JPS60169525A - Method for cooling steel strip in cooling zone of continuous annealing furnace - Google Patents

Abstract

PURPOSE:To cool a steel strip having a thickness change without a defective shape and breakdown by starting the resetting of the angle for winding the steel strip on cooling rolls in a cooling zone of a continuous annealing furnace at the time shifted by as much as the response time for the change in the winding angle. CONSTITUTION:A continuous annealing furnace which subjects a strip 1 after cold rolling to heating in a heating zone A, holding in a soaking zone B, cooling in the 1st cooling zone C, an overaging in an overaging zone D and secondary cooling is so constituted that the strip 1 is put around cooling rolls 2-6 passed internally with a refrigerant in said zone C and the cooling temp. is changed by moving the rolls 2-6 and changing the winding angle. The point of the time when the strip 1 arrives at the inlet of the zone C in the boundary part is calculated by a boundary part detector 17, a pulse generator 17, a pulse counter 16, a line speed detector 18, etc. and the resetting of the winding angle is started earlier by as much as the response time for the change in the above-mentioned winding angle in the case of changing the preceding strip to the succeeding strip having the thickness smaller than the thickness of the preceding strip.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling a steel strip in a cooling zone having a roll cooling device for cooling the copper strip by contact heat transfer to the steel strip.

The continuous annealing furnace has a structure shown in FIG. 1 as an example, and is a furnace equipment for heat-treating a cold-rolled copper strip (hereinafter referred to as IJ wrap). The equipment includes, for example, a heating zone A, a soaking zone B, a first cooling zone C, and an il! ': 1 aging zone, 2nd cooling zone E, the heat cycle shown in FIG. 2 is realized. That is, when the strip 1 shown in FIG.
It is heated to about 00°C, and then heated for 20 seconds in soaking zone B.
Keep it at 00℃ and heat it evenly, then turn to the first cooling zone C.
The temperature is cooled by 50°C per second, and then the overaging treatment is performed at 400°C for 2 minutes in the overaging zone D, and then the cooling is performed in the second cooling zone EV.
The process of cooling is followed by cooling.

In such equipment, in the first cooling zone C and the second cooling zone E, when cooling the strips 17, conventionally, the so-called gas is used to blow the entire strip of cooling gas flK and perform cooling by forced convection. The jet method was being used. However, recently, a roll cooling method has been proposed which has higher cooling capacity and lower Sycamore running cost than this gas jet method. In this roll cooling method, a refrigerant is passed through the roll on which the strips F are applied, thereby cooling the roll and cooling the IJ tube that comes into contact with the roll. Furthermore, we have proposed a cooling method (published in Japanese Patent Application Laid-Open No. 56-35730) that adjusts the cooling temperature according to the thickness of the strip by changing the winding angle between the strip and the roll when the thickness of the strip changes. has been done.

An example of such a roll cooling device is shown in FIG. In FIG. 3, numerals 2 to 6 are cooling rolls through which a refrigerant is circulated. Of these, cooling roll 3
and 5 are disposed so as to be movable in the direction below the ground in the drawing to adjust the winding angle, and this movement is performed by roll drive devices 7 and 8.
It will be held at Note that, after the refrigerant is sent from the cooling roll to the heat exchanger and cooled, it is supplied to the cooling roll again.

The problem with this type of roll cooling method is that part of the strip does not come into contact with the cooling roll because of the elongation (edge (edge) or middle elongation) that exists before and after the passing strip fVrCo. This phenomenon occurs, resulting in uneven cooling and the appearance of wrinkles.

In order to solve this problem, Japanese Patent Application No. 57-129069 proposes a cooling method that sets an upper limit on the amount of temperature drop per roll to reduce uneven cooling. . Here, in the formula above, ΔTs: strike IJ knob 17ffi per roll [
Amount of drop, ['C] TS,: Strip temperature at contact initiation force with the cooling roll. [°C] Tw: Latency of refrigerant in cooling roll, [°C] V Niline speed, [m/h] d: Plate thickness, [m] C Nistrip specific heat, [kcal/ky”c] γ: Strip specific weight, Ck'/m3) k: Heat transfer rate between strip and refrigerant, [kcal/J h °C] θ: Roll winding angle (for one roll), [stability] DR: Outer diameter of cooling roll, [m] be.

