of degrees, when the ratio of the height of the nozzles 12 from the steel plate 2 to the nozzle mounting pitch is set to 1, the heat transfer characteristics on the nozzle mounting line become uniform. In addition, this ratio is 0.5
In this case, the heat transfer coefficient of the intermediate portion between the nozzles is about twice as large as the heat transfer coefficient of the nozzle alone. How to set this ratio may be determined in consideration of the required cooling performance. In the flat spray nozzle, the nozzle mounting height directly affects the cooling performance. Lowering the height improves cooling performance, but if it is too low,
The vertical movement of the steel plate may cause physical interference between the steel plate 2 and the nozzle, and it becomes difficult to thread the steel plate 2 at the start of rolling at the run-out table. Although it is possible to facilitate threading to some extent by the restraint roller 3, the steel plate 2 is generally used.
The height of the nozzle 12 with respect to should not be less than 20 mm. Conversely, if the nozzle mounting height is set to 200 mm or more, the heat transfer coefficient obtained by using the lamina pipe cooling method will not differ greatly. Should be. The distance between the nozzle rows arranged in this manner in the traveling direction of the steel plate 2 should be made as small as possible, but if they are too close to each other, the cooling water accumulated between these nozzle arrays will not work properly, so it will be about 50 mm. Should be set to the minimum value.

On the lower surface of the steel plate 2, the direction in which the jet liquid film from the nozzle 13 spreads is the traveling direction of the steel plate 2.
This is because the installation location of the cooling water header 6 is physically limited by the roller 4 of the runout table, and the area of the collision area 16 of the jet liquid film is increased as much as possible. In this case, heat transfer cannot be expected to be promoted due to the interference between the jet liquid films 14 like the cooling water header 5 on the upper surface of the steel plate 2, so that the number can be compensated by increasing the number of nozzles to be arranged.

If the upper surface and the lower surface of the runout table are not substantially equal in cooling performance, it may cause warpage of the steel plate 2 or the like. Therefore, the amounts of cooling water to be supplied to the respective cooling water headers should be equal to each other. To decide.

FIG. 4 shows a plurality of cooling water headers 5 and suction headers 11 housed in one header. In the figure, the moving direction of the steel plate 2 is from left to right. The cooling water supplied from the pipe 8 is distributed to the nozzles 12 at the cooling water header portion 18 to form the jet liquid film 14 and collide with the steel plate 2. The cooling water that has not contributed to the cooling spreads on the steel plate 2 as a liquid film 19, and the liquid films collide with each other to splash upward like the liquid film 17. The suction port sucks the splashed cooling water 17 together with the surrounding air and removes it from the steel plate 2. The suction header 21 having a suction port is always depressurized to atmospheric pressure or less by the ejector pump 22, and the sucked cooling water and air 23 are
It is guided to the gas-liquid separator 24 via the ejector pump 22 to separate air and cooling water. The separated cooling water 26 is sent to the high-pressure pump 27 and again sent to the pipe 8 for recycling. The ejector pump 22 may be one in which the nozzle 24 is inserted with a gap kept in the hole on the funnel. The nozzle 22 jets high-pressure water from the pipe 8. This makes it possible to construct a decompression pump having a large exhaust capacity. Since the ejector pump has no moving parts, it will not be damaged even if dust or the like is mixed therein, and is optimal as the decompression pump used in the present invention.

[0017]

According to the present invention, the cooling performance of the run-out table can be further improved as compared with the prior art without arranging the cooling equipment so that it is difficult to pass the steel plate, so that the cooling rate of the steel plate can be increased. It is possible to obtain a high quality rolled steel sheet.

[Brief description of drawings]

FIG. 1 is an explanatory view of a hot-rolled steel sheet cooling facility showing an embodiment of the present invention.

FIG. 2 is an explanatory view of a hot-rolled steel sheet cooling equipment showing a second embodiment of the present invention.

FIG. 3 is an explanatory view of a nozzle mounting arrangement of the cooling water header of the first and second embodiments of the present invention.

FIG. 4 is an explanatory diagram of a cooling water header and a suction header according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... Rolling mill, 2 ... Steel plate, 3 ... Restraint roller, 5, 6 ... Cooling water header, 8 ... Piping, 10 ... Suction header.

Claims (1)

[Claims] 1. A hot-rolled steel sheet cooling facility comprising a vertical movement control device for a steel sheet, a cooling water pipe connected to a cooling water supply pipe, and a jet port attached to the cooling water pipe and facing the hot-rolled steel plate. One or a plurality of cooling water jet header groups, and one or a plurality of compressed air jet header groups having a plurality of compressed air jet ports facing the hot rolled steel sheet and connected to a compressed air supply pipe, or the hot strip One or a plurality of cooling water suction header groups having a large number of opening holes facing the steel plate,
A hot-rolled steel sheet cooling facility characterized by being arranged alternately in the steel sheet moving direction.