JPH023641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a speed control method in a continuous rolling mill.

[Conventional technology]

Inter-stand tension fluctuations and loop amount fluctuations due to fluctuations in mass flow of rolled material between continuous rolling stands are absorbed by a tension control system based on tension detection or a looper control system based on looper position detection. However, since these control systems are feedback control systems, the control effect tends to be delayed in response to rapid fluctuations in the mass flow of the rolled material, and the tension between the stands or the loop amount cannot be maintained properly and become unstable. It has a negative effect on the quality of rolling and finished products.

[Problem to be solved by the invention]

Therefore, there is a need for a feedforward speed control method that absorbs fluctuations in the mass flow of the rolled material due to AGC (automatic plate thickness control), skid marks, etc. that cause tension fluctuations, loop amount fluctuations, etc.

Conventionally, this type of speed control method involves detecting reduction rate fluctuations (plate thickness fluctuations) due to fluctuations in rolling conditions and correcting the roll speed.
Actual rolling tests revealed that the effect is not sufficient against rapid changes in the rolling position caused by AGC, etc.

The first object of the invention is to control the flow of material to be rolled between stands to be constant. That is, the tension or loop amount is controlled to be constant by absorbing fluctuations in the mass flow of the rolled material between each stand. The second purpose is to provide a speed control method that actively detects mass flow fluctuations in the rolled material due to fluctuations in tension between stands due to fluctuations in rolling conditions, AGC, skid marks, etc. that cause loop amount fluctuations, and controls the mass flow. An object of the present invention is to provide a feedforward speed control method that stably and quickly absorbs fluctuations in speed.

[Details of conventional technology]

First, the conventional method will be explained with reference to FIG. 1, which shows an arbitrary i-th stand and an i+1-th stand of a continuous rolling mill. In the symbols in FIG. 1, the device whose first digit is 1 indicates a device related to the i-th stand 21, the device whose first digit is 2 indicates a device related to the i+1-th stand 22, and the second digit is the same. Devices indicate devices with the same configuration. Note that 1 indicates a material to be rolled.

The inter-stand tension and loop amount of the i-th stand 21 and the i+1-th stand 22 are determined by the integral of the speed difference between the exit plate speed of the i-th stand 21 and the inlet plate speed of the i+1-th stand 22 of the rolled material 1, This speed difference Di is expressed by the following equation (1).

Di=(1+fi)Vi-(1+bi ₊ 1)Vi ₊₁ (1) where the subscript i represents the stand number, f represents the forward rate, b represents the backward rate, and V represents the roll speed. This speed difference Di is expressed by the following equation using a certain reference value (represented by a subscript *) Di ^* and a variation amount ΔDi (represented by a prefix Δ) from the reference value Di ^* .

Di=Di ^* +ΔDi ……(2) Di ^* = (1+fi ^* )Vi ^* −(1+bi ₊₁ ^* )Vi ₊₁ ^* ……(3) ΔDi=(1+fi ^* )ΔVi+Vi ^* Δfi −(1+bi ₊₁ ^* ) ΔVi ₊₁ ^* −Vi ₊₁ ^* Δbi ₊₁ ...(4) Speed difference reference value expressed by formula (3) in formula (2)
Di ^* is a DC component, and the tension and loop amount determined by its integral can be controlled by a feedback control system such as a tension control system or a looper control system. Therefore, consider absorbing the variation ΔDi in the speed difference expressed by equation (4), which gives a dynamic disturbance to the control system, by correcting the roll speed.

In other words, the i-th stand 2 due to variation in rolling conditions.
1 advanced rate fluctuation Δfi and i+1st stand 22
The speed difference variation ΔDi due to the backward movement rate variation Δbi ₊₁ is absorbed by the roll speed correction. Now, a case will be described below in which the roll speed of the i-th stand 21 is corrected to absorb inter-stand tension fluctuations and loop amount fluctuations due to speed difference fluctuations.

By setting ΔDi=0 in equation (4) and considering equation (3), the following equation (5) can be obtained. According to rolling theory, the leading coefficient variation rate Δf/(1+f ^* ) and the backward coefficient variation rate Δb/(1+b ^* ) are the exit plate thickness variation rate Δh/h ^* and the entry plate thickness variation rate ΔH/H ^* is expressed by the following equations (6) and (7).

