JP2013193116A - Method of manufacturing cold-rolled steel plate and cold rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a cold-rolled steel plate and a cold rolling mill which can prevent deterioration of product quality of a steel plate caused by vibration by preventing the vibration of a roll and also can prevent wear of a roll bearing in manufacturing the cold-rolled steel plate by the cold rolling mill.SOLUTION: A natural vibration frequency of a rolling stand and a vibrational frequency of a roll are calculated, and an operation condition of the rolling stand is set so that the vibrational frequency of the roll does not correspond to a previously-set percentage range of the natural vibration frequency of a rolling mill.

Description

  In the present invention, after pickling a rolled steel sheet, when rolling to a predetermined thickness with a cold rolling mill, the appearance of the steel sheet surface is prevented from being poor due to rolling mill vibration caused by wear of the roll bearing. Furthermore, the present invention relates to a method for manufacturing a cold-rolled steel sheet that can extend the life of a roll bearing, and a cold rolling mill that performs this manufacturing method.

In the production of a cold-rolled steel sheet using a cold rolling mill, the vibration of the rolls of the rolling stand is exemplified as a cause of poor surface properties such as the occurrence of patterns and uneven thickness.
As a cause of the vibration of the roll of the rolling stand, wear of the roll bearing that supports the roll is known.

In general, as countermeasures against vibration caused by wear of the roll bearing, prevention of wear of the roll bearing and suppression of vibration of the rolling stand are known.
Examples of methods for preventing wear of the roll bearing include changing the material of the roll bearing, such as using a material that does not easily wear, and changing the structure of the roll bearing, such as making the structure difficult to wear. Further, as a vibration suppression method for the rolling stand, a method of increasing the damping ratio of the rolling stand by installing a dynamic vibration absorber (for example, Patent Document 1) is known.

However, modifications such as material changes and configuration changes of roll bearings take a long time to study and test. Moreover, a large construction and cost are required for changing the roll bearing.
Similarly, installation of a dynamic vibration absorber in a rolling stand requires a large amount of work and cost.

In addition, a method of suppressing vibration by reducing the rolling speed when vibration has occurred is also known.
However, if the rolling speed is reduced, it goes without saying that the production efficiency decreases.
Furthermore, the fact that the roll vibrates greatly means that the wear of the bearing is progressing accordingly. For this reason, when large roll vibrations occur, it is eventually necessary to replace the rolls, or to care for or replace the worn bearings, and further, setup time is required.

Japanese Patent Laid-Open No. 5-104117

  An object of the present invention is to solve the problems of the prior art described above, and in the production of cold rolled steel sheet using a cold rolling mill, to suppress the vibration of the roll of the rolling stand due to the wear of the roll bearing. Further, it is an object of the present invention to provide a method for producing a cold-rolled steel sheet capable of extending the life of a roll bearing, and a cold rolling mill for carrying out the method for producing the cold-rolled steel sheet.

  In order to achieve the above object, a method for producing a cold-rolled steel sheet according to the present invention is the production of a cold-rolled steel sheet using a cold rolling mill. By calculating the natural frequency and the vibration frequency of each roll, it is detected whether the vibration frequency of each roll coincides with a predetermined% range of the natural frequency of the rolling stand, When the vibration frequency of the roll does not coincide with a preset range of% of the natural frequency of the rolling stand, cold rolling of the steel sheet is performed with the provisional operation condition as the operation condition, and the vibration frequency of each roll is In the case where the predetermined range of the natural frequency of the rolling stand coincides with the predetermined range, the temporary operating condition is changed, and again, the natural frequency of the rolling stand and the vibration frequency of each roll Calculating and detecting whether or not the vibration frequency of each roll coincides with a preset% range of the natural frequency of the rolling stand. Provided is a method for producing a cold-rolled steel sheet, which is repeated until the natural frequency does not coincide with a preset% range.

