JPH07851A - Method and apparatus for removing ferrous substance from rolling oil - Google Patents

Abstract

PURPOSE:To make the concentration of ferrous impurities in rolling oil controllable and provide stainless steel products with good gloss by immersing a magnet saparator to which a magnet having specified magnetic flux density is attached in rolling oil in a rolling oil tank for a prescribed time to remove the ferrous impurities as low as a specified concentration or less. CONSTITUTION:The lower part of a chain conveyer 3 to which magnet plates 2 with 2000 gauss or more magnetic flux density are attached is immersed in an oil in a rolling oil tank 1 and the chain conveyer 3 is moved in direction shown as the arrow (a) or (b). While passing the liquid surface, the chain conveyer 3 rotates at 30-90 deg. tilting angle against the liquid surface. A plurality of the magnet plates 2 are immersed in the rolling oil for a prescribed time and while moving in the oil, the plates 2 absorb the ferrous impurities, squeeze the effective rolling oil including the ferrous impurities and separate the ferrous impurities based on the magnetic force function, and thus decrease the ferrous impurities concentration to 2000ppm or less in the rolling oil. Then, the absorbed ferrous impurities are scratched and recovered in a scum tank 7 through a scum guide 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an emulsion in which mineral oil is suspended in water as a rolling oil in cold rolling of a stainless steel plate or a steel strip (generally referred to as a stainless steel plate) and has a good surface gloss. The present invention relates to a method and an apparatus for removing iron impurities from the rolling oil to obtain a product.

[0002]

2. Description of the Related Art Since a stainless steel sheet is required to have a product with a good surface gloss, mineral oil is used as a rolling oil as it is during cold rolling, but when high-speed rolling under high pressure is carried out, There is a problem that a seizure phenomenon called heat streak occurs on the surface of the steel sheet, and seizure of the intermediate insertion sheet occurs. On the other hand, using an emulsion in which mineral oil is suspended in water as rolling oil has excellent cooling properties and lubricity, but on the other hand, cold rolling causes severe contamination of the rolling oil, resulting in products with good surface gloss. Since it is not used, it is only used for cold rolling of some austenitic steels and materials for polished finish products. Mineral oil was suspended in water for ferritic steel grades such as SUS430 or martensitic steel grades such as SUS410. It was impossible to carry out cold rolling at high pressure and high speed using the emulsion as rolling oil.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 61-172604, at the time of cold rolling of a Cr-based stainless steel sheet, the concentration of iron contaminants in a rolling oil emulsion containing mineral oil as a base oil is 200 ppm. The following method of rolling is proposed. This method collects and stores the used rolling oil, removes the scum and the rolling oil with a high concentration of iron contaminants in the upper layer below the liquid surface, and then installs a magnetic separator in the clean tank to leave it. Iron impurities are removed and the concentration of iron impurities in the rolling oil is maintained at 200 ppm or less. This magnet separator has been conventionally applied to the field of rolling ordinary steel and the like, and is used for the purpose of removing iron impurities in the rolling oil during cold rolling to reduce the iron concentration to 1000 to 500 ppm or less. It is generally well known that a magnet having a magnetic flux density of 1000 to 1800 gauss has been mainly used.

When this technique is directly applied to the rolling of stainless steel plates, the iron impurities contain a ferromagnetic material like the ordinary steel rolling oil, but have a lower magnetism than the ordinary steel iron impurities. In addition, in the case of a magnet with a magnetic flux density of 1000 to 1800 Gauss, a long immersion time (approximately 1 week) and a large liquid contact surface area are required for adsorption, which makes the separator length too large and the tank capacity also large. However, since the ability to squeeze out the effective rolling oil from the adsorbed iron content impurities is low, there is a drawback in that the effective rolling oil is taken out excessively. Therefore, collect this effective rolling oil,
In order to regenerate, it was essential to install an oil content circulation and recovery device for the coolant scum, which was installed together with the rolling mill as disclosed in Japanese Utility Model Publication No. 57-141813.

As described above, in the cold rolling of stainless steel sheets, it has been desired to develop a method and an apparatus for effectively removing the iron contaminants in the rolling oil without requiring any additional equipment.