ΔVi/Vi ^* = Δfi/(1+fi ^* )+〈Vi ₊₁ ^* (1+bi ₊₁ ^*
)/[Vi ^* (1+fi ^* )]> × [(∆bi ₊₁ / (1+bi ₊₁ ^* ) + (∆Vi ₊₁ / (
1−Vi ₊₁ ^* )……(5) Δf/(1+f ^* )=−A ^* Δh/h ^* +B ^* ΔH/H ^* ……(6) Δb/(1+b ^* )=(1=A ^* ) Δh/h ^* −(1−B ^* )ΔH/H ^* ...(7) However, A ^* and B ^* are constants determined by the rolling conditions in the above standard state, and according to the knowledge of rolling theory, Expressed by the following formula, usually 0.1
Takes a value of ~0.25.

^{A * = √ * ・ 〈 ( √2} /4π√( ^{* *} )π〔0.5ln(h
^* /H ^* )+1〕0.5√〔 ^* ( ^* − ^* )〕〉 =A ^* +√ ^* (√2/8π√ ^{* *} ln(h ^* /H ^* )…
...(7') The following equation (8) obtained by substituting equations (6) and (7) into equation (5) is the and represents the roll speed correction amount ΔVi+Vi ^* of the i-th stand 21 to make the speed difference variation ΔDi between the i+1-th stands zero.

ΔVi + Vi ^* = [Ai ^*・(Δhi/hi ^* )−Bi ^*・(ΔHi/Hi
^* )〕+〈Vi ₊₁ ^*・(1+bi ₊₁ ^* ) /Vi ^*・(1+fi ^* )〕〉・〈〔(1−Ai ₊₁ ^* )・
(Δhi ₊₁ ^* hi ₊₁ ^* )−1−Bi ₊₁ ^* ) ・(ΔHi ₊₁ ／Hi ₊₁ ^* )＋(ΔVi ₊₁ ／Vi ₊₁ ^* )〕〉...
…(8) However, hi=Si+Fi/Mi) …(9) Hi=hi _-1 (t−τi) …(10) Δhi=hi−hi ^* …(11) ΔHi=Hi−Hi ^* … ...(12) where Si is the rolling position obtained by the rolling position detecting devices 31 and 32 of the i-th stand, Fi is the rolling force obtained by the rolling force detecting devices 41 and 42 of the i-th stand, and Mi is the rolling force obtained by the rolling force detecting devices 41 and 42 of the i-th stand. stands Mill constant, (9)
The formula is realized by the exit side plate thickness calculation devices 51 and 52.
t is the current time, τi is the transfer time of the rolled material 1 between the i-1st stand (not shown) and the i-th stand 21, and equation (10) is realized by the delay devices 61 and 62. The speed correction amount calculation device 71
hi obtained by 1, 52, 61, 62, hi ₊₁ , Hi,
Hi ₊₁ and ΔVi/Vi ^* obtained by the speed correction amount calculation device 72 are calculated, and the roll speed of the i-th stand 21 is corrected through the speed control device 81.

However, the conventional method of speed correction using equation (8) cannot sufficiently absorb rapid changes in the rolling position. The reason for this is that equations (6), (7), and (9) represent static relationships, which no longer hold true when the rolling position changes rapidly.

[Means to solve the problem]

Therefore, in the present invention, among the items of the roll speed correction amount ΔVi/Vi ^* of the i-th stand in equation (8), the hi term represents the rolling position fluctuation at the current time. Considering the rapid fluctuation of , we do the following. For the sake of simplicity, the subscript i is omitted and the principle of the present invention will be explained with respect to the variation of each physical quantity.
Consider the equivalent exit plate thickness Δh expressed by the following equation (14) with respect to the variation Δh of the outlet plate thickness expressed by the equation.

Δh=ΔS+ΔF/M……(13) Δh=ΔS+[K/(1+TP)]×ΔF/M
...(14) However, P is the Laplace symbol, and P≡d/dt
It is. [K/(1+TP)] represents a low-pass filter with time constant T and gain K.

On the other hand, the rolling force variation ΔF with respect to the rolling force variation ΔF' due to the exit side plate thickness variation Δh, the input side plate thickness variation ΔH, and other rolling condition variations based on the plastic conditions is expressed by the following equation (15).