In such a method for producing a cold-rolled steel sheet according to the present invention, it is preferable that the temporary operating condition is set corresponding to the maximum set speed of the cold rolling mill.
Moreover, it is preferable that the preset% range is within ± 5%.
Furthermore, it is preferable to change the temporary operating condition by changing at least one of the rolling reduction, the tension applied to the steel plate, and the rolling load.

  Further, the cold rolling mill of the present invention includes a plurality of rolling stands, a condition control unit that is provided corresponding to each of the rolling stands, and that controls operating conditions of the rolling stand, and at least one of the rolling stands. With respect to the above, the provisional operating conditions are set, and the natural frequency of the rolling stand and the vibration frequency of each roll in the temporary operation condition are calculated, and the vibration frequency of each roll is the characteristic of the rolling stand. And a calculation unit that detects whether or not the frequency range matches a preset% range, and the calculation unit further sets a vibration frequency of each roll in advance as a natural frequency of the rolling stand. If it does not agree with the% range, the condition control unit is instructed to set the provisional operation condition as the operation condition in the corresponding rolling stand, and the vibration of each roll is When the frequency coincides with a preset range of% of the natural frequency of the rolling stand, change the set temporary operating condition, and again, the natural frequency of the rolling stand and each roll The vibration frequency of each roll is calculated by calculating whether the vibration frequency of each roll coincides with a predetermined% range of the natural frequency of the rolling stand. A cold rolling mill is provided, which is performed until the natural frequency of the rolling stand does not coincide with a predetermined range of%.

In such a cold rolling mill of the present invention, it is preferable that the calculation unit sets the temporary operating conditions in accordance with the maximum set speed of the cold rolling mill.
Moreover, it is preferable that the said calculating part sets the range of the said preset% within +/- 5%.
Furthermore, it is preferable that the calculation unit changes the temporary operating condition by changing at least one of a rolling reduction, a tension applied to the steel plate, and a rolling load.

In the cold rolling mill according to the present invention having the above-described configuration, the vibration frequency of the roll is not matched with a preset% range (for example, within ± 5% of the natural frequency) of the natural frequency of the rolling stand. Then, operating conditions (pass schedule) are set, and a cold-rolled steel sheet is manufactured.
Therefore, according to this invention, it can roll in the state which suppressed the roll and the rolling stand resonated and the vibration of a roll became large.

Therefore, according to this invention, generation | occurrence | production of defects, such as plate | board thickness nonuniformity resulting from the vibration of the roll of a rolling stand, and the pattern generation of a steel plate surface, can be suppressed.
Further, since the vibration of the roll can be prevented from increasing due to the resonance, it is possible to suppress the progress of wear of the roll bearing due to the vibration. And since progress of wear of a roll bearing can be suppressed, generation | occurrence | production of the vibration of the rolling stand and roll resulting from wear of a roll bearing can also be suppressed over a long period of time.

  Moreover, according to the present invention, it is not a time-consuming, large-scale construction and cost-intensive method such as material modification or structural change of roll bearings, dynamic vibration absorbers, etc. In addition, it is possible to take measures to suppress vibrations of the rolling stand and roll in the cold rolling mill by a simple and low-cost method that can be studied offline.

It is a figure which shows notionally the cold rolling mill of this invention which enforces the manufacturing method of the cold rolled steel plate of this invention. It is a figure which shows notionally the bearing used for the cold rolling mill shown in FIG. It is a flowchart for demonstrating an example of the manufacturing method of the cold rolled sheet steel of this invention. It is a graph which shows the relationship between a frequency ratio and a vibration transmission coefficient. It is a flowchart corresponding to the Example of the manufacturing method of the cold rolled sheet steel of this invention. It is a graph which shows the relationship between the rolling distance and the vibration value in the Example of this invention.

  Hereinafter, the manufacturing method of a cold-rolled steel sheet and a cold rolling mill according to the present invention will be described in detail on the basis of preferred examples shown in the accompanying drawings.

