JPH051333A - Roll cooling device for metal strip - Google Patents

Abstract

PURPOSE:To prevent the occurrence of nonuniform cooling in the width direction of a metal strip independently of the amount of metal strip to be cooled and the amount of metal strip to be treated and also to prevent the occurrence of scratch, etc., in the surface of the metal strip, in a roll cooling device for cooling the metal strip by the use of cooling rolls in continuous annealing equipment. CONSTITUTION:The shell thickness of cooling rolls is regulated so that it is larger on the former-stage side than on the latter-stage side. Further, a roughness of Ra3-7mum is provided to respective outside peripheral surfaces of shells of the cooling rolls to perform roughing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roll cooling device for cooling a metal strip such as a high temperature steel strip by arranging a plurality of cooling rolls having an internal cooling structure in series in a continuous annealing facility or the like. is there.

[0002]

2. Description of the Related Art A roll cooling device is known as a cooling device for continuous annealing equipment. This roll cooling device is characterized in that the cooling rate can be freely controlled, the facility cost is lower than that of a cooling device having another structure, and the energy consumption is small. The roll cooling device has a plurality of cooling rolls having an internal cooling structure arranged in series, and while contacting the metal strip with the cooling roll, heat conduction between the outer peripheral surface of the body part of the cooling roll and the metal strip causes This is a device for cooling the strip. The control of the cooling amount is controlled by changing the contact angle θ between the cooling roll and the metal strip, that is, the winding length L. When cooling metal strips with this chill roll, the most important thing is to cool the strips as evenly as possible across the width, and many improvements have been made for this. That is, when the cooling amount and the processing amount (T / H) of the metal strip are small, the contact angle θ between the cooling roll and the metal strip (or the winding length L).
Becomes smaller, uniform cooling in the width direction of the metal strip cannot be achieved, and a defective shape may occur. Further, since the contact angle θ (or the winding length L) is small, the cooling roll and the metal strip may slip, and scratches may be generated on the strip surface. On the other hand, if the cooling amount of the metal strip is too large, the cooling rate is too high to allow uniform cooling in the width direction of the metal strip, and the shape of the strip collapses. There is a possibility that the line in the furnace will be stopped due to the restriction in the furnace.

In continuous annealing equipment, the metal strip is annealed in a predetermined heat cycle for the purpose of improving the material. A roll cooling device has been adopted in recent years as a primary cooling means for this heat cycle, and the strip temperature is rapidly cooled from about 650 ° C to about 400 ° C. When cooling the metal strip, it is desirable to make the amount of temperature drop of each cooling roll as uniform as possible. Especially, since the cooling roll on the front side has a higher temperature of the metal strip than the cooling roll on the rear side,
The amount of temperature drop of the strip becomes large, uniform cooling cannot be performed in the width direction of the strip, the shape becomes defective, and the above-described cooling buckle in-furnace throttling may occur.

Therefore, conventionally, the contact angle θ (or the winding length L) between the cooling roll on the front side and the metal strip is reduced, and the contact angle θ (or the winding length) between the cooling roll on the rear side and the metal strip (or the winding length). The length L) is increased to control the temperature drop amount of each cooling roll to be uniform. However, in the above-mentioned prior art, it is possible when the cooling amount or the processing amount (T / H) of the metal strip is large, but when the cooling amount or the processing amount (T / H) of the metal strip is small, it is possible. The contact angle θ (or the winding length L) between the cooling roll and the metal strip on the preceding stage side is further reduced, and slip is induced between the cooling roll and the metal strip, so that the surface of the strip has scratches. May occur,
Since the winding length L between the cooling roll and the metal strip is short, the cooling rate becomes high, the shape collapses, and the in-furnace throttle called a cooling buckle may occur.

As described above, the roll cooling device is cheaper in energy cost and equipment cost than other cooling methods, and is thus said to be most suitable for the production of thin soft steel plates. The cooling amount and cooling rate of the metal strip are
This is achieved by changing the contact angle θ (or the winding length L) between the cooling roll and the metal strip. The outer peripheral surface of the cooling roll is not flat but has microscopic unevenness, and the shape of the metal strip to be cooled is not uniform in the width direction, which causes uneven cooling in the width direction. In particular, since the plate temperature of the metal strip is higher in the front-stage cooling roll than in the rear-stage cooling roll, the cooling amount becomes large at the same contact angle θ (or winding length L). 7, the metal strip 2 wound around the cooling roll 1
The defective shape is promoted.