ΔF=−Qh・Δh+Q _H・ΔH+ΔF′……(15) However, Qh is the influence coefficient of the exit side plate thickness variation on the rolling force variation, and _QH is the influence coefficient of the input side plate thickness variation on the rolling force variation. From the elastic conditions of the mill, the rolling condition variation ΔF with respect to the exit plate thickness variation Δh and the rolling position variation ΔS is expressed by the following equation (16), which is equivalent to equation (13).

ΔF=M(Δh−ΔS)……(16) From equations (15) and (16), we obtain the following equation.

ΔF/M=-QhΔS/(M+Qh)+Q _H ΔH/(M+Qh)+ΔF′/(M+Qh)
...(17) Substituting equation (17) into equation (14), we obtain the following equation.

Δh=ΔS〈[M+(1-K)Qh]/(M+Qh)+TP
〉/(1+TP) +[K/(1+TP)][QhΔH/(M+Qh)+
ΔF'/(M+Qh)...(18) Also, Δh obtained from equation (13) is when K=1 and T=0 in equation (18), and becomes the following equation [in equation (13), 17) It can also be obtained by substituting Eq. ] Δh=M・ΔS/(M+Qh)+Q _H・ΔH/(M+Qh)+ΔF′/(M+Qh)...(19) As is clear from equations (18) and (19),
Compared to Δh, Δh has a phase lead in the vicinity of the frequency range from [M+(1-K)Qh]/(M+Qh)T to 1/T with respect to ΔS, and [M+(1-K) Qh]/(M+Qh) The signal becomes large at frequencies higher than T. On the other hand, for ΔH and ΔF', frequency components of 1/T or more are cut out, and rolling force noise is cut out. Note that when K=1, Δh=Δh in the low frequency region.

These frequency characteristics are shown in FIG. 2 (relationship between Δh/Δh and ΔS) and FIG. 3 (relationship between Δh/Δh and ΔH, ΔF') for the case of K=1.

Based on the above considerations, in this invention, the roll speed correction amount ΔVi/Vi ^* of the i-th stand is determined using the following equation for equations (8) to (12).

ΔVi/Vi ^* = [Ai ^*・(Δhi ^F /hi ^F* )−Bi ^*・(ΔHi ^F
/Hi ^F* )〕＋〈Vi ₊₁ ^*・(1+bi ₊₁ ^* ) ／〔Vi ^*・(1+fi ^* )〕〉・[(1−Ai ₊₁ ^* )・
(Δhi ^F ₊₁ /hi ^F ₊₁ ^* )−(1−Bi ₊₁ ^* ) ・(ΔHi ^F ₊₁ /Hi ^F ₊₁ ^* )+(ΔVi ₊₁ /Vi ₊₁ ^* )]…
…(20) hi ^F = Si + [Ki/(1+TiP)] ・(Fi/Mi) …(21) Hi ^F = [i/(1+iP)]・Hi …(22) Δhi ^F =hi ^F −hi ^F* ...(23) ΔHi ^F =Hi ^F −Hi ^F* ...(24) Here, [i/(1+iP)] in equation (22) is
It is a filter for phasing the effect of Hi on Δhi ^F according to equation (20), and in general, gain i=
It is sufficient to set Ki and time constant i = Ti, but if it is necessary to weight Hi ^F with respect to the rolling phenomenon, i
and i may not necessarily be equal to Ki and Ti. Moreover, this filter has the effect of removing Hi noise caused by the rolling force noise of the i-1th stand.

If the roll speed of the i-th stand is corrected using the roll speed correction amount ΔVi/Vi ^* obtained from equations (20) to (24) above, the mass flow of the rolled material will change due to rapid changes in the rolling position. It has a sufficient absorption effect compared to the conventional method, and the same absorption effect as the conventional method can be obtained for fluctuations in the mass flow of the rolled material due to normal rolling position fluctuations and other physical quantity fluctuations. Tension fluctuations and loop amount fluctuations can be reduced.

