JP7259797B2 - Anti-slip method and anti-slip device for cold rolling mill - Google Patents

Description

TECHNICAL FIELD The present invention relates to a slip prevention method and slip prevention device for preventing slip between a work roll and a steel plate in a cold rolling mill.

A cold rolling mill that cold-rolls a steel plate is equipped with multiple roll stands. Stable operation is carried out using means (hereinafter referred to as rolling control means) for controlling the acting tension, the amount and type of rolling oil supplied to each roll stand (that is, lubrication condition), and the like.

However, the friction between the work roll and the steel sheet decreased due to factors such as the wear of the work roll arranged on one of the multiple roll stands and the decrease in the surface roughness, or the change in the lubrication state. In this case, the speed W of the work roll and the speed V of the steel plate do not match, and slip tends to occur. Such slip causes various problems such as the occurrence of scratches on the surface of the steel sheet or work roll, the thickness of the steel sheet being out of the target range, and the breaking of the steel sheet.

Therefore, in order to prevent slippage, a technology has been studied to change the setting of the roll stand via a rolling control means when an abnormality in the steel plate or roll stand is detected during operation of the cold rolling mill. For example, the speed W (hereinafter referred to as the roll peripheral speed) calculated from the circumference length (m) of the work roll and the rotation speed (times/min) and the speed V (m/min) of the steel sheet discharged from the work roll ) to monitor the advancement rate δ (%) during operation using a computing means. This technique utilizes the well-known phenomenon that slip tends to occur when the forward rate δ is too low.

The advance rate δ fluctuates under the influence of the load acting on the steel sheet, reduction rate, tension, lubrication state, work roll diameter (that is, circumference length), and the like. Specifically, when the tension acting on the steel sheet on the entry side of the roll stand is low, when the tension acting on the steel sheet on the exit side of the roll stand is high, or when the coefficient of friction on the roll stand is high, the advance rate δ Rise. As a result, slips are less likely to occur. Therefore, when slip occurs or is expected to occur, the speed V of the steel sheet is reduced via the rolling control means in order to increase the advance rate δ, thereby increasing the coefficient of friction. , the occurrence of slip can be avoided.

For example, Patent Document 1 discloses a technique for preventing the occurrence of slips in hot rolling as a technique that utilizes the advance rate as an index for avoiding the occurrence of slips. With this technology, the lower limit of the advance rate required to stabilize the operation is set in advance, and when the actual value of the advance rate calculated continuously during operation falls below the lower limit of the allowable range, The speed of the steel plate is reduced according to the difference. Then, if the actual value of the advance rate is below the allowable lower limit even after the speed of the steel plate is reduced, the reduction amount is also reduced to prevent slippage.

Further, in Japanese Patent Laid-Open No. 2002-100001, the accuracy of the calculation of the advance rate is increased, and then a condition for the advance rate that does not cause slip is set. Techniques have been disclosed for preventing slippage by reducing the tension acting on the steel plate on the entry side of the stand and slowing down the speed of the steel plate.

Patent Document 3 discloses a technique for preventing slippage by reducing the tension acting on the steel sheet on the entry side of the roll stand when the measured value of the advance rate is below a preset threshold.

In Patent Document 4, the rate of change is obtained from the actually measured advance rate, and when the rate of change in the advance rate exceeds a predetermined value, the gap between the work rolls is changed, so that the steel plate is formed on the entry side of the roll stand. Techniques have been disclosed to prevent slippage by reducing the tension acting on the

All of these techniques are techniques for preventing slippage, but have various problems. For example, reducing the speed of the steel sheet results in a decrease in the productivity of the cold rolling mill. When the amount of reduction is reduced, the tension acting on the steel sheet on the entry side increases in cold rolling, causing a reduction in the advance rate (that is, an increase in the frequency of slip occurrence). Reducing the tension acting on the steel plate on the entry side is effective in increasing the advance rate, but in a roll stand where the surface roughness has decreased due to wear of the work rolls, the tension on the entry side should be reduced to the limit of the equipment specifications. Since the operation is performed with the rolling control means set so as to lower the tension (or raise the tension on the delivery side to the limit), it is difficult to further change the tension in order to avoid the occurrence of slip.

In particular, since the technique disclosed in Patent Document 1 performs hot rolling without applying tension to the steel sheet, it is difficult to apply the technique to applying tension to the steel sheet like cold rolling. be.