[0006]

DISCLOSURE OF THE INVENTION The present invention satisfies the above-mentioned needs and, in order to obtain a product having a good surface gloss, a rolling oil which is provided in a cold rolling system of a stainless steel sheet and which stores a rolling oil to be circulated and used. When recovering the rolling oil waste oil used in rolling in the tank and reusing it, dip a magnet with a higher magnetic flux density in the rolling oil for a desired time to effectively reduce the concentration of iron contaminants in the rolling oil. It is an object of the present invention to provide a method and an apparatus for removing to less than 200 ppm and maintaining the concentration controllable level.

A second object is to suppress the discharge of the effective rolling oil component accompanying the discharge of the iron contaminants to a level at which the rolling oil concentration can be controlled.

[0008]

In order to achieve the above object, in the present invention, (1) a rolling oil containing an iron contaminant used for cold rolling of a stainless steel plate or a steel strip is recovered,
In the method for purifying rolling oil that is stored and circulated, a magnet separator equipped with a magnet having a magnetic flux density of 2000 gauss or more is immersed in a rolling oil tank while being inclined with respect to the liquid level of the rolling oil for a predetermined time to contaminate iron in the rolling oil. The concentration of the object is 200
(2) A method for removing iron in rolling oil, which is characterized by decreasing to ppm or less, and (2) an angle of inclination of the magnet separator with respect to the oil surface within a range of 30 to 90 ° and a liquid contact surface area / rolling oil (m ² / l). ) Is adjusted to 3 × 10 ⁻⁵ m ² / l (l is liter, the same applies hereinafter) and the immersion time of each magnet is set to 2 minutes or more. Iron removal from rolling oil according to the preceding paragraph, Method, and (3) a rolling oil tank for storing the rolling oil that collects and supplies the rolling oil discharged from the rolling equipment is provided with a conveyor equipped with a magnetic separator made of a magnet plate having a magnetic flux density of 2000 gauss or more. The conveyor is disposed at an inclination angle of 30 to 90 ° with respect to the liquid surface, is provided with a scraper that is in contact with a magnet plate outside the rolling oil tank and scrapes off iron impurities adsorbed on the magnet plate. An iron removing apparatus during rolling oil.

The present invention will be described in detail below. Generally, the rolling oil is circulated through the filter, but since the particle size of the oil droplets of the rolling oil emulsion is usually about 5 μm, a filter having a coarser mesh than this is used. When chrome-based stainless steel is cold-rolled, most of the iron impurities contained in the recovered rolling oil have a grain size of 1 μm.
It is said that it cannot be removed by a filter because it is a fine particle of m or less. In addition, the concentration of iron contaminants is 200 when rolled around 1500 tons from the state of fresh oil.
Although it exceeds ppm, the relationship between the rolling amount and the increase in concentration is not always constant, and increasing the frequency of new oil replacement is not preferable in terms of cost. Therefore, the concentration of iron impurities should be 200
To maintain below ppm, scum (iron contaminants, grease, bearing oil,
Contains impurities such as waste oil. ) And the oil above the liquid surface above which the concentration of iron contaminants is high, the concentration of iron contaminants is reduced to 3
After the concentration is reduced to about 50 ppm, it is preferable to further provide a magnet separator in the clean tank to remove the residual iron contaminants and reduce the concentration of the iron contaminants to 200 ppm or less.

In order to remove iron contaminants in oil, it is preferable to immerse and move the magnet plate in a clean tank for a predetermined time. In the present invention, a conventional magnet having a low magnetic flux density is used.
By using a magnet with a high magnetic flux density of 0 gauss or more, the adsorption capacity is improved, and the concentration of iron impurities is reduced to 200 ppm or less. FIG. 1 shows the relationship between the iron content in the oil and the magnetic flux density of the magnet. As is clear from the figure, the conventional 1000 to 180
With a magnet having a magnetic flux density of 0 Gauss, it is impossible to achieve a control limit of 200 ppm or less for the concentration of iron impurities in rolling oil. Therefore, in the present invention, it is essential to use a magnet having a high magnetic flux density of 2000 Gauss or more.

On the other hand, in the present invention, it is preferable to further satisfy the following conditions in order to stably achieve the concentration of iron contaminants at the control limit of 200 ppm or less.
First, the immersion time of the high magnetic flux density magnet in oil and the wetted surface area should be within a predetermined range, that is, the wetted surface area ratio of the magnet (wetted surface area / rolling oil (m ² / l)) 3x
It was found that adjusting to 10 ^-5 m ² / l or more is also an important requirement.