〔Example〕

Next, one configuration of a speed control device for carrying out this invention is shown in FIG. 4, and the speed control thereby will be explained. In FIG. 4, devices with the same symbols as in FIG. Devices 101, 201, and 202 represented by a heavy frame are devices added to implement the present invention. i-th stand 21
In this step, the rolling position Si detected by the rolling position detection device 31 and the rolling force Fi detected by the rolling force detection device 41 are input to the outlet side plate thickness calculating device 51. The calculation device 51 calculates the plate thickness hi based on equation (9).

The i-1st stand exit plate thickness hi _-1 calculated in the i-1st stand (not shown) in the same way is:
Through the delay device 61, the entry side plate thickness is determined by the delay of equation (10).
Hi is given to the equivalent inlet thickness calculating device 101, and the calculating device 101 calculates the equivalent inlet thickness Hi ^F based on equation (22). The above-mentioned rolling force Fi and rolling position Si are input to the equivalent exit side plate thickness calculation device 201, and the calculation device 201 calculates the equivalent exit side plate thickness hi ^F based on equation (21). The above equivalent entrance plate thickness Hi and equivalent exit plate thickness hi ^F are the equivalent entrance plate thicknesses obtained in the i+1th stand in the same manner as the i-th stand.
Hi ^F ₊₁ , the equivalent outlet plate thickness hi ^F ₊₁ , and the roll speed correction amount ΔVi ₊₁ /Vi ₊₁ ^* of the i+1th stand are input to the speed correction amount calculation device 71.

The speed correction amount calculation device 71 calculates that the rolled material 1 is
At an arbitrary time after being bitten by the +1 stand 22, the physical quantities with the subscript * on the right side of equation (20) are calculated and stored (Hi ^F , hi ^F , hi ^F ₊₁ , ΔVi ^F ₊₁ /Vi ₊₁ (Input signals for physical quantities other than ^* are omitted from illustration), and the roll speed of the i-th stand is corrected using equations (20), (23), and (24) for changes in rolling conditions after the memorized time. Thus, fluctuations in the mass flow of the rolled material 1 between the i-th stand 21 and the i+1-th stand 22 are absorbed.

As described in detail above, the present invention calculates the equivalent exit side plate thickness in the i-stand from the rolling reaction force smoothed by a low-pass filter with a time constant Ti and a gain Ki, and the rolling position. The exit side plate thickness is weighted by the time constant Ti and gain Ki of the low-pass filter against rapid fluctuations in the rolling position (speed, frequency).
Changes in rolling reaction force that change at high speeds (high frequencies) due to noise, etc. are suppressed, and changes in rolling reaction force that change at relatively low speeds (low frequency) due to AGC, skid marks, etc. are extracted.

Therefore, this equivalent exit side plate thickness, as well as the equivalent inlet side plate thickness after removing the noise of the inlet side plate thickness due to the noise of the rolling force of the front stand, that is, the time constant Ti,
The roll speed is corrected based on the time constant i corresponding to the gain Ki and the equivalent entrance side plate thickness smoothed by a low-pass filter of gain i.

This equivalent entrance side plate thickness also has the above-mentioned time constant Ti and gain
Since it is smoothed by a low-pass filter with a time constant i and a gain i corresponding to Ki, the low-pass filter is effective against rapid fluctuations (speed, frequency) in the entrance plate thickness due to noise in the rolling force of the front stand, etc. It is weighted by time constant i and gain i, and changes in rolling reaction force that change at high speed (high frequency) due to noise etc. are suppressed.
Relatively low speed (low frequency) rolling reaction force changes due to AGC, skid marks, etc. are extracted.

〔Effect of the invention〕

As a result, the correction of the roll speed can be expected to have a sufficient effect of absorbing the fluctuations in the mass flow of the rolled material due to rapid changes in the rolling position, compared to the conventional method, and can be expected to have a sufficient effect in absorbing fluctuations in the mass flow of the rolled material due to rapid changes in the rolling position. Since the filter and the low-pass filter that obtains the equivalent inlet plate thickness have corresponding time constants and gains, the variation response characteristics of the equivalent outlet plate thickness and equivalent inlet plate thickness (change speed, that is, weighting for the varying frequency)
correspond to each other, and the roll speed correction becomes stable. Furthermore, since the correction signal does not contain noise, it is possible to measure correction accuracy to a large extent.

