JP2002224731A - Lubricant supply method for cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant supply method which prevents heat scratch without deterioration of yield of lubricant. SOLUTION: The lubricant supply method for cold rolling is characterized in setting and controlling lubricant supply quantity QL [liter.min-1] on the steel strip at the rolling stand, based on the calculation equation composed of strip width W [m], lubricant concentration of emulsion type lubrication oil QC [%], strip rolling speed V [m.min-1], and such parameters as distance between the application point of emulsion lubricant on the strip or the rolling roll and the entrance point of roll bite L [m], and a constant χSP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolling mill for a steel sheet, particularly a cold tandem rolling mill having a group of four or more cold rolling mills, capable of improving productivity and reducing manufacturing costs. The present invention relates to a lubricating oil supply method in rolling.

[0002]

2. Description of the Related Art In a cold tandem rolling mill, when the work roll speed is increased or the rolling reduction is increased, heat scratch is likely to occur. The heat scratch is a seizure flaw caused by a metal contact caused by an oil film rupture in the roll tool due to an increase in the interface temperature between the work roll in the roll tool and the steel plate. When heat scratches occur, surface defects occur in the steel sheet, so that not only the yield decreases, but also the productivity is significantly reduced because the work rolls of the rolling mill in which the heat scratches occur need to be replaced.

[0003] It is possible to prevent heat scratches by increasing the lubricating oil supply to improve the lubricity between the work roll and the steel sheet. However, using a large amount of lubricating oil increases the manufacturing cost. It is not preferable because it leads. For this reason, efforts have been made to improve the lubricating oil yield as much as possible by improving the lubricating oil deposition efficiency or by estimating the required amount of lubricating oil from certain parameters and determining the lubricating oil supply amount. Was. For example,
For example, JP-A-62-68607 and JP-A-63-7
As disclosed in Japanese Patent No. 2417, a method of defining a supply amount based on a friction coefficient obtained by back calculation from a rolling force and a rolling load formula (prior art 1), and Japanese Patent Application Laid-Open No. 64-15215 As disclosed, a method of applying a precoat oil to the surface of a steel sheet to improve the adhesion of a lubricating oil and performing rolling (prior art 2), or as disclosed in JP-A-2000-94013, Time required for oil-water separation when lubricating oil adheres to a steel plate (plate-out) (phase inversion time)
In consideration of the above, a method of determining a lubricating oil supply nozzle position (Prior Art 3), or as disclosed in JP-A-11-129017, defines a lubricating oil supply amount from a specific device using an equation. Method (prior art 4).

[0004]

In the prior art 1, the friction coefficient is an effective method for grasping the lubrication state. However, there is a time lag between the change of the lubricating oil supply amount and the change of the friction coefficient. Because of its existence, it is a problem that it cannot cope with a rapid change. In the prior art 2, the precoat oil has an effect on improving the adhesion of the lubricating oil, but the application of the precoat oil leads to an increase in cost, The problem is that the equipment becomes complicated. In the case of the prior art 3, a phase change time is required to plate out the emulsion, and it is certainly effective to set the position of the lubricating oil supply end in consideration of the phase change time. However, there is a problem that the position cannot be accurately determined because the method for determining the phase inversion time has not been determined. Depending group there is a problem such that a space for installing the device can not be secured. A common problem with these is that a model for determining the amount of lubricating oil supply has not been completed, and it is difficult to determine the amount of lubricating oil supply according to each condition.

[0005] The present invention solves the above problems, and provides a lubricating oil supply method for supplying a required minimum amount of lubricating oil according to a model developed for improving the lubricating oil yield and minimizing manufacturing costs. According to this method, heat scratch does not occur, and the yield does not deteriorate due to excessive lubricating oil supply. Therefore, it is possible to improve the productivity and realize cold rolling at low cost.

