JPH0484614A - Method for automatically controlling sheet thickness - Google Patents

Abstract

PURPOSE:To reduce the front end part of a sheet to be disposed as scrap by forward feeding the sheet thickness deviation to the ensuing stage stand when the front end of the sheet engages with a front stage stand and setting up the ensuing stage stand, then executing absolute value control when the front end of the sheet engages with the ensuing stage stand. CONSTITUTION:The correction rate of a draft is calculated by the deviation between the actual value determined by a gage meter and a target value when the front end of the sheet engages with the front stage stand. This value is fed forward to the ensuing stage stand by which the draft position is adjusted and the ensuing stage stand is set up again. The speed of the ensuing stage stand is then corrected according to the change component of the mass flow by the correction of the draft position of the stand to correct the inter-stand tension at the time of engaging with the next stand is controlled to the target value. This stage is combined with the stage of correcting the draft position so as to decrease the deviation between the actual value at the stand and the target thickness to 0 when the front end of the sheet engages with the stand. The time before the completion of the control is shortened in such a manner by which the off-gage part is decreased. The front end part of the sheet to be disposed as the scrap is reduced, as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic plate thickness control method in a rolling mill. ) related to the method.

The conventional AGC system uses a roll force method that stores the plate thickness at lock-on and controls it as the target plate thickness. A roll force monitor AGC that corrects the thickness deviation by adding it to the memorized target thickness mentioned above is usually used, but in addition to this, an absolute target thickness is determined in advance and measured by a load cell when the plate is caught in the roll. Calculate the plate thickness based on the following formula from the rolling load F,
Absolute value AGC is also used to control the rolling down device so that the deviation from the absolute target plate thickness becomes zero.

h = S + Sp + 5ops ・−・・・(
11 Here, S is the rolling position, Sp is the mill elongation amount, S op
s is an offset.

Problems to be Solved by the Invention In the roll force monitor AGC, if there is an error in the plate thickness memorized at the time of lock-on, this will be maintained as it is, and the plate thickness deviation from the target value will be determined after being measured with a thickness gauge. Corrections are made in addition to the feedbanked and memorized target plate thickness, but the corrections are made only after the tip of the plate reaches the thickness gauge, and the correction is not started until the plate thickness is within the allowable range. Since there is a time lag before the plate is inserted, the plate thickness does not fall within the allowable range during this time, resulting in a so-called off-gauge section.

Even when using absolute value AGC, correction is made so that the deviation Δh between the thickness measured when the plate bites into the roll and the absolute target thickness becomes O (see Figure 6), but the effect is An off-gauge section occurs until it appears.

A first object of the present invention is to provide an AGC method that makes it possible to control the tip end of a plate, which has conventionally been scrapped as an off-gauge part, to a target thickness.

A second object of the present invention is to correct the mill speed to prevent the mass flow from collapsing and tension fluctuations from occurring when the rolling position is corrected during re-safety milling for plate thickness control. be.

Solution to the Problem The method to achieve the first objective is to calculate the reduction correction amount from the deviation between the target plate thickness and the actual value determined using a gauge meter when the tip of the plate is caught in the front stand. Feed forward to the next stage stand, adjust the rolling position and raise the next stage stand again, and correct the speed of the previous stage stand according to the change in mass flow due to the correction of the rolling position of the next stand. The process of controlling the tension between the stands at the time of loading to the target value, and the process of correcting the rolling position so that when the tip of the plate is bit into the stand, the deviation between the actual value at the stand and the target plate thickness becomes 0. It is characterized in that it consists of a combination.

-) In another method for achieving the above object, after the thickness of the outlet side is further measured in the above method, the deviation from the target thickness is fed back to each stand.

The method to achieve the second objective is to feed forward the deviation between the actual value obtained using a gauge meter and the target thickness when the tip of the plate is bitten into the previous stand to the next stand, and then adjust the rolling position. The method of adjusting and re-setting up the next stage stand is characterized in that the roll speed of the previous stage stand is corrected using the following equation.

