JPS585731B2 - Lubricating method in cold rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of lubricating a cold rolling mill, and more specifically, the present invention relates to a lubricating method for a cold rolling mill, and more specifically, a method for circulating a low-temperature, low-concentration rolling oil emulsion as a roll coolant at the exit side of each stand of a rolling mill. The present invention relates to a lubricating method for a cold rolling mill that is excellent in rolling properties, unit consumption, workability, etc., by injecting a high temperature and highly concentrated rolling oil emulsion liquid as a rolling lubricant at the entrance side of each stand.

Generally, in cold rolling of steel plates, rolling lubricants are used to reduce the frictional resistance between the work rolls and the strip during rolling, and the temperatures of the rolls and strip increase due to the heat of plastic working. This may deteriorate the shape of the strip or cause surface defects such as heat leaks on the surface of the strip, so it is necessary to supply roll coolant to the roll and strip in order to cool the roll and strip.

In addition, in the circulation method, a relatively low concentration emulsion liquid of rolling oil is circulated and used as both rolling lubricant and roll coolant without having to supply them separately. In this method, a relatively high concentration emulsion liquid of rolling oil is used as a rolling lubricant, and cold water is used as a roll coolant, and neither the cold water nor the emulsion liquid is recycled, and the emulsion liquid is directly installed in a wastewater treatment facility or , a portion of the rolling oil is sent to recovery equipment, and each of these methods is used depending on the characteristics of the rolling mill and the characteristics of the material being rolled.

Note that the rolling oil used here as a rolling lubricant and roll coolant or as a rolling lubricant is usually prepared by adding oil improvers, emulsifiers, extreme pressure additives, etc. to various oils and fats and dissolving them in hot water. It is an emulsion liquid consisting of

That is, FIGS. 1a and 1b are flow sheets of an example of the circulation method and the direct method, respectively, and are designated by reference numerals 1a and 1.
b is the spray nozzle for the upper and lower surfaces of the strip before each stand is inserted, 2 is the spray nozzle on the outlet side of each stand, 3 and 4 are the supply lines, 5 is the stirring tank, 6 is the return pipe, and 6a is the drainage line, 7 is the feed pump,
8 is a rolling oil storage tank, 9 is a rolling oil supply pump, 10 is a rolling lubricant mixing tank, 11 is a rolling lubricant boost pump,
20 is an agitator, 21 is a backup roll, 22 is a work roll, 23 is a strip, 24 is a heater, 26
27 is a hot water supply pipe, 28 is a rolling oil supply pipe, 30 is a hot water supply pump, 31 is a hot water tank, 32 is a wastewater treatment facility, 33 is a wastewater feed pump, and 34 is a cold water supply pipe.

First, in the circulation system, as shown in Fig. 1a, a low-concentration rolling oil emulsion is fed from the stirring tank 5 to the supply line 4 as a rolling lubricant and roll coolant, and from the spray nozzles 1a and 1b. It is injected from the injection nozzle 2 at the same time as the injection.

The used emulsion liquid is returned to the stirring tank 5 via the return pipe 6, and in this tank 5, rolling oil and hot water are replenished from the storage tank 8 and the hot water tank 31 as required, and then stirred by the agitator 20. and filter 26
It is then recycled and reused.

This circulation method circulates a low-concentration rolling oil emulsion and can be used repeatedly, so the unit consumption of rolling oil is low, and it is extremely advantageous in terms of oil cost compared to the direct method shown later. This method has the advantage that the amount of wastewater discharged outside the system is small and that large-scale wastewater treatment equipment is not required.

However, this is inherently disadvantageous because the circulating emulsion liquid itself has both lubrication and cooling functions.

Next, in the direct method, as shown in FIG. 1b, rolling oil and hot water are supplied from the storage tank 8 and the hot water tank 31 to the mixing tank 10, heated and stirred, and an emulsion of this highly concentrated rolling oil is formed. The liquid is injected as a rolling lubricant from spray nozzles 1a and 1b via a line 3, while cold water is injected as a roll coolant via a supply line 4, and the waste water after use is sent to waste water treatment via a drain line 6a. Discharge to equipment 32.

