JPS6026604B2 - Current control method for continuous rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling rolling current in a continuous hot rolling mill for metal plates such as steel plates.

Figure 1 shows a hot continuous rolling mill with six stands 2...6, each stand 1, 2...6 having a pair of upper and lower backup rolls and a pair of upper and lower work rolls. A four-layer rolling mill, electric motors 21, 22...26 that rotationally drive work rolls, and electric motor 2
Consisting of rolling current detectors 31, 32, . As shown by the arrow, the rolling mill is fed from the first stand 1 to the continuous rolling mill, passed through the second to fifth stands arranged in tandem, exited from the sixth stand, passed through the hot run table, and then passed through the winding machine (none of which are shown in the figure). It is now sent to Loopers 11, 12, 13, 14, and 15 are arranged between the first to sixth stands arranged in tandem to apply appropriate tension to the rolling village 7. Now, using such a continuous rolling mill, the rolled material 7 with a thickness of ~ is reduced to a thickness of hF.
When rolling into a product, the roll gap Si of each stand
(i is a subscript indicating that it relates to the i-th stand.

The following methods are commonly used to determine the number of rotations (number of rotations per unit time) Ni of the work rolls (the same applies hereinafter) and the number of rotations per unit time Ni. ■ Thickness of plate after rolling at each stand,
In other words, determine the outlet thickness (armpit).

For this purpose, a so-called HHT curve is used to find the vertical axis coordinate W (ho) corresponding to the machine axis coordinate ho and the machine axis coordinate W (hF) corresponding to the machine axis coordinate hF, and the space between them is divided into six equal parts. The machine axis coordinates corresponding to the two vertical axis coordinates are h, , L...L, respectively.
It is determined by Note that h6=hF. (2) Calculate the rolling load Pi generated when rolling to the trowel exit thickness hi for each stand using the following {1'' formula (known Sims formula).

Pi=1.1 arc {mi no Ri(hi-,-hi)Qpj
...'1} However, Kfmi: Average deformation resistance of the rolled material at the i-th stand (k9/rail) Ri: Roll radius (female) at the i-th stand Qpi: The i-th stand 'Reduction force function (h
function of i-, and hi) ■ Roll gap S of each stand
Calculate j (job) using the following {2} formula (known gauge meter formula).

Si=hi-cotton-. However, Mi: Mill stiffness coefficient at the i-th stand (Rin/fence) ■ Calculate the advance rate fi at each stand.

For this purpose, the following glue formula (known as Mr. Sims' formula) is used. fi:02Ri'/hi...
{3'However,? i = side skin cover n-・Yuko Furano-Misaki Suga×I cow] Pi M; M [10 COBi ■ H-M] Co: constant Bi: target board width of the i-th stand (kite) this In the case, the speed Vf of the rolled material at the exit side of the i-th stand
i (side/sec) is given by the following formula (2).

vfi = vessel RiNi (10fi). ...■ However, Ni: the number of roll rotations per unit time (r.p.m.) of the i-th stand.■ The number of roll rotations of the last stand, in this case the sixth stand, is The roll rotation speed Ni is determined by the following formula (2).

(10fi)PINi=(10f6)R6N6 ・
...[5] If Sj and Ni are determined in this manner and rolling is performed according to these values, a product with the desired plate thickness hF should be obtained.

However, the temperature of the rolled material 7 changes as shown schematically in FIG. 2 due to the influence of thermal rungs and skid marks, so the temperature distribution in the longitudinal direction of the rolled material 7 is not uniform, and the average change resistance Kfmi in each stand fluctuates. However, since the rolling load Pi changes accordingly, the exit thickness hi also changes. In order to suppress this variation in hi, an automatic plate thickness control device is provided for each stand. At this point, this automatic plate thickness control device changes the roll gap Si to increase the exit thickness hi.
The control is performed to maintain a constant value hF, and to obtain the desired product thickness hF, but due to this control, the currents (rolling currents) of the motors 21, 22, . . . , 26 vary greatly, and in some cases Problems that sometimes occur when tolerances are exceeded and the mill stops, and a solution has been awaited. The present invention has been made in view of the above circumstances, and it monitors the motor current during rolling using a rolling current detector installed in each motor, and when the current value of any stand exceeds a predetermined value, When changing the rolling current, the roll gap, roll rotation speed, and inter-stand tension are also changed so that the amount of change and the amount of change in the roll gap, roll rotation speed, and inter-stand tension have a specific function, It is an object of the present invention to provide a current control method that prevents the rolling current from exceeding a permissible value and causing a mill stop, and also does not cause variations in the thickness hF of the finished product.

