JPS6049041B2 - Rolling lubrication control method in cold rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling lubrication control method in cold rolling, and a method for controlling lubrication between a rolling roll and a strip material when a thin metal plate, particularly a steel strip, is obtained by cold rolling. It attempts to maintain a stable state.

When cold rolling a thin metal plate, for example a steel strip, rolling oil is supplied between the strip material and the rolling rolls to facilitate rolling and to give the strip a beautiful surface appearance. The rolling oil is selected depending on the type and size of the strip material to be rolled. for example,
When rolling a thick plate of carbon steel with a finishing thickness of about 0.8 nm, oil with a composition mainly composed of mineral oil or synthetic ester is used, and when rolling a thin plate with a finishing thickness of about 0.2 mm, use beef tallow or palm oil. Oils with a composition mainly composed of animal and vegetable oils, such as, are generally used. The rolling oil is injected onto the strip material or the rolling rolls in the form of an emulsion in water, in each case at a suitable concentration, usually from 3 to 20%.

By the way, rolling rolls are polished to a suitable surface roughness, usually around 0.5 μm with a centerline average roughness Ra, and installed in a rolling mill, and are pulled out and re-rolled each time a certain amount of strip material is rolled. Perform polishing.

That is, during rolling of the strip material, unavoidable slippage between the material causes friction on the surface irregularities, and the surface roughness decreases in accordance with the amount of rolling. Note that if the rolling amount is excessive, the roll surface becomes rough due to fatigue, and the surface roughness increases. As the surface roughness decreases with the amount of rolling, the friction coefficient naturally decreases and the plate becomes easier to stretch, but the rolling state becomes unstable.

In other words, the value of the friction coefficient μ decreases to 0.01-0.0 degree, and the circumferential speed of the rolling roll and the strip material in the contact arc along the roll surface in the gap between the rolling rolls. If the neutral point, where the material speed matches, is closer to the exit side, it will be more susceptible to changes in plate thickness and tension, and sometimes the neutral point will protrude outside the exit of the contact arc, causing the rolling rolls and strip material to As soon as the material is removed, the board material stops advancing and breaks due to the tension on the exit side. In conventional cold rolling, stable rolling is achieved by maintaining an appropriate lubrication state by adjusting the rolling speed in proportion to the rolling speed.

The present invention obtains, as an actual measured value, the change in the coefficient of friction between the rolling roll and the metal strip material due to changes over time in the surface roughness of the rolling roll during cold rolling of the metal strip material.
The neutral point where the circumferential speed of the rolling roll and the speed of the strip material coincide sets the critical friction coefficient that protrudes to the exit side of the contact arc between the roll and the material; Compare the measured calculated value of , and determine whether the measured calculated value exceeds the minimum friction coefficient by adjusting any of the flow rate, concentration, temperature, and type of the rolling lubricating oil emulsion, including the safety margin. This is a rolling lubrication control method in cold rolling, which involves implementing control to control the rolling lubrication in cold rolling.

The invention will be explained below by way of examples.

Thickness 0.2 to 0.3 mm, width 700 mm with cold tandem rolling mill
When rolling a thin steel plate such as a tin plate of approximately 8,007 T$L, change the flow rate of the rolling emulsion according to the rolling length of the thin steel plate so that the amount of adhesion to the rolling roll and strip material does not change. As the surface roughness of the rolling roll decreases as the rolling amount increases, the force with which the rolling roll restrains the plate, that is, the coefficient of friction, decreases, making it easier to slide. , the rolling oil is replaced with a roll; initially its friction coefficient μ is 0.07 to 0.1.
There was a problem in that the rolls were being supplied in the same way as when they were relatively large, and as a countermeasure to this problem, the rolls were replaced, assuming that it was simply the friction limit of the rolling rolls.

As a result, the rolls must be changed frequently, which is extremely disadvantageous in terms of rolling efficiency and roll consumption. In order to solve the above-mentioned disadvantages and advantages, the present invention aims to solve the problem of roll abrasion, which reduces the surface roughness and lowers the friction coefficient due to roll abrasion as the amount of rolling increases, and as a result, the rolling state becomes unstable. This is based on the idea of adjusting the lubrication conditions in order to prevent the wear coefficient from decreasing regardless of the situation.

That is, the change Ra (μ7T1.
) is the 141st. As shown in the figure, for example, cold-rolled low carbon steel is used as the rolled material and palm oil is used as the oil agent.
At the beginning of rolling, it decreases rapidly during the first 5 to 10 degrees of rolling, but after that, it decreases at an almost constant rate from around 10 degrees.If the conventional method is followed without changing the supply condition of the rolling lubricating oil emulsion, the gap between the roll and the plate is shown by the broken line in the same figure. The friction coefficient μ generally follows almost the same trend. Such fluctuations in the coefficient of friction depending on the amount of rolling can be grasped by collecting rolling performance data, and in the present invention, this is taken as a factor in lubrication control.