[0006]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems of the conventional method, and the gist thereof is as follows. (1) cold rolling of the lubricating oil and sets the minimum amount of the lubricating oil supplied Q _L supplies steel upper and lower surfaces simultaneously in the stand so as to satisfy the following formula in the lubricating oil supply in the cold rolling Supply method. _{Q L = (χ sp × 2W} × V 2) / (600 × Q C × L) where, chi _sp; constants, W; strip width [m], V; plate speed [m ·
min ^-1], Q _C; lubricant concentration [vol%], L; length of the farthest portion from the roll bite of the lubricating oil supplied from the roll bite immediately below and lubrication nozzle arcuate intersecting on steel [ _M ], QL; minimum lubricating oil supply [liter · m
in ^-1 ] (2) A constant χ _sp is independently set for the upper surface and the lower surface of the steel plate at the stand so that the lubricating oil supply in cold rolling satisfies the following expression, and the minimum lubricating oil supply amount Q _A method of supplying lubricating oil for cold rolling, wherein _L is set. _{Q L = (χ sp × W} × V 2) / (600 × Q C × L) where, chi _sp; constants, W; strip width [m], V; plate speed [m ·
min ^-1], Q _C; lubricant concentration [vol%], L; length of the farthest portion from the roll bite of the lubricating oil supplied from the roll bite immediately below and lubrication nozzle arcuate intersecting on steel [ _M ], QL; minimum lubricating oil supply [liter · m
in ^-1 ] (3) The lubricating oil supply nozzle is variable in the plate width direction, and the nozzle direction is changed according to the plate width such that the plate width end matches the supplied lubricating oil end. The lubricating oil supply method for cold rolling according to (1) or (2). (4) The lubricating oil injection direction of the nozzle that supplies the lubricating oil to the steel sheet is variable, and at the time of high-speed rolling at least 1500 m · min ⁻¹ , the lubricating oil injection direction from the nozzle is a vector component in the opposite direction to the steel sheet advancing direction. The lubricating oil supply method for cold rolling according to any one of (1) to (3), comprising:

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The main lubricating oil in cold tandem rolling is an emulsion type in which a lubricating oil based on palm oil, tallow, fish oil or synthetic ester is mixed with water. As a method of supplying lubricating oil, a method of supplying lubricating oil directly to the vicinity of a roll bite with a nozzle is currently the mainstream. The lubricating oil supplied near the roll bite is almost separated into water and oil, and adheres to the steel plate and the roll surface. The amount of oil adhering to the steel plate and the roll is called a plate-out amount, and this amount has a great effect on lubricity. If the plate-out amount is sufficiently secured, sufficient oil is introduced into the roll bite, but as the rolling speed increases,
Also, the plate-out amount decreases as the temperature of the steel plate increases. Therefore, how to secure a sufficient plate-out amount during high-speed rolling, in which insufficient lubrication tends to occur, becomes an issue. Increasing the amount of lubricating oil supply is one of the means for ensuring a sufficient plate-out amount.However, if the amount of lubricating oil supply is increased, the yield of lubricating oil will deteriorate. How to supply lubricating oil,
The development of a model capable of estimating the required minimum amount has been desired.

The present inventors have examined the lubrication state in the roll bite.
Insufficient lubrication in rolling experiments conducted to elucidate
Speed and lubricating oil at which heat scratch begins to occur
Table 1 and Table 2 show the results of investigation of the concentration and lubricating oil supply.
In the boundary condition where heat scratch starts to occur
Is shown in the following equation (1), although there is a difference depending on the base oil.
_spIs almost constant. Where the width W is
The reason for the doubling is as follows. χ_spCalculate
Consider the area where lubricating oil is supplied within a certain time when
I have. Consider the amount of lubricating oil supplied to the upper and lower surfaces of the steel sheet
The area of the upper and lower surfaces of the steel sheet
Double. That is, in equation (1), the upper and lower surfaces are considered together.
I am considering. For each of the upper and lower surfaces_spWhere to calculate
In that case, you need to consider the supply area of each of the top and bottom
Therefore, it is not necessary to double the plate width. Also, this equation (1)
Is established under rolling conditions equivalent to general cold rolling mills.
It is. However, L → infinity, Q_LIt does not hold when = 0
No. χ_sp= (600 × Q_L× Q_C× L) / (2W × V^Two(1) In the present invention, the lubricating oil supply amount is determined using the above principle.
Provided is a cold rolling lubricating oil supply method.