Therefore, in the prior art, as described above, the contact angle θ (or the winding length L) between the front-stage cooling roll and the metal strip is calculated as the contact angle θ (or the winding length) between the rear-stage cooling roll and the metal strip. The length L) is smaller than the length L) so that the amount of temperature drop is uniform for each cooling roll. However,
When the cooling amount and the processing amount (T / H) of the metal strip are small, the contact angle θ (or the winding length) between the cooling roll and the metal strip on the preceding stage side becomes further smaller, and the cooling roll and the metal strip Slip between the strips causes scratches on the strip surface, and the winding length L is short, which increases the cooling rate and causes the strip shape to collapse, resulting in a furnace buckle called a cooling buckle. It may occur.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to prevent uneven cooling in the width direction of a metal strip and to prevent scratches on the surface of the strip regardless of the cooling amount and the processing amount (T / H) of the metal strip. The present invention is to provide a roll cooling device in which such problems do not occur.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a roll cooling device in which a high temperature strip is wound around a cooling roll having an internal cooling structure to cool the shell, and the shell thickness of the cooling roll on the front side is set to the cooling thickness on the rear side. It is a roll cooling device for metal strips, which is thicker than the shell thickness.

Further, the present invention is characterized in that the outer peripheral surface of the shell of the cooling roll is roughened by imparting a roughness of Ra 3 to 7 μm.

[0010]

According to the present invention, a plurality of cooling rolls are arranged in series, and the thickness of the shell of the cooling roll on the front stage side is made thicker than the thickness of the shell of the cooling roll on the rear stage side. Thereby, even if the contact angle θ (or the winding length L) between each cooling roll and the metal strip is the same, the temperature drop amount of the strip on each cooling roll can be made uniform. That is, the shell thickness of the cooling roll on the upstream side where the plate temperature of the metal strip is relatively high is made thicker, so that the overall heat transfer coefficient U _{0 is} increased.
Is made smaller, the shell thickness of the cooling roll on the rear stage side is made thinner successively, and the overall heat transfer coefficient U ₀ is made larger successively. As a result, the metal strip can be cooled with a uniform temperature distribution in the width direction irrespective of the cooling amount and the processing amount (T / H) of the metal strip, and the surface of the strip has scratches or the like due to slip with the cooling roll. Can be prevented and stable operation can be performed.

Further, according to the present invention, the shell outer peripheral surface of the cooling roll is a rough surface having a roughness Ra of 3 to 7 μm, and these rough surfaces are provided on all of the plurality of cooling rolls arranged in series. They are formed with the same structure. This roughness is preferably 4
μm. If the roughness Ra is made too large, it is necessary to make the shell thickness small in order to make the overall heat transfer coefficient U ₀ large. If this is done, the strength of the cooling roll is lowered and strain is likely to occur. Further, if the roughness Ra is made too small, the overall heat transfer coefficient becomes small. Therefore, if the shell thickness having sufficient strength is maintained, the contact angle θ between the metal strip and the cooling roll must be made small. If this is done, slippage between the metal strip and the cooling roll will occur, resulting in scratches. Therefore, in the present invention,
While making the thickness of the cooling roll smaller as it goes from the front stage side to the rear stage side as described above, the outer peripheral surface of the shell of each cooling roll is roughened, thus securing the thickness of the cooling roll and preventing deformation, and By preventing the contact angle with the strip from becoming too small, slippage with the metal strip is prevented and scratches are prevented.

The overall heat transfer coefficient U ₀ of the cooling roll is expressed by the equation 1.

