JPS638172B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a strip cooling device for cooling a strip while it is running, and is particularly suitable for use in continuous annealing or galvanizing of steel plates.

In galvanizing lines that perform continuous annealing and continuous galvanizing when manufacturing strips such as steel plates, it is necessary to cool the strips, and the quality and characteristics of the product are greatly affected by the quality of this cooling. Various cooling devices have been proposed to accommodate this problem.

For example, in one of the cooling devices for metal strips in a continuous annealing furnace, etc., the strip 1 is wound around a water-cooled roll 2 having the structure shown in FIG. 1a, as shown in FIG. A device that does this is known. This water-cooled roll 2 is rotatably supported by a bearing 5, and a cooling water passage 6 is formed in a spiral shape on its inner wall. Cooling water is supplied and drained to a cooling water passage 6 via a rotary joint 4 attached to a rotating shaft 3 of a water-cooled roll 2. Further, the number of water-cooled rolls 2 installed may be increased or decreased as necessary.

A cooling device using such a water-cooled roll 2 has the disadvantage that the strip is likely to suffer shape defects such as wilting after cooling. The reason for this is that the strip usually has a side elongation of around 0.1% (edge elongation or middle elongation), so there are parts that make good contact with the water cooling roll 2 and are rapidly cooled, and parts that make poor contact. This causes defects in shape such as wrinkling and wilting.

On the other hand, as a cooling device for metal strips, a gas jet cooling device as shown in FIG. 2 is also known. In this gas jet cooling device, two supporting rolls 7 and 8 are placed at a predetermined interval.
is installed, and a metal strip 1 runs between these two support rolls 7 and 8,
A pair of headers 9 and 10 are installed between the two rolls 7 and 8 and sandwich the front and back surfaces of the metal strip 1, and a blower (not shown) or the like is ejected from a slit-shaped or circular nozzle 11 formed on the surface of the headers 9 and 10. Cooling gas 12 is jetted out and cooled.

The cooling capacity of such a gas jet cooling device depends on the heat transfer coefficient between the cooling gas 12 and the metal strip 1, and the distance between the nozzle 11 and the metal strip 1, that is, the nozzle gap L, is large for this heat transfer coefficient. influence In other words, the velocity of the cooling gas 12 injected from the nozzle 11 decreases as the nozzle gap L increases, and the velocity of the cooling gas 12 colliding with the surface of the metal strip 1 decreases, resulting in a decrease in heat transfer coefficient. .

Therefore, for effective cooling,
It is important to make this nozzle gap L small.

However, in the above-mentioned gas jet cooling device, the metal strip 1 may be warped or otherwise deformed after cooling, and the headers 9, which face the front and back surfaces of the metal strip 1, respectively.
The metal strip 1 comes into contact with the nozzle 11 due to deflection of the metal strip due to vibrations caused by the pressure balance in the nozzle 10 or the equipment before and after the cooling device.
There is a limit to how small the nozzle gap L can be due to the risk of so-called scratches.
It cannot be made smaller than 100mm and the heat transfer coefficient is low.
Therefore, in order to obtain a predetermined cooling capacity, a large blower and a large amount of power are required.

The inventors of the present invention have previously developed a strip cooling system based on the
proposed the invention related to No. 56-10973. The gist of this invention is to cool the metal strip by bringing it into contact with a cooling roll, and to spray cooling gas from a header onto the surface of the metal strip that does not come into contact with the cooling roll. In addition to eliminating cooling, the nozzle gap L can be reduced by absorbing deformation and vibration of the metal strip. That is, in this strip cooling device, as shown in FIG. 3, the metal strip 1 is wound around a large-diameter cooling roll 13 in the cooling position, and the metal strip 1 is run while applying tension, and the cooling roll 13 and the metal strip 1 are sandwiched between each other. A header 14 having an arc concentric with the cooling roll 13 and a substantially sector-shaped cross section is installed at a position facing the cooling roll 13, and the header 14 is fed under pressure by a blower or the like (not shown) through a slit-shaped or circular nozzle 15 formed on the surface of the header 14. Cooling is achieved by blowing out cooling gas 16.

Such a strip cooling device has the advantage that since there is no possibility that the metal strip 1 will come into contact with the nozzle 15, the nozzle gap L can be made small and a high heat transfer coefficient can be obtained. In other words, the nozzle gap L can be brought close to the distance L ₀ that provides the highest heat transfer coefficient under the operating conditions. It is experimentally confirmed and generally known that this nozzle gap L ₀ satisfies L ₀ ≦(6 to 8) d, where d is the nozzle width.

