JPH0118131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cooling device for metal strips using a roll cooling contact method.

[Conventional technology]

In continuous annealing equipment for metal strips, a method is known in which the strip is cooled by bringing it into contact with a cooling roll.

Figure 4 shows continuous annealing equipment using this type of cooling method, with a soaking zone 5 and an overaging zone 7.
A cooling roll strip 6, 8 with a plurality of cooling rolls 12 is provided on each rear side of the cooling roll strip 6,8. The cooling roll 12 includes a spiral refrigerant liquid passage 14 inside the roll shell 13, as shown in FIG.
A refrigerant liquid such as cooling water is circulated in the refrigerant liquid passage 14 by a passage 15 provided on the roll shaft of the cooling roll and a rotary joint 16 connected to the end of the roll shaft. I'm starting to get it.

FIG. 6 shows the thermal cycle in the continuous annealing equipment shown in FIG. 4, in which the metal strip After being sent to the tropical zone 5 and heated to about 700°C, it is rapidly cooled to about 400°C in a cooling roll zone 6 at a cooling rate of 100 to 200°C/sec. Then metal strip
After being treated in the overaging treatment zone 7, it is transferred to the cooling roll zone 8 again.
It is cooled, passed through an exit looper 9 and a temper mill 10, and then wound onto a tension reel 11.

When the metal strip X is cooled by the cooling roll as described above, the shape of the metal strip X is easily distorted due to thermal stress generated during the cooling process.
There is a drawback that buckling is likely to occur in the non-contact portion between the cooling rolls 12. In extreme cases, this buckling causes vertical wrinkles in the line direction called "squeezing", which becomes a serious problem that may lead to breakage of the metal strip X within the line.

[Problem that the invention seeks to solve]

Conventionally, regarding the thermal stress generated in metal strips and the resulting buckling/restriction, buckling-prone areas are areas where compressive stress occurs in the width direction of the strip, and if this value exceeds the buckling resistance value, It has been clarified that the risk of buckling and throttling is extremely high, and that the basic idea of preventing throttling is to reduce the thermal stress generated by roll cooling to below the buckling resistance value. Regarding thermal stress and aperture characteristics, the following points have also been clarified.

(1) If other conditions are the same, the thinner the plate, the faster the cooling rate will be when cooling with the same roll.
This results in large thermal stress. Furthermore, it is thought that the thinner the plate, the lower the buckling resistance, making it extremely easy to draw.

(2) If other conditions are the same, the larger the plate width, the greater the generated thermal stress, and the smaller the buckling resistance of the plate, making it very easy to draw.

(3) The slower the line speed, the greater the thermal stress generated and the easier it is to squeeze.

In view of the above-mentioned characteristics, the present inventors first used a high boiling point heat medium for internal cooling of the roll, based on the viewpoint of controlling the cooling capacity of the cooling roll according to the sheet passing conditions. We proposed a method and equipment that controls the cooling capacity of the roll by changing its operating temperature to prevent the strip from constricting depending on the sheet conditions. However, roll cooling equipment using this high-boiling point medium requires a heat exchange device and has safety problems in that it is difficult to handle the highly flammable high-boiling point medium.

The present invention was made in view of these conventional problems, and an object of the present invention is to provide a roll contact cooling device that can easily control the thermal stress generated in the strip depending on the strip passing conditions and can be used safely. It is something.

[Means to solve the problem]

Therefore, the present invention focuses on the fact that even if the same cooling fluid is used, the cooling capacity of the cooling roll can be changed over a relatively wide range depending on the roll shell thickness, roll material, etc., and uses cooling rolls with different cooling capacities as appropriate. The aim is to provide a device that enables this.

That is, in the present invention, a plurality of pairs of cooling rolls having different cooling capacities and facing each other at intervals are arranged in the line direction, and both cooling rolls constituting each pair are movable in the arrangement direction. According to
The metal strip passing between the two cooling rolls is constructed so as to be able to selectively come into contact with either one of the cooling rolls.

[Effect]

The metal strip is passed between a pair of cooling rolls having different cooling capacities. The pair of cooling rolls can be moved in the direction in which they are arranged, generally perpendicular to the strip passing line, and can be brought into contact with one of the cooling rolls by adjusting their position. Since a plurality of pairs of cooling rolls having different cooling capacities are arranged in the line direction, the strip is wound around the cooling rolls in a meandering manner in the line direction, thereby cooling the strip.

〔Example〕

FIG. 1 shows an embodiment of the apparatus of the present invention.

Deflector rolls 17 are installed on the inlet and outlet sides of the device.
a and 17b are arranged, and both deflector rolls 17
A cooling roll is arranged between a and 17b.

The cooling rolls include a low cooling capacity roll _18A and a high cooling capacity roll _18B as one set, and a plurality of pairs of rolls R are arranged in the line direction. The low cooling capacity roll _18A and the high cooling capacity roll _18B are rotatably supported on both sides of the connecting member 19 so as to face each other with a gap between them. Such a plurality of cooling roll pairs R are arranged such that the arrangement direction of both rolls is perpendicular to the line direction, and each pair of cooling rolls connected by the connecting member 19 is arranged in the arrangement direction of both rolls, that is, It is configured to be movable in a direction perpendicular to the line.