  In FIG. 1, an example of the cold rolling mill of this invention which implements an example of the manufacturing method of the cold rolled steel plate of this invention is shown notionally.

A cold rolling mill 10 (hereinafter, referred to as a rolling mill 10) shown in FIG. 1 performs cold rolling of the steel sheet S while conveying the steel sheet S in the direction of the arrow x in the figure.
The rolling mill 10 has five rolling stands, a first stand 12a, a second stand 12b, a third stand 12c, a fourth stand 12d, and a fifth stand 12e.

In the rolling mill 10, each of the first stand 12 a to the fourth stand 12 d includes a pair of work rolls 14 that roll the steel sheet S and a pair of backup rolls 16 that press the work roll 14. The
The fifth stand 12e includes a pair of work rolls 18 for rolling the steel sheet S, a pair of intermediate rolls 20 for pressing the work rolls 18, and a pair of backups for pressing the work rolls by pressing the intermediate rolls 20. And a roll 24.

These 1st stand 12a-5th stand 12e are all the well-known rolling stands used for various cold rolling mills.
In the following description, the first stand 12a to the fifth stand 12e are also collectively referred to as “rolling stands” unless there is a need to distinguish them.

Rolls constituting each rolling stand are rotatably supported on a chock 36 by roll bearings 34 (hereinafter referred to as bearings 34) as conceptually shown in FIG. .
The bearing 34 includes a bearing outer ring 38 fixed to the chock 36, a bearing inner ring 40 that rotates together with the work roll 14 (its rotating shaft 14 a), and a bearing roller 42 that is disposed between the bearing outer ring 38 and the bearing inner ring 40. A known bearing having a lubricating oil filled between the bearing outer ring 38 and the bearing inner ring 40.
In the present invention, various known bearings (bearings) such as a conical roller bearing and a cylindrical roller bearing can be used as long as the bearing 34 can rotatably support each roll.

The first stand 12a has a condition control unit 28a, the second stand 12b has a condition control unit 28b, the third stand 12c has a condition control unit 28c, the fourth stand 12d has a condition control unit 28d, Furthermore, a condition control unit 28e is provided in each of the fifth stands 12e.
The condition control units 28a to 28e control pass schedules (operation conditions) in a corresponding rolling stand such as a rolling reduction, a rolling load, a tension applied to the steel sheet S, and a rolling speed. The condition control units 28a to 28e are known units that control the pass schedule of each rolling stand in the cold rolling mill.
Furthermore, the calculation part 30 is connected to all the condition control parts 28a-28e. The computing unit 30 is configured by, for example, a computer or a workstation.

Hereinafter, the method for determining a pass schedule in the rolling mill 10 shown in FIG. 1 will be described in detail with reference to the flowchart of FIG. .
In the rolling mill 10 of the present invention, the rolling schedule of the steel sheet S in the rolling mill 10, that is, the production of the cold-rolled steel sheet, is performed in the previously determined pass schedule even during the operation shown in the following flowchart. Depending on the situation.

First, the calculating part 30 sets a temporary pass schedule about each rolling stand of the 1st stand 12a-the 5th stand 12e.
Here, the calculation unit 30 basically sets the provisional pass schedule corresponding to the set maximum speed in the rolling mill 10. By having such a configuration, it is possible to make the most of the production capacity of the rolling mill 10 and to suppress roll vibration described later.

When the temporary pass schedule is set, the calculation unit 30 calculates the natural frequency of each rolling stand in this pass schedule.
The calculation method of the natural frequency is a publicly known method according to the set temporary pass schedule using the specifications of each roll constituting the rolling stand (the mass of each roll, the spring constant between each roll, etc.), etc. Calculate with
In addition, as a calculation method of the natural frequency of the rolling stand, the calculation method described in Chapter 8 of “Theory and Practice of Plate Rolling” by the Japan Iron and Steel Institute, “Kawasaki Steel Technical Report 1976 vol. 8 No. The calculation method described in “Analysis of“ chattering ”phenomenon in cold rolling of ultrathin steel sheet” ”of“ 1 ”may be used.