As shown in FIG. 2, which shows the relationship between the wetted surface area ratio of the magnet and the iron concentration in the rolling oil, this ratio is 3 × 10 ^-5 m ²
If it is less than / l, the rolling oil is a magnetic separator (magnet).
The amount of iron that remains is large even though it has the ability to adsorb iron. Therefore, in order to reduce the residual iron content to 200 ppm or less, the content should be 3 × 10 ⁻⁵ m ² / l or more.

Further, it is necessary to control the immersion (oil contact) time of the magnet. Fig. 3 shows the relationship between the iron adsorption capacity of the magnet and the immersion time in oil. That is, the iron content in the rolling oil exists in the state of iron soap and the like, and exhibits hydrophilicity. 2 in this state
When attracted by a magnetic force of 000 Gauss or more, a large amount of water is involved (at 2000 Gauss or less, the attracting force in this state drops significantly). That is, rolling oil accumulates on the magnet surface and the adsorption force decreases. After 2 minutes, only the iron component is attracted to the magnet surface to squeeze out water, and the rolling oil is eliminated. Therefore, the iron adsorption efficiency rises sharply, but reaches a peak in about 5 minutes. After that, the concentrated iron adsorbate is deposited on the surface of the magnet, and the magnetic force of the liquid contact surface gradually decreases.
Although the inclination is gentle, the adsorption ability sharply decreases when the surface magnetic force becomes 2000 gauss or less due to the deposit. A 10 minute soak (2000 gauss) reduces efficiency to 75% of peak. Therefore, it is necessary to remove iron regularly. At 2 minutes it reaches 90% of the peak. On the other hand, iron that is adsorbed adheres to the magnet along with oil.

FIG. 4 shows the relationship between the total amount of adsorbed iron / adsorbed iron content as the iron selective adsorption capacity and the magnet immersion time, using the magnet of 2000 Gauss having a high magnetic flux density used in the present invention. As is apparent, the optimum concentration limit for rolling oil is 400% of the total amount of adsorbed iron to adsorbed iron.
Since the double is the limit value, it is understood that the iron selective adsorption ability is remarkably improved when the magnet immersion time is set to 2 minutes or more. The reason why the ratio of the total amount of adsorption to the amount of adsorbed iron is 400 times is set as a management standard, because when it exceeds this, the oil concentration required for the rolling oil decreases, which causes a hindrance to rolling characteristics.

The magnet used in the present invention may be either a permanent magnet or an electromagnet, but it is preferable to form it into a plate shape. For example, the magnet separator is loaded on the surface of a chain conveyor and immersed in a rolling oil tank. It is advisable to adopt a method of adsorbing the iron contaminants on the surface of the magnet by moving the iron contaminants in the above state. In particular, by inclining the conveyor with respect to the liquid surface, that is, maintaining the inclination angle of 30 ° or more and 90 ° or less, the immersion time of the magnet plate in oil can be adjusted, and the concentration of iron contaminants in oil can easily be 200 ppm.
It becomes possible to reduce to the following. Further, by setting the wetted (oil) surface area (m ² ) of the magnet plate to 3 × 10 ⁻⁵ m ² / l or more per rolling oil (l: liter), it is easy to achieve the iron content in oil to the target value. Become.

FIG. 5 shows an example of a device for removing iron in oil according to the present invention. That is, the rolling oil sent from the dirty tank (not shown) through the filter is the rolling oil tank 1
Magnet plate (magnet plate) 2 that is introduced deep inside
Introduce part of the chain conveyor 3 equipped with
By rotating the motor M, the chain conveyor 3 is operated in the direction of arrow a or b via the speed reducer r. This chain conveyor 3 passes the liquid surface and is at an angle of 30 ° to the liquid surface.
As described above, the magnet plate 2 is installed so as to rotate at an inclination angle of 90 ° or less and move the magnet plate 2. Chain conveyor 3
The plurality of magnet plates 2 mounted on the are immersed in the rolling oil 4 for a predetermined time (2 minutes or more) along with the movement of the chain conveyor 3, and while advancing in the liquid, adsorbing iron contaminants,
Effective rolling oil that encloses impurities is squeezed and separated by the action of magnetic force. Next, the magnet plate 2 that has adsorbed iron and foreign matters moves to the outside of the tank 1 by the operation of the chain conveyor 3,
A magnet plate 2 is provided by a scraper 5 installed near the tank 1 at a position in contact with the magnet plate 2.
The iron contaminants adsorbed on the surface and conveyed to the outside of the tank 1 are scraped off and collected in the scum tank 7 via the scum guide 6.

