JP2002346614A - Control method of forwarding rate in cold rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of forwarding rate in cold rolling which efficiently prevents occurrence of chattering. SOLUTION: The forwarding rate at the last stand F1 is calculated based on a plate speed at the exit of the last stand F1 and a roll circumferential speed at the last stand F1. If it is detected that the calculated forwarding rate deviates from the preset range of the safety forwarding rate where the occurrence of chattering is prevented, the density of rolling mill lubricant supplied at the last stand F1 is adjusted so that the forwarding rate becomes within the safety forwarding rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal strip (hereinafter referred to as "strip") such as a steel strip by a cold tandem mill.
, Especially chattering (resonance phenomenon) in cold rolling found in thin materials such as hard steel strip
The present invention relates to a method for controlling an advanced rate in cold rolling, which is effective for prevention of cracking.

[0002]

2. Description of the Related Art As a method of controlling the advance rate, for example, there is a method described in Japanese Patent Application Laid-Open No. 61-199507.
In this advanced rate control method, the friction coefficient is determined from the plate thickness, tension, plate speed, etc., and the influence coefficient of the friction coefficient model formula using the amount of rolling lubricating oil as a variable is corrected based on the friction coefficient model formula. The rolling factors (e.g., tension, inlet side plate thickness, rolling lubricating oil amount) are controlled so that the advanced rate falls within an allowable range. Thus, even if the rolling conditions are changed, the advanced ratio can be predicted with sufficient accuracy for practical use, so that stable high-speed rolling is to be ensured.

In the advanced rate control method described in Japanese Patent Application Laid-Open No. 62-292209, the tension between stands is adjusted so that the advanced rate becomes a preset target advanced rate. Further, in the advanced ratio control method described in Japanese Patent Application Laid-Open No. 62-72409, a friction coefficient that is a target advanced ratio is estimated, and a rolling-rolling lubricating oil amount is calculated from a friction coefficient model based on the estimated friction coefficient. The advanced rate is controlled to the target advanced rate by controlling the amount of the lubricating oil for the rolling so that the calculated amount is obtained.

In Japanese Patent Application Laid-Open No. 3-151106, a current advanced ratio is determined, a friction coefficient prediction formula is created from the advanced ratio, and a rolling lubricant concentration that reaches a target advanced ratio is determined from the friction coefficient predicted expression. The advanced rate is controlled by controlling the rolling lubricating oil concentration.

[0005]

On the other hand, recently, it has become clear that the deformation resistance changes during rolling due to factors of the mother plate, which induces chattering. Therefore, in the method described in JP-A-61-199507, it is difficult to control the longitudinal direction of the coil, and if the rolling load or the tension is changed so as to follow the deformation resistance change, the thickness of the sheet may fluctuate. is there.

In Japanese Patent Application Laid-Open No. 62-292209, the tension between stands is controlled to be constant.
Since the change of the deformation resistance occurs rapidly, there is a problem that the responsiveness is insufficient in the control of the advance rate by the tension control. Further, Japanese Patent Application Laid-Open No. 62-72409 and Japanese Patent Application Laid-Open
The control described in JP-A-151106 is a technique of estimating the friction coefficient at each stand from the advance rate and controlling the supply amount of the rolling lubricant or the concentration of the rolling lubricant from the estimated friction coefficient. In this technique, control is performed using the estimated friction coefficient.However, the estimated friction coefficient does not always match the actual friction coefficient, and the accuracy is inferior, because there is always some deviation, In some cases, it was not possible to follow a sudden change in rolling conditions caused by a change in deformation resistance, and the frequency of chattering could not be sufficiently reduced.