JP-A-7-51716 JP-A-9-295017 JP 2017-70953 A JP-A-4-59113

The present invention solves the problems of the prior art, maintains a constant strip speed of the strip passing through each roll stand during the operation of the cold rolling mill without deceleration, and changes the tension acting on the strip. It is an object of the present invention to provide a method and apparatus for preventing slippage while keeping the slippage constant.

In order to prevent slips, it is necessary to predict the occurrence of slips with high accuracy. Therefore, in order to make it possible to predict slip before it occurs, the present inventor studied a technology that effectively uses the advance rate as an index that is constantly monitored during the operation of the cold rolling mill, and as a result, It has been found that the occurrence of a slip can be predicted with a high degree of accuracy by setting a threshold to a suitable numerical value in advance and determining that the risk of occurrence of a slip is high when the advance rate falls below the threshold.

The inventor then studied in detail the technique of adjusting the cold mill settings via the rolling control means such that the advance rate is increased when the advance rate is below a threshold value. Then, the inventors have found that by adjusting the draft, it is possible to increase the advance rate without reducing the speed of the steel plate and without changing the tension acting on the steel plate.

In other words, according to the research of the present inventor, when the coefficient of friction between the steel plate and the work roll is large, the advance rate increases as the rolling reduction increases, but when the coefficient of friction is small (for example, 0.027 or less), The advance rate increases as the reduction rate decreases (see FIG. 2). As already explained, it is the roll stand with a small coefficient of friction that slips. Therefore, since the coefficient of friction of the roll stand, in which the occurrence of slip is predicted with high accuracy, is lowered, the advance rate can be increased by reducing the reduction rate, and as a result, the occurrence of slip can be avoided.

The present invention has been made based on such findings.
That is, the present invention is a cold rolling mill equipped with a total of N roll stands (N: an integer of 3 or more) from the first stand located upstream in the direction of travel of the steel sheet to the Nth stand located downstream, The thickness of the steel plate at the entry side of the [i-1]-th stand arranged upstream of the i-th stand (i: an integer from 2 to N) is T _i-1 (mm), and the speed of the steel plate is V _{i- 1} (m/min), the plate thickness of the steel plate on the entry side of the i-th stand is _Ti (mm), and the plate speed of the steel plate on the entry side of the i-th stand is calculated from the following equation (1): V _i (m/min) Calculate the roll peripheral speed W i (m _/ min) from the circumference length (m) of the work roll of the i-th stand and the rotation speed (times / min) of the work roll, then the plate speed V _i and The advance rate δ _i (%) at the i-th stand is calculated using the following equation (2) using the roll peripheral speed W _i , and the obtained advance rate δ _i and the preset threshold value _Mi are expressed by the following equation (3). This slip prevention method prevents the occurrence of slips in the i-th stand by reducing the roll reduction η _i (%) of the i-th stand calculated by the following equation (4) when the conditions are satisfied.

In the slip prevention method of the present invention, the rolling reduction ratio η _i (%) of the i-th stand is reduced, and the rolling reduction ratio η ₂ to η _i of each roll stand from the second stand to the [i−1]-th stand is reduced. It is preferable to increase _-1 to prevent the occurrence of slip at the i-th stand. Further, it is preferable to increase the rolling reduction ratios η ₂ to η i-1 by increasing the roll peripheral velocities W ₂ to W _{i- 1} from the second stand to the [i-1]th stand. Furthermore, it is preferable to set the threshold M _i within the range of -3% to 0%.

Further, the present invention provides a cold rolling mill equipped with a total of N roll stands (N: an integer of 3 or more) from the first stand located upstream in the traveling direction of the steel sheet to the Nth stand located downstream. The thickness of the steel plate at the entry side of the [i-1]th stand arranged on the upstream side of the stand (i: an integer from 2 to N) is T _i-1 (mm), and the speed of the steel plate is V _i-1 ( m/min), and the thickness of the steel plate on the entry side of the i-th stand is _Ti (mm), and the plate speed _Vi (m/min) of the steel plate on the entry side of the i-th stand is calculated from the following equation (1): a computing means for
A calculation means for calculating the roll peripheral speed _W i (m/min) from the circumference length (m) of the work roll of the i-th stand and the rotation speed (times/min) of the work roll;
A calculation means for calculating the advance rate δ _i (%) at the i-th stand by the following equation (2) using the plate speed V _i and the roll peripheral speed W _i ;
computing means for comparing the obtained advance rate δ _i with a preset threshold value M _i ;
A slip prevention device having a rolling control means that reduces the rolling reduction η _i (%) of the i-th stand calculated by the following equation (4) when the advance rate δ _i and the threshold M _i satisfy the following equation (3) is.