On the other hand, FORD regarding cold rolling. , Ells and B
According to land's theory, the neutral angle φ.

is given by the following equations (1) to (5). Here φ.

: Neutral angle (Rad) h1, H2: Inlet side, outlet side plate thickness (WO
n) R. ．． R″: Roll original radius and flattened radius (TWL)
p: Friction coefficient Q,, Q,: Front and rear tension of the plate (K
gId) k1, K2: Deformation resistance (
K9ld) α: contact angle (Rad) b: plate width (WL) CO: constant (DltOn) P: rolling load (TOn).

The neutral point protrudes outside the exit at φ, as shown in an example in Fig. 2.

<0, so from equations (1) and (2), the friction coefficient μ at that time is Hl. l-Qdk21μ葡0ge(1-) ・・・(6) H2
When the relationship l-QJkl$μLO becomes smaller than the limit friction coefficient μLO, the neutral point protrudes from the contact arc and rolling becomes unstable as described above.

As can be seen from equation (6), μLO is related to rolling conditions. Therefore, in order to perform stable rolling, μ > μo, and μLO depends on the magnitude of variation in rolling conditions. Considering the change, μ≧μ.

〉μLa expressed as μLO is K (K=1~2)
It is sufficient to define μLa=K'PLO...(7) with K as a constant, where K is a constant that provides a stability margin, and μL, is a stability margin taken into account for the critical friction coefficient. For example, according to the change curve of the friction coefficient μ depending on the rolling length shown by the dotted line in FIG. 1, it is given as a virtual line that intersects at point B, in which case μ=μ.

When the rolling length becomes longer than point B, where μ〈
μ, the rolling condition may become unstable due to fluctuations in rolling conditions. FIG. 2 shows the neutral point position φ due to a decrease in the friction coefficient. ．． An example of the relationship of /α is shown, and the above B
A case is shown in which the friction coefficient μ rapidly shifts to the point where the neutral point position is significantly shifted toward the exit side of the rolling roll contact arc.

Therefore, the friction number μ that depends on the rolling amount of the rolling roll based on actual rolling data is always μ. Control the lubrication conditions so that the Among the lubrication conditions, does it affect the friction coefficient?
These include the flow rate concentration of the rolling oil emulsion, the temperature, the emulsification state, the amount of oiliness improver (for example, fatty acid), and the type of oil. For example, changing the concentration or flow rate changes the amount of rolling oil supplied to the plate, and therefore the amount of rolling oil deposited, changes the amount of oil drawn into the contact arc, and changes the friction coefficient μ. Also, when the temperature changes, the viscosity of the rolling oil changes, the amount of oil flowing into the contact arc changes, and μ changes.

The emulsification state is related to the amount of adhesion, and the oiliness improver is directly related to μ. FIG. 3 shows an example of the relationship between the rolling length and the friction coefficient using the amount of rolling oil deposited as a parameter.

However, the rolled material was a cold-rolled carbon steel material, and by using palm oil as an oil agent and changing the water-in-water emulsion concentration or flow rate, the rolling oil adhesion amount d was 10.29 novo, 20.5yI, 3
1. y177f', 42.0y1a and 53.0y1
In each case of d, the relationship between the pressure extension and the friction coefficient μ is shown in a diagram. In this case, the value of the limit friction coefficient plus the stability margin is calculated as μ as shown in the figure. = 0. 02, even if the C rolling lubricating oil adhesion amount d=1.0qI7T1 is used and the rolling length is about 40 km, it becomes μ'-0.02 and it becomes 3 roll changes. As soon as the equation point 7 is reached, if the concentration or flow rate of the rolling lubricating oil emulsion is reduced so that d=0.5yIa, then the friction coefficient μ becomes larger than PLa as shown at point D2. , the rolling extension can be further extended by about 20 km while reaching point B2 without changing the roll.

Similarly, if d=0.2yId is set at point B2, the friction coefficient μ increases dramatically at point D1, and the rolling extension can be further extended by approximately 30 times to point B. Note that curve 1
is the limit for the occurrence of so-called heat streaks in which the plate and roll are locally seized, and since the amount of rolling lubricant applied cannot be lowered below this limit, the rolls must be replaced at this point. Heat streaks are more likely to occur as the rolling reduction rate and rolling speed increase, and in such cases, it is natural that the critical amount of rolling lubricating oil must be increased.

Note that it is more preferable that the friction coefficient μ be smaller as long as it exceeds the value μLa, which takes a stability margin into the limit friction coefficient, because rolling becomes easier.

