JPH0811243B2 - Final stand control method for cold rolling mill - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control method for cold rolling mill final stand dull roll rolling.

[Conventional technology]

The rolling mill setup control consists of set value calculation and adaptive correction calculation. In the set value calculation, the plate thickness target value (draft schedule) and tension set value are calculated for each stand for the input rolling specifications (base material thickness, target finish thickness, strip width, etc.), and deformation resistance, rolling The load is calculated,
Set values for roll gap, roll speed, etc. are required ("Theory and practice of sheet rolling" published by The Iron and Steel Institute of Japan in 1984.
(See Chapters 2.4 and 11.5). In the adaptive correction calculation, the same model formula as that used in the set value calculation is used, the solid line rolling load is calculated from the rolling result data, the ratio between the calculated load and the actual load is calculated, and the result is stored as the load correction coefficient. In the next set value calculation, this correction coefficient is multiplied by the calculation load to correct the calculated value (see the above "Theory and practice of sheet rolling", section 11.4).

[Problems to be Solved by the Invention]

The dull roll has a rougher roll surface than other rolls, and the material rolled by this roll has a rough plate surface. As a result, the adhesion of the plating is improved in the plating line which is the downstream process, so the dull roll is used for the final stand (finishing stand) of the cold rolling mill. The characteristic of rolling when using dull rolls is that the surface of the roll is rough, so the frictional force generated between the plate and the roll is large, and the rolling load is as large as 2.0 to 3.0 times the rolling load when rolling the same schedule with bright rolls. It will be. The characteristics of the cold rolling mill are slightly different for each rolling mill, but when the final stand is a dull roll, there are cases in which the following problems occur.

: The target reduction rate cannot be obtained, and the actual reduction rate becomes very small compared to the set reduction rate.

(Example: Actual reduction of 2% against set reduction of 6%): Estimated rolling load at setup is unstable.

: Due to the above, the plate thickness accuracy deteriorates.

FIG. 4 shows an example of rolling record data in which such a problem occurs. The rolling mill in this case consists of 4 stands,
Bright rolls are used for 1 to 3 stands, and dull rolls are used for the final stand (4 stands). Rolling record No. 1 ~
10 is base material thickness 2.3mm, target finish plate thickness 0.406mm, plate width 1263mm
In the actual data when the same schedule is continuously rolled, h ₃ is the strip thickness on the 3 stand output side, and h ₄ is the strip thickness on the ₄ stand output side. Since the rolling schedule is exactly the same,
The actual value should be almost the same in each rolling.
However, the rolling ratio r ₃ and rolling load Pa ₃ of the three stands are almost the same, but the rolling ratio r ₄ and rolling load of the four stands are
Pa ₄ has a large variation. As the cause of this phenomenon,
It is conceivable that rolling of four stands is performed in the vicinity of the unrollable region indicated by the theory of the minimum rollable sheet thickness. The minimum plate thickness theory that can be rolled is described in detail in "Theory and practice of plate rolling" in Chapter 2.5.5, and its outline is as follows. The rolling load can be solved by combining the rolling load type and the roll flat type, and there is usually a compatible solution (intersection point of both curves) as shown in Fig. 5, but in some cases both curves do not intersect. There is. This means that as the plate thickness becomes thinner, the roll flatness becomes relatively large, and the given reduction ratio cannot be obtained, and this limit plate thickness is called the minimum rollable plate thickness.

It is considered that the rolling schedule of the dull rolling final stand is such that the flatness of the roll is large and the rolling is performed near the rolling limit because the sheet thickness is thin and the rolling load is large. Figure 6 shows the rolling load formula Bland & Ford near the rolling limit.
The changes in the formula (the above-mentioned theory and practice of sheet rolling refer to Chapter 2.4) with respect to the rolling reduction are shown. As shown in the figure, in the vicinity of the rolling limit, even if the rolling load is increased, the flatness of the roll is large, so that it is impossible to obtain a rolling reduction higher than a certain value (the maximum rolling reduction possible for rolling). In this region, the rolling load changes abruptly with a slight change in the rolling reduction.Therefore, even if the error contained in the actual value of the plate thickness used in the load adaptive correction calculation is small, the adaptive correction calculation can be performed based on this. The calculated load correction coefficient fluctuates greatly, and as a result, the next load setting value will show a large error that cannot be ignored.

