JP3608469B2 - Metal strip degreasing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal strip degreasing device for removing rolling oil and metal powder adhering to a metal strip after cold rolling.
[0002]
[Prior art]
When cold rolling a metal strip, rolling oil or metal powder adheres to the surface of the metal strip. When heat treatment or surface treatment or the like is performed on the metal strip in a subsequent process with the rolling oil or metal powder attached, defects related to the surface quality of the metal strip are generated. Therefore, the rolling oil and metal powder adhering to the metal strip after cold rolling must be removed. As a technique for removing these deposits (hereinafter referred to as degreasing), chemical degreasing and electrolytic degreasing using an alkaline aqueous solution are generally known.
[0003]
In chemical degreasing, a metal strip is continuously immersed in an alkaline aqueous solution (hereinafter referred to as degreasing liquid) such as caustic soda and orthosilicate sodium in a degreasing tank, and a chemical reaction between rolling oil and an alkaline component (hereinafter referred to as “degreasing liquid”). Soap is produced by the saponification reaction, and the rolling oil is removed from the metal strip. At this time, the metal powder is also removed from the metal strip as the metal strip travels in the degreasing liquid. The degreasing tank is provided with a temperature control device including a heating device, and the temperature of the degreasing solution is maintained at 70 to 80 ° C. in order to promote the saponification reaction.
[0004]
Moreover, in order to accelerate | stimulate peeling of rolling oil, electrolytic degreasing is often performed. In electrolytic degreasing, O ₂ gas and H ₂ gas are generated from the surface of the metal strip, and peeling of the rolling oil is promoted by the effect of these gases and the saponification reaction.
As the saponification reaction proceeds, soap is produced and dissolved in the degreasing solution. At the same time, the metal strip travels in the degreasing tank, whereby the degreasing liquid is stirred and the soap is foamed. In particular, when the traveling speed of the metal plate is high, or when the current density of electrolytic degreasing is high, foaming is intense. When soap is foamed, bubbles overflow from the degreasing tank and contaminate the surroundings, resulting in a worse working environment. Further, when the degreasing liquid flows out of the degreasing tank, there is a problem that not only the basic unit of the degreasing liquid is deteriorated but also the operation is hindered and the productivity is lowered.
[0005]
In order to prevent this, it is necessary to lower the traveling speed of the metal strip or to frequently stop the operation and replace the degreasing liquid with a new one, which causes a decrease in productivity. Therefore, it is necessary to suppress the foaming of the soap in the degreasing liquid and to prevent the degreasing liquid from being deteriorated by separating and removing the soap and the metal powder in the degreasing liquid.
Japanese Patent Application Laid-Open No. 11-350176 discloses a continuous treatment line for metal bands. This technique is intended to separate and remove the deposited soap by cooling the degreasing liquid that has been used continuously and has a high concentration of soap. However, in this method, the metal powder mixed in the degreasing liquid cannot be separated and removed, so that there is a problem that the frequency of replacing the degreasing liquid increases because the metal powder stays in the tank.
[0006]
Japanese Patent Laid-Open No. 6-122987 discloses a metal strip cleaning apparatus. This technique is intended to suppress air entrainment by controlling the level of the cleaning liquid to suppress foaming and to remove iron by an iron removal filter. However, this method is disadvantageous economically because the iron removal filter must be frequently replaced with a new one, and the soap concentration in the degreasing liquid rises because the soap dissolved in the degreasing liquid cannot be separated and removed, There was a problem that the degreasing liquid had to be changed frequently.
[0007]
[Problems to be solved by the invention]
The present invention eliminates the above-mentioned problems, suppresses soap foaming caused by a saponification reaction when degreasing a metal strip, and removes soap and metal powder in the degreasing liquid from the degreasing liquid. The purpose is to provide.
[0008]
[Means for Solving the Problems]
The present invention is a degreasing apparatus for degreasing a metal strip by immersing a metal strip in a degreasing liquid in a degreasing tank, and controlling the liquid level of the degreasing liquid in the degreasing tank to a constant level. a device, the degreasing solution soap removal apparatus is cooled to precipitate a soap in the degreasing liquid is removed and a metal dust removing device which is disposed at the bottom a magnet for removing by adsorb the metal powder in the degreasing solution It is a degreasing apparatus of the metal strip which has.
[0009]
In the above-described invention, as a preferred embodiment, the metal strip is preferably a steel strip and the metal powder is preferably iron powder.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a layout view showing an example of the degreasing apparatus of the present invention, and is shown together with a block diagram of a degreasing liquid circulation system.