[0013]

[Equation 1]

Here, U ₀ : Overall heat transfer coefficient (kcal / m ² · h · ° C.) hw: Heat transfer coefficient (kcal / k) of cooling medium (eg, water)
m ² · h · ° C) λr: Thermal conductivity of the cooling roll shell 13 (kcal / m
・ H ・ ℃) hc: Contact thermal conductance (kcal / m ²・ h ・
℃) λs: Thermal conductivity of the metal strip 4 (kcal / m · h)
-° C) dr: thickness of cooling roll shell 13 (m) ds: plate thickness of metal strip 4 (m) Next, considering the heat balance between the metal strip 4 and the cooling roll R, the overall heat transfer of the cooling roll R1 The coefficient U ₀ is expressed by Equation 2.

[0015]

[Equation 2]

[0016]

[Equation 3]

As can be seen from the above equation, the overall heat transfer coefficient U ₀ of the cooling roll R1 is inversely proportional to the thickness dr of the cooling roll shell, and depends on the throughput W of the metal strip 4 and the temperature drop ΔT of the metal strip 4. Proportional. Therefore, when the throughput W of the metal strip 4 is small, a small overall heat transfer coefficient U ₀ is required. Although the above description was mainly made with respect to the cooling roll R1, the same applies to the other cooling rolls R2 to R5.

In this case, if the overall heat transfer coefficient U ₀ is large, and the contact angle θ1 (or the winding length L1) between the metal strip 4 and the cooling roll R1 is constant, the metal strip 4 and the cooling roll R1 are constant. The contact area A becomes constant and the temperature drop amount ΔT of the metal strip 4 becomes large, which leads to the occurrence of the cooling buckle as described above. On the contrary, if the temperature drop amount ΔT of the metal strip 4 is controlled to be constant, the contact area A between the metal strip 4 and the cooling roll R1 becomes small, and the surface of the strip has scratches. The above-mentioned phenomenon is more prominent in the cooling roll R1 on the front side as compared to the cooling roll R5 on the rear side. However, since the overall heat transfer coefficient U ₀ is inversely proportional to the cooling roll shell thickness dr as shown in FIG. 5, the shell thickness dr of the cooling roll may be increased to reduce the overall heat transfer coefficient U _0. It turns out that.
In FIG. 4, the roughness Ra of the outer peripheral surface of the shell 6 is 4 μm. Therefore, the shell thickness dr of the cooling roll on the front side where the plate temperature of the metal strip is relatively high is increased to reduce the overall heat transfer coefficient U _0, and the shell thickness dr of the cooling roll on the post stage side is sequentially decreased to reduce the overall thickness. Thus, the roll cooling device in which the heat transfer coefficient U ₀ is successively increased can be stably operated regardless of the cooling amount or the processing amount (T / H) of the metal strip. Thus, the thickness dr of the shell 13 is made thinner from the front stage to the rear stage as shown in FIG. 6C.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram of a continuous annealing equipment for a metal strip which is a steel strip according to an embodiment of the present invention, and FIG. 2 is a diagram showing a heating / cooling cycle of the strip in the continuous annealing equipment. The strip 4 from the pay-off reel 3 passes through an electrolytic degreasing device 5, is heated in a heating zone 6, and is heated to a uniform temperature.
In the first cooling zone 8 and the roll cooling device 9 according to the embodiment of the present invention. Then, the strip is guided from the overaging zone 10 to the second cooling zone 11 to be secondarily cooled, and wound by the take-up reel 12. In the roll cooling device 9, a total of five cooling rolls R1 arranged in series for sequentially cooling the strip 4 are used.
To R5 are arranged, and the strip 4 is wound around each of the rolls R1 to R5 as shown in FIG.

FIG. 3 is a simplified side view of the cooling device 9. The contact angles of the strip 4 wound around the rolls R1 to R5 are indicated by θ1 to θ5, and the winding length is L
1 to L5. These contact angles θ1 to θ5 may be collectively indicated by reference numeral θ, and the winding lengths L1 to L5 are
It may be generally indicated by a reference sign L.

FIG. 4 is a sectional view of the cooling roll R1.
The shell 13 of the cooling roll R1 is formed of a good heat conductor such as steel. The cooling medium is supplied from one shaft 15, passes through a cooling medium passage 23 formed in a spiral shape on the inner peripheral surface of the shell 13, and is discharged from a passage in the other shaft 16. The shafts 15 and 16 are connected by a rotary pipe joint.
The thickness of the cooling medium passage 23 of the shell 13 is indicated by reference numeral dr.