[0009]

[Table 1]

[0010]

[Table 2]

[0011] There is a stated rolling conditions so chi _sp is almost constant, if the chi _sp regarded as _{constants, Q L = (χ sp ×} 2W × V 2) / (600 × Q C × L) ·····・ ・ (2) is obtained. Considering that only the supply amount is changed without changing the conditions other than the supply amount of the lubricating oil, if the supply amount is reduced below this amount, heat scratch occurs. It can be considered the required minimum amount of supply. Conversely, if the lubricating oil is supplied under the rolling conditions at a supply amount calculated by the formula (2), lubrication shortage does not occur. However, the value of chi _sp so varies with the type of oil, it is necessary to previously calculate the chi _sp corresponding to these. In addition, although a separate n number among those surveyed is small, also χ _sp by steel species was changed.

The above will be described with reference to FIG. Figure 1
Shows the relationship between χ _sp and the rolling speed at each supply rate calculated from the rolling conditions in Table 1 (when ordinary steel is rolled using refined palm oil). From Table 1, χ _sp under the above conditions is 0.0401, so if that part is shown by a thick line, the required minimum amount of lubricating oil supply at a certain rolling speed and seizure when the lubricating oil supply is set in advance will occur. Not the highest rolling speed can be determined.

For example, when it is desired to set the rolling speed to 2000 m · min ⁻¹ , the lubricating oil supply amount is about 40 liter · min.
It is understood that ^-1 is the lower limit at which no image sticking occurs, and that no image sticking occurs when supplied at a higher level. Further, when it is desired to set the lubricating oil supply amount to 30 liter · min ⁻¹ , the maximum rolling speed at which seizure does not occur at the lubricating oil supply amount is 1
Since it is 730 m · min ⁻¹ , it must be rolled at that speed or less. Similarly, the lubricating oil supply is 45 liters / mi
When it is desired to set n ⁻¹ , it can be seen that the maximum rolling speed at which seizure does not occur at the lubricating oil supply amount is 2120 m · min ⁻¹ . In the present invention, the method for calculating the minimum necessary lubricating oil supply amount from the rolling conditions is defined, but in this way the lubricating oil supply amount is first set to calculate the limit rolling speed,
Similarly, it is also possible to calculate the lubricating oil concentration and the like.

While rolling conditions change during rolling, the speed that changes every moment in the equation of the present invention is the speed. The formula holds even when the speed changes, so if there is equipment that can change the lubricating oil supply amount in response to the speed change,
It is desirable to perform feedback control according to the speed change. As the value of the speed, it is preferable to use the plate speed. However, when the measurement is difficult, the roll peripheral speed may be used as V in the above equation. Further, it is also possible to control the lubricating oil supply amount according to the change in the plate speed at the acceleration / deceleration section near the joint.

So far, for one rolling stand,
It has been discussed in consideration of one rolling condition. However, there are many cases where the installation position of the nozzle is different between the upper and lower surfaces of the steel plate, and the adhesion efficiency (the amount of adhesion) of the lubricating oil to the steel plate and the roll is also different between the upper and lower surfaces of the steel plate. Therefore, it is natural that it is more reasonable to set the lubricating oil supply amount for each of the upper and lower surfaces of the steel sheet. In this case, the following equation (3) holds. Here, as described above, since only one side of the steel sheet is considered, the sheet width is not doubled. _{Q L = (χ sp × W} × V 2) / (600 × Q C × L) ······· (3)

In equation (3), the sheet width W [m] and the sheet speed V [m ·
min ⁻¹ ] depends on the steel plate and is therefore equal on the upper and lower surfaces of the steel plate. Therefore, the same value is used in the equations respectively corresponding to the upper and lower surfaces of the steel plate. The length L [m] up to the roll bite varies depending on the installation position of the nozzle and the like. When lubricating oil is supplied to the upper and lower surfaces of a steel plate from one tank, the lubricant oil concentration is the same at the upper and lower surfaces of the steel plate. Therefore, the same value is used in equation (3). When supplying lubricating oils having different lubricating oil concentrations, different values are used. Because chi _sp changes deposition efficiency of the lubricating oil is different, it is necessary to calculate each steel plate upper and lower surfaces. When these preparations are completed, the minimum required amount of lubricating oil can be supplied to each of the upper and lower surfaces of the steel sheet. Further improvement in yield can be expected.