  In addition, after calculating the natural frequency of each rolling stand, the arithmetic unit 30 detects whether or not the number of repetitions of this calculation is equal to or less than a predetermined number of times J set in advance (the number of repetition calculations ≦ J).

As will be described in detail later, in the manufacturing method of the present invention, the vibration frequency of the roll is compared with the natural frequency of the corresponding rolling stand, and the vibration frequency of the roll is set in advance to the natural frequency of the corresponding rolling stand. % (In the illustrated example, within ± 5% of the natural frequency), the temporary path schedule is changed, and the vibration frequency and natural frequency are calculated and compared again.
In the present invention, this routine is repeated until the vibration frequency of the roll does not coincide with the preset range of% of the natural frequency of the corresponding rolling stand.

If the number of repetitions is too large, the manufacturing method of the present invention is likely to have a problem that the occurrence of vibration cannot be solved, such as severe wear of the bearing 34 or damage of some parts. .
Therefore, in the present invention, when the number of repetitions of this calculation exceeds a preset predetermined number J (in the case of N), the processing of the flowchart shown in FIG. It is preferable to consider other vibration solution methods.
The predetermined number J is not particularly limited, and may be set as appropriate according to the configuration of the rolling mill 10 and the like.
Here, according to the study of the present inventor, it is preferable to set the predetermined number J to about 1 to 10 times. By setting the predetermined number of times J within the above range, vibrations other than the resonance phenomenon such as bearing wear can be efficiently detected, which is preferable.

Furthermore, the calculating part 30 calculates a rolling speed for each rolling stand from the set temporary pass schedule. Next, based on the calculated rolling speed, the vibration frequency of each roll constituting each rolling stand is calculated using the specifications of the bearings 34 used in each roll of each rolling stand.
The specifications of the bearing 34 are specifically the PCD (pitch circle diameter) of the bearing, the diameter of the roller, the number of rollers, the contact angle, the number of rotations of the roll, and the like.

The calculation unit 30 calculates the vibration frequency of each roll of each rolling stand, calculates the natural frequency of each rolling stand, and the number of repeated calculations is equal to or less than the predetermined number J (the number of repeated calculations ≦ J is “ Y ”), for each rolling stand, the vibration frequency of the roll and the natural frequency of the rolling stand are compared for all the rolls.
Specifically, it is detected whether or not the vibration frequency of the roll matches a preset% range of the natural frequency of the rolling stand. In the illustrated example, it is detected whether or not the vibration frequency of the roll is within ± 5% of the natural frequency of the rolling stand.

As a result of this comparison, when the vibration frequency of the roll does not match within ± 5% of the natural frequency of the rolling stand (in the case of N), that is, the vibration frequency of the roll is 95% to 95% of the natural frequency of the rolling stand. If it does not fall within the range of 105%, the set temporary path schedule is determined as the path schedule.
Conversely, as a result of this comparison, when the vibration frequency of the roll matches within ± 5% of the natural frequency of the rolling stand (in the case of Y), the set temporary pass schedule is changed and the roll The same calculation is repeated until the vibration frequency does not match within ± 5% of the natural frequency of the rolling stand.
In the present invention, by having such a configuration, in each rolling stand of the cold rolling mill, the vibration of the roll is suppressed, and the thickness unevenness of the cold rolled steel sheet and the deterioration of the surface properties due to the vibration of the roll. In addition, the life of the bearing 34 used in the rolling stand is extended.

In a cold rolling mill, bearing wear is exemplified as a cause of vibration of a roll of a rolling stand.
The frequency band of vibration generated by the roll when the bearing 34 is worn is determined by the rolling speed, the specifications of the bearing 34, and the like.

