JPS6124086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for circulating rolling oil in cold rolling of steel sheets.

During cooling rolling of steel plates, rolling oil (also commonly called coolant) is used for both cooling and lubrication.
is used in large quantities. This method is broadly divided into two types: direct system and recirculation system. Direct systems use only new rolling oil, and recirculation systems recycle rolling oil.

In the recirculation system, rolling oil is mixed with water and stirred to form an emulsion with a predetermined concentration, which is supplied to the rolling mill and the rolled material. After use, a filter removes foreign matter mixed in during rolling and the oil is collected in a tank. Then use this cyclically.

Rolling oil usually contains various additives. When the rolling oil is recycled in this manner, the rolling oil deteriorates between the rolling rolls during rolling, or is attached to the product and carried on, resulting in a change in performance at the initial stage of circulation. Therefore, replenish new oil in the tank. However, it takes a considerable amount of time to uniformly mix the new oil with the rolling oil in the tank, so there is a problem in that rolling oil with desired properties cannot be obtained during that time.

In addition, a magnetic separator is installed in the tank to remove fine iron powder mixed into the rolling oil during circulation, but this magnetic separator carries the rolling oil out of the tank along with the iron in the oil. . The amount carried away is 6 parts oil to 2 parts Fe.
~7 parts, about 2 parts water.

Additionally, some additives added to rolling oil have the property of easily bonding with iron, such as extreme pressure additives, and it has been observed that these are also removed to a large extent. Furthermore, although the new rolling oil replenished has a higher concentration than the rolling oil normally used in circulation, it may be carried away from the system by the magnetic separator and wasted before it is sufficiently homogenized in the tank. .

In this way, rolling oil is also consumed by the magnetic separator. As described above, the wear caused by the magnetic separator lowers the concentration of rolling oil and the concentration of additives since the rate of oil carried away is higher than that of water. Conventionally, the oil removed from the circulation system in the form of scum by the magnetic separator was discarded.

As described above, conventional rolling oil recirculation systems equipped with iron removal devices such as magnetic separators have various drawbacks, and the present invention is intended to solve these drawbacks. This is because in a rolling oil recirculation system, the iron removal device collects the oil that has been taken out of the circulation system along with iron to obtain recovered oil, and then adds additives to the recovered oil. This is a method of supplying oil in a rolling oil recirculation system, characterized in that after adjusting the concentration, the oil is supplied to a material to be rolled or to a roll to join a circulation system.

In the present invention, a mixture of iron and rolling oil (in the form of scum) discharged outside the circulation system by an iron recovery device installed in a rolling oil tank is passed through a centrifuge or the like to separate and remove the iron, and only the rolling oil is recovered. Appropriate amounts of additives such as emulsifiers, oiliness improvers, and extreme pressure additives are added to the recovered rolling oil to improve the properties of the recovered rolling oil. Next, the concentration is adjusted by adding water (warm water), new oil, etc. to the recovered rolling oil according to the usage mode (rolling conditions at that time, etc.), and the mixture is stirred to form an emulsion, which is then added to the circulation system. It is fed directly to the material to be rolled or to the rolling rolls in a separate supply system, and is made to join the rolling oil in the circulation system. During rolling, rolling oil is carried out by strips, humps, etc. Although this amount of oil is much smaller than the amount of oil that is removed together with iron by a magnetic separator or the like, the concentration of rolling oil in the circulation system changes (decreases). New oil is also supplied to compensate for this concentration.

FIG. 1 shows the properties of the rolling oil thus recovered in terms of friction coefficient. Figure 1a shows the friction coefficient of recovered rolling oil along with the usage ratio, and even if only recovered rolling oil is used, the friction coefficient is
It can be seen that it is 0.18 and can be used satisfactorily.

Figure 1b shows the change in the coefficient of friction when an extreme pressure additive is added to a mixture of equal amounts of recovered rolling oil and new oil, and the coefficient of friction decreases to about 0.09 by adding just under 2% of the extreme pressure additive. It can be seen that the coefficient of friction can be lowered.