In the roll cooling device 9 according to the present invention,
As shown in FIG. 6 (1), the contact angles θ1 to θ5 of the rolls R1 to R5 are set to substantially the same value to prevent slipping with the strip 4 and to cool the strip 4 with a uniform temperature distribution in the width direction. Ensure that is done. In this way, the contact angle θ between the cooling rolls R1 to R5 and the strip 4 is
1 to θ5 are kept large enough not to slip, and the strip temperature drop amount ΔT is set to the cooling rolls R1 to R5.
In order to make them substantially equal for each of the cooling rolls R1 to R5, the overall heat transfer coefficient U ₀ may be set larger as shown in FIG. In the present invention, as described above, the thickness dr of the shell 13 of the cooling roll R1 at the frontmost stage and the thickness dr of the shell of the subsequent cooling rolls R2 to R5 are successively reduced as shown in FIG. 6 (3). To configure.

The experimental results of the present inventor will be described. Cold rolled steel strip as metal strip 4 (sheet thickness 0.6 mm, sheet width 1
219 mm) in a continuous annealing equipment as shown in FIG. 1 at a line speed of 200 m / min, the strip strip temperature at the inlet of the roll cooling device 9 is 650 ° C., and the strip strip temperature at the outlet of the roll cooling device 9 is 650 mm. Was controlled at 400 ° C. Cooling rolls R1 to R1 of the roll cooling device 9
Five R5s are arranged in series, and the roll diameter is 15
It is 00 mmφ. Also, five cooling rolls R1 to R5
Roughness of Ra = 4 μm is given to the outer peripheral surface of the shell of
The shell thickness dr of each of the cooling rolls R1 to R5 is 20 mm for the second cooling rolls R1 and R2 from the entrance side of the roll cooling device 9 with respect to the traveling direction of the metal strip 4.
The subsequent three cooling rolls R3 to R5 were set to 10 mm. Water is used as the cooling medium. In such an embodiment, the metal strip was flat without impairing its shape, and there was no occurrence of a cooling buckle due to a defective shape of the strip 4. No scratches or the like were formed on the surface of the metal strip 4.

[0024]

As described above, according to the roll cooling apparatus of the present invention, it is possible to uniformly cool the thin strip to the thick strip in the width direction of the metal strip, and to eliminate the cooling buckle caused by the non-uniform cooling in the width direction. It enables stable operation. Further, since the contact angle between the cooling roll on the upstream side and the metal strip is large, scratches and the like do not occur on the surface of the metal strip, and the quality is greatly improved.

[Brief description of drawings]

FIG. 1 is a system diagram of continuous annealing equipment according to an embodiment of the present invention.

FIG. 2 is a diagram showing a heating / cooling cycle of the continuous annealing equipment shown in FIG.

FIG. 3 is a simplified side view of a roll cooling device 9.

FIG. 4 is a sectional view of a cooling roll R1.

FIG. 5 is a graph showing the relationship between the shell thickness dr of the cooling roll R1 and the overall heat transfer coefficient U ₀ .

FIG. 6 is a diagram for explaining the operation of the roll cooling device 9.

FIG. 7 is a cross-sectional view showing a state in which a metal strip 2 wound around a cooling roll 1 of the related art has a defective shape.

[Explanation of symbols]

4 steel strip 9 roll cooling device 13 shells R1-R5 cooling roll

Claims (2)

[Claims] 1. In a roll cooling device in which a high-temperature strip is wound around a cooling roll having an internal cooling structure to cool the cooling roll, the shell thickness of the cooling roll on the front stage side is made thicker than the shell thickness of the cooling roll on the rear stage side. Characteristic roll cooling device for metal strip. 2. On the outer peripheral surface of the shell of the cooling roll, Ra3 to
The roll cooling device for a metal strip according to claim 1, wherein the roll cooling device is roughened by imparting a roughness of 7 μm.