JPH05320964A - Device for continuously pickling metallic strip - Google Patents

Abstract

(57) [Summary] [Purpose] The temperature of the metal strip entering the pickling tank is lowered to prevent seizure of the draining roll, and the flow rate of the cooling water from the cooling water injection means is reduced as much as possible so that the alkaline substance becomes water-soluble. Try to reduce the amount of processed liquid. [Structure] A salt bath, an air cooling means, a hot water tank, a cooling water injection means, and a pickling tank are arranged in this order, and the temperature of the metal strip is controlled by the first temperature detection means on the outlet side of the cooling water injection means, It is detected by the second temperature detecting means on the outlet side of the water tank, and the temperature of the metal strip on the inlet side of the pickling tank is changed to the inlet side of the pickling tank by the outputs of the first and second temperature detecting means. The respective values of the cooling air flow rate and the cooling water flow rate are controlled so as to be lowered to a temperature at which seizure of the provided draining roll does not occur, and further, the flow rate of the cooling water from the cooling water injection means is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous pickling apparatus for metal strips such as stainless steel strips and titanium plates.

[0002]

2. Description of the Related Art Conventionally, a cold rolled stainless steel strip is passed through a salt bath as a pretreatment for pickling in the step of continuously annealing and pickling. The temperature of the salt bath is maintained at about 773K, and the stainless steel strip exits the salt bath and is cooled by the air cooling means, the hot water tank and the cooling water jetting means. After being cooled with water, the steel strip passes through a draining roll provided on the inlet side of the pickling tank. At that time, if the steel strip reaches a temperature higher than the heat resistant temperature of the draining roll, seizure occurs on the steel strip. Therefore, the steel strip must be kept below the heat-resistant temperature of the draining roll. At present, the temperature of the hot water tank is measured, and the flow rate of the cooling water injection means is manually controlled so that the temperature becomes less than about 373K. ing. However, the control differs depending on the operator, and the flow rate may be too large to exceed the maximum amount of water treatment in the hot water tank, and it is a very difficult task to keep the temperature of the steel strip constant. It was Here, the water treatment in the hot water tank is to remove the water-soluble alkaline substance adhering to the surface of the steel strip in the salt bath in the hot water tank, and drain the water. Therefore, it is necessary to consider not only the temperature but also the throughput of water to control the flow rate of the cooling water injection means.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the amount of cooling water used as much as possible and to prevent the temperature of the metal strip immediately before the pickling tank from becoming abnormally high. It is an object of the present invention to provide a continuous pickling device for a metal strip.

[0004]

According to the present invention, a salt bath for immersing a metal strip, an air cooling unit for cooling the metal strip from the salt bath with cooling air, and a metal strip for immersing the metal strip in the water are immersed in water. A hot water tank for cooling, a cooling water jetting means for jetting cooling water to cool the metal strip from the hot water tank, and a pickling bath for pickling the metal strip from the cooling water jetting means by dipping it in a pickling solution. First temperature detecting means for detecting the temperature of the metal strip on the outlet side of the cooling water injection means, and second for detecting the temperature of the metal strip on the outlet side of the hot water tank.
In response to the outputs of the temperature detecting means and the first and second temperature detecting means, the temperature detected by the first temperature detecting means is controlled to be less than a predetermined value, and the cooling water flow rate from the cooling water injection means is A continuous pickling device for a metal strip, comprising means for controlling the respective values of the cooling air flow rate and the cooling water flow rate so as to be as small as possible.

[0005]