In consideration of the yield of the lubricating oil, the nozzle is preferably variable in the width direction of the plate so that the lubricating oil supply end from the nozzle to the steel plate or roll can coincide with the plate end. desirable. Any method of changing the nozzle may be used. For example, only the tip of the nozzle is freely movable in three dimensions, and the nozzle is supplied according to the plate width so that the lubricating oil end coincides with the plate width end. Alternatively, a method may be adopted in which not only the nozzle tip but also the entire nozzle is movable in the plate width direction.

Further, as is apparent from the equations (2) and (3), the longer the length L [m] of the emulsion lubricating oil supply point on the steel plate or on the roll and immediately below the roll bite, the smaller the supply amount becomes. Good. Therefore, if the lubrication nozzle can be set apart from the stand, it may be set apart. However, in a cold tandem rolling mill, the stand interval is about 5 m, during which a thickness gauge, a speedometer, etc. In many cases, there is not enough space because the detector is installed. Even in such a case, in order to increase the length L [m] from the emulsion lubricating oil supply point on the steel plate or the roll to immediately below the roll bite, the lubricating nozzle needs to apply the lubricating oil toward the upstream stand at the current position. A supply method is conceivable.

Here, the results of an experiment conducted to determine the effect of lubricating oil supply to the upstream are shown. Use tallow containing a small amount of emulsifier and extreme pressure additive as lubricating oil base oil, lubricating oil concentration 2
0%, lubricating oil supply amount 40 l · min ^-1 , passing through a 998 mm wide plate, gradually increasing the speed,
Normal nozzle orientation (lubricating oil is supplied toward the roll bite) and when the nozzle is directed upstream (L = 2.6
Comparison of the lubrication state of m) was performed. FIG. 2 shows the result of evaluating the lubrication state by the friction coefficient. Friction coefficient is Brand & F
The ord's model was used to determine the values of the measured rolling load and the advanced ratio so as to match the calculated values. The coefficient of friction is 1500 m · mi both when lubricating oil is supplied to the roll bite and when lubricating oil is supplied to the upstream stand.
The values are almost the same up to n- ¹ . At higher speeds, the coefficient of friction when supplying to the roll bite increased. Since the above rolling conditions are typical rolling conditions for normal operation, the effect of supplying the lubricating oil to the upstream side is 1500 m.
-It was confirmed that it was particularly effective at min- ¹ or more.

[0020]

FIG. 3 schematically shows a cold tandem rolling mill used in an experiment conducted to confirm the effects of the present invention. FIG.
, The cold tandem rolling mill is a four-stand four-high rolling mill, and includes work rolls 1a and 1b, backup rolls 2a and 2b, a lubricating oil supply nozzle 3, and a steel plate 4. This time, the presented following formula _{Q L = (χ sp × 2W} × V 2) / on the basis of _{(600 × Q C × L)} ······· ( wherein in the case of the upper and lower surfaces collectively considered), lubricants An experiment was conducted in which the lubrication was gradually reduced from a sufficient case, and a lubrication deficiency was intentionally caused to induce heat scratch. If the lubricating oil supply amount is changed, the effect cannot be obtained instantaneously. Therefore, if heat scratch does not occur one minute after the supply amount is changed, heat scratch occurs under the rolling conditions. I decided not to. To use the above equation it is essential to obtain the chi _sp. Since in this experiment using refined palm oil was used the average value of the chi _sp as shown in Table 1 above.