The metal strip 1 on which the rolling oil or metal powder adheres to the surface by cold rolling is immersed in the degreasing liquid 3 in the degreasing tank 2, and the rolling oil is converted into a metal by a saponification reaction with an alkali component in the degreasing liquid 3. The soap removed from the plate 1 and generated by the saponification reaction is dissolved in the degreasing liquid 3. The temperature of the degreasing liquid 3 is maintained at 70 to 80 ° C. in order to promote the saponification reaction. The metal powder is removed from the metal band 1 when the metal band 1 is immersed in the degreasing liquid 3.
[0011]
The degreasing liquid 3 in the degreasing tank 2 is fed to the circulation tank 5 through the return pipe 4 together with soap and metal powder. The circulation tank 5 is divided by a partition plate 10, and receives a degreasing liquid 3 from the degreasing tank 2 via the return pipe 4 (hereinafter referred to as a return tank 16) and the degreasing liquid 3 to the degreasing tank 2 via the feed pipe 6. And a tank (hereinafter referred to as “feed tank 17”).
[0012]
Since the metal powder in the degreasing liquid 3 in the return tank 16 has a large specific gravity, it settles at the bottom of the return tank 16, and the soap floats to the upper layer of the degreasing liquid 3 because the specific gravity is small.
The degreasing liquid 3 at the bottom of the return tank 16 is fed to the metal powder removing device 9 together with the mixed metal powder. Also in the metal powder removing device 9, the metal powder settles to the bottom. A magnet 14 is disposed at the bottom of the metal powder removing device 9, and the settled metal powder is attracted to the magnet 14. The degreasing liquid 3 from which the metal powder has been removed in this way is fed to the feed tank 17 of the circulation tank 5.
[0013]
When discharging the metal powder adsorbed by the magnet 14 of the metal powder removing device 9, the magnetic force of the magnet 14 is released, and the drain valve 18 is opened and discharged. In the present invention, an electromagnet may be used as the magnet 14 or a permanent magnet may be used. When the magnet 14 is an electromagnet, the magnetic force can be released by turning off the current, and when the magnet 14 is a permanent magnet, the magnetic force can be released by removing the magnet 14. However, it is preferable to use an electromagnet because the magnetic force can be easily released.
[0014]
A flow path of the degreasing liquid 3 is provided between the lower end of the partition plate 10 and the bottom surface of the circulation tank 5, and the degreasing liquid 3 circulates between the return tank 16 and the feed tank 17. Therefore, when the drain valve 18 is opened and the metal powder at the bottom of the metal powder removing device 9 is discharged, the rapid fluctuation of the liquid level in the return tank 16 can be suppressed, and the foaming of soap in the degreasing liquid 3 can be suppressed. Therefore, the outflow of the degreasing liquid by foaming of soap can be suppressed. However, since the degreasing liquid 3 decreases by opening the drain valve 18, a new liquid must be replenished. However, since the frequency is low, the influence on the basic unit is small.
[0015]
On the other hand, the upper layer of the degreasing solution 3 is fed to the soap removing device 7 together with the dissolved soap. The degreasing liquid 3 in the soap removing device 7 is cooled to a temperature equal to or lower than the soap precipitation temperature, and dissolved soap is deposited. Although the example of the structure which cools the degreasing liquid 3 in the soap removal apparatus 7 using the cooling water 8 as the soap removal apparatus 7 was shown in FIG. 1, in this invention, about cooling of the degreasing liquid 3, it is a specific structure. However, the cooling may be performed using a refrigerant or a cooling bath. The deposited soap is removed by the filter 15, and the degreasing liquid 3 is fed to the feeding tank 17 of the circulation tank 5.
[0016]
The degreasing liquid 3 from which the soap and metal powder have been removed in this way is once stored in the feed tank 17 and fed from the feed tank 17 to the degreasing tank 2 via the feed pipe 6. Since the degreasing liquid 3 from which the soap has been removed is at a low temperature, the temperature of the degreasing liquid 3 in the degreasing tank 2 is temporarily lowered when the degreasing liquid 3 is fed from the feeding tank 17 to the degreasing tank 2. However, since the heating device and the temperature control device are disposed in the degreasing tank 2, there is no particular problem.