The fundamental mistake of the conventional setup method is to consider the fact that the final stand-up rolling is a rolling in a region where the rolling theory does not hold, and try to apply a similar rolling model to both bright rolling and dull rolling. There is a point.
As a result, the unstable rolling load actual value of the dull roll final stand disturbs the load correction coefficient calculated using the rolling load formula, and the load set value calculated using this load correction coefficient varies. Usually, the load correction factor is
Since statistically processed and stored in the table, the variation decreases and the load setting accuracy increases as the number of rolling increases, but in the case of dull rolling, the set load is not stable as described above. Even with the same schedule, rolling changes from coil to coil, the load correction factor is not stable, and the load setting accuracy cannot be improved. For this reason, the off-gauge length of the rolled material becomes long, and the yield of the product decreases.

In view of the above problems, an object of the present invention is to make dull roll rolling more stable and reduce the off-gauge length.

[Means for solving the problem]

In the control method of the cold rolling mill in which the dull roll is attached to the final stand among the plurality of rolling stands, first, the target rolling load of the final stand is determined from the rolling load of the stand in the stage before the final stand. Achieved by

The above problem can also be achieved by the final stand control method for a cold rolling mill according to claim 1, wherein the rolling load of the former stand is calculated from actual data.

The cold rolling mill according to claim 2, wherein the above-mentioned problem is also to calculate the target rolling load of the final stand by using a load balance coefficient which is set in advance for each plant and which represents a rolling load ratio between the final stand and the preceding stand. Is also achieved by the final stand control method of.

The above-mentioned subject is further controlled by the rolling position control which keeps the rolling load of the final stand constant during rolling.
It is also achieved by the final stand control method for a cold rolling mill as described in any one of 1.

[Operation] In the present invention, the set rolling load of the final stand is calculated by multiplying the actual rolling load of the final-1 stand by a coefficient, instead of being estimated and calculated from the rolling reduction. At this time, the coefficient multiplied by the actual load of the last-1 stand is a value indicating the load balance between the last stand and the last-1 stand, and the operator of each steel mill or rolling mill empirically understands that Use the load balance coefficient of rolling load between each stand that enables stable operation. In the same rolling plant and rolling with the same rolling specification, the load balance coefficient is constant, and when different, the load balance coefficient is different, but the coefficient may be stored for each rolling specification category. Since the final −1 stand has a small variation in the actual value as described above, the set load is not disturbed by the disturbance of the actual value of the final stand unlike the conventional method.

By using the constant load control method as the rolling control method, the dull rolling becomes more stable. The final stand-up roll rolling is, as described above, rolling in a region where the rolling load is abruptly changed by a slight change in the rolling reduction. From the opposite viewpoint, it means that the variation of the rolling reduction is small with respect to the variation of the rolling load, and the variation of the delivery side plate thickness is extremely small, so that the variation of the rolling position is small. Since the constant load control method is a method of freely varying the reduction position and keeping the rolling load constant, the rolling load having a large variation amount is controlled and the reduction position having a small variation amount is freely set. On the other hand, the constant rolling position control is a system in which a rolling load having a large fluctuation amount can be freely set. Therefore, in the dull rolling, using the constant load control makes the rolling more stable.

〔Example〕

 The inventors paid attention to the following facts.

(1) When a dull roll is used in the final stand, rolling is performed in a region where the rolling load formula based on the rolling theory does not hold in the final stand, and it is not always possible to obtain a large reduction rate even if the rolling load is increased. Absent.

(2) When the dull roll is used in the final stand, the actual rolling load values are the same rolling specifications (steel type, strip width, entry side strip thickness,
Even if the target finish plate thickness is the same), there are large variations.

From the above facts, it can be said that the effect of the rolling load on the finished strip thickness is smaller in the final stand-up rolling than in other rollings. In other words, it is impossible to accurately predict and calculate the rolling load necessary to obtain a certain finishing target plate thickness, and in order to improve product quality, it is better to improve rolling load prediction accuracy than to devise. It is important to stabilize the set load.

Given the above considerations, the embodiment described below features the following set-up method:

(1) In the case of the last stand and dull roll, using the steel type of the rolling specification data and the target finish plate thickness as key data, the rolling load table of the preceding stand of the final stand (hereinafter referred to as the final-1 stand) is indexed, and the final- The rolling load of one stand is multiplied by a predetermined coefficient to determine the target rolling load of the final stand. Next, similarly, using the steel type and the target plate thickness as key data, the final stand reduction ratio table is indexed to determine the reduction ratio.

(2) The result collection function collects the rolling load results of the last −1 stand and the final stand entry side and exit side plate thickness actual values, converts the rolling load into a load per unit width, and from the actual plate thickness values The reduction rate is calculated and stored in each table. At this time, exponential smoothing processing is performed to remove noise included in the actual value.