In addition, in the above embodiment, a method was explained in which the mass flow fluctuation of the rolled material between the i-th and i+1-th stands was absorbed by correcting the roll speed of the i-th stand, but as is clear from equation (20), Needless to say, it can be absorbed in the same way by modifying the roll speed. Furthermore, it is clear that the filter used in equations (21) and (22) may be any low-pass filter.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a conventional speed control device, Fig. 2 is a graph showing that variations in the equivalent exit side plate thickness are weighted with respect to variations in the rolling position according to the present invention, and Fig. 3 is a graph showing the present invention. FIG. 4 is a graph showing that the equivalent exit plate thickness variation is smoothed with respect to the variations in each physical quantity due to the input plate thickness variation and other changes in rolling conditions. FIG. 2 is a block diagram showing the configuration. 1... Rolled material, 21, 22... Stand, 3
1, 32... Lowering position detection device, 41, 42...
Rolling force detection device, 51, 52... Output plate thickness calculation device, 61, 62... Delay device, 71, 72... Speed correction amount calculation device, 81, 82... Speed control device, 101, 102... Equivalent Entry side plate thickness calculation device,
201, 202... Equivalent exit side plate thickness calculating device.

Claims (1)

[Scope of Claims] 1. A continuous rolling mill that adjusts the roll speed in order to control the inter-stand tension or loop amount caused by the speed difference between the plate speed at the exit side of the previous stand and the plate speed at the inlet side of the next stand of a continuous rolling mill. In the rolling mill speed control method, in the i-stand, the i-stand equivalent exit side plate thickness is calculated by the i-stand rolling reaction force smoothed by a low-pass filter with a time constant Ti and gain Ki, and the i-stand rolling position; The i-stand entrance plate thickness obtained by transferring the i-1 stand outlet plate thickness calculated by the i-1 stand rolling reaction force and the i-1 stand rolling position to the next stand is calculated using the time constant Ti and the gain. The equivalent inlet thickness of the i stand smoothed by a low-pass filter with a time constant and gain corresponding to Ki, and the i+
The roll speed correction amount of the i stand is calculated from the 1 stand equivalent exit side plate thickness and the i + 1 stand equivalent inlet side plate thickness, and the roll speed of the i stand is controlled thereby, and the rolled material between the i and i + 1 stands is A method for controlling the speed of a continuous rolling mill, which is characterized by absorbing fluctuations in the mass flow of a material and controlling the tension or loop amount to a constant value. 2 Each stand i-1, i, arranged in the rolling direction
From the rolling position S and rolling force F of i+1,..., calculate the equivalent exit plate thickness hi ^F and hi ^F ₊₁ using the following formula, h ^F = S + [K/(1+TP)]・F/M K: Gain T: Time constant P: Laplace symbol M: Mill constant of rolling mill Calculate the exit plate thickness hi and hi ₊₁ using the following formula, h ^F = S + F/M Delayed entry plate thickness Hi and Hi ₊₁ using the following formula Find H=h(t-τ) t: Current time τ: Transfer time of rolled material between front and rear stands Hi and Hi ₊₁ and the equivalent entrance plate thicknesses Hi ^F and Hi ^F using the following formulas.
Find ₊₁ , H ^F =H・/(1+P) Furthermore, use the following formula to find the roll speed correction amount ΔVi/Vi ^* of the i stand, ΔVi/Vi ^* = [Ai ^*・Δhi ^F /hi ^F* − Bi ^*・Δ〓Hi〓／Hi ^F*
] + [Vi ^* ₊₁ (1+bi ₊₁ ^* )/Vi ^* (1+fi ^* )] × [(1−Ai ₊₁ ^* )・Δhi ^F ₊₁ /hi ^F ₊₁ ^* −(1−
Bi ₊₁ ^* )・ΔHi ^F ₊₁ /Hi ^F ₊₁ ^* +ΔVi ₊₁ /Vi ₊₁ ^* ] *: Standard value, Δ: Variation from standard value, A, B: Depending on rolling conditions in standard state A fixed constant, f: advance rate, b: backward rate, Δhi ^F =hi ^F −hi ^F* , ΔHi ^F =Hi ^F −Hi ^F* , corresponding to the roll speed correction amount ΔVi/Vi ^* , i
A speed control method for a continuous rolling mill according to claim 1, which comprises controlling the roll speed of a stand.