Therefore, the current control method according to the present invention eliminates the difference Δli between the rolling current of each stand of a continuous hot rolling mill having n stands (n is plural) and the rolling current target value of each stand. Therefore, the roll gap in each stand, the number of roll rotations per unit time in each stand (hereinafter simply referred to as the number of roll rotations), and the tension between adjacent stands are as follows (1)
It is characterized by simultaneous change operations based on formulas.

However, △li: i-th (i=1, 2・
Difference A from the same target value of rolling current at stand 'n) △Si: Roll gap change amount (stiffness) at the i-th stand △Ni: Unit time at the i-th stand Amount of change in roll rotation speed per unit (r.p.m.
．． ) △.

i: Similarly, the amount of tension change between the i-th stand and the i+1-th stand (k9 place) bi, i: Matrix RRA (3n-1) rows and (Yo-12) columns
The element in the i-th row and i-th column of the (orbit-1) row and n column consisting of the column vector from the third column to the (n+2)th column of ARRAt)-1 (i=1, 2...Kiichi 1, i D1, 2...n) A: Determined from material information such as the steel type of the rolled material and rolling schedule of each stand, etc., and having the function of the following formula (0) Matrix △hF: Amount of change in plate thickness at the exit of the final stand △bF: Amount of change in plate width at the exit of the final continuous stand △ui: Amount of change in volume velocity at the i-th stand from the entrance side of the rolled material (i = 1, 2 ...n) At: Inversion matrix R of A: A diagonal matrix representing the weight of the (1) row and (1) column. ΔhP, Δbp, and Δui are set to 0 in the above range.

Now, the process of deriving the above-mentioned formula '1} will be specifically explained by taking as an example a finishing rolling mill having six stands shown in the figure.

The meanings of the symbols used in the following formulas are shown below.
11: Rolling current G before change at the i-th stand
i: Rolling torque before change at the i-th stand (k
9・m) Ni: Roll rotation speed before change in the i-th stand (r.p.m.) Qi: Plasticity coefficient in the i-th stand (■n/skin) bi: Exit of the i-th stand Rate of change in rolling load due to change in plate width (column) ticket (also known as mashi b) front magnetic force (also known as back cooperation) (subscript i)
means that the i-th stand is related.

Same hereafter) [Matsu n/(k9/ground)] Rate of change in rolling torque due to change in front magnetic force (also known as rear tension) [k9・m/([9/no)] Ticket (assistance): Rate of change in advance rate due to changes in wake (also rear rib) [1/(k9/fence)] Shibu (
Also, the rate of change in the width of the rolled material due to changes in the front tension (or rear tension) [fence/(k9/uniform)] The rate of change in the thickness of the moat exit is the rate of change on the Hime-no-toru side [k9. /rib] Hair: The thickness of the exit is the rate of change in the rate of weaving [1/rib] The thickness of the entrance to the basket is the change in the thickness of the boat. Gutter Side Ratio [N/Rib] First, the effects of changes in the roll gap, roll rotation speed, and tension between adjacent stands of each stand on plate thickness, plate width, rolling warm flow, and volume velocity are determined.

The amount of change in plate thickness at the exit of the stand 6, ie, the amount of change in thickness of the finished product ΔhF, is given by the following formula. △hF: Nakasu (Saba) BM person is fake Juunarihiro △s6 Juchumoto (ticket) 8M5
...The amount of change in the width of