(3) The set value calculation result is transmitted to the rolling mill controller,
The rolling mill control device controls the rolling mill based on this calculation result. As the control method of the rolling mill, the rolling position is kept constant at the set rolling position and the rolling load is freely changed, and the rolling position is controlled to the constant rolling position. There is a constant load control method in which the pressure reduction position is freely changed while the above is maintained, but the latter constant load control method is used.

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a part of the control device of the cold rolling mill according to the present invention. The final stand rolling mill control device 3 connected to the reduction device 1A of the final stand rolling mill 1 and the input of the final stand rolling mill 1 are shown. Gauge for detecting the strip thickness of the rolled material on the output side and the output side and outputting it to the final stand rolling mill control device 3
9, 10 are connected to the final stand load measuring device 11 for detecting the rolling load of the final stand and outputting it to the final stand rolling mill control device 3, and the rolling load measuring device 12 of the final -1 stand rolling mill 2. Final-1 stand rolling mill controller 4
And a setup control device 5 connected to the final stand rolling mill control device 3 and the final -1 stand rolling mill control device 4.

The setup control device 5 includes a set value calculation function 6, an adaptive correction function 7, and a result collection function 8. Adaptive correction function 7
Since the above is the same as that of the conventional method, the description thereof is omitted here.

First, the flow of rolling mill control of the final stand will be described. The results (rolling load of the final stand rolling mill 1, target strip thickness, rolling position, roll speed, etc.) calculated by the set value integration function 6 based on the rolling specification data are sent to the final stand rolling mill control device 3. Sent. The final stand rolling mill control device 3 controls the rolling mill 1 of the final stand according to the set data. When rolling is started, the final stand rolling mill control device 3 periodically reads the actual rolling load from the final stand load measuring device 11, and moves the final stand rolling device 1A so that the actual load value matches the set load. . After accelerating the rolling mill, when the rolling speed becomes constant, the actual result collecting function 8 of the setup control device 5 uses the actual load from the rolling load measuring device 12 of the last −1 stand and the final stand entry side plate from the plate thickness gauge 9. The actual thickness and the actual strip thickness of the final stand from the thickness gauge 10 are input via the rolling mill control units 3 and 4, and the rolling load table 1 is used by using these data.
4. Update the rolling reduction table 15. These table values are referred to in the next set value calculation.

A setting value calculation flow that is an embodiment of the present invention will be described with reference to FIG. In setting value calculation, rolling specifications are first input. The rolling specification data is manufacturing specification data (steel type of rolled material, plate width, base material thickness, target plate thickness for finishing, etc.) and roll data (roll diameter, roll surface classification). It is determined from the roll surface classification whether the final stand is dull roll. If it is dull roll, the process proceeds to block 102. Otherwise, the process proceeds to block 112. Where block 112
Is the same as the conventional setting value calculation flow, and a description thereof will be omitted.

In block 102, the steel type of the material to be rolled this time and the finishing target thickness category are determined, the rolling load table 14 is indexed using this data as a key, and the average rolling load average value of the last −1 stand is extracted. A configuration example of the rolling load table 14 is shown in FIG. 3A. In this example, as shown in FIG. 3B, the rolled material is classified into 1 to 11 categories according to the yield point of the rolled material, and the finishing target plate thickness is classified into 1 to 10 categories as shown in FIG. 3C and rolled. The load table 14 has this division. The rolling load table 14 is
The rolling load (value obtained by dividing the rolling load by the strip width) per unit width of the last −1 stand is stored in association with the strip thickness segment and the steel grade segment. The rolling load per unit width (P _mf-1 ) of this final-1 stand is multiplied by the load balance factor (α) to determine the unit width rolling load of the final stand, which is multiplied by the strip width (b) to obtain the target. The rolling load (Pf) is calculated.

Pf = P _mf-1 × α × b (1) α: Load balance coefficient (0.8 to 0.95) This load balance coefficient is also stored in the table having the same stratification as the rolling load table in Fig. 3A. The value can be changed depending on the rolling schedule.

In block 103, the steel type classification and finish thickness classification determined in block 102 are used as key data, and the rolling reduction table is indexed to determine the rolling reduction of the final stand. The rolling reduction table has the same structure as the rolling load table in FIG. 3A.