In the anti-slip device of the present invention, the rolling control means reduces the rolling reduction η _i (%) of the i-th stand, and reduces the rolling reduction of each roll stand from the second stand to the [i−1]-th stand. It is preferable to increase η ₂ to η _i-1 . Further, it is preferable that the rolling control means increases the reduction ratios η ₂ to η i-1 by increasing the peripheral roll speeds W ₂ to W _{i-1 from} the second stand to the [i-1] stand. . Furthermore, it is preferable that the threshold M _i is in the range of -3% to 0%.
T _i-1 ×V _i-1 =T _i ×V _i (1)
δ _i (%) = 100 × (V _{i +1} - W _i )/W _i (2)
δ _i <M _i (3)
η _i (%)=100×(T _i −T _i+1 )/T _i (4)

According to the present invention, it is possible to prevent slippage without reducing the speed of the steel sheet passing through each roll stand during operation of the cold rolling mill and without changing the tension acting on the steel sheet. , has a remarkable effect on the industry.

FIG. 4 is a cross-sectional view schematically showing an example of two adjacent roll stands of a cold rolling mill having N roll stands. It is a graph which shows the size relationship of a coefficient of friction and an advanced rate. 4 is a graph showing an example of a rolling reduction set for each roll stand.

FIG. 1 shows the i-th stand (i: an integer of 2 to N) of a cold rolling mill equipped with a total of N roll stands (N: an integer of 3 or more), and the No. [ i-1] is a sectional view schematically showing the relationship between the stand and the steel plate 1. FIG. Arrow A in FIG. 1 indicates the direction in which the steel plate 1 advances. The illustration of the [i+1]-th stand arranged downstream of the i-th stand is omitted.

As shown in FIG. 1, the plate thickness of the steel plate 1 on the entry side of the [i-1]th stand is T _i-1 (mm), and the plate speed is V _i-1 (m/min). In addition, the peripheral speed of the work roll 2 of the [i−1]th stand calculated from the circumferential length (m) and the rotation speed (times/min) is W _i−1 (m/min).

The steel plate 1 entering from the entry side of the [i-1]th stand is rolled down by the work rolls 2 and discharged to the exit side. Since the delivery side of the [i-1]-th stand is the entry side of the i-th stand, the thickness of the steel plate 1 discharged from the [i-1]-th stand is T _i (that is, the plate on the entry side of the i-th stand thickness), and let the plate speed be V _i (that is, the plate speed at the entry side of the i-th stand). Also, the roll peripheral speed of the work roll 2 of the i-th stand is W _i .

Then, the steel plate 1 entering from the entry side of the i-th stand is rolled down by the work rolls 2 and discharged to the exit side. Since the exit side of the i-th stand is the entry side of the [i+1]-th stand (not shown), the thickness of the steel sheet 1 discharged from the i-th stand is T _{i +1} , and the velocity is V _{i +1.} do.

In FIG. 1, when i=2, _T1 means the thickness of the material supplied to the cold rolling mill, and _V1 means the advancing speed of the material. When i=N, T _N+1 is the thickness of the product discharged from the cold rolling mill, and V _N+1 is the advancing speed of the product.

In the cold rolling mill, the work rolls 2 of each roll stand reduce the thickness of the steel sheet, but the volume of the steel sheet 1 does not change, so the speed increases with each reduction. In the example shown in Figure 1,
T _i-1 ×V _i-1 =T _i ×V _i (1)
holds. In other words, the thickness of the material supplied to the cold rolling mill is T ₁ , the advancing speed of the material is V ₁ , and the thickness T ₂ at the exit side of the first stand (that is, the entry side of the second stand) is the second Since the value is determined by the spacing of the work rolls 2 of one stand, the plate speed _V2 at the entry side of the second stand is calculated from the above equation (1) as _V2 = ( _T1 x _V1 )/ _T2 . can.

From the third stand onwards (up to the N-th stand), it is also possible to sequentially obtain the strip thickness T _i and the strip velocity V _i in each roll stand. Such calculations are performed by using calculation means while performing cold rolling.