In order to improve the effect of removing iron contaminants, the rolling oil 4 stored in the tank 1 may be agitated by some means, or the chain conveyor 3 immersed in the tank 1 may be swung. Further, the speed reducer r also functions as a speed changing means for fine adjustment to the iron foreign matter recovery speed or further to the optimum economic speed for the effective rolling oil extraction (separation) efficiency.

[0018]

[Examples] SUS430 was prepared by using a 20-high Sendzimir rolling machine to prepare an emulsion obtained by suspending mineral oil in water as a rolling oil.
Ferrite stainless steel with a plate thickness of 3.8 mm to 0.6 mm
Table 1 shows changes in the reflectance of the cold-rolled sheet when cold-rolled up to. The rolling oil was purified by the apparatus shown in FIG. 3, and in the method of the present invention, a magnet plate having a magnetic flux density of 2500 gauss was used, and one cycle of the conveyor of the portion immersed in oil was set to 2 minutes, and the rolling oil was immersed. On the other hand, the conventional method has a low magnetic flux density (1500 to 1500).
A chain conveyor equipped with a magnet plate of 1800 gauss) was installed while being immersed in the oil in the tank.

[0019]

[Table 1]

As can be seen from the above results, in the conventional method, the cumulative rolling amount is 2000 tons, the concentration of iron impurities exceeds 200 ppm, and the reflectance (JIS Z 874) which represents the gloss of the cold-rolled sheet.
However, it was impossible to use a ferrite-based or martensite-based 2B finished product (measured by Method 4 of 1), but the method of the present invention reduced the concentration of iron impurities to 200 ppm or less. It was possible to suppress, and the reflectance of the cold-rolled sheet remained glossy even after the rolling of 16000 tons, and the 2B finished product could be secured.

[0021]

As described above, according to the present invention, when the rolling oil used for cold rolling of stainless steel is circulated and used, by reliably lowering the iron contaminant concentration in the rolling oil to 200 ppm or less, A bright stainless steel product is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing the iron removal limit in rolling oil by the relationship between the iron content and the magnetic flux density of an attraction magnet plate.

FIG. 2 is a diagram showing a relationship between a contact area ratio of a magnet and an iron content concentration in rolling oil.

FIG. 3 is a diagram showing a relationship between a magnet immersion time in oil and iron adsorption capacity.

FIG. 4 is a diagram showing the iron selective adsorption capacity as a relationship between the ratio of total adsorption / adsorbed iron content and immersion time.

FIG. 5 is a diagram showing an example of a device for purifying rolling oil.

[Explanation of symbols]

 1 Rolling Oil Tank 2 Magnet Plate 3 Chain Conveyor 4 Rolling Oil 5 Scraper 6 Scum Guide a, b Moving Direction r Reducer M Motor

Claims (3)

[Claims] 1. A method of purifying rolling oil which collects and stores and circulates rolling oil containing iron impurities used for cold rolling of stainless steel plate or steel strip, wherein a magnetic flux density of 2000 Gauss is stored in a rolling oil tank. A method for removing iron in rolling oil, which comprises lowering the concentration of iron contaminants in the rolling oil to 200 ppm or less by inclining the magnet separator equipped with the above magnets with respect to the liquid surface of the rolling oil and immersing the magnet separator for a predetermined time. . 2. The inclination angle of the magnet separator with respect to the oil surface is set in the range of 30 to 90 °, and the liquid contact surface area /
The method for removing iron in rolling oil according to claim 1, wherein the rolling oil (m ² / l) is adjusted to 3 × 10 ⁻⁵ or more and the immersion time of each magnet is set to 2 minutes or more. 3. A rolling oil tank for storing the rolling oil that collects and supplies the rolling oil discharged from the rolling equipment is provided with a conveyor equipped with a magnetic separator made of a magnet plate having a magnetic flux density of 2000 gauss or more, and A rolling operation characterized in that the conveyor is arranged at an inclination angle of 30 to 90 ° with respect to the liquid surface, and is provided with a scraper that is in contact with a magnet plate outside the rolling oil tank and scrapes iron contaminants adsorbed on the magnet plate. Equipment for removing iron from oil.