Further, when controlling the advance rate by controlling the supply amount of the rolling lubricating oil, if the supply amount is limited, it becomes difficult to uniformly spray the strip, and the rolling state in the width direction of the strip becomes difficult. And the shape of the plate may be deteriorated. In Japanese Patent Application Laid-Open No. 3-151106, the rolling lubricating oil concentration is controlled. However, as described in the upper right column on page 3, the higher the concentration, the larger the amount of oil and the lower the friction coefficient. I have. In addition, control is always performed so that the target density corresponds to the target advanced rate.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an advanced rate control method in cold rolling capable of efficiently preventing chattering from occurring.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an advanced rate at a final stand in a cold tandem mill on the basis of a plate speed at the exit side of the final stand and a roll peripheral speed at the final stand. When the calculated advance rate is out of the range of the safety advance rate in which chattering occurrence is determined in advance, the rolling lubrication supplied at the final stand is adjusted so that the advance rate falls within the range of the safety advance rate. An object of the present invention is to provide an advanced rate control method in cold rolling, which is characterized by adjusting the concentration of oil.

Here, it has been confirmed that as the rolling lubricating oil concentration increases, the advanced ratio decreases. For example, when the upper limit of the stable advanced ratio is exceeded, the rolling ratio is offset by the offset from the upper limit. Change the oil concentration to be higher,
In addition, when the safety advanced rate is lower than the lower limit, the rolling oil concentration may be changed so as to be reduced by the offset from the lower limit.

When the present inventors investigated, most of the chattering occurred in the final stand of rolling, which had the smallest thickness and high deformation resistance. From this point of view, in the present invention, the efficiency of control is improved by controlling only the final stand in the cold tandem mill. Further, if control is performed so that the rolling conditions of the former stand are also changed, the change of the former stage affects the rolling state of the final stand, and there is a possibility that quick control may be difficult. This problem can be solved by using That is, the control of the advance rate becomes simpler than in the past.

Further, the above-mentioned advanced ratio is adjusted by controlling the rolling lubricating oil.
The change in the amount of oil supplied by the control is kept small, and the adverse effect on the rolling is kept small. Note that, as will be described in an embodiment to be described later, it is possible to set a higher responsiveness when changing the density than when changing the supply amount.

Further, since the rolling oil concentration is not always adjusted but is changed only when the rolling oil concentration is out of a predetermined allowable range, the adverse effect on the rolling can be suppressed from this point.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating the rolling mill equipment of the present embodiment. That is, a plurality of stands 1A to 1F of the cold tandem mill 1 are arranged along the strip 2 conveyance direction, and in FIG. 1, the strip 2 is conveyed from left to right while each stand 1A to 1F.
In order to be rolled in order.

A bridle roll 3 and a coiler are arranged downstream of the final stand 1F. The strip 2 coming out of the final stand 1F is applied with a predetermined tension by the bridle roll 3 and the coiler 4 is wound.
It is wound up. Then, the rotation speed of the work roll 5 of the final stand 1F is detected by the first rotation speed sensor 6, and the first rotation speed sensor 6 outputs a detection signal to the advanced rate control device 8. Further, the rotation speed of the bridle roll 3 is detected by the second rotation speed sensor 7, and
The rotation speed sensor 7 outputs a detection signal to the advanced rate control device 7.

Further, the advanced rate control device 8 includes an advanced rate calculation section 8A, a dead zone determination section 8B, and an output section 8C. The advanced rate calculator 8A calculates the peripheral speed Vr of the work roll 5 of the final stand 1F based on the detection signal from the first rotation speed sensor 6, and calculates the bridle roll 3 based on the detection signal from the second rotation speed sensor 7. Peripheral speed, ie, sheet speed V
s is calculated, the advanced rate f is calculated by the following equation (1), and the calculation result is output to the dead zone determination unit 8B.

[0017] The dead zone determination unit 8B determines whether the input advanced rate f is out of the range of the set safety advanced rate,
If it is determined that the advanced rate f is smaller than the lower limit L or larger than the upper limit H of the above range, the density change amount according to the relative value from the upper limit H or the lower limit L is calculated based on the graph shown in FIG. Calculate and output to the output unit.