Δνl Δfl Δf” Δkl
□ Tan−□+□− vl 1+H1+4j h! Here, Δvi/shii: Rate of increase in roll speed before the front stand fi: Advancement rate of the front stand Δfi: Rate of increase in the advance rate of the front stand hi: Target plate thickness on the side of the mini front stand Δhi: Increase in plate thickness on the exit side of the front stand Quantity 138 Advancement rate of the next stage stand Δfj: Increase rate of the advance rate of the next stage stand In this method as well, the reduction position may be corrected in combination with absolute value control, and furthermore, the plate thickness on the exit side and the target plate This may be done by feeding back the deviation from the thickness to each stand.

As shown in Fig. 3, in the i-stand, when the plate thickness on the entry side is h, the rolling position is set at S in consideration of the mill constant M in order to obtain the target plate thickness hai. If the actual load F, , is higher than the set predicted load F8, the actual plate thickness h1□ obtained from this will also be thicker than the target plate thickness hsi by Δh. In the j+1 stand, as shown in Figure 4, the entrance plate thickness is initially set to hmi, but the actual entrance plate thickness is l1ffil, so the initial target plate thickness h□mm+, is obtained. Therefore, the lowering position is changed by ΔS and set up again to S+++. This re-setup caused the tip of the board to get caught in the i-stand in the previous stage, resulting in the actual board thickness being 6. is determined based on the output signal. When the tip of the board gets caught in the i+l stand next,
Rolling is performed at the re-centred rolling position, but the actual plate thickness determined from the actual load and the target plate J9Ch-++□
If there is a deviation between , the rolling position is corrected so that the deviation becomes zero.

As described above, when the tip of the plate is caught in the previous stand i, the plate thickness deviation Δh is fed forward to the next stand i+l, and the next stand is reset. When the tip of the plate then bites into stand i+1, absolute value control is carried out, and the position of rolling down in the next stage stand is controlled in two stages. As a result, as shown in Fig. 5, the deviation Δh in absolute value control
, and the reduction amount also decreases, so the time T until the control is completed is also shorter than the time T (
(see Figure 6). Therefore, the effect of the correction will appear more quickly, and the number of off-gauge parts will be reduced.

Note that FIG. 5 shows the amount of variation in plate thickness when three-stage control is performed by measuring the plate thickness on the exit side and feeding back the deviation from the target plate thickness.

Next, correction of roll speed will be explained.

In FIG. 7, the following equation holds between the i-stand and the j-stand.

(1+fi)vi ==<1+bj)vj −・−−
---(2) The advanced rate of i-stand is now fi + Δfi,
, the backward movement rate of stand j changes to bj + Δbj, the roll speed of stand i changes to vi + Δvis, and the roll speed of stand j changes to j + Δvj. In order to keep the mass flow constant, the following equation holds true.

(1+fi+Δfi)(vi+Δvi)=(1+bj+
Δbj) (vj+Δvj) -=(3) Expanding equation (3) and rearranging it as ΔffΔvi#o+ ΔbjΔvJ#o, we get Δfivi+(1+fi)Δvi=Δbjvj + (
1+bj) Δvj. Dividing both sides by (1+fi)vi and rearranging by setting Δvj=o, in the νI 1+fl 1+bJj stand, from the constant volume law, (hf +Δhi)(1+bJ+Δbj)νj= (1
+fj+Δfj)vj(hj+Δhj),
Expanding this and dividing both sides by hj (1+bj), we get Δbj Δh1 ΔfJ Δh
J−−−+ −+ □ ・・・・・・・・・ (5)1
+bj hL 1+fj hj
is required. Therefore, equation (4) is Δvi hf1 Δfj Δhi
Δhj knee---fog---■ten－－－＋－"
...e・vl 1+fl 1+fj
It is expressed as bl bj. Here, the exit side of the j stand is pushed down so that it becomes bj, so Δh3
= o.

Therefore, the roll speed correction at the front stand is as follows: Δvi Δfi Δfj Δh+, −−
＋ −−□ ・・・・・・・・・ (7) vl 1
It is expressed as +fl 1+fJ hl.

Embodiment In FIG. 1, the rolling load measured by the load cell 3 of each stand 2 and the rolling position from the rolling position detection device 4 are input to the controller 1, and the plate thickness measured by the thickness gauge 5 on the exit side is inputted to the controller 1. is now entered.