Therefore, in the direct method, the lubrication and cooling functions are not combined and are separated, so a small amount of highly concentrated, high temperature emulsion liquid can be supplied for lubrication, while a large amount of low temperature emulsion liquid can be supplied for cooling. Since cooling water can be supplied, it is possible to maintain good lubricity and to sufficiently lower the temperature of the strip and roll, which allows the strip to maintain its shape well and prevents scratches from seizing on the surface of the strip. But it is advantageous.

Furthermore, the direct method allows the concentration and temperature of the rolling oil to be easily changed in a relatively short time when the rolling conditions change, and has good workability.

In short, the direct method is advantageous except for the cost of rolling oil and the problem of wastewater treatment, but due to recent efforts to save resources and take measures against environmental problems, the circulation method also has great advantages.

The purpose of the present invention is to solve the above-mentioned drawbacks, and specifically, the present invention aims to provide a rolling method that is superior in lubricity, cooling performance, workability, etc. like the direct method in equipment equivalent to the circulation method, is also economical, and has excellent quality. We propose a lubrication method that yields wood.

The present invention will be explained in detail below.

First of all, the factors that determine the lubricity during cold rolling are (l) a large amount of the emulsion liquid sprayed on the strip surface is plated out and adheres to the surface; and (2) the strip is caught in the roll bite. During the rolling process, the oil film does not break and the formation of an oil film that separates the strip and roll with a sufficient area ratio is maintained. (3) Shearing of the oil film formed between the roll and the strip The resistance is sufficiently low and the frictional force can be suppressed.

Among these, (1) is an item that is generally evaluated as the plate-out property of rolling oil, and in addition to the effects of the components and additives of the rolling oil itself, it also depends on the emulsion concentration, temperature,
Spray pressure (impact velocity on the slip strip surface) has a very large influence.

When this point was investigated, the relationships between the concentration, pressure (pump pressure), and temperature and the amount of rolling oil deposited were as shown in FIGS. 2, 3, and 4.

As a result, in order to improve lubricity, it is better to inject as high a concentration and high temperature emulsion liquid as possible onto the strip before roll bite at high pressure.

Further, after roll bite, it is preferable to inject a large amount of roll coolant at as low temperature and concentration as possible in order to cool the strip and roll.

From this point of view, in the method of the present invention, a low-concentration and extremely low-temperature rolling oil emulsion liquid is circulated as the roll coolant solely for the purpose of cooling, while a part of this emulsion liquid is extracted, and this extracted liquid is used as the roll coolant. is further added with rolling oil to make it highly concentrated, heated and pressurized, and is injected as a rolling lubricant at high temperature, high concentration, and high pressure.

That is, FIG. 5 is a flow sheet of an example of equipment for implementing the method of the present invention, and elements equivalent to those shown in FIGS. 1a and 1b are designated by the same reference numerals. , 1b are high concentration rolling lubricant spray nozzles, 2 is a roll coolant spray nozzle,
The cooling roll coolant is stored in a storage tank 5, where it is stirred by an agitator 20 to form a uniform emulsion.

Its concentration can be determined by taking into account that it will be partially extracted as a high-concentration rolling lubricant, and is usually 0.02 to 5.0.
It is 0%.

Further, the roll coolant is pressurized by the pump 7, passes through the filter 26, removes foreign matter, and then passes through the supply line 4 from each spray nozzle 2 to each stand, that is, the #2 stand 15. #3 stand 16
, #4 stand 17, #5 stand 18 backup roll 21, war roll 22 and strip 23.

In this case, unlike the conventional circulation system, there is no need to consider the lubricity of the roll coolant.
As much as possible, the concentration and temperature of the emulsion liquid can be lowered and the cooling efficiency will be improved.

Further, after the low concentration roll coolant passes through the filter 26, a part of it is extracted from the extraction line 29, and the rolling oil stored in the tank 8 is transferred to the extraction section by the pump 9 in the mixing tank 10. After increasing the pressure, it is supplied to a high concentration suitable as a rolling lubricant.

To explain in detail, depending on the supply ratio of the rolling oil from the tank 8 and the extracted roll coolant to the tank 10, the concentration of the emulsion liquid in the tank 10 can be increased, for example, as shown in equation (1).

However, b: Concentration in mixing tank 10 (%) UL: Rolling oil from tank 8 (l/min) Uc: Coolant extraction flow rate from coolant tank 5 (l/min) a: Extraction port - Le coolant flow rate (l/min) Concentration (%) By the way, concentration (a) 3. By extracting 5% roll coolant at a rate of 96.4 l/min and adding rolling oil from tank 8 at a rate of 3.6 l/min, the concentration in mixing tank 10 can be increased to about 7%. .

In the mixing tank 10, the temperature is raised by a heater 24 such as a steam heater, and the pressure is further increased by a pump 11, and this highly concentrated rolling lubricant is delivered to the nozzles 1a, 1.
b is sprayed onto the strip in front of each stand.

In addition, the raw material coil 25 charged into the payoff reel 13
has its surface coated with pre-coat oil, which acts as a rolling lubricant in the first stand 14.

Therefore, water or other roll coolant can be supplied to the first stand 14 simply by the roll cooling piping 12.

As described above, according to the present invention, the rolling lubrication function and the roll and strip cooling function are separated in, for example, the second to fifth stands 15, 16, 17, and 18 of the cold rolling mill. For lubrication, a high-concentration, high-temperature rolling oil emulsion is supplied at a high pressure sufficient for lubrication, while for cooling, a low-temperature, low-concentration rolling oil emulsion is supplied at a pressure sufficient for cooling. Can be supplied in large quantities at low pressure.

Furthermore, the waste water can be returned to the coolant tank 5 and recycled without being disposed of.

In this regard, it is conceivable to circulate an emulsion liquid of rolling oil for the rolling lubrication function, as in the conventional circulation system, and to supply water as a roll coolant for the cooling function by a direct system.

However, at this time, in addition to replenishing rolling oil and water that are lost due to drag-out due to adhesion to the strip, evaporation in the rolling mill, leakage, etc., a large amount of rolling Oil must be replenished, and such a large amount of emulsion exceeds the capacity of the system and must eventually be discarded.

However, according to the present invention, as shown in FIG. 5, since the emulsion liquid of rolling oil is extracted from the tank 8 to the mixing tank 10, it is sufficient to supply water to the tank 7 through the pipe 27.

That is, in the present invention, the supplied rolling oil is effectively used only for the purpose of lubrication.

Note that even in the conventional direct method, an emulsion liquid of highly concentrated rolling oil is supplied.

However, in the present invention, for example, a low-concentration rolling oil emulsion liquid is extracted through the pipe 29, and only the insufficient amount of rolling oil is supplied from the pipe 28, so that the amount of rolling oil can be extremely small. .

In addition, in the case of the circulation method, rolling oil is supplied to the tank 5 shown in FIG.
It has an extremely large capacity of 0.00 to 100,000 liters, and the amount of rolling oil required to increase the concentration by 1% is extremely large.Furthermore, the refilled rolling oil is diluted by that much and becomes a lubrication agent. It cannot be said that it is effective just because it is supplied.

Further, although the present invention has been mainly illustrated with reference to an example of a 5-stand tandem mill shown in FIG. 5, the present invention is not limited to this example, and can be applied to all cold rolling mills regardless of the number of stands. Applicable to

For example, FIG. 6 is a flowchart when the present invention is applied to a reverse rolling mill, and in FIG. 6, each reference numeral indicates the same element as shown in FIG. shows.

Next, examples will be described.

First, as shown in Fig. 7, piping was installed in a 3-stand tandem cold mill as shown in the diagram, and at the same time, the oil supply and cooling were carried out according to the present invention, and for comparison, the oil supply and cooling were carried out using the circulation method and the direct method as in the conventional example. .

In this case, in FIG. 7 as well, the same elements in FIGS. 1 a and b and FIG. The piping was as follows, and the method of the present invention, the circulation method, and the direct method were carried out using these nozzles as follows.

(a) Emulsion liquid coolant (55°C) made by adding 3.51% rolling oil to hot water in the tank 5 of the present invention and emulsifying it with the agitator 20 is supplied to each supply pipe 4 through the pump 7 and the filter 26. Nozzle Cl, C2,
The coolant was supplied to C3 and C4 for cooling, and the coolant after cooling was returned to the tank 5 from the return pipe 6 to form a coolant circulation system.

Also, a part of this circulating coolant is transferred from the pipe 29 to the valve 3.
1 and into a mixing tank 10, and to this, rolling oil is added from tank 8 to form a highly concentrated emulsion liquid (7%
The rolling oil (75°C) passes through piping 3 to a pair of nozzles A and A.
It was sprayed from '.

At this time, the injection amount and pressure were adjusted by the rotation speed of the pump 11.

(b) Circulation method Similar to (a), a coolant circulation system was constructed, but a portion of the coolant was used as a rolling lubricant and the valve 30 was opened to inject it from a pair of nozzles B and B'.

The rolling lubricant in this case is 3.5% rolling oil at a temperature of 55°C, similar to the coolant in (a), and the supply amount is 30°C.
Adjusted by.

(c) Direct method First, an emulsion liquid (75°C) made by adding 7% rolling oil to water is used as a rolling lubricant, and a pair of nozzles A, A'
While the supply amount and pressure were adjusted by the pump 11, water was used as the coolant and was injected from each nozzle C1, C2, C3, and C4.

In addition, when lubricating according to (a), (b), and (c), the rolled material is a low-carbon rimmed steel plate that has been plastic-worked in advance with a cold reduction rate of 90%.
#1 stand 14 and #3 stand 16.
The rolling reduction ratio was set to almost zero, and the longitudinal tension of #2 stand 15 was controlled to be kept constant.

When oil was supplied and cooled as described above, the effect on the rolling pressure was as shown in FIGS. 8 and 9.

That is, in FIG. 8, the ○ mark indicates the method of the present invention, the Δ mark indicates the direct method, and the × mark in FIG. 9 indicates the circulation method.
As is clear from FIG. 9, when a low-concentration, low-temperature emulsion liquid is injected from a pair of nozzles B and B', a decrease in pressure force is observed as the flow rate increases, but the
At 0 l/min or more, it becomes saturated.

On the other hand, as shown in Fig. 8, in the case of the emulsion liquid made by adding highly concentrated rolling oil to circulating coolant or water according to the method of the present invention and the direct method, as the flow rate increases, rolling and pressure increases significantly. A decrease of about 90% was observed, especially from the saturation point of the circulation system (shown in Figure 8a).
The rolling force decreases.

In addition, the flow rate increment until the rolling pressure decreases to the same rolling pressure is 13 l/min when injecting from a pair of nozzles A and A'.
, 950 l/m when spraying from a pair of nozzles B and B'
In the case of the method of the present invention or the direct method, even if the concentration of rolling oil was twice as high, it was found to be about 35 times more effective than the circulation method.

That is, with the method of the present invention, the rolling pressure can be reduced compared to the circulation method with a lower flow rate, similar to the direct method.

In addition, in #2 stand 15, the current values of each of the above methods (a), (b), and (c) were determined, and the results were as shown in Fig. 10. In the same figure, the symbol ○ indicates the invention The symbol Δ indicates the direct method, and the symbol X indicates the circulation method. As is clear from FIG. 10, it can be seen that the electric power is also lower according to the method of the present invention than in the circulation method.

Further, when the basic unit of rolling oil was compared, as shown in Table 1, it can be seen that the method of the present invention is superior.

Further, when cold rolling is normally performed in a tandem mill, the rolling reduction ratio of each stand is 25 to 40%, so the temperature of the strip increases as it goes to subsequent stands due to plastic working heat.

For this reason, the temperature of the coolant returns to the coolant tank at a higher temperature than when it was supplied, and a coolant cooler is used to keep the temperature of the roll coolant constant.

However, when special materials with a small total cold reduction are rolled in tandem mills or in reverse rolling mills, the temperature of the strip does not rise that much, and the roll coolant returns to the tank with a lower temperature. , requires a heater in the tank to keep the coolant temperature constant.

In this regard, with the method of the present invention, it is only necessary to supply a small amount of high-temperature lubricant for lubrication, and the coolant temperature can also be lowered.
There is less heat loss due to evaporation, and the total amount of circulation is significantly smaller than in the circulation method, so the amount of heat required for heating can be saved.

Moreover, FIG. 11 shows the apparatus shown in FIG. 7, and the above (a),
This shows the steam consumption rate when rolling with oil supply and cooling using methods (B) and (B). Regardless of the rolling efficiency, the method of the present invention is inferior to the direct method, but it is better than the circulation method. It can be seen that this method is advantageous (in FIG. 11, the mark ◯ indicates the method of the present invention, the mark △ indicates the direct method, and the mark x indicates the circulation method).

As described above, the method of the present invention has the same rolling properties (rolling force, electric power) as the direct method and is superior to the circulation method, and the consumption of rolling oil is also better than the direct method and the circulation method.

It can also be seen that when the processing heat in the mill is low, the steam consumption rate is also superior to the circulation method.

In addition, the concentration can be changed by changing the amount of rolling oil supplied to the mixing tank, the temperature can be changed by a heater, the supply pressure can be changed by a supply pump, etc.
The flow rate can be easily adjusted, and variations in rollability due to the rolling material can be dealt with in a responsive manner, improving workability.

In addition, the cooling capacity for the roll and strip is greater than in the circulation method, preventing surface scratches and making it easier to adjust the thermal crown of the work roll, resulting in a better shape.

[Brief explanation of drawings]

Figures 1a and b are flow sheets of the conventional oil supply system, and Figure 2 is the relationship between the concentration of rolling oil in the rolling lubricant and the amount of adhesion.
3 is a graph showing the relationship between rolling lubricant temperature and the amount of adhesion. FIG. 4 is a graph showing the relationship between the rolling lubricant supply pump, pressure and amount of adhesion. FIG. 6 is a flow sheet of an example of an apparatus for carrying out the method of the present invention. FIG. 6 is a flow sheet of an example in which the method of the present invention is applied to a reverse rolling mill. FIG. Figure 8 is a graph showing the relationship between the flow rate of rolling lubricant and rolling pressure. Figure 9 is a graph of the relationship between the rolling lubricant flow rate and rolling pressure. Figure 10 is a graph showing the relationship between rolling lubricant flow rate and rolling pressure. FIG. 11 is a graph showing the relationship between speed and current value, and FIG. 11 is a graph showing the relationship between rolling efficiency and steam consumption rate. Codes 1a, 1b... Spray nozzles for the upper and lower surfaces of the strip, 2... Spray nozzles on the exit side of each stand, 3, 4... Supply line, 5.・・・
... Stirring tank, 6... Return piping, 6a...
... Drain line, 1 ... Feed pump, 8.
...Rolling oil storage tank, 9...Rolling oil supply pump, 10...Rolling lubricant mixing tank, 1
1... Rolling lubricant boost pump, 12...
・Cooling piping, 13...Payoff reel, 14
・・・・・・1st stand, 15, 16, 17, 18・
...Each stand from 2 to 5. 19...Tension reel, 20...Agitator, 22...
... Work roll, 21 ... Backup roll, 23 ... Strip, 24 ...
・Heater, 25...Material coil, 26...
... Filter, 27 ... Hot water supply piping, 28.
...Rolling oil supply piping, 29...Extraction line, 30...Hot water supply pump, 31...
Hot water tank, 32... Wastewater treatment equipment, 33...
... Drain feed pump, 34 ... Cold water supply piping.

Claims (1)

[Claims] 1. While circulating a low-concentration and low-temperature rolling oil emulsion liquid as a roll coolant injected to the exit side of each stand of a cold rolling mill, rolling oil 2 is added to the extraction section extracted from the circulating emulsion liquid. A cold rolling mill characterized in that it is made into a highly concentrated emulsion liquid, heated and pressurized as necessary, and then sprayed as a rolling lubricant before the biting of each stand, and then merged with the circulating emulsion liquid. How to refuel.