Here, the upper limit value H of the range of the safety advance rate
And the lower limit L are obtained in advance as follows. That is, as a range of the stable advanced rate, a region in which chattering is likely to occur if the range is exceeded is determined in advance by experiments or the like, and a safe advanced rate range is set within this range. In this embodiment, the range of the safety advance rate is 1%
More than 4%. However, the allowable width is 0.5
In view of%, the range of the safety advance ratio is set with the limit value being 0.5% smaller than each of the above boundary values. That is, the lower limit L is set to 1.5% and the upper limit H is set to 3.5%.

Although setting the range of the safety advance rate in consideration of the allowable range as described above is advantageous in that chattering can be more reliably prevented, the safety advance rate is not expected in view of the allowable range. It may be set as the same range as the stable advance rate. The output unit 8C outputs the input amount of concentration change to the concentration controller 24 of the rolling oil supply device 9. The rolling oil supply device 9 injects the rolling lubricating oil from the nozzles of each header 14 onto the surface of the strip 2 while controlling so that the target density is changed by the input density change amount.

Next, the configuration of the rolling oil supply device 9 of the present embodiment will be described. FIG. 3 is a schematic configuration diagram illustrating the rolling oil supply device 9 according to the present embodiment. That is, reference numeral 12 denotes a high-concentration tank for supplying high-concentration rolling oil, which is connected to a mixer 20 disposed directly below the header 14 through a high-concentration supply path 22. A booster pump 25 and a precision gear pump 21 are interposed in the high-concentration supply path 22 from the upstream side so that the supply flow rate of the rolling oil discharged to the mixer 20 can be controlled with high response. Note that reference numeral 17
Indicates a return path.

Reference numeral 11 denotes a low-concentration tank for supplying water or low-concentration rolling oil. The low-concentration tank is connected to the mixer 20 through a low-concentration supply path 23 and is interposed in the low-concentration supply path 23. The low-concentration pump 15 can supply water or low-concentration rolling oil to the mixer 20. Note that the concentration of the low-concentration rolling oil may be, for example, the lowest concentration that can be assumed as the rolling oil supplied to the target strip.

The mixer 20 is disposed immediately before the header 14 and continuously mixes high-concentration rolling oil supplied from the tank 12 with water or low-concentration rolling oil supplied from the tank 11. And discharge it to the header 14. The header 14 is capable of spraying the supplied rolling oil of a predetermined concentration toward the surface of the strip 2 on the side of the final stand 1F.

The control of the concentration of the rolling oil in the rolling oil supply device 9 having the above configuration will be described.
Is controlled to a constant flow rate of the water or the low-concentration rolling oil fed from the plant. Then, the precision gear pump 2 is controlled by the concentration controller 24 so that the required target concentration is obtained.
1 is controlled. However, concentration controller 2
4 controls the discharge flow rate of the precision gear pump 21 so that when the density change amount is inputted from the advanced rate control device 8, the density value is changed by the target density by the density change amount. That is, the concentration controller 24 controls the header 14 based on the supply flow rate from the low concentration tank 11, the rolling oil concentration, and the target concentration (when the concentration change amount is input, the concentration value considering the concentration change amount). The supply flow rate of the high-concentration rolling oil at which the rolling oil supplied from is supplied to the target concentration is determined, and a discharge amount command is sent to the precision gear pump 21 so as to achieve the supply flow rate. The mixer 20 from the low concentration tank 11
The supply flow rate may be set so that, for example, the ejection flow rate from the nozzle of the header 14 becomes the target flow rate (when a change in density is input, the flow rate takes into account the flow rate change due to the density change).

Next, the operation and effect of the above-mentioned equipment will be described. The strip 2 is provided at each of the stands 1A to 1
The rolls are sequentially rolled at F, and subsequently sent to the coiler from the final stand 1F via bridle rolls and wound.
If the calculated advance rate at the final stand 1F is within the range of the set safety advance rate, it is estimated that chattering will not occur. Therefore, adjustment of the rolling lubricant concentration for advance rate control is performed. Not performed. On the other hand, if the calculated advanced rate at the final stand 1F is out of the range of the safe advanced rate,
Based on FIG. 2 described above, the amount of concentration change is obtained and supplied to the rolling oil supply device 9. The rolling oil supply device 9 uses a high concentration tank to produce a concentration change corresponding to the input concentration change amount from the target concentration. The supply flow rate of the rolling oil from No. 12 to the mixing tank is changed.