Next, as in the conventional method, the reduction rate of one stand is obtained from the reduction rate constant table, and the total reduction amount (the reduction amount for changing the base metal thickness to the finish target plate thickness) is reduced by one stand and the reduction is performed by the final stand. The remaining reduction amount minus the amount is distributed to the intermediate stand, and the reduction rate of the intermediate stand is determined. Below, the tension, deformation resistance, rolling load, roll speed, and rolling position are calculated. However, the value determined in block 102 is used for the final stand target rolling load.

Next, the achievement collection of the present invention will be described. The actual rolling load (Pa) of the final −1 stand collected when the rolling speed becomes constant is divided by the strip width (b) and converted into rolling load per unit width (Pm).

Pm = Pa / b (2) The applicable case no. In the rolling load table is determined from the steel type classification of the material currently being rolled and the finishing target thickness classification determined by the set value calculation, and the table value (P _{mf -1} ) and the current value (Pm) are exponentially smoothed and stored in the corresponding case.

Pmf = P _mf-1 + (Pm-P _mf-1 ) × δ (3) δ: Exponential smoothing coefficient (0.3 to 0.7) Also, the actual value of the final stand input side thickness (Hf) and the output side thickness The final stand reduction rate actual value (ra) is calculated from the value (hf).

ra ＝ (Hf-hf) / Hf ……… (4) Similar to rolling load, the case no. in the rolling reduction table is obtained, and the exponential smoothing process of the table value (ra-1) and the current value (ra) is performed. Is performed and stored in the corresponding case. The final stand reduction rate actual value (ra) stored in the reduction rate table is used for the next set value calculation, as described above.

ra = ra-1 + (ra-ra-1) x ω (5) ω: exponential smoothing coefficient (0.3 to 0.7) The conventional method calculates the set values such as rolling load based on the set rolling reduction and For the reduction ratio, the check whether or not it is within the rollable range has not been made at all, so if the reduction ratio as set in the final stand cannot be obtained,
Since it has to be rolled by another stand, the setup schedule and the actual schedule do not match, which not only deteriorates the plate thickness accuracy, but in continuous rolling, it is necessary to change the setting of each stand upstream during rolling. Since the steps are performed sequentially from the stand, the mass flow with the preceding stand will not match, the tension will be excessive or excessive, and the plate will easily break. In the present embodiment, since the rolling load and the rolling reduction are determined from the actual values, the actual rolling schedule does not greatly differ from the setup schedule, and the number of plate breaks also decreases.

〔The invention's effect〕

The present invention estimates the target load by the table created from the actual data of the last −1 stand instead of the rolling load formula for the final stand dull roll rolling for which the rolling theory does not hold. It is possible to prevent that the set value is disturbed by the actual rolling value of the stand, the setup accuracy is deteriorated, and the off-gauge portion becomes long.

Further, conventionally, in the conventional method, it took a great deal of time to finely adjust the rolling load type of the dull roll rolling, which is originally impossible to adjust. It is only necessary to determine the load balance coefficient for estimating the load, and it is possible to launch the setup model in a short period of time.

[Brief description of drawings]

FIG. 1 is a procedure diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3A is a diagram showing a configuration example of a rolling load table according to the present invention, FIG. 3B, FIG. Fig. 3C is a diagram showing examples of steel grade classification and strip thickness classification, Fig. 4 is a diagram showing a conventional example of actual data during dull rolling, and Fig. 5 is a conceptual diagram showing the relationship between rolling load and roll flatness. FIG. 6 is a conceptual diagram showing the calculated load values for the rolling reduction near the rolling limit region. 1 …… Final stand rolling mill 2 …… Final -1 stand rolling mill 3 …… Final stand rolling mill control device 5 …… Setup control device 6 …… Set value calculation function 8 …… Result collection function 14 …… Rolling load table 15 …… Reduction ratio table

Claims (4)

[Claims] 1. A method for controlling a cold rolling mill in which a dull roll is mounted on a final stand of a plurality of rolling stands, wherein a target rolling load of the final stand is first determined from a rolling load of a stand preceding the final stand. A method of controlling a final stand of a cold rolling mill, the method comprising: 2. The method of controlling a final stand of a cold rolling mill according to claim 1, wherein the rolling load of the former stand is calculated from actual data. 3. The target rolling load of the final stand is calculated by using a load balance coefficient, which is preset for each plant and represents a rolling load ratio of the final stand and the preceding stand. Final stand control method for cold rolling mill. 4. The rolling position control for maintaining a constant rolling load of the final stand during rolling is performed.
4. The final stand control method for a cold rolling mill according to any one of items 1 to 3.