On the other hand, in the rolling mill 10, each rolling stand also vibrates inherently.
FIG. 4 shows the relationship between the frequency ratio β and the vibration transmissibility λ in the damped forced vibration using a general model.
As shown in FIG. 4, the vibration transmissibility λ increases as the frequency ratio β is closer to 1. That is, when the vibration frequency band of the roll matches the natural frequency of the rolling stand itself (when the frequency ratio β = 1), a resonance phenomenon occurs between the rolling stand and the roll, Vibration increases. When such large roll vibrations due to resonance occur, surface quality defects such as generation of patterns, unevenness in plate thickness, and the like occur, resulting in a decrease in product quality, a decrease in yield, and the like.

Further, one of the causes of wear of the bearing 34 in the rolling stand is accumulation of vibration generated during rolling.
As described above, when the vibration frequency band of the roll coincides with the natural frequency of the rolling stand itself and a resonance state is established, vibration increases. For this reason, if rolling is continued in a region where the rolling stand and the roll resonate, there is a high possibility that the wear of the bearing 34 will proceed faster due to large roll vibrations as compared to rolling in a state where no resonance occurs.

On the other hand, in the present invention, in the cold rolling mill, the pass schedule is a range in which the vibration frequency of the roll is a preset% of the natural frequency of the rolling stand (in this example, as shown in FIG. Cold rolled steel sheet is manufactured as a pass schedule that does not match 5% or less.
Therefore, according to the present invention, rolling can be performed in a state in which the roll and the rolling stand resonate and vibrations of both are suppressed from increasing.
Therefore, according to the present invention, it is possible to manufacture a high-quality cold-rolled steel sheet with a high yield by suppressing the occurrence of defects such as unevenness of the plate thickness due to roll vibration and the occurrence of a pattern on the steel sheet surface.
Further, since the vibration of the rolling stand and the roll can be prevented from increasing due to the resonance, the progress of the wear of the bearing due to the vibration can be suppressed. And since progress of wear of a bearing can be suppressed, generation | occurrence | production of the vibration of the rolling stand and roll resulting from wear of the above-mentioned bearing can also be suppressed over a long period of time.

In this example, as shown in FIG. 4, a range of a preset% of the natural frequency of the rolling stand that is the target of whether or not the vibration frequency of the roll matches (determined that the vibration frequency matches the natural frequency). However, the present invention is not limited to within ± 5%. In other words, the preset% range of the natural frequency, which is a reference for comparison between the vibration frequency of the roll and the natural frequency of the rolling stand, is not limited to the above ± 5%.
That is, the pre-set range of% as a reference for comparison is that the vibration frequency of the roll and the natural frequency of the rolling stand are close to each other depending on the configuration of the rolling mill 10 (rolling stand) and the bearing used. What is necessary is just to determine suitably the range which can suppress suitably by experience, simulation, etc.

Here, according to the study of the present inventors, in the rolling stand of the cold rolling mill, if the vibration frequency of the roll and the natural frequency of the rolling stand do not match, the thickness and surface properties of the cold rolled steel sheet In addition, there is no resonance that greatly increases the wear of the bearing. In addition, the smaller the preset% range (the narrower the preset% range), the higher the degree of freedom of the path schedule, but the greater the possibility of large vibrations due to resonance. The greater the preset percentage range, the higher the vibration suppression effect, but the lower the degree of freedom of the path schedule.
In consideration of this point, in the present invention, as described above, it is preferable to set the pass schedule so as to remove the natural frequency of the rolling stand from within ± 5%, and the pass schedule so as to exclude the natural frequency from within ± 10%. It is more preferable to set a schedule.

In all the rolling stands, when the vibration frequency of all the rolls does not match within ± 5% of the natural frequency of the corresponding rolling stand (in the case of N), the calculation unit 30 sets the temporary setting previously set. The pass schedule is determined as a subsequent pass schedule.
Next, the calculation unit 30 issues an instruction to the condition control units 28a to 28e of each rolling stand so as to roll the steel sheet S according to the determined pass schedule.
In response to this, the condition control units 28a to 28e control the pass schedule so that the corresponding rolling stand performs rolling with the determined pass schedule.