If the rolling oil recovered in this way is supplied directly to the material to be rolled or to the rolling rolls through a supply system separate from the circulation system, it will be used for rolling lubrication when it joins the circulation system, making it more likely to get mixed up. The materials are thoroughly mixed and agitated as they pass through the collection pits, piping, pumps, etc. at the bottom of each rolling stand. At the same time, there is a shortage of additives in the rolling oil that are lost together with the iron in the iron removal device.

In a recirculation system, if the recovered rolling oil is used as is, extreme pressure additives, etc. will change and decrease over time as it is recycled, and eventually the rolling lubricity (particularly the boundary film strength) will deteriorate. Since it deteriorates and causes roll defects such as heat slips, it is necessary to add additives appropriately as described above.

As described above, according to the present invention, the expensive rolling oil that was previously disposed of with the iron removed by the iron removal device, recovered and used, and was not recovered and used can be effectively reused in the circulation system, thereby saving oil resources. can. Furthermore, a secondary effect of the present invention is that the properties and concentration of the recovered oil can be appropriately adjusted and supplied directly to the material to be rolled through a supply system separate from the circulation system, making it possible to adjust the lubrication ability during rolling. At the same time, the concentration of the entire coolant system can be kept constant. For example, in a tandem rolling mill, high-concentration oil with good properties is supplied only to the latter stand, which is subject to particularly high loads, to improve lubricity, or when strip is passed through each stand,
It is also possible to increase the amount of oil supplied only during high-tension rolling at the time of tail-off to improve lubrication and prevent deterioration of shape due to high-tension rolling, which is also advantageous for high-reduction rolling. FIG. 2 is a diagram showing a conventional general rolling oil recirculation system.
In the figure, 1 is a group of cold rolling mill stands, 2 is an oil recovery pit, 3 is a dirty tank that receives used dirty oil from the recovery pit, and 4 is a Hoffmann that continuously leaks oil from the dirty tank. Filter, 5 is a clean tank, 6 is a rolling oil (new oil) supply device,
7 and 8 are magnetic separators, 9 and 10 are agitators, and S is a rolled material (strip). The oil to be circulated is mixed with commercially available rolling oil and water or hot water in a clean tank 5, adjusted to an appropriate concentration (for example, 4 to 6% for thin rolling, 1 to 3% for thick rolling), and stirred. It is called an emulsion.

Commercially available rolling oils contain additives such as those listed below.

Oiliness improver 1.5% (weight ratio) Surfactant 0.5 (weight ratio) Extreme pressure additive 2.0 (〃) Other additives 1.5 (〃) The emulsion stirred by the stirrer 9 is sent from the clean tank 5 as circulating oil. A pump P1 supplies the rolling mill ₁ via a filter F and a cooler C via a supply pipe 11 to a header 12, a nozzle 13,
After being injected onto the strip S and roll R through 14 and used for cooling the rolls and lubricating the rolling process,
Through the collection pipe 15 collected in the collection pit 2,
First, in the dirty tank 3, the iron content is removed by the magnetic separator 7, but here, along with the iron content, oil content is carried out of the system in the form of scum. Furthermore, since the circulating oil contains additives that easily bind to iron, the additives are removed along with the iron that is removed. Therefore, the additive concentration in the circulating oil decreases, which is disadvantageous. The circulating oil leaving the dirty tank 3 by the pump P ₂ is filtered by a Hoffman filter 4 to remove foreign matter (wood chips, iron pieces, etc.), and then returned to the clean tank 5 by the pump P ₃ . A magnetic separator 8 may also be provided in the cree tank 5. New rolling oil (new oil) is supplied to the clean tank 5 from the supply device 6.
However, as mentioned above, new oil has a higher concentration than circulating oil, so it takes time to stir it uniformly in the tank.