Therefore, in areas where the surface roughness is relatively large immediately after the rolls are changed, if the amount of rolling oil adhered is set to be large and gradually decreases with rolling, it will be equal to or exceed μ as shown in Figure 3. Sliding control is possible.

The initial setting of the rolling oil adhesion amount is determined to the extent that its consumption is balanced with the improvement in the power unit consumption due to the reduction in friction 5. Figure 4 shows an example of application to a 5-stand dandem cold mill.

A mother plate coil 1 for strip material is rolled in a rolling mill stand 2, and during rolling, the strip is sprayed by a rolling oil spray nozzle 4 on the entrance side of each rolling stand through a rolling oil flow rate control valve 3, and the final oil is sprayed onto the strip. After passing through the rolling stand, the thickness of the sheet is measured using an X-ray thickness meter 5, and the sheet is wound into a coil 6. 35 As for the method of supplying the rolling oil, for example, a rolling lubricating oil emulsion (for example, palm oil) is supplied from the rolling oil tank 7 using the rolling oil pump 8, and hot water is supplied from the hot water tank 9 using the hot water pump 10, The rolling oil is supplied to the mixing tank 14 through the oil flow rate and hot water ratio regulator 11, the rolling oil flow rate adjusting valve 12, and the hot water flow rate adjusting valve 13 so as to have a predetermined concentration of rolling oil, and is mixed in the mixer 15. , a rolling lubricating oil emulsion 16 is prepared.

The rolling oil emulsion 16 is pumped up by a rolling oil emulsion pump 17, passed through a rolling oil emulsion distributor 18 by a feeder pump 19 for each rolling stand, and sent to the rolling oil at the inlet side of each rolling stand through a rolling oil flow control valve 3. Oil spray ● is supplied to nozzle 4 and sprayed onto the strip.

The flow rate change accompanying the change in rolling speed is performed, for example, by changing the rotation speed of the feeder pump 19. The flow rate change for lubrication control according to the present invention is preferably performed by the rolling oil flow rate control valve 3, but may also be performed by the rotation speed of the feeder pump 19. The supply device for the rolling oil emulsion 16 can normally be divided into two systems as shown in the figure, one for the front stands #2 and #3 and one for the stands #4 and #5 of the rear stage.

Note that in the #1 stand, rolling oil is already applied to the base plate, so the rolling oil emulsion 16 does not need to be supplied. The specifications of the rolled material and the roll diameter Ri are input to the friction coefficient calculation device 20, as well as the rolling load Pjl of each rolling stand, roll rotation speed Nil2 #1, #5
The stand outlet plate thickness Hl, h5, the tension between the stands Qi,
It is input as a measurement value by a measuring device (not shown) installed in the rolling mill, and for example, during rolling of one coil, the first half and Similarly for each of the second and second half coils), data such as rolling load Pil, roll rotation speed Nil #1, #5 stand outlet plate thickness Hl, tension between stands Qi, etc. of each stand are obtained from the above measuring device. The friction coefficient μ is read and calculated, and based on this, the rolling oil emulsion flow rate and the mixing ratio of the rolling oil and hot water flow rates are controlled by the emitter 3' flow rate regulator 21 and the ratio regulator 11, respectively.

The coefficient of friction between the rolled material for the strip and the rolling roll is determined as follows based on rolling load equations (8) to (12).

Rolling load type ~ ---- ノ14L ↓l1
1 (1 oto no here C.

: Constant rolling load determined by roll material Pil roll rotation speed Ni, outlet plate thickness H2l, H25 inter-stand tension Q, (=Qfi=Qbi+1 is measured, roll diameter R,,
Since the plate width b1 and the mother plate thickness Hll are given separately, first, by combining the mass flow law equations (13) to (15) and the neutral angle equations (1) to (5), the plate thicknesses H2, h3,
Find h. Mass flow rule Jll & e Todoro'JV'7V, Ba5 (13)
There is Fi in the formula to find H2i in the formula, and F in formula (15),
Since H2 is included in the formula for calculating, by iterative convergence calculation,
Find the solution.

Next, using this plate thickness and actual measurement data, the rolling load formula (8)
- Calculate the print from equation (12). In other words, from equation (8), Q
, and μ from equation (9). Then, calculate R″ from equation (1), and then convert K.i to the deformation resistance equations (16) to (20). Expression one
0 (ZU here K: Stephan Boltzmann's constant, Cll, n: constant determined by the material p: find the constant 5, calculate this by a(j
Calculate K6 by giving it to the l formula.

For the strip temperature Ti in equation (16), an actual value may be used, or a value predicted and calculated using an appropriate method that takes into consideration plastic working heat, friction heat, conduction loss heat (to the roll), and cooling by coolant may be used. As described above, the coefficient of friction Pi is calculated using one coil a suitable number of times.