However, on the other hand, there is a problem in that the smaller the nozzle gap L is, the more the heat transfer coefficient across the width of the metal strip 1 varies.

This is because, as shown in FIG. 4, which shows the flow of cooling gas 16 on the surface of metal strip 1, cooling gas 16 injected from nozzle 15 collides with the surface of metal strip 1, and then moves the nozzle gap L into the area indicated by the arrow in the figure. As shown in , the cooling gas 16 flows toward the ends in the plate width direction and is discharged at the ends, so the discharge speed of the cooling gas 16 increases as it approaches the ends, and the heat transfer coefficient also increases. This tendency is caused by the distance between the nozzle 15 and the metal strip 1,
That is, the smaller the nozzle gap L becomes, the narrower the flow path of the cooling gas 16 becomes, which becomes more noticeable, and the degree of non-uniform cooling increases. When this phenomenon was confirmed through experiments, the results shown in FIG. 5 were obtained. In FIG. 5, the horizontal axis indicates the ratio of the nozzle gap L to the nozzle width d (L/d), and the left vertical axis indicates L/d.
= 8, the heat transfer coefficient α ₀ is used as a reference, and the ratio (α/α ₀ ) of the heat transfer coefficient α when L/d is changed with respect to this α ₀ is shown, and the right vertical axis is L When /d=8, the ratio of the heat transfer coefficient increment Δα at the end of the strip to the heat transfer coefficient α _c at the center in the width direction of the strip (Δα/αc
The ratio ( _c ) of the heat transfer coefficient increment at the ends of the strip to the heat transfer coefficient at the center in the strip width direction when changing L/d with respect to C ₀ is the ratio (C/ C ₀ ). However, the width of the strip is 1200mm.

As shown in the figure, α/α ₀ is indicated by the dashed line.
The value of becomes larger as L/d becomes smaller,
This means that if the nozzle gap L is made smaller, the heat transfer coefficient α becomes larger, and the value of C/C ₀ shown by the dotted line becomes larger as L/d becomes smaller. means that if the nozzle gap L is made smaller, the difference in heat transfer coefficient in the width direction of the strip becomes larger.

The present invention solves the above-mentioned drawbacks of the prior art, can prevent uneven cooling due to poor initial shape of the metal strip, absorbs deformation and vibration of the metal strip, and reduces the nozzle gap L, and furthermore, can reduce the nozzle gap L in the width direction of the metal strip. An object of the present invention is to provide a strip cooling device that can make the heat transfer coefficient uniform across the strip. The structure of the present invention to achieve such an object is to install a header through which cooling gas is sent and discharged facing a cooling roll around which a high-temperature strip is wound, and to jet cooling gas to the front surface of the header facing the cooling roll. a plurality of suction nozzles for suctioning the cooling gas collided with and reflected by the strip plate, a means for forcefully feeding the cooling gas to the jetting nozzles, and a means for forcibly exhausting the cooling gas from the suction nozzles. It is characterized by having the following.

Hereinafter, one embodiment of the strip cooling device of the present invention will be described in detail with reference to the drawings.

FIG. 6 shows an embodiment of the present invention. As shown in the figure, a metal strip 1 is placed on a cooling roll 20.
A header 21 for supplying and discharging cooling gas is installed at a position facing the cooling roll 20 and the metal strip 1 between them. The cooling roll 20 cools the metal strip by retaining or circulating a coolant such as water at the contact portion thereof, and is rotatably supported by bearings or the like. The header 21 has a double structure along the circumferential surface of the cooling roll 20, consisting of an outer header 21a and an inner header 21b, which have an arc concentric with the cooling roll 20 and have a substantially fan-shaped cross section. On the front surface facing the cooling roll 20, jet nozzles 22 and suction nozzles 23 are alternately arranged at equal intervals along the circumferential direction. This suction nozzle 23 is connected to the inner header 2 through a pipe 23'.
1b, and accordingly, the outer header 21
The cooling gas pumped into a is ejected from the ejection nozzle 22, collides with the metal strip 1, and is reflected.
At this time, if the inner header 21b is forcibly evacuated, the cooling gas that collides with the metal strip 1 and is reflected can be immediately sucked into the suction nozzle 23. The shape of the ejection nozzle 22 may be a slit shape extending in the width direction of the metal strip 1, as shown in FIGS. 6b and 6c, but is not limited to this shape.
The shape of the suction nozzle 23 is preferably slit-like or arc-like as shown in FIGS. 6b and 6c. The arrangement of the ejection nozzles 22 and the suction nozzles 23 is not limited to being arranged alternately as shown in the figure, but may be arranged in an evenly distributed manner, for example.

