JPS6231055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal strip cooling method using a cooling roll, in which a high-temperature strip is brought into contact with the outer peripheral surface of a cooling roll through which a refrigerant is circulated, and the strip is cooled by running at a constant speed.

Metallurgically, steel strips (metal strips) must be heated to a predetermined annealing temperature in a continuous annealing furnace, soaked, and then cooled at a rate of 30 to 150°C/S to the overaging start temperature. There are several cooling methods: gas jets, water sprays, fogs, and cooling rolls with refrigerant flowing inside. Not only does the power required to form the steel strip significantly increase, resulting in a loss of economic efficiency, but it also becomes impossible to plan the equipment.In addition, when water spray or fog is used, water comes into contact with the surface of the steel strip, causing damage to the steel strip. Since the surface is oxidized, it is necessary to clean the surface by pickling, etc., which not only complicates the equipment, but also reduces the bondability of the steel plate surface. As a cooling method in strip heat treatment equipment, it is considered advantageous to wind the high temperature metal strip around a cooling roll to form a contact state and cool the strip.

The metal strip is cooled by a cooling roll, as shown in FIGS. 1A and 1B, a cooling roll 1 is supported by a bearing 5 and is fixed to a rotating shaft 3 via rotary joints 4, 4. Refrigerant supply and drain pipes 13 and 11 are connected, and the supply and drain pipes 13 and 1
1 and the rotating shaft 3 allow the refrigerant to flow within the chamber 6 of the cooling roll 1.
A high-temperature metal strip a running at a predetermined constant speed passes through cooling rolls 1, 1, . . . as shown in FIG. 1B.
It is designed to be cooled by being in contact with the air.

However, when water is used as the refrigerant flowing through the cooling roll in the cooling of the metal strip using the cooling roll, if the amount of water in the cooling roll is small and the temperature of the metal strip exceeds 100°C, When the refrigerant water boils, the amount of cooling in the width direction of the metal strip becomes uneven, and the temperature difference in the width direction of the metal strip causes the metal strip to become defective due to wrinkles, cracks, etc., and the product value is lost. In addition, even if there is a large amount of refrigerant water in the cooling roll that does not boil, the contact of the metal strip to the cooling roll is insufficient and unbalancedness cannot be avoided, resulting in poor transmission between the two. This causes a difference of about 1:5 to 1:10 in the amount of heat, so if the wrapping angle (contact length) of the metal strip with respect to the cooling roll and the amount of temperature drop of the metal strip per cooling roll are large, the metal strip will The problem is that the same phenomenon as described above occurs and the product value is lost.

The present invention was developed in order to solve the above-mentioned difficulties in the conventional method of cooling a metal strip using a cooling roll. In a cooling method in which the high-temperature metal strip is cooled by running at a constant speed, the critical temperature drop ΔT _SCR per roll in the high-temperature metal strip is determined by the temperature T _S1 of the same strip before contact with the same roll and the temperature difference ΔT _S before and after contact with the roll. In connection with this, one or more of the high temperature metal strips are held in the range from ΔT _SCR = 120-T _S1 /20 (°C) to ΔT _S ≦ΔT _SCR by the setting of the cooling roll and the refrigerant. It is characterized in that it is continuously cooled by the cooling roll, and its purpose is to improve the relationship between the temperature conditions of the high-temperature metal strip in a cooling method using a cooling roll in which the metal strip is not brought into contact with a refrigerant. cooling roll 1
The object of the present invention is to provide a method for cooling a metal strip using a cooling roll, which can prevent the shape of the metal strip from being disturbed by specifying the critical temperature drop in the actual metal strip.