As shown in FIG. 2, the controller 1 determines the plate thickness when the plate is bitten based on the rolling load F input from the load cell 3 of each stand, the mill constant M, and the rolling position S as described above (
The calculation is performed based on Equation 11, and the deviation Δh from the target plate thickness set for each stand is calculated. Based on the obtained deviation Δh, the correction amount ΔS of the rolling position in the next stage stand is ΔS
= (M+Q)7M·Δh, and the control signal is output to the lowering device 6 of the next stage stand. Then, the initially set up position is corrected on the next stage stand.

A correction amount ΔS of the rolling position in the stand is calculated from the determined deviation Δh, and a control signal thereof is output to the rolling device 6 of the stand.

Based on the obtained deviation Δh, a calculation for correcting the roll speed in the front stage stand is performed using the above equation (7), and based on this, a control signal is output to the roll drive motor 7 of the front stage stand.

The controller 1 also calculates the deviation from the target plate thickness from the plate thickness input from the thickness meter 5, and calculates the amount of correction of the rolling position to be distributed to each stand. The information is then fed back to each stand, and each lowering device 6 is controlled.

Effects of the Invention The present invention is configured as described above, and has the following effects.

In the method according to claim 1, when the tip of the plate is bitten by the previous stand, the plate thickness deviation is fed forward to the next stand, and the next stand is re-centred and the tip of the plate is bitten by the next stand. Absolute value control is performed at the same time, and the rolling position at the next stand is controlled in two stages.Since the rolling amount under absolute value control is smaller, the time required to complete the control is also shorter. This reduces the number of off-gauge parts and reduces the number of plate tip parts that become scrap.

Further, as in the method according to claim 2, if the deviation between the outlet side plate thickness measured with a thickness gauge and the target plate thickness is fed back after carrying out the method according to claim 1, the target plate thickness can be controlled with high accuracy. be able to.

In the method according to claim 3, the rolling position of the next stage stand (l1) is corrected according to the plate thickness deviation when the tip of the plate is bitten by the front stand, and the roll speed of the front stand is corrected accordingly to keep the roll speed constant. The tension is maintained, so even if the rolling position is corrected, the mass flow will not collapse and the plate thickness will not change.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the method of the present invention, Figure 2 is a functional block diagram of the controller, Figures 3 and 4 are diagrams showing the relationship between rolling load and plate thickness, and Figure 5 is the absolute value of the method of the present invention. Figure i1!1 shows the deviation when the control is performed, Figure 6 is a diagram in conventional absolute value control, and Figure 7 is a diagram showing the setting conditions at the stand. 1. Controller 2. Stand

Claims (3)

[Claims] (1) When the tip of the plate gets caught in the previous stand, the deviation between the actual value determined by the gauge meter method and the target plate thickness is fed forward to the next stand, the rolling position is corrected, and the next stand is set up again. The process of adjusting the speed of the previous stand according to the mass flow change due to the correction of the rolling position of the next stand, and the process of controlling the tension between the stands to the target value when the next stand bites, and the process of controlling the tension between the stands to the target value when the tip of the plate bites into the stand. An automatic plate thickness control method comprising the steps of: correcting the rolling position so that the deviation between the target plate thickness and the actual value at the stand becomes zero; (2) An automatic plate thickness control method by combining the automatic plate thickness control according to claim 1 with control in which the deviation from the target plate thickness is fed back to each stand after the plate thickness on the outlet side is measured. (3) When the tip of the plate gets caught in the previous stand, the deviation between the actual value determined by the gauge meter method and the target plate thickness is fed forward to the next stand, the rolling position is adjusted, and the next stand is set up again. An automatic plate thickness control method characterized in that the roll speed before the front stand is corrected by the following formula. (Δvi)/(vi)=-(Δfi)/(1+fi)+
(Δfj)/(1+fj)-(Δhi)/(hi) where Δvi/vi: Rate of increase in roll speed of the front stand fi: Advancement rate of the front stand Δfi: Rate of increase in advance rate of the front stand hi: Rate of increase in the advance rate of the front stand Output side plate thickness target Δhi: Increase in the exit side plate thickness of the previous stand fj: Advancement rate of the next stand Δfj: Increase rate of the advance rate of the next stand