The spacing between each pair of low cooling capacity roll _18A and high cooling capacity roll _18B is configured such that the strip can be inserted therethrough, and by selecting the moving position of the roll pair R, the strip It is possible to selectively contact the roll.

The cooling capacity of the cooling roll can be selected from a wide range by selecting its material and shell thickness. The overall heat transfer coefficient U, which is the roll cooling capacity, is defined by the following equation, and is greatly influenced by the thickness of the cooling roll shell.

U=ρcdV/Llnθ _c −θ _w /θ _d −θ _w (Kcal/m ² h℃
) Here, ρ: Strip density c: Specific heat d: Thickness V: Line speed L: Contact length between roll and strip θc: Strip inlet temperature _θd : Outlet temperature _{θw :} Cooling water temperature Figure 3 shows the results of investigating the effect of the thickness of the roll shell on the overall heat transfer coefficient of the cooling roll for SS41 steel and SUS304 steel at a water temperature of 40°C. The roll is 30mm thick and has twice the cooling capacity of a cooling roll with a shell made of SUS304 material. Therefore, these types of cooling rolls can be used as the low cooling capacity roll _18A and the high cooling capacity roll _18B, respectively.

In the embodiments described above, a pair of cooling rolls having different cooling capacities are connected by a connecting member so that they can be moved together, but in some cases,
It is also possible to adopt a configuration in which they are moved separately without being connected.

Furthermore, when the strip is cooled by several stages of cooling rolls in the line direction, there is a tendency for constriction to occur in the roll cooling section on the high temperature side, and for this reason, a low cooling capacity roll _18A is placed on the inlet side of the roll cooling device. It is also possible to provide a plurality of roll pairs R consisting of a high cooling capacity roll _18B and a high cooling capacity roll 18B, and to provide a normal cooling roll (for example, a high cooling capacity roll) on the exit side.

Furthermore, the cooling device can also be constructed vertically, with deflector rolls passing the strip longitudinally and each pair of cooling rolls moving horizontally.

Further, in the present invention, three or more types of cooling rolls having different cooling capacities can be used.

In the apparatus of the present invention as described above, in the case of threading conditions that make it easy to draw the strip, the low cooling capacity roll 1
The strip is cooled by contacting it with roller 8 _A , while under normal threading conditions, it is cooled by a high cooling capacity roll 18 _B. This controls the thermal stress caused by cooling the strip and properly prevents drawing. cooling can be performed. That is, in the present invention, such switching of the cooling rolls can be performed by simply moving a pair of rolls without path switching. Figures 2A and 2B show the switching mode of use. In Figure 2B, the steel strip is all cooled by the low cooling capacity roll _18A , and in Figure 2B, all the steel strips are cooled by the high cooling capacity roll 18A. It shows the state where it is being cooled by the roll _18B , and the usage mode is not limited to this, but it can also be used with the low cooling capacity roll _18A and the high cooling capacity roll _18B.
It is possible to adopt various combinations of the above.
In the cooling device shown in Fig. 1, the roll shell is SUS304 as the low cooling capacity roll _18A .
A steel strip was cooled using a water-cooled roll with a thickness of 30 mm and a high cooling capacity roll 18 _B with a roll shell of SS41 and a thickness of 10 mm. As a result, the strip thickness was 0.4 to 1.2 mm, and the strip width was 1600 mm. In operation at ~1240 mm and line speeds of 80 to 180 mpm, there was almost no throttling. In particular, conventional water-cooled rolls are prone to squeezing.
Under the conditions of threading a sheet with a thickness of 0.4 to 0.6 mm and a width of 1000 to 1240 mm, slow cooling was performed using the water-cooled roll arrangement shown in FIG.

〔Effect of the invention〕

According to the present invention described above, it is possible to switch between cooling rolls with different cooling capacities without performing pass switching, and by appropriately performing such switching according to the sheet passing conditions, it is possible to prevent throttling. The strip can be cooled at the same time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. FIGS. 2A and 2B are explanatory diagrams showing switching usage states of the apparatus shown in FIG. 1. FIG. 3 shows the relationship between the roll shell thickness of the cooling roll and the overall heat transmission coefficient. FIG. 4 is an explanatory diagram showing a continuous annealing line of the strip. FIG. 5 is a longitudinal sectional view of the cooling roll. FIG. 6 shows a thermal cycle in the continuous annealing line of FIG. 4. In the figure, 18 _A is a low cooling capacity roll, 18 _B
indicates high cooling capacity rolls.

Claims (1)

[Claims] 1. Different cooling capacities, 1 facing each other at intervals.
A plurality of pairs of cooling rolls are arranged in the line direction,
By making both the cooling rolls constituting each pair movable in the arrangement direction, the metal strip passing between the cooling rolls can be brought into selective contact with one of the cooling rolls. A roll contact cooling device for metal strips.