The method of the present invention has the above-mentioned configuration, and in the method of cooling a metal strip using a cooling roll, the critical temperature drop ΔT _SCR per cooling roll in a high-temperature metal strip is determined by the temperature T _S1 of the same strip before contact with the same roll. In relation to the temperature difference ΔT _S before and after the roll contact, ΔT _SCR = 120−T _S1 /20 (℃), ΔT _S ≦ΔT _SCR
The high-temperature metal strip is held within this range by setting the cooling roll and refrigerant, and the high-temperature metal strip is continuously cooled by one or more cooling rolls, so that it runs in contact with the outer peripheral surface of the cooling roll and cools. The temperature difference in the width direction of the high-temperature metal strip that is processed is extremely small, and the high-temperature metal strip has almost no wrinkles, wilting, etc., and can be cooled continuously and efficiently, significantly improving the product value. can.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The method for cooling a metal strip according to an embodiment of the present invention is carried out using an apparatus as shown in FIGS. 1A and B and FIG. 2, and the cooling roll 1 used for cooling is As shown in FIG. 1A, refrigerant flows from the liquid supply pipe 13 through the rotary joint 4 and the rotary shaft 3 into the chamber 6 (general cavity or annular cavity in cross section) of the cooling roll 1. is supplied, the cooling roll 1 is cooled from inside by the refrigerant, and the refrigerant is discharged from the drain pipe 11 through the through hole of the rotating shaft 3 and the rotary joint 4 on the right side of the drawing. One or more cooling rolls 1 are arranged at appropriate intervals as shown in FIG. They are in contact with each other and run at a predetermined constant speed to be continuously cooled.

Further, the refrigerant flowing inside the cooling roll 1 is passed through a refrigerant circulation path which is connected from a refrigerant drain pipe 11 fixed by a rotary joint 4 to a refrigerant supply pipe 13, as shown in FIG. The refrigerant is circulated through the drain pipe 11 and sent to the storage tank 7 equipped with a level meter, and the refrigerant in the storage tank 7 is sent into the heat exchanger 9 via the supply pipe 12' by the pump 8 for cooling. After that, the cooling roll 1 is removed from the liquid supply pipe 13 side.
The heat exchanger 9
Since the amount of cooling liquid in the cooling pipe 15 can be adjusted by the flow rate control valve 10, the temperature of the refrigerant supplied into the cooling roll can be adjusted. Note that when water is used as a refrigerant, the heat exchanger 9, the storage tank 7, and the piping 12 between the storage tank 7 and the pump 8 are not necessarily required, and instead, the pump 8 is connected from the water supply source. The refrigerant water can be replenished at the drain pipe 11, and the drain pipe 11 can be connected to a drain pit, etc. In addition, the refrigerant circulation path shown in FIG.
A replacement mechanism (not shown) is provided to replace the refrigerant with water, oil, molten salt, etc.

The high-temperature metal strip a to be cooled is passed around an appropriate number of chill rolls 1 arranged at a predetermined contact angle as shown in FIG. It contacts the outer circumferential surface of the cooling roll 1 which is being rotated within a predetermined contact range and is cooled by running at a predetermined constant speed.

In the cooling, if the surface temperature of the cooling roll 1 is T _R , the temperature before the high-temperature metal strip a contacts the roll 1 is T _S1 , and the temperature after contacting the roll 1 is T _S2 , then T _R <T In the state _S2 , the high temperature metal strip a is cooled by removing heat from it by the cooling roll 1. What is important in this cooling is the ideal relationship between the cooling roll 1 and the same metal strip a. In other words, the two should maintain a sufficiently even contact state in the width direction and the length direction within the contact angle, but in practice this cannot be expected and uneven contact tends to occur. There will be a difference in the amount of heat removed between the metal strips a and the metal strip a, which will cause the metal strip a to have a disordered shape, which will impair the product value.

Therefore, in the present invention, the following result was obtained through experiments regarding the critical temperature drop ΔT _SCR in the metal strip a per 11 cooling rolls, which does not cause any disturbance in the shape of the metal strip a. That is, ΔT _SCR = 120-T _S1 /20 (℃) ... (1) where T _S1 is the temperature of the metal strip before contact with the roll. Also, the temperature of the metal strip a before contact with the roll T
The difference between _S1 and the temperature after contact with the roll T _S2 is T _S1 − T _S2 =
Assuming that ΔT _S (temperature difference before and after roll contact), the temperature difference ΔT _S before and after roll contact is as follows: ΔT _S = CK ( _S − _W ) ...(2) However, K is the heat transfer rate between the refrigerant and the metal strip (Kcal /m ² /℃) _S is the average temperature of the metal strip in contact with the cooling roll (℃) _W is the average temperature of the refrigerant (℃) C is the roll diameter, wrapping angle, and speed of the metal strip , a constant determined by thickness, specific heat, and specific weight (m ² h
°C/Kcal) It was found that it can be expressed by the above formula.