According to the present invention, a salt bath called a soft bath is used as a pretreatment for pickling a metal strip such as a stainless steel strip in a pickling bath. The salt bath, the air cooling means, the hot water tank, the cooling water spraying means, and the pickling tank are arranged in this order, and the temperature of the metal strip is adjusted by the first temperature detecting means on the outlet side of the cooling water spraying means and the temperature of the hot water tank. The temperature detected by the second temperature detecting means on the side, and in response to the respective outputs of the first and second temperature detecting means, the temperature detected by the first temperature detecting means, that is, the acid from the outlet side of the cooling water injection means. The temperature of the metal strip entering the washing tank is lower than a predetermined value, for example, the draining roll provided on the inlet side of the pickling tank does not cause seizure, and the cooling water from the cooling water injection means is used. The respective values of the flow rate of cooling air and the flow rate of cooling water are controlled so that the flow rate of is as small as possible. This reduces the throughput of cooling water.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall simplified system diagram of an embodiment of the present invention. The stainless steel strip 1 is formed by pickling and removing the surface scale and the like generated during the annealing in the previous step,
As a pretreatment for making it easier to remove by this pickling, first, for example, it is introduced into an oxidizing salt bath 2. The stainless steel strip 1 is guided from the deflector roll 3 to the sink roll 4 and immersed in the molten salt in the bath to be subjected to a salt bath treatment, and is guided to the air cooling means 6 via the deflector roll 5. The molten salt 7 used in the salt bath 2 is, for example, NaO.
Add NaNO ₃ or KNO ₃ to H to give about 480-52
Heat to 0 ° C. The stainless steel strip 1 immersed in such molten salt 7 is cooled by cooling air in the air cooling means 6. Cooling air at room temperature, for example, is pressure-fed to the air-cooling means 6 by the fan 8 and is jetted from the nozzle 9 onto the stainless steel strip 1. The rotation speed of the fan 8 can be changed, whereby the flow rate of the cooling air can be adjusted. The stainless steel strip 1 air-cooled by the air-cooling means 6 is guided by the sink roll 11 in the hot water tank 10 and immersed in the hot water 12 for cooling. The stainless steel strip 1 cooled in the warm water tank 10 is cooled by the cooling water jetted from the nozzle 14 in the cooling water jetting means 13. The cooling water jetted from the nozzle 14 comes into contact with the stainless steel strip to lower the temperature of the stainless steel strip, and then flows on the bottom 15 of the cooling water jetting means 13 to reach the hot water tank 10.
Stored in. The stainless steel strip 1 cooled in the cooling water jetting means 13 passes through the draining roll 17 of the pickling tank 16 and is dipped in a pickling solution such as H ₂ SO ₄ , HNO ₃ and HF for pickling.

FIG. 2 is a block diagram showing the electrical construction of the embodiment shown in FIG. The temperature of the stainless steel strip 1 on the outlet side of the cooling water jetting means 13 is detected by the first temperature detecting means 18. The temperature of the stainless steel strip 1 on the outlet side of the hot water tank 10 is detected by the second temperature detecting means 19. The outputs of these temperature detecting means 18 and 19 are given to an arithmetic processing circuit 20 realized by a microcomputer or the like. From the input means 21, the upper limit value of the temperature detected by the first temperature detection means 18 on the outlet side of the cooling water injection means 13 is input. When the detected temperature is equal to or lower than the upper limit value, the heat of the stainless steel strip 1 is input. As a result, there is no risk of seizure of the draining roll 17 of the pickling tank 16, and the amount of cooling water to be treated can be reduced. The control means 22 responsive to the output of the arithmetic processing circuit 20 controls the rotation speed of the fan 8, and thus the flow rate of the cooling air, and
The opening degree of the flow control valve 23 is controlled. Cooling water from a cooling water source 24 including a pump or the like is supplied from the flow control valve 23 to the nozzle 14 of the cooling water injection means 13.

FIG. 3 is a flow chart for explaining the operation of the arithmetic processing circuit 20. When the temperature T1 detected by the first temperature detecting means 18 is less than the upper limit value T0 set by the input means 21, the process proceeds from step a1 to step a2, and the fan 8 is operated at step a11.
The rotation speed N of is reduced. When the temperature T1 detected by the first temperature detecting means 18 in step a2 is equal to or higher than the predetermined temperature T0, the process proceeds to step a3, in which the rotation speed N of the fan 8 is increased to increase the cooling air supplied to the air cooling means 6. Increase the flow rate. In step a4, the rotation speed N of the fan 8 is a predetermined value, for example, the rated speed N0.
When it is judged that the above is the case, the following step a
5, the control means 22 is operated to keep the rotation speed N of the fan 8 constant at the rated speed N0.