On the other hand, in any of the rolling stands, when the vibration frequency of any of the rolls matches within ± 5% of the natural frequency of the corresponding rolling stand (in the case of Y), in one or more rolling stands, Change a part of the provisional pass schedule and recalculate the provisional pass schedule for all rolling stands.
For example, the rolling pass distribution of all rolling stands is changed by changing the rolling rate distribution in the rolling stands upstream and downstream in the direction of conveying the steel sheet S of the rolling stands whose vibration frequency matches within ± 5% of the natural frequency. Is recalculated.

Here, the conditions to be changed in the path schedule are not particularly limited, and various conditions constituting the path schedule can be used. Among these, one or more of the rolling reduction, the tension applied to the steel sheet S, and the rolling load are preferably exemplified.
By changing the above conditions and changing the path schedule, it is possible to change the path schedule without making a major change such as a facility change and to calculate a new temporary path schedule.

  After calculating the new temporary pass schedule, the arithmetic unit 30 checks whether or not the pass schedule satisfies the motor capacity, the upper limit of the rolling load, the upper limit of the rolling reduction, and the like, and can be executed in the rolling mill 10. (Temporary pass schedule check).

When the calculated pass schedule is a pass schedule that can be implemented in the rolling mill 10, the calculation unit 30 sets the pass schedule again as a new temporary pass schedule.
In addition, when the calculated pass schedule is not a pass schedule that can be performed in the rolling mill 10, the arithmetic unit 30 returns to the upstream of the flowchart, and changes and calculates the temporary pass schedule again.

  After setting the provisional pass schedule again, the calculation unit 30 calculates the natural frequency of each rolling stand and checks the number of repeated calculations, and calculates the roll vibration frequency. It is detected whether the vibration frequency matches within ± 5% of the natural frequency of the corresponding rolling stand.

  As a result, if the vibration frequency of the roll does not match within ± 5% of the natural frequency of the corresponding rolling stand, the temporary pass schedule is determined as the pass schedule as before, and the condition control unit Instructions are given to 28a to 28e.

Conversely, if the roll vibration frequency matches within ± 5% of the natural frequency of the corresponding rolling stand, the temporary pass schedule is changed and calculated again to check the pass schedule as before. , Reset the temporary pass schedule, calculate the natural frequency and roll vibration frequency of the rolling stand, and compare the calculated vibration frequency and natural frequency. This is done until it does not match within ± 5% of the natural frequency.
In the middle of performing this repeated calculation, if the number of repeated calculations exceeds a preset number J, the operation of the flowchart shown in FIG. 3 is terminated as described above.

In the present invention, there is no particular limitation on the timing of recalculating the path schedule (revising the path schedule) for suppressing the roll vibration shown in the flowchart of FIG.
As an example, when there is a change in a component (component) of the rolling mill 10 such as roll replacement or repair, bearing replacement or repair, vibrations of one or more rolling stands and / or one or more rolls are predetermined. It may be carried out as necessary, for example, when the state is exceeded.

  As mentioned above, although the manufacturing method and cold rolling mill of the cold-rolled steel sheet of this invention were demonstrated in detail, this invention is not limited to the above-mentioned example, In the range which does not deviate from the summary of this invention, various improvement and Of course, changes may be made.

For example, in the above example, as a preferred embodiment, the pass schedule was set with a comparison between the natural frequency and the vibration frequency of the roll in all the rolling stands of the cold rolling mill. There is no limitation.
That is, among the rolling stands that the cold rolling mill has, such a schedule is set only for the rolling stands that are greatly affected by vibration, such as at least one of the rolling stands that the cold rolling mill has. Alternatively, settings may be made to avoid resonance.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Using a (cold tandem) rolling mill 10 shown in FIG. 1, a cold rolled steel sheet was manufactured by cold rolling a low-carbon steel hot-rolled steel sheet having a width of 1600 mm.
The thickness of the steel sheet S before rolling was 3.0 mm, and the finished thickness was 0.6 mm.