[0017]
The degreasing tank 2 is provided with a liquid level detector 11 for detecting the liquid level. The liquid level data detected by the liquid level detector 11 is processed by the liquid level controller 12 as an input signal, and the obtained output signal is transmitted to the regulating valve 13. By controlling the flow rate of the return pipe 4 in this way, the liquid level of the degreasing liquid 3 in the degreasing tank 2 is controlled to be constant. If the liquid level of the degreasing liquid 3 in the degreasing tank 2 is controlled to be constant, fluctuations in the liquid level of the degreasing liquid 3 in the degreasing tank 2 are suppressed, and foaming of soap in the degreasing liquid 3 can be suppressed. Therefore, the outflow of the degreasing liquid 3 due to soap foaming can be prevented.
[0018]
In addition, although the example which arrange | positions the soap removal apparatus 7 and the metal powder removal apparatus 9 in the circulation tank 5 was demonstrated here, even if it arrange | positions the soap removal apparatus 7 and the metal powder removal apparatus 9 in the degreasing tank 2, it is the same. The effect can be obtained, and the same effect can be obtained even if the degreasing tank 2 and the circulation tank 5 are disposed.
Moreover, although the example which chemically degreases by immersing the inside of the degreasing liquid 3 in the degreasing tank 2 was demonstrated here, the same effect is acquired also when providing an electrode in the degreasing tank 2 and performing electrolytic degreasing. It is done.
[0019]
If the metal strip 1 is a metal having magnetism, the present invention can be applied because the metal powder produced by cold rolling also has magnetism. In particular, when the metal strip 1 is a cold-rolled steel sheet, it is preferable because it has magnetism and is produced continuously and in large quantities, so that a great effect can be obtained.
[0020]
【Example】
Using the degreasing apparatus shown in FIG. 1, cold rolled cold rolled steel sheets (thickness 0.25 mm, width 900 mm) were degreased. As the degreasing solution 3, an aqueous sodium orthosilicate solution having a concentration of 2% by mass was used. The sheeting speed of the cold rolled steel sheet was 1100 m / min. When the degreasing liquid 3 decreased due to discharge of iron powder at the bottom of the metal powder removing device 9 or the like, the new liquid was supplied and the operation was continued. This is an invention example.
[0021]
Furthermore, as a comparative example, using a conventional degreasing device that does not have the soap removing device 7 and the metal powder removing device 9 as shown in FIG. The dimensions of the cold-rolled steel sheet, the sheet passing speed, and the components of the degreasing liquid are the same as those of the invention example. When the degreasing liquid 3 decreased due to soap foaming, a new liquid was replenished. When the soap concentration increased and the degreasing liquid 3 deteriorated, the degreasing liquid 3 was replaced with a new liquid and the operation was continued.
[0022]
In the invention example, the scattering of the degreasing liquid 3 due to foaming of the soap in the degreasing liquid 3 and the deterioration of the degreasing liquid 3 due to an increase in soap and iron powder in the degreasing liquid 3 can be suppressed. The ratio of the used amount (kg) of the degreasing liquid 3 to that of the degreasing liquid, that is, the basic unit (kg / t) of the degreasing liquid 3 was reduced by 24% compared to the comparative example.
[0023]
【The invention's effect】
According to the present invention, when degreasing a cold-rolled metal strip, the outflow of the degreasing liquid is suppressed by suppressing soap foaming caused by the saponification reaction, and the soap and metal powder in the degreasing liquid are separated. By removing, the deterioration of the degreasing liquid can be prevented, thereby preventing the working environment from deteriorating and reducing the basic unit of the degreasing liquid.
[Brief description of the drawings]
FIG. 1 is a layout view showing an example of a degreasing apparatus according to the present invention, together with a block diagram of a degreasing liquid circulation system.
FIG. 2 is a layout view showing an example of a conventional degreasing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal strip 2 Degreasing tank 3 Degreasing liquid 4 Return pipe 5 Circulating tank 6 Feeding pipe 7 Soap removal apparatus 8 Cooling water 9 Metal powder removal apparatus 10 Partition plate 11 Liquid level detector 12 Liquid level controller 13 Adjustment valve 14 Magnet 15 Filter 16 Return tank 17 Feed tank 18 Drain valve

Claims (2)

A degreasing apparatus for degreasing the metal band by immersing a metal band in a degreasing liquid in a degreasing tank, wherein the liquid level of the degreasing liquid in the degreasing tank is controlled to be constant, and , and soap removal device for removing by precipitating soaps degreasing solution by cooling the degreasing solution, the metal dust removing device of the metal powder is disposed at the bottom a magnet for removing by adsorb in said degreasing solution A metal strip degreasing device characterized by comprising: The metal strip degreasing device according to claim 1, wherein the metal strip is a steel strip and the metal powder is an iron powder.

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