Using ordinary steel having a width of 1000 mm, the final stand was accelerated to a rolling speed of 2000 m · min ⁻¹ and became constant, and then the amount of lubricating oil supplied to the final stand was reduced, resulting in heat scratching. By the way, the experiment was finished. As the lubricating oil, refined palm oil having a concentration of 12% and a temperature of 70 ° C. was used. The rolling reduction in the final stand is about 20%, and the final thickness is 0.95 mm. Further, the length between the roll bite and the lubricating oil supply point was set to 1.5 m. Under this condition, the supply amount is 29.7 liter · min ⁻¹ , and the heat scratch is calculated. The supply amount was started from 40 liter · min ⁻¹ of the upper and lower sides of the steel sheet. 40-3
No heat scratch occurred up to 0 liter · min ^−1, and heat scratch occurred at 29 liter · min ⁻¹ . From this, it was confirmed that the formula can estimate the supply amount at the time of occurrence of heat scratch.

[0022]

According to the lubricating oil supply method for cold rolling of the present invention described above, it is possible to calculate the minimum necessary lubricating oil supply amount capable of preventing heat scratching, and thus the productivity is improved. Can be improved, and the manufacturing cost can be reduced. Although the description has been given so far with respect to the tandem rolling mill, the formulas shown in the present invention have no variables unique to the tandem rolling mill, and can be applied to a single-stand rolling mill.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example for obtaining a required minimum lubricating oil supply amount and a maximum rolling speed under a certain rolling condition from a constant χ _sp .

FIG. 2 shows the effect of lubricating oil supply on the coefficient of friction (L length)
FIG.

FIG. 3 is a diagram showing a four-stand cold tandem rolling mill used in a rolling experiment performed to determine the effects of the model formula of the present invention.

[Explanation of symbols]

 1a, 1b: Work roll 2a, 2b: Backup roll 3: Lubricating oil supply nozzle 4: Steel plate

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C10M 173/02 C10M 173/02 // C10N 40:24 C10N 40:24 Z (72) Inventor Shigeru Ogawa Futtsu-shi, Chiba 20-1 Shintomi Nippon Steel Corporation Technology Development Division F term (reference) 4H104 AA01C BB31A DA06A PA28 QA02

Claims (4)

[Claims] 1. A cold rolling and sets the stand minimal supplies steel top and bottom surfaces simultaneously by the lubricating oil supply amount Q _L so as to satisfy the following formula in the lubricating oil supply in the cold rolling Lubricating oil supply method. _{Q L = (χ sp × 2W} × V 2) / (600 × Q C × L) where, chi _sp; constants, W; strip width [m], V; plate speed [m ·
min ^-1], Q _C; lubricant concentration [vol%], L; length of the farthest portion from the roll bite of the lubricating oil supplied from the roll bite immediately below and lubrication nozzle arcuate intersecting on steel [ _M ], QL; minimum lubricating oil supply [liter · m
in ^-1 ] 2. A set constants chi _sp independently to the steel plate upper and lower surfaces in the stand so as to satisfy the following formula in the lubricating oil supply in the cold rolling, the minimum lubricating oil supply amount Q _L A lubricating oil supply method for cold rolling, characterized in that it is set. _{Q L = (χ sp × W} × V 2) / (600 × Q C × L) where, chi _sp; constants, W; strip width [m], V; plate speed [m ·
min ^-1], Q _C; lubricant concentration [vol%], L; length of the farthest portion from the roll bite of the lubricating oil supplied from the roll bite immediately below and lubrication nozzle arcuate intersecting on steel [ _M ], QL; minimum lubricating oil supply [liter · m
in ^-1 ] 3. The lubricating oil supply nozzle is variable in the plate width direction, and the nozzle direction is changed according to the plate width so that the plate width end and the supplied lubricating oil end coincide with each other. The method for supplying a lubricating oil for cold rolling according to claim 1 or 2. 4. A nozzle for supplying lubricating oil to a steel sheet has a variable lubricating oil injection direction, and is at least 1500 m · min.
The cold rolling according to any one of claims 1 to 3, wherein at the time of high speed rolling of ^-1 or more, the injection direction of the lubricating oil from the nozzle has a vector component in a direction opposite to the traveling direction of the steel sheet. Lubricating oil supply method.