Further, a blower 24, a gas cooler 25, etc. are provided as means for forcefully feeding the cooling gas to the jet nozzle 22 and as means for forcibly exhausting the cooling gas from the suction nozzle 23. That is, as shown in FIG. 6a, a pipe or the like (not shown) is attached to the outer header 21a.
The blower outlet of the blower 24 is connected to the blower 24 through the blower 24, so that cooling gas can be pumped from the blower 24 to the outer header 21a. The suction port of the blower 24 is connected to the inner header 21b via a pipe or the like (not shown), and a gas cooler 25 is interposed in the pipe or the like, so that the cooling gas is cooled from the inner header 21b to the blower 24. It can be inhaled. In this embodiment, the cooling gas is circulated and used, so it is suitable when using something other than air as the cooling gas, but when air is used as the cooling gas, the cooling gas is not circulated. You may also use it in

The strip cooling device of the present invention having the above configuration has the following effects.

(b) Since both sides of the metal strip 1 are cooled by the cooling roll 20 and the cooling gas, uneven cooling due to the initial shape defect of the metal strip 1 can be prevented, and uneven elongation (edge expansion or middle expansion) can occur. There is no.

(b) Since the cooling gas is sprayed onto the metal strip 1 that is wrapped around the cooling roll 20, the strip 1 may sway and cause the nozzle 22,
23, which allows the nozzles 22, 23 to be placed close to the strip 1, resulting in a high heat transfer coefficient. In other words, as shown in FIG. 5, the nozzle gap is L,
If the width of the jet nozzle 22 is d, then L/d≦
(6 to 8), and even if other factors such as nozzle pitch and gas flow rate are changed, the nozzle gap L can be adjusted to obtain the best heat transfer under the changed conditions. It can be done.

(c) Since the jet nozzle 22 and the suction nozzle 23 are arranged on the front surface of the header 20 facing the strip 1, the cooling gas that collides with the strip 1 and is reflected can be immediately sucked by the suction nozzle 23. Therefore, the cooling gas does not flow toward the ends in the width direction of the strip and is not discharged, so that the heat transfer coefficient across the width of the strip 1 can be made uniform.

(d) In this embodiment, since the cooling gas is circulated and used, there is no dissipation of the cooling gas and there is no adverse effect on the surroundings.

The header is not limited to the shape and structure of the above embodiments, but may be any header as long as it has a plurality of jet nozzles and suction nozzles on the front surface of the header facing the cooling roll. Further, the arrangement of the ejection nozzle and the suction nozzle, their diameter or width, their pitch, etc. can be appropriately designed depending on other conditions.

As explained above in detail based on the embodiments, the embodiments can prevent uneven cooling due to poor initial shape of the metal strip, reduce the nozzle gap by sucking out the deformation and deflection of the metal strip, and The transmission rate across the width of the strip can be made uniform. Further, the present invention can be applied to a steel plate cooling device in a continuous annealing furnace, a cooling device in a galvanizing line, etc.

[Brief explanation of the drawing]

Figures 1 to 4 relate to a conventional strip cooling device, Figure 1a is a sectional view of a water-cooled roll, and Figure 1b is a cross-sectional view of a water-cooled roll.
is an explanatory diagram showing a strip wound around a water-cooled roll, FIG. 2 is a cross-sectional view of a gas jet cooling device, FIG. 3 is a cross-sectional view of a strip cooling device according to Japanese Patent Publication No. 10973/1983, and FIGS. 4 a and b are An explanatory diagram showing the flow of cooling gas, Fig. 5 is a graph showing α/α ₀ and c/c ₀ when L/d is changed, Fig. 6 a
is a sectional view of one embodiment of the strip cooling device of the present invention, FIG. It is a diagram. In the drawing, 20 is a cooling roll, 21 is a header, 2
1a is an outer header, 21b is an inner header, 22 is a jet nozzle, 23 is a suction nozzle, 24 is a blower,
25 is a gas cooler.

Claims (1)

[Claims] 1. A header through which cooling gas is sent and discharged is installed opposite to the cooling roll around which the high-temperature strip is wrapped, and a jet nozzle for spouting cooling gas and a header that hits the strip is installed on the front surface of the header facing the cooling roll. A strip characterized in that a plurality of suction nozzles are provided for sucking the cooling gas reflected by the strip, and means for forcefully feeding the cooling gas to the jetting nozzle and means for forcibly exhausting the cooling gas from the suction nozzle are provided. Cooling system.