FIG. 3 shows an example of an embodiment of the present invention, which is an improvement on such a conventional recirculation system. Components that are the same as those in FIG. 1 are given the same reference numerals, and their explanations will be omitted below.

In Fig. 3, the scum containing iron is removed from the centrifuge 1 by magnetic separators 7 and 8.
6 to separate iron and oil, the iron is discharged to a discharge system 17, and the oil is led to an adjustment tank 18. In the adjustment tank 18, after confirming the properties of the recovered oil, the required amount of additives (emulsifier, oiliness improver, extreme pressure additive, etc.) is added from the additive supply device 19 to obtain a product with properties similar to new oil. It's oil and eggplant.

The oil is then led to a mixing tank 20 and mixed with water to obtain a rolling oil emulsion of the desired concentration. The rolling oil with the required concentration is supplied to the header 22 and the nozzle 2 by a supply system 21 having a pump _P4 .
3 to the strip S. 24 in the figure is a tank for replenishing new oil.

Since the present invention has a supply system separate from the conventional circulation system, the recovered oil is sufficiently adjusted in advance to obtain the required properties in the adjustment tank 18 and mixing 20 arranged in the new system. ,
Since a concentrated rolling oil emulsion is supplied to the strip S or roll R, used for lubrication and cooling, and then mixed into the circulation system, the oil in the circulation is It has the feature that it is easy to mix the oil and the oil being replenished.
This improves the properties of circulating oil.

Further, by adjusting the amount of oil supplied from the replenishment oil supply device 24 as necessary, it is possible to supply oil with high concentration and good properties. At that time, the emulsion is sufficiently stirred and mixed in the mixing tank 20 to form a homogeneous emulsion, and the high-quality rolling oil emulsion is directly supplied to the strip S or roll R. This leads to prevention of iron soap formation.

Since the method of the present invention has a supply system 21 separate from the conventional supply piping 11, the method other than the above for supplying oil to the strip S or roll R through the supply system 21 is to operate the valve 25. During strip rolling, a particularly high amount of rolling oil is supplied to each stand at the time of passing the strip (at the beginning of biting) and at the time of strip removal to improve lubrication and prevent problems such as strip breakage due to the application of high tension. Deterioration of the shape of the strip can be prevented. In addition, by supplying oil only to the latter part of the rolling stand group, which is subjected to particularly heavy loads during thin-material rolling,
A supply method that improves the lubrication of this latter stage stand is also possible. In implementing these measures, Valp 25
For the opening/closing or adjustment of the opening/closing, known automatic control means can be employed as appropriate.

According to the present invention, since the oil supply system is separated into two lines in the rolling oil recirculation system, the oil carried away by the iron removed by the iron removal device is effectively brought back into the circulation system.
This has the effect of saving make-up oil, improving the properties of circulating oil, and enabling controlled rolling by adjusting the concentration of rolling oil.

[Brief explanation of the drawing]

Figure 1a shows the properties of recovered rolling oil in terms of friction coefficient for each usage ratio, Figure 1b shows changes in the friction coefficient due to the addition of extreme pressure additives to recovered rolling oil, and Figure 2 FIG. 3 is a diagram showing an example of a conventional rolling oil recirculation system, and FIG. 3 is a diagram showing an example of the rolling oil recirculation system of the present invention. 1... Cold rolling mill group, 2... Oil recovery pit, 3
...Dirty tank, 5...Clean tank,
7, 8... Magnetic separator, 13, 14...
... Nozzle, 16 ... Centrifugal separator, 18 ... Adjustment tank, 19 ... Additive supply device, 2
0...Mixing tank, S...Strip, R
...Rolling roll.

Claims (1)

[Claims] 1. In a rolling oil recirculation system, oil removed from the circulation system along with iron was collected by an iron removal device to obtain recovered oil, and additives were added to the recovered oil and the concentration was adjusted. A method for consolidating oil in a rolling oil recirculation system, characterized in that the oil is then fed to the material to be rolled or to the rolls through a supply system separate from the circulation system to join the circulation system.