By adjusting the concentration of the rolling oil and lubricating oil in this way, the advanced rate is controlled so as to be within the range of the safe advanced rate, and chattering occurs in the final stand 1F where chattering is most likely to occur. Is prevented. Here, in the rolling oil supply device 9 having the above configuration, the header 14 is supplied to the water or the low concentration rolling oil supplied from the low concentration tank 11.
Immediately before, a necessary amount of high-concentration rolling oil is additionally mixed and supplied to the header 14, so that the rolling oil adjusted to the target concentration is supplied to the strip 2. As described above, since the concentration is adjusted immediately before the header 4, the responsiveness of the concentration adjustment of the rolling oil is high. That is, it is possible to control the advanced rate with high response.

In the case where water and rolling oil are mixed in the mixer 20 disposed immediately before the header 14 to adjust the concentration, EMI (Emulsion S) is used due to insufficient mixing.
(ability index: emulsification stability) tends to be low, and the particle size of the emulsion supplied from the header tends to be large. In particular, when such a point is considered to be a problem, if a low-concentration rolling oil is supplied from the low-concentration tank 11, the rolling oils will be mixed with each other, resulting in good emulsification stability and an increase in particle size. It is preferable because it does not accompany.

Here, in the above embodiment,
Although the density is changed by an amount that is linearly proportional to the displacement of the advanced ratio calculated from the upper limit H or the lower limit L of the safe advanced ratio, the present invention is not limited to this. For example, the displacement amount and the density change amount may be associated in a stepwise manner. The concentration of the low-concentration rolling oil is preferably 1% or more in order to secure high ESI. Further, in order to make it possible to cope with all the strips 2, it is preferable that the lower limit of the concentration of the high-concentration rolling oil is a concentration that exceeds the assumed highest concentration of the rolling oil. The upper limit of the concentration of the high-concentration rolling oil is 100% (the concentration of crude oil in the rolling oil). From the viewpoint that the concentration of the rolling oil in the mixer 20 can be adjusted with high response with a small change in the high-concentration rolling oil, it is preferable that the high-concentration rolling oil be a stock solution of the rolling oil.

In the above embodiment, the mixer is arranged immediately before the header. However, this mixer may be arranged in the header.

[0029]

As described above, according to the advanced rate control of the present invention, chattering can be efficiently prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a cold rolling facility according to an embodiment based on the present invention.

FIG. 2 is a diagram illustrating a relationship between an advanced rate and a density change amount according to the embodiment based on the present invention.

FIG. 3 is a schematic configuration diagram showing a rolling oil supply device according to an embodiment based on the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous rolling mill 1F Final stand 2 Strip 3 Bridle roller 4 Coiler 5 Work roll of final stand 6, 7 Rotation speed sensor 8 Advanced rate control device 8A Advanced rate calculation section 8B Dead zone determination section 8C Output section 9 Rolling oil supply device 11 Low Concentration tank 12 High concentration tank 14 Header 15 Low concentration pump 20 Mixer 21 Precision gear pump (High concentration pump) 22 High concentration supply path 23 Low concentration supply path 24 Concentration controller 25 Booster pump

Claims (1)

[Claims] 1. An advanced rate at a final stand in a cold tandem mill is calculated from a sheet speed at the exit side of the final stand and a roll peripheral speed at the final stand. The cold rolling is characterized by adjusting the concentration of the rolling lubricating oil supplied at the final stand so that the advanced rate is within the range of the safe advanced rate when the advanced rate is out of the range of the reduced safety advanced rate. Advanced rate control method.