In the first stand 12a to the fourth stand 12d, the roll diameter of the work roll 14 was 568 mm for the first stand 12a; 542 mm for the second stand 12b; 581 mm for the third stand 12c; As the work rolls 14, those having a surface roughness Ra of 0.3 μm (cylindrical polishing) were used.
In the work rolls 14 of the first stand 12a to the fourth stand 12d, the bearings 34 are all cones having a roller diameter of 30.78 mm, a number of rollers of 38, a PCD of 419.24 mm, and a contact angle of 15 °. A roller bearing was used.
Further, in each of the first stand 12a to the fourth stand 12d, the roll diameter of the backup roll 16 is 1440 mm. Further, the bearings 34 of the backup roll 16 were all cylindrical roller bearings having a roller diameter of 60 mm, a number of rollers of 48, a PCD of 978 mm, and a contact angle of 90 °.

On the other hand, in the fifth stand 12e, the roll diameter of the work roll 18 is 400 mm. In addition, the work roll 18 used the thing whose surface roughness Ra is 3.2 micrometers (electric discharge dull process). The bearings 34 of the work roll 18 were conical roller bearings having a roller diameter of 23.96 mm, a number of rollers of 33, a PCD of 401.639 mm, and a contact angle of 17.5 °.
In the fifth stand 12e, the roll diameter of the intermediate roll 20 was 510 mm. As the bearing 34 of the intermediate roll 20, a conical roller bearing having a roller diameter of 32.8 mm, a roller count of 31, the PCD of 369.36 mm, and a contact angle of 17.3 ° was used.
Further, in the fifth stand 12e, the roll diameter of the backup roll 24 was 1310 mm. Further, as the bearing 34 of the backup roll, a cylindrical roller bearing having a roller diameter of 56 mm, a number of rollers of 43, a PCD of 823 mm, and a contact angle of 90 ° was used.

In the rolling mill 10 as described above, a conventional manufacturing method (Condition 1) in which the steel sheet S is rolled by setting a pass schedule according to the product to be manufactured regardless of the vibration frequency of the roll and the natural frequency of the rolling stand. : Comparative Example) and a cold-rolled steel sheet was manufactured by the manufacturing method of the present invention (Condition 2: Example) in which the steel sheet S is rolled by setting a pass schedule according to the flowchart shown in FIG.
A specific flowchart is shown in FIG. In the example shown in FIG. 5, the “temporary pass schedule change / calculation” is performed by reducing the motor power ratio or the load ratio of the target stand by 2% and calculating the temporary pass schedule.
The meaning of reducing the motor power ratio or load ratio of the target stand by 2% is, for example, that the load ratio is
1st stand: 2nd stand: 3rd stand: 4th stand
= 1: 1: 0.95: 0.9
If, for example, the vibration frequency of the roll in the fourth stand matches within 5% of the natural frequency as a result of the setting calculation,
1st stand: 2nd stand: 3rd stand: 4th stand
= 1: 1: 0.95: 0.88
This means that the temporary path schedule is recalculated.
The vibration value was measured by attaching a vibration acceleration sensor to the upper part of the rolling mill housing, amplifying the voltage generated by the vibration with a sensor amplifier, and taking it into a personal computer.

As shown in FIG. 6, in the conventional manufacturing method (condition 1: comparative example), the vibration value gradually increases as the rolling distance increases. Furthermore, there are some events in which the vibration varies greatly depending on the rolling distance, for example, the vibration value suddenly increases before the rolling distance of 100,000 km.
On the other hand, according to the manufacturing method of the present invention (Condition 2: Example), the vibration value is about 0.1 mm / s, almost constant, regardless of the rolling distance, and stable rolling over a long period of time. Is possible.
In this example, the conventional manufacturing method uses a backup roll of 135000 T / chance (corresponding to rolling by one roll polishing), but according to the manufacturing method of the present invention, the backup roll uses a backup roll. It was confirmed that the roll usage distance was 147000 T / chance and the backup roll usage distance could be expanded.
From the above results, the effects of the present invention are clear.