Further, using the calculating means, the advance rate δ _i (%) and the rolling reduction rate η _i (%) at the i-th stand are calculated from the following equations (2) and (4). As the calculation means, the calculation means for obtaining the plate thickness T _i and the plate speed V _i may be used together, or may be provided separately.
δ _i (%) = 100 × (V _{i +1} - W _i )/W _i (2)
η _i (%)=100×(T _i −T _i+1 )/T _i (4)
Then, for the 2nd to Nth _stands , the calculation means compares the advance rate δ _i at the i-th stand with a preset threshold Mi, and if the following formula (3) is satisfied, the slip occurs at the i-th stand. It is determined that there is a high risk of occurrence of the roll reduction _ηi of the i-th stand via the rolling control means.
δ _i <M _i (3)
The threshold M _i may be set to an individual value for each roll stand, or may be set to the same value for all roll stands. In either case, it is preferable to set the threshold M _i within the range of -3% to 0%. It is preferably in the range of -2% to 0%.

In order to reduce the rolling reduction η _i at the i-th stand, the thickness T _i on the entry side of the i-th stand is reduced, or the thickness T _{i +1} on the delivery side of the i-th stand is increased. The rolling reduction η _i can be controlled by adjusting the gap between the work rolls 2 via the control means. Therefore, the present invention can be applied to a cold rolling mill having a function of reducing the draft η _i by changing the thickness T _i .

However, if the interval between the work rolls 2 (the so-called roll gap) is changed, the tension will also fluctuate in continuous cold rolling, so there is a risk that slippage will rather easily occur.

Therefore, without changing the interval between the work rolls 2 in each roll stand, the roll peripheral speed of the roll stand arranged on the upstream side from the [i-1]th stand (for example, W _i-1 , W _i-2 , etc. ), it is preferable to control the advancing rate δ _i of the steel plate 1 . In other words, by increasing the roll peripheral speeds W ₂ to W i _-1 of the work rolls 2 of the 2nd stand to the [i−1]th stand, the reduction ratios η ₂ to η _i-1 can be increased, As a result, the draft η _i can be reduced (see FIG. 2).

In operating the cold rolling mill while preventing the occurrence of slip at the i-th stand in this way, the thickness T ₁ of the material supplied to the first stand and the thickness of the product discharged from the N-th stand A predetermined numerical value is defined for T _N+1 in order to smoothly perform operations in the pre-process and post-process of cold rolling. Therefore, when the rolling reduction _ηi of the i-th stand is reduced to avoid the occurrence of slip, the gap between the work rolls 2 of all the roll stands is not changed, and the second stand located upstream of the i-th stand is It is preferable to increase the rolling reduction ratio η ₂ to η _i-1 of the [i-1]th stand. As a measure for increasing the rolling reduction ratios η ₂ to η _i-1 , it is preferable to increase the roll peripheral velocities W ₂ to W _i-1 of the second stand to the [i-1]th stand.

However, when it is determined that there is a high risk of slip occurring at the first stand, since there is no roll stand on the upstream side, such adjustment of the roll peripheral velocity is impossible. Therefore, the roll stand for judging the risk of slip occurrence according to the formula (3) is the 2nd stand to the Nth stand (i: an integer from 2 to N).

In this way, if slippage is prevented by adjusting the roll peripheral speed of the work rolls without changing the intervals between the work rolls of the first stand to the Nth stand, the entry side (that is, the exit side) of each roll stand can be prevented. It is possible to suppress fluctuations in the tension of the steel sheet on the side), and to stably maintain smooth operation of the cold rolling mill.

The present invention is applied to a cold rolling mill (N = 6) equipped with a total of six roll stands from the first stand located upstream in the direction of movement of the steel plate to the sixth stand located downstream. The cold rolling of the steel sheet was performed while evaluating the risk of slip occurrence between the stand and the sixth stand. The plate thickness T ₁ (that is, the thickness of the raw material) on the entry side of the first stand was 3.0 mm, and the plate thickness T ₇ (that is, the thickness of the product) on the exit side of the sixth stand was 0.8 mm.

During operation, the advance rate δ ₆ of Stand 6 fell below the preset threshold value of -1.5%. By increasing the roll peripheral velocities W ₂ and W ₃ of the work rolls, the plate thickness T ₆ on the entry side of the sixth stand was reduced, and as a result, the rolling reduction η ₆ was reduced (see FIG. 3). .