Therefore, the relationship between equations (1) and (2) above is (1)≧(2)
The formula becomes ΔT _SCR ≧ΔT _S ... (3), and from the above equations (1) and (3), ΔT _SCR = 120−T _S1 /20 (℃), ΔT _S ≦ ΔT _SCR The basic condition for each cooling roll 1 is that the metal strip a can be cooled without disturbing its shape.

As shown in equation (1) above, ΔT _SCR is directly affected by T _S1 , and when T _S1 changes, the equation (2) above changes.
In relation to _S − _{W, W} will be regulated, and T _S1
In relation to ΔT S and ΔT _S , a condition is required in which T _W must be set to 100°C or higher.

Therefore, it corresponds to the temperature conditions of the refrigerant, and furthermore,
It became necessary to use water, oil, and molten salt liquid as refrigerants, and the following results were obtained through experiments.

Refrigerant temperature range Type of refrigerant T _W <100℃ Water 50℃≦T _W ≦300℃ Oil 150℃≦T _W ≦700℃ Molten salt liquid Furthermore, when calculating ΔT _S in equation (2) above, It was found that the value of the heat transfer coefficient K between the refrigerant and the metal strip a is affected, and this K value is determined by the heat transfer coefficient between the refrigerant and the inner surface of the cooling roll 1, the shell thickness of the roll, and the mechanical finish of the roll surface. It is a function of the heat transfer coefficient and the heat transfer coefficient of the gaseous substance interposed in the gap caused by the unevenness and the rolling finish of the metal strip. Therefore, the heat transfer rate K between the refrigerant and the metal strip a is determined by the material of the roll shell, the contact (wrapping)
Considering angle, roll surface roughness, etc., K=a/ln〓...(4) However, β is the contact (wrapping) angle, and a and b are the roll shell material, surface roughness, and type of refrigerant. , a constant determined by the thickness of the roll shell, line speed, etc. It can be expressed by the above formula (4), and further, a=3640~15000 b=1~10 However, 3653≦a×b≦15000 and , 10°<β<180°.

Furthermore, T _W , that is, the refrigerant temperature, can be changed as a factor that determines ΔT _S . For this purpose, as shown in FIG. 2, an adjustable heat exchanger 9 is provided in the refrigerant circulation path, and by changing the flow rate and temperature of the refrigerant, the refrigerant supplied into the cooling roll 1 can be set and controlled. That's what I do.

As described above, when cooling a high-temperature metal strip with a cooling roll, the cooling roll is set as described above so that the critical temperature drop per cooling roll on the high-temperature metal strip falls within a specific range.
By regulating the type of refrigerant and setting the temperature, etc., it is possible to efficiently and continuously cool the metal strip without causing any disturbance in its shape, and the product value can be significantly improved. .

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

FIG. 1A is a longitudinal sectional view of a cooling roll for carrying out the method of the present invention, FIG. 1B is a layout diagram of the cooling roll and metal strip in FIG. 1A, and FIG. 2 is a diagram of the refrigerant supply mechanism to the cooling roll. be. 1: Cooling roll, 3: Rotating shaft, 4: Rotary joint, 5: Bearing, 6: Chamber, 7: Storage tank, 8: Pump, 9: Heat exchanger, 10: Flow rate control valve, 11: Drain pipe , 13: Liquid supply pipe, a: Metal strip.

Claims (1)

[Scope of Claims] 1. In a cooling method in which a high-temperature metal strip is brought into contact with the outer peripheral surface of a cooling roll through which a refrigerant is circulated and is run at a constant speed to cool the roll, the limit per roll of the high-temperature metal strip is provided. The temperature drop ΔT _SCR is calculated by the temperature T _S1 of the same strip before contact with the same roll and the temperature difference ΔT _S before and after contact with the same roll.
In connection with this, one or more of the high-temperature metal strips are held in the range from ΔT _SCR =120−T _S1 /20 (°C) to ΔT _S ≦ΔT _SCR by the settings of the cooling roll and the coolant. A method for cooling a metal strip using a cooling roll, characterized in that the metal strip is continuously cooled by the cooling roll.