As can be seen from this formula, the strip plate J? -d,
The overall condition is to make the strip temperature drop ΔTs equal to the upper limit ΔTSCR according to the line speed V, etc., and also annealing at a winding angle that keeps the final cooling temperature of the II tube within a predetermined tolerance range. This is the optimum operation to obtain the desired material at maximum production efficiency without producing any sound or defective shapes.

However, in reality, there are problems as follows.

In other words, while it takes only a few seconds for the strip to pass through the cooling zone, the speed of roll movement for adjusting the winding angle is limited to control the tension of the strip, so as not to completely immerse the strip. Ru. - As an example, the time to move the rolls to change the winding angle from 60 degrees to 120 degrees takes approximately 2 minutes.

Therefore, as shown in FIG. 4(a), if there is a relationship such as (the leading phase plate of the strip is thick and the trailing side plate N is thick), or as shown in FIG. 4(b) (the leading controlling plate thickness of the strip
In any case where there is a relationship between the thickness of the trailing material and the thickness of the trailing material, the boundary part (weld part) between the leading phase and the trailing material with different thicknesses passes through the entrance of the cooling zone and at the same time wraps around the trailing phase. An angle change is made. In other words, as the plate thickness changes, the final cooling temperature of the trailing strip is cooled to within a predetermined tolerance range, and ΔTs≦
The winding angle is changed to a value necessary to achieve ΔTscR.

However, due to the low responsiveness of the winding angle described above, ΔTs>ΔTSCR may temporarily occur, which may result in a defective plate shape.

This is particularly noticeable when the trailing material is thinner than the preceding material, as shown in FIG. 4(b).

1. Once the shape of the strip is disturbed, the subsequent strike IJ
Even after Δ'I's<ΔTscn, it is difficult to restore the shape of the strike IJ knob to its normal shape, and in the worst case, the plate may break.

Therefore, the present invention--copper strip cooling in a continuous annealing furnace cooling zone that maintains the above-mentioned relationship of ΔTs≦ΔTSCH even if the thickness of the strike IJ tube changes and prevents strip shape defects and strip breakage. The purpose is to provide a method.

The present invention achieves this object by passing a copper strip around a cooling roll through which a refrigerant is circulated, and when changing the cooling temperature of the copper strip, moving the cooling roll to connect the steel strip and the cooling roll. In the cooling zone of a continuous annealing furnace where the wrapping angle is changed.

When the thickness of the succeeding material of the above steel strip is thinner than that of the preceding material V
C starts changing the setting of the winding angle at a time corresponding to the winding angle change response time before the time when the boundary between the trailing material and the leading material reaches the entrance of the cooling zone. It is characterized by

The present invention will now be described in detail with reference to FIGS. 5 and 6. FIG. 5 shows the equipment for the example method. The roll driving device 7.8 for the cooling rolls 5, 3 measures the winding angle from the roll position obtained by the roll position detector 9.10.
It is controlled by a winding angle control device 11.12 which operates so that the winding angle of the bracket becomes the inputted winding angle setting value (3). Therefore, roll drive device Ff: 7,
8 is a winding angle control device which is driven based on the command of 11.12 and moves the roll 5.3.

The setting value ■ of the winding + j angle is output from the calculation device 13, but this calculation device 13 calculates the IJ tongue length LT, plate thickness,
The line speed and target heat cycle are input, the required winding angle is calculated from these, and the set value (2), which is the calculation result, is output at a timing of 91 seconds.

A deflector roll 14 is arranged at the entrance of the heating zone A,
A pulse generator 15 is attached to the shaft of the deflector roll 14, and a pulse counter 16 connected to the DA pulse generator 15 measures the number of revolutions.
be called.・The armature counter 16 has a boundary (welding point)
Boundary detector 17 outputs υ set a upon passage of
is connected, the IJ tube length LT proportional to the rotational speed can be obtained from the count value of the pulse counter 16.

Furthermore, a line speed detector 18 is arranged in the heating zone A. The speed signal of the line speed detector 18 and the lag length LT of the preceding line are processed by the following equation in the arithmetic unit 13 to obtain the timing at which the boundary passes through the cooling zone entrance.

ΔL=Lo LT When LT≧Lc, ΔT-ΔL/V 1LC/V When LT<LC, ΔT=LC/V-LT/'TJ Here, ΔL; Leading material at the position of the boundary detector Lo: Total length of the preceding material LT: Strip length of the preceding material passing through the boundary detector, Lc: Distance from the boundary detector to the cooling zone inlet, 717 The next boundary is the cooling zone The time it takes to completely pass through the entrance is V niline speed.