  The present invention can be suitably used for various cold-rolled steel sheet production lines.

10 (cold) rolling mill 12a 1st stand 12b 2nd stand 12c 3rd stand 12d 4th stand 12e 5th stand 14,18 Work roll 16,24 Backup roll 20 Intermediate roll 28a, 28b, 28c, 28d, 28e Conditions Control unit 30 Calculation unit 34 (Roll) bearing 36 Chock 38 Bearing outer ring 40 Bearing inner ring 42 Bearing roller 46 Lubricating oil

Claims (8)

In the production of cold-rolled steel sheet using a cold rolling mill,
In at least one rolling stand, calculate the natural frequency of the rolling stand under the set temporary operating conditions and the vibration frequency of each roll,
Detecting whether the vibration frequency of each roll matches within a preset% of the natural frequency of the rolling stand;
When the vibration frequency of each of the rolls does not coincide with a preset% of the natural frequency of the rolling stand, cold rolling of the steel sheet is performed with the temporary operating conditions as operating conditions,
When the vibration frequency of each roll coincides with a preset range of% of the natural frequency of the rolling stand, change the temporary operating conditions, again, the natural frequency of the rolling stand, The vibration frequency of each roll is calculated by detecting whether the vibration frequency of each roll is equal to or less than a preset percentage of the natural frequency of the rolling stand. The method for producing a cold-rolled steel sheet, characterized in that the method is repeated until the natural frequency of the rolling stand does not coincide with a preset percentage.   The method for producing a cold-rolled steel sheet according to claim 1, wherein the temporary operating condition is set in correspondence with a maximum set speed of a cold rolling mill.   The method for producing a cold-rolled steel sheet according to claim 1 or 2, wherein the preset% range is within ± 5%.   The method for producing a cold-rolled steel sheet according to any one of claims 1 to 3, wherein the temporary operating condition is changed by changing at least one of a rolling reduction, a tension applied to the steel sheet, and a rolling load. A plurality of rolling stands;
A condition control unit for controlling the operating conditions of the rolling stand, provided corresponding to each of the rolling stands,
For at least one of the rolling stands, a temporary operating condition is set, and the natural frequency of the rolling stand in the temporary operating condition and the vibration frequency of each roll are calculated, and the vibration frequency of each roll is calculated. Has a calculation unit that detects whether or not it coincides with a preset% range of the natural frequency of the rolling stand,
Furthermore, when the vibration frequency of each of the rolls does not coincide with a preset% range of the natural frequency of the rolling stand, the calculation unit sets the provisional operating condition in the corresponding rolling stand. Instruct the condition control unit to set the operating conditions,
When the vibration frequency of each roll coincides with a preset range of% of the natural frequency of the rolling stand, change the set temporary operating condition, and again, the natural frequency of the rolling stand. Calculating the vibration frequency of each roll, and detecting whether or not the vibration frequency of each roll coincides with a preset range of% of the natural frequency of the rolling stand. The cold rolling mill is performed until the vibration frequency does not coincide with a preset% range of the natural frequency of the rolling stand.   The said calculating part is a cold rolling mill of Claim 5 which sets the said temporary operating conditions corresponding to the setting maximum speed of a cold rolling mill.   The cold rolling mill according to claim 5 or 6, wherein the calculation unit sets the preset% range within ± 5%.   The said calculating part performs the change of the said temporary operating conditions by changing at least 1 of a rolling reduction, the tension | tensile_strength applied to a steel plate, and a rolling load, The cold rolling in any one of Claims 5-7 Machine.

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