Furthermore, the 2nd and 3rd stands were selected from the 2nd to 5th stands located upstream of the 6th stand, and their rolling reductions η ₂ and η ₃ were increased (see Fig. 3). .

These reduction ratios were changed (that is, decreased or increased) within the range allowed by the equipment specifications of each roll stand.

In this way, when the risk of slip occurrence increases at the 6th stand, the rolling reduction of the 6th stand and the upstream roll stand can be adjusted while continuing the operation of the cold rolling mill. Thus, it was possible to prevent the occurrence of slips in the sixth stand.

1 steel plate 2 work roll

Claims (4)

In a cold rolling mill equipped with a total of N roll stands (N: an integer of 3 or more) from the first stand located upstream in the direction of movement of the steel plate to the Nth stand located downstream, the i-th stand (i : an integer from 2 to N), the plate thickness of the steel plate at the entrance side of the [i-1]th stand arranged on the upstream side is T _i-1 (mm), and the plate speed is V _i-1 (m/ and the plate thickness of the steel plate on the entry side of the i-th stand is _Ti (mm), and the plate speed of the steel plate on the entry side of the i-th stand is calculated from the following equation (1): V _i (m/min) is calculated, and the roll peripheral speed _W i (m/min) is calculated from the circumferential length (m) of the work roll of the i-th stand and the rotation speed (times/min) of the work roll, and then the plate speed Using V _i and the roll peripheral velocity W _i , the advance rate δ _i (%) at the i-th stand is calculated by the following equation (2), and the obtained advance rate δ _i and the preset threshold value _Mi is compared, and when the advance rate δ _i and the threshold M _i satisfy the following formula (3), the rolling reduction rate η _i (%) of the i-th stand calculated by the following formula (4) is reduced , In each roll stand from the second stand to the [i-1]th stand, the roll peripheral speeds W ₂ to W _i-1 are increased to increase the rolling reduction ratios η ₂ to η _i without changing the roll gap. An anti-slip method, comprising: increasing _-1 to prevent occurrence of slip in the i-th stand.
T _i-1 ×V _i-1 =T _i ×V _i (1)
δ _i (%) = 100 × (V _{i +1} - W _i )/W _i (2)
V _i+1 : Plate speed of steel plate on delivery side of i-th stand (m/min)
δ _i <M _i (3)
η _i (%)=100×(T _i −T _i+1 )/T _i (4)
T _i+1 : Thickness of steel plate at delivery side of i-th stand (mm) 2. The slip prevention method according to claim 1, wherein said threshold M _i is set within a range of -3% to 0%. The i-th stand (i: 2 The plate thickness of the steel plate at the entry side of the [i-1]-th stand arranged upstream of (integer of ~N) is T _i-1 (mm), and the plate speed is V _i-1 (m / min) Assuming that the thickness of the steel plate on the entry side of the i-th stand is Ti ₍ mm), the plate speed V _i (m/min) of the steel plate on the entry side of the i-th stand is calculated from the following equation (1): a computing means for
A calculation means for calculating a roll peripheral speed _W i (m/min) from the circumferential length (m) of the work roll of the i-th stand and the rotation speed (times/min) of the work roll;
A calculation means for calculating the advance rate δ _i (%) at the i-th stand by the following equation (2) using the plate speed V _i and the roll peripheral speed W _i ;
computing means for comparing the obtained advance rate δ _i with a preset threshold value M _i ;
When the advance rate δ _i and the threshold M _i satisfy the following formula (3), the rolling reduction rate η _i (%) of the i-th stand calculated by the following formula (4) is reduced , and the second stand to the [i-1]th stand, the roll peripheral speeds W ₂ to W _i-1 are increased to increase the rolling reduction ratios η 2 _to η _i-1 without changing the roll gap. An anti-slip device, characterized in that it has rolling control means for allowing
T _i-1 ×V _i-1 =T _i ×V _i (1)
δ _i (%) = 100 × (V _{i +1} - W _i )/W _i (2)
V _i+1 : Plate speed of steel plate on delivery side of i-th stand (m/min)
δ _i <M _i (3)
η _i (%)=100×(T _i −T _i+1 )/T _i (4)
T _i+1 : Thickness of steel plate at delivery side of i-th stand (mm) 4. An anti-slip device according to claim 3 , wherein said threshold M _i is in the range of -3% to 0%.

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