For example, when calculating twice with one coil, the measured value of the j-th coil from the roll change is Pi2, + E, Pi2
J+, as shown in equations (21) and (22), a moving average is determined for each calculation. On the other hand, using equation (6) for the rolling conditions of this coil, the limiting atmospheric friction coefficient PL. , find (
7) From the formula, the value PL that takes into account the stability margin for the critical friction coefficient
Find ai. Add this to J+11I52j+2
Compared with -STi\2j+11pox)2J+, 冫PLai
In the case of , the rolling condition is stable, so the lubrication conditions are not changed. Furthermore, if Yi2J+1 or Ti2j+KPLajj, the rolling condition is 1 unstable, so the lubrication conditions are changed to make it Pp.

In other words, in order to roll the remaining portion of this coil in a stable state, P, l, shown in Fig. 3, which was determined in advance by experiment,
Relationship of d P, = Fi (H...Mountain) ・In (23), where W,: coil weight, Rk: specific weight of material, find the peak that satisfies equation (23). Let this be the mountain. do.

In addition, in consideration of the occurrence of heat streaks, there are
Lower limit value D. i is determined in advance, and d is determined in advance. Change the small value within the range of i. The emulsion flow rate or concentration to achieve the desired amount of adhesion is calculated using a relational expression determined experimentally in advance, and the emulsion flow rate regulator 21 or
The change flow rate or the target value of the ratio is given to the ratio adjuster 11 by the friction coefficient calculation control device 20 to change the flow rate. Note that although the flow rate can be changed for each stand, the concentration change is performed for each system, so it goes without saying that in order to realize the ton for each related stand, it is necessary to change the flow rate at the same time.

The above example shows a method of controlling by actually measuring the coefficient of friction and predicting the necessary changes to PLa (flow rate or concentration of rolling oil emulsion), but other methods are also possible.

For example, the measured friction coefficient 7L,, and the limit friction coefficient PL. ,
It is also possible to perform linear feedback control of the flow rate of the rolling oil emulsion in accordance with the difference in . That is, here′
Pij: Yi soj+1 or 1ゐ+2Pi: Proportional gain (p>0) 1i: Integral gain (Ii>0) 8Qeij: Find the change in rolling oil emulsion flow rate as flow rate change 21
You can output it to .

As another example, for the rolling length h, the rolling oil emulsion flow rate Qei is determined in advance based on the rolling length h, and is given to the control device 20.

There is also a method of program-controlling the emulsion by extracting Qe corresponding to the rolling length h from 20 and applying it to the emulsion flow rate regulator 21 as the rolling progresses. In this case, the friction coefficient may be actually measured for each coil, and the programmed flow rate may be corrected by, for example, adding Q, of equation (25) to Qe. Based on this invention, the roll change can be postponed by changing the emulsion flow rate so that the friction coefficient p does not fall below the limit friction coefficient PL.

An example is shown in the table below. As shown in the table, the rolling tonnage until roll change is 200t for #2 to 3 stands, 200t for #4 stand, 10 (b) for #5 stand, which improves the roll consumption rate and also increases the roll change time. The rolling efficiency is greatly improved.

Furthermore, since the flow rate or concentration of rolling oil is reduced, this invention has many benefits such as improving the unit consumption of rolling oil.

[Brief explanation of drawings]

FIG. 1 shows the change in roll surface roughness and friction coefficient depending on the rolling length, and FIG. 2 shows the relationship between the friction coefficient and the neutral point position. 3 and 4 are explanatory diagrams of the invention, and FIG. 3 shows a method of changing the coefficient of friction by changing the amount of rolling oil deposited as rolling progresses. FIG. 4 shows an example of a 5-dandem cold mill. 3...Rolling oil flow control valve, 4.
...Rolling oil spray nozzle, 6...Rolling oil tank, 7...Rolling oil pump, 11...
・・Rolling oil amount control valve, 13・・・Mixion tank, 19・・・・Rolling oil emulsion ●Pump, 20
... Friction coefficient calculation control device, 21 ... Emulsion flow rate regulator.

Claims (1)

[Claims] 1. During cold rolling of a metal strip material, the fluctuation trend of the coefficient of friction between the rolling roll and the metal strip material due to changes over time in the surface roughness of the rolling roll is obtained as an actual measured calculated value. The critical friction coefficient at which the neutral point where the circumferential speed and strip material speed coincide protrudes to the exit side of the contact arc between the roll and the material is calculated according to the rolling conditions, and a stability margin is included in this critical friction coefficient. Compare the actual measured calculated value of the friction coefficient with the above value, and use this measured calculated value to determine the stability margin for the critical friction coefficient by adjusting any of the flow rate, concentration, temperature, and type of the rolling lubricating oil emulsion. A rolling lubrication control method in cold rolling that involves controlling the lubrication to be equal to or greater than the expected value.