At this time, when the temperature T1 detected by the first temperature detecting means 18 in step a6 becomes equal to or higher than the predetermined temperature T0, the process proceeds to step a7 and the temperature difference ΔT.
(= T2-T1) is calculated. Where temperature T2
Is the temperature of the stainless steel strip 1 on the outlet side of the hot water tank 10 detected by the second temperature difference detection means 19. This temperature difference ΔT is the cooling temperature of the stainless steel strip 1 to be cooled by the cooling water in the cooling water jetting means 13. In step a8, the cooling water flow rate Q corresponding to this temperature difference ΔT is determined in accordance with the speed, size and shape of the stainless steel strip 1. In the input means 21, the width, thickness, etc. of the stainless steel strip 1 are input in advance.

At step a9, the first temperature detecting means 18
When it is determined that the temperature T1 detected by is the predetermined temperature T0, the operation is stopped in step a12. When it is determined that the temperature T1 of the stainless steel strip 1 detected by the temperature detecting means 18 is less than the predetermined value T0 described above, the flow rate control valve is maintained at the constant cooling water flow rate Q in step a13. The operation is continued with the cooling water sprayed from the nozzle 23 through the nozzle 14.

In this way, the flow rate of the cooling air supplied from the nozzle 9 in the air cooling means 6 is increased as much as possible, while the flow rate of the cooling water injected from the nozzle 14 of the cooling water injection means 13 is reduced as much as possible. In addition, the pickling tank 16 is controlled by suppressing an abnormally high temperature of the stainless steel strip 1 detected by the first temperature detecting means 18.
Prevents seizure of the draining roll 17 of the hot water tank 1
It is possible to reduce the flow rate of water to be treated in the treatment tank 25 for neutralizing the hot water 12 of 0.

The present invention can be broadly implemented for continuous pickling of stainless steel strips as well as other metal strips.

[0013]

As described above, according to the present invention, the metal strip is guided to the pickling tank through the salt bath, the air cooling means, the hot water tank and the cooling water injection means, and the temperature of the metal strip is output from the cooling water injection means. First on the side
The temperature of the metal strip detected by the temperature detecting means and the second temperature detecting means on the outlet side of the hot water tank and detected by the first temperature detecting means when entering the pickling tank is less than a predetermined value. Moreover, each value of the cooling air flow rate and the cooling water flow rate is controlled so that the cooling water flow rate from the cooling water injection means is reduced as much as possible, so that the temperature of the metal strip supplied to the pickling tank becomes abnormally high. This prevents, for example, the draining roll on the inlet side of the pickling tank from causing seizure, and the cooling water flow rate can be reduced, so that the alkaline substance from the warm water tank is dissolved. It requires less amount of liquid to be processed and drained.

[Brief description of drawings]

FIG. 1 is an overall system diagram of an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the embodiment shown in FIG.

FIG. 3 is a flowchart for explaining the operation of the arithmetic processing circuit 20 shown in FIGS. 1 and 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stainless steel strip 2 Salt bath 6 Air cooling means 7 Molten salt 8 Fan 9 Nozzle 10 Hot water tank 13 Cooling water injection means 14 Nozzle 16 Pickling tank 17 Draining roll 18 First temperature detecting means 19 Second temperature detecting means 20 Arithmetic processing circuit 21 Input Means 22 Control Means 23 Flow Control Valve 24 Cooling Water Source 25 Waste Water Treatment Tank

Claims (1)

[Claims] 1. A salt bath for immersing a metal strip, air cooling means for cooling the metal strip from the salt bath with cooling air, a hot water tank for immersing and cooling the metal strip from the air cooling means, and a hot water tank. Cooling water spraying means for spraying and cooling cooling water on the metal strips from, the pickling tank for dipping the metal strips from the cooling water spraying means in the pickling solution and pickling, and the outlet side of the cooling water spraying means The first temperature detecting means for detecting the temperature of the metal strip, the second temperature detecting means for detecting the temperature of the metal strip on the outlet side of the hot water tank, and the first temperature detecting means for responding to the outputs of the first and second temperature detecting means. 1. Each value of the cooling air flow rate and the cooling water flow rate is controlled so that the temperature detected by the temperature detection means becomes less than a predetermined value, and further, the cooling water flow rate from the cooling water injection means becomes as small as possible. A continuous pickling apparatus for a metal strip, which comprises: