JPS6372417A - Cold rolling lubrication method - Google Patents

Abstract

PURPOSE:To improve the sticking efficiency of a lubricant layer and the rolling efficiency by inversely calculating a friction coefficient of a work roll by a rolling load equation based on rolling data of a rolled stock and adjusting a lubricant supply amount to header nozzles in accordance with the above friction coefficient. CONSTITUTION:During cold rolling, a controller 16 comprising a control system 12 momently receives rolling speed data of a rolled stock 8 detected based on the rotating speed of a work roll 9 through a rolling speed signal conductor 17. Further, friction coefficients of a roll biting part found by inverse calculation by a rolling load equation based on rolling data such as momently detected rolling loads and tensions are succeedingly inputted to the controller 16, which calculates a proper oil supply amount based on the inputted rolling speed data so that a lubricant oil layer thickness is constant. A proper friction coefficient range is previously inputted to the controller 16; the controller 16 automatically changes an oil supply factor, controls a spray amount from nozzles 7a and 7b to make the oil layer thickness constant when an inputted actual friction coefficient deviates from the proper friction coefficient range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a cold rolling lubrication method, particularly to an improvement in a lubricant supply method using a direct lubrication method.

[Conventional technology]

Conventional lubrication methods in cold rolling include spraying a highly concentrated rolling oil/water emulsion based on palm oil or the like directly onto the strip, and cooling the roll by spraying cooling water from a separate nozzle. There is a so-called direct lubrication method.

FIG. 4 is a system diagram of this oil supply system. Rolling oil and hot water are sent at a fixed ratio through a rolling oil supply pipe 1 and a W water supply pipe 2, respectively, to a mixing unit 3, where an agitator 4 The mixed emulsion is fed to a plurality of nozzles 7 constituting a lubricant injection header via an emulsion supply pump 5 and piping 6, and is injected from these nozzles 7 toward a material to be rolled 8.

The injected emulsion is destroyed by collision with the material to be rolled 8, and only the oil layer is spread out on the surface (plate out), providing lubrication during rolling. Note that 9 is a work role and 10 is its backup role.

[Problem that the invention seeks to solve]

However, in such conventional lubrication methods,
The adhesion efficiency of the oil layer is low and the concentration of the emulsion tends to be non-uniform, resulting in unstable rolling, which impairs rolling efficiency and product quality.

In other words, C1) Regarding adhesion efficiency, in order to enable lubrication between the rolling rolls and the rolled material under high pressure, the oil layer of the injected emulsion must reach 80% of the rolled material.
It is necessary to spread on the surface and form a strong oil film. However, with the conventional direct oil supply method, the spreading force is weak, and only a portion of the oil layer in the injected emulsion is plated out. Most of the lubricant falls off from the rolled material 8 without functioning as a lubricant before flowing into the roll bite area, and in reality only exhibits an adhesion efficiency of about 15%. This means that, for example, the thickness of the oil film calculated from the amount of emulsion sprayed is 2.0 μm, whereas the actual value of the oil film attached to the 8 surfaces of the rolled material after rolling is 0.0 μm.
This can be said to be clear from the fact that it is only 3 μm.

Furthermore, the adhesion efficiency changes depending on the particle size of the emulsion and the temperatures of the rolled material 8 and work roll 9. For this reason, the oil film thickness at the roll bite portion varies, and this variation causes a change in the frictional force between the rolled material 8 and the roll 9, which induces the rolling instability phenomenon described below.

Regarding (2) stability of emulsion concentration, the rolling oil used in the direct oil supply system is generally formed in such a way that emulsification is difficult to occur.

This is to increase the adhesion of the oil layer to the rolled material 8 and to facilitate separation of rolling oil mixed into the waste water of the roll cooling water after rolling lubrication is completed.

However, as a result, the emulsion supplied from the mixing tank 3 to the nozzle 7 by the emulsion supply pump 5 becomes unstable, and oil and water are likely to separate in the middle of the supply pipe 6, resulting in uneven concentration. By the way, Figure 5 shows the results of measuring the concentration of the emulsion injected from the nozzle 7 of the injection header at multiple points in the longitudinal direction of the header, and it is approximately 5.
Variations in concentration ranging from % to 25% were observed.

Such concentration non-uniformity is also one of the major causes of rolling instability.

Here, the rolling instability phenomenon refers to chattering (repeated neutral point fluctuations) and slip (between the work roll and the rolled material) that occur when the friction coefficient in the roll bite section of the rolling mill becomes excessively low due to excessive lubrication. On the other hand, heat streaks (seizing) occur when the coefficient of friction becomes excessively high due to insufficient lubrication.

In order to prevent such rolling instability phenomena and perform stable rolling, it is necessary to suppress variations in the thickness of the lubricating oil film, which influences the frictional force of the roll bite portion, and to always maintain it within an appropriate range. In other words, specifically, fluctuations in the adhesion efficiency to the rolled material and fluctuations in the concentration of the lubricant emulsion,
It must be stabilized as much as possible.

However, regarding the point of increasing adhesion efficiency by using electrostatic force, for example, it has been known that anti-rust oil is applied to a steel plate via an electrostatic oil applicator, and rolling oil using this is known. A supply method is disclosed in Japanese Patent Laid-Open No. 57-137021. However, the adjustment of the amount of adhesion is
This is done by controlling the amount of charge on the oil particles by changing the voltage of the power supply, and although it is possible to adhere firmly and efficiently, it is necessary to adjust the amount of adhesion immediately to changes in the coefficient of friction during rolling, so that it is constantly online. It was not properly maintained.

This invention was made to solve these conventional problems, and it not only uses electrostatic force to apply lubricant to the rolled material, but also applies the lubricant to the rolled material and work roll, which is calculated backward during rolling. By adjusting the amount of lubricant supplied to the header according to the coefficient of friction between The object of the present invention is to provide a cold rolling lubrication method that prevents this and improves rolling efficiency and product quality.

[Means for solving problems]

The cold rolling lubrication method of the present invention is a cold rolling lubrication method in which a lubricant is applied to a rolled material using the electrostatic force of an electrostatic field formed between a lubricant spray header nozzle and the rolled material. In , the friction coefficient of the work roll is calculated backward from the rolling load formula based on the rolling data of the rolled material during rolling,
The amount of lubricant supplied to the header nozzle is adjusted depending on the friction coefficient.

[Effect]

The lubricant particles sprayed from the header nozzle are charged in the electrostatic field formed between them and the rolled material, and are attracted to the rolled material by the electrostatic force, so almost the entire amount of the sprayed lubricant can be applied. Therefore, the adhesion efficiency of the oil layer can be greatly improved.

In addition, when the value of the friction coefficient calculated based on the rolling data during rolling deviates from the preset normal friction coefficient range, the lubricant supply amount is adjusted to correct the deviation. Since the amount, ie, the thickness of the coating film, is always maintained at an appropriate level, the rolling instability phenomenon that occurs in the past cannot occur.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing an example of a cold rolling oil supply device to which the present invention is applicable. In addition, in the drawings, the same reference numerals are given to the same or corresponding parts as in the conventional art.

In Fig. 1, electrostatic oil applicator A is a cold rolling stand S.
lubricant spray header nozzle 7.
The header has a DC high voltage generator 11 that forms an electrostatic field between the header and the rolled material 8, and a control system 12 that controls the amount of lubricant supplied to the header. For example, the negative electrode side of the DC high voltage generator 11 has a nozzle 7 arranged in the header.
(Front side nozzle 7a, back side nozzle 7b of rolled material 8)
The positive electrode side is connected to via a high voltage application line 13, and the positive electrode side is grounded via a high voltage ground line 14. Each nozzle 7a, 7b
are connected via piping 6 to lubricant emulsion supply pump devices 5a and 5b.

In order to control the discharge amount of each pump device 5a, 5b, the control system 12 includes, for example, a pump oil supply amount control panel 15 that controls the rotation speed of a DC motor or a variable speed AC motor that is a pump drive source, and The oil supply control panel 15 is equipped with a controller 16 for instructing the amount of oil to be supplied. To this controller 16, rolling speed data obtained from the rotational speed of the work roll 9 is inputted from the rolling speed signal line 17, and the data is calculated backward from the rolling load formula based on data such as rolling load and rolling tension. The friction coefficient is input from a friction coefficient signal line 18.

The lubrication command amount output to the pump lubrication amount control panel 15 is calculated according to these input values from an arithmetic expression described below so that the thickness of the lubricating oil film is constant. .

Next, a cold rolling lubrication method of the present invention performed according to the configuration of the electrostatic oil applicator A shown in FIG. 1 will be explained.

From the DC high voltage generator 11 to the injection nozzle 7a.

When the lubricant is palm oil, the optimum DC voltage applied to 7b is 50,000 to 1 oooooov. As a result, an electrostatic field is formed between the nozzles 7a, 7b and the grounded material 8 to be rolled, and the nozzle 7a.

The emulsion particles injected from 7b are negatively charged and are attracted to the 8 surfaces of the rolled material by the electrostatic force, and the rolling oil is approximately 1
00% is completely spread and becomes a strong lubricating oil film. Therefore, it does not fall off from the 8 surfaces of the rolled material as in the past, but instead flows into the roll bite section and can perform the lubricating function.

In addition, since the high adhesion efficiency is compensated for in this way, there is no need to take the trouble of creating an emulsion that is difficult to emulsify as in the past. Therefore, it is possible to prevent the inconvenience of the rolling oil and water separating in the supply pipe 6, resulting in non-uniform emulsion concentration, and resulting in concentration variations in the longitudinal direction of the header as shown in FIG. Ru.

During the above-mentioned cold rolling, the rolling speed data ■ of the material to be rolled 8 detected from the rotational speed of the work roll 9 is inputted every moment to the controller 16 constituting the control system 12 via the rolling speed signal line 17. Ru. Furthermore, the friction coefficient μ of the roll bit part, which is obtained by back calculation from a known rolling load formula using rolling data such as rolling load and tension detected from moment to moment, is also input one after another in parallel with the above rolling speed data. . The controller 16 uses the input rolling speed data V (m/a+in) to supply appropriate lubrication ft Q (
1/min) is calculated using the following equation (1).

Q = a - W - V O5 to 0.200) is entered, and if the input actual friction coefficient μ deviates from this appropriate friction coefficient range, the oil supply coefficient a is automatically changed.

The above change in the lubrication coefficient a is based on the relationship between the lubrication coefficient a and the friction coefficient μ under the same rolling conditions as shown in FIG.
This is done depending on whether the coefficient of friction is too high or too low.

For example, when the oil supply coefficient a is set to 200 and the oil supply amount is calculated and rolling is performed, if for some reason the actual friction coefficient value becomes μm, as is clear from Fig. 3, This is the upper limit of the appropriate friction coefficient of 0.200.
exceeds. Therefore, in this case, the value of the oil supply coefficient a is changed to a value larger than 200. As a result, (1)
The oil supply amount Q calculated from the formula increases, and the calculated value is used as the oil supply command value to be sent from the controller 16 to the pump oil supply amount control panel 1.
5, emulsion supply pump 5a, 5
The rotational speed of the drive motor b and thus the pump discharge amount increase. As a result, the amount of spray from the nozzles 7a and 7b increases, and the oil film adhering to the rolled material 8 becomes thicker, making it possible to quickly correct the friction coefficient of the roll bite part to an appropriate range below the upper limit of 0.200. can.

On the other hand, if the actual value of the friction coefficient is lower than the lower limit value of 0.005 of the appropriate friction coefficient, the value of the oil supply coefficient a may be made smaller than 500, for example. As a result, the pump discharge amount decreases, the oil film becomes thinner, and the friction coefficient of the roll bite portion can be quickly corrected to an appropriate range of lower limit value 0.0 O5 or more.

In this manner, if the value of the friction coefficient of the roll bite portion during rolling operation is always maintained within an appropriate range, occurrence of rolling instability phenomena such as chattering, slipping, and heat streaks can be completely prevented.

Table 1 Table 1 shows an example of how to determine the appropriate amount of oil supply that does not induce rolling instability for each stand in the case of the rolling oil supply system for a tandem mill with six stands shown in Figure 2. The electrostatic lubrication device A is provided on the entrance side of each stand.

As is clear from the table, the amount of oil supplied is determined depending on the rolling speed, which differs for each stand.

According to this embodiment, it is possible to completely prevent the rolling instability phenomenon and improve rolling efficiency and rolling quality, and the adhesion efficiency of rolling oil is 100%, which is 10% higher than the conventional rolling efficiency.
Since the reduction is significantly increased compared to ~20%, rolling oil can be saved and costs can be reduced.

In the above embodiment, a case has been described in which the oil supply amount is controlled by giving a command from the pump oil supply amount control panel 1 to the pump drive motor, but the invention is not limited to this. Alternatively, the valve lift may be controlled by a command from the pump oil supply control panel 15.

Further, in the above embodiment, the nozzle 7a of the header.

Although the sprayed particles are charged by applying a high voltage to 7b, the invention is not limited to this, and the sprayed particles may also be charged via a separately provided charging plate similar to a known electrostatic oil application device. It is possible.

When charging the sprayed particles using such electrostatic force, it is needless to say that the sprayed particles do not necessarily have to be negatively charged, and on the contrary, may be positively charged.

〔Effect of the invention〕

As explained above, according to the present invention, the lubricant is applied to the rolled material using electrostatic force, and the lubricant is applied to the header according to the friction coefficient between the rolled material and the work roll during rolling. By adjusting the supply amount of the lubricant, it increases the adhesion efficiency of the lubricant oil layer to the rolled material, and
The thickness of the deposited oil film can be maintained at an appropriate level at all times, resulting in the effect that instability of rolling can be prevented and rolling efficiency and product quality can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an example of a cold rolling oil supply device to which the present invention is applied, Fig. 2 is an explanatory diagram of application of the device shown in Fig. 1 to a tandem mill having 6 stands, and Fig. 3 is an oil supplying device. A correlation graph between the coefficient and the friction coefficient, FIG. 4 is a conventional rolling oil supply system diagram, and FIG. 5 is a graph showing the concentration distribution of conventional rolling oil in the longitudinal direction of the header. 5a and 5b are emulsion supply pumps, 6 is a supply pipe,
7a and 7b are nozzles, 8 is a material to be rolled, 9 is a work roll, 11 is a direct fL voltage generator, 12 is a control system, and A is an electrostatic oil application device.

Claims (1)

[Claims] In a cold rolling lubrication method in which a lubricant is applied to a rolled material using the electrostatic force of an electrostatic field formed between a lubricant spray header nozzle and the rolled material, the lubricant is applied to the rolled material during rolling. A cold rolling lubrication method comprising: calculating the friction coefficient of the work roll from a rolling load formula based on rolling data, and adjusting the amount of lubricant supplied to the header nozzle according to the friction coefficient.