In this way, the time ΔT for the boundary portion to reach the cooling zone entrance is determined according to the above conditions.

Further, the response time of the winding angle may be obtained in advance through experiments or the like and stored in the arithmetic unit 13.

FIG. 6 shows the time response of the final cooling temperature of the cooling zone and the winding angle. i@6 Figure (a) shows the case where the trailing material is 1'% and the preceding material is J2. The angle setting value is changed, and the wrapping angle starts changing from this point. Therefore, when the boundary of the strip reaches the outlet of the cooling zone, the temperature of the strip IJ becomes difficult to cool due to its thickness, and therefore the temperature of the strip f increases. Therefore, the amount of drop in hot water temperature of the strip decreases as shown at the end of FIG. 6(a). In such a case, the aforementioned ΔTs≦TS
The CR relationship is maintained and there are no problems.

On the other hand, FIG. 6(b) shows a case where the succeeding material is thicker and the preceding material is thicker. In other words, if the thickness of the trailing material is thinner than that of the leading material, from the point at which the boundary between the trailing material and the leading material reaches the entrance of the cooling zone, the winding angle is changed by the response time. The winding angle setting was changed at the previous time. The time for this setting change is such that the time ΔT for the boundary portion to reach the cooling zone entrance corresponds to the response time for changing the winding angle. As a result, when the boundary reaches the cooling zone inlet, a winding angle corresponding to the thickness of the trailing material is obtained, so the strip temperature drop ΔTs does not exceed the upper limit value ATSCR.

Therefore, the relationship ΔT3♀T8CR is maintained.

As explained above, according to the present invention, S) If the thickness of the trailing material of the IJ Tsude is thicker than the thickness of the preceding material, the thickness of the trailing material is equal to the thickness of the leading material. Even if the strip is thin, the response time of the winding angle is calculated in advance to determine the strip temperature drop Δ.
Since the winding angle setting is changed so that 1゛S does not become thicker than the upper limit ΔT SCR, it is possible to prevent a defective strip shape or, in the worst case, breakage of the strip. Annealing operation is now possible.゛

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an example of continuous annealing equipment, Figure 2 is a graph showing the heat cycle when heat treatment is performed in a continuous annealing furnace, and Figure 3 is an example of equipment for a continuous annealing furnace cooling zone using cooling rolls. Fig. 4 is a time response example of an example of conventional IJ tube cooling. A time chart showing the cases in which the plate thickness of the row material is thinner than that of the preceding material, Fig. 5 is an equipment configuration diagram for explaining an embodiment of the method of the present invention, and Fig. 6 is a diagram showing the case where the plate thickness of the steel of the present invention is thinner than that of the preceding material. This is an example of the time response of an example of the zone cooling method. (a) shows when the thickness of the trailing material is υ thicker than that of the preceding material, and (b) shows that the thickness of the trailing material is υ thicker than that of the leading material. This is a time chart showing all cases of thinness. In the drawing, ■ is a strip, 2; 3, 4, and 5.6 are cooling rolls, 7.8 is a roll drive device, 9.10 is a roll position detector, 11.12 is a winding angle control device, and 13 is a Performance, equipment, 14 is the deflector roll, 15 is the noguru soenator, 16 is the pulse counter, 17 is the boundary detector, 18 is the line speed detector, ■ is the setting value of the winding angle, A is the heating zone, B is the Soaking zone, C is the first cooling zone, Dil-1 is the overaging zone, E is the 2.2 cooling zone, ΔTs is the strip temperature drop, ΔTscn is the upper limit value 1, Patent applicant: Mitsubishi Heavy Industries, Ltd. Kawasaki Steel Patent Attorney Sub-Agent, Patent Attorney Shibu Mitsuishi (1 other person) Figure 1 Capital 11F; 11! (0) Figure 4

Claims (1)

[Claims] A copper strip is wrapped around a cooling roll with refrigerant flowing inside.
In the continuous annealing furnace cooling zone where the cooling roll is moved completely to change the winding angle between the steel strip and the cooling roll when the copper strip cooling temperature is changed, the plate thickness of the trailing side of the steel strip is is thinner than the plate thickness of the leading ladle, the time when the boundary between the trailing material and the leading material reaches the entrance of the cooling zone is also a time earlier than the time corresponding to the response time of the winding angle. A method for cooling a copper strip in a continuous annealing furnace cooling zone, characterized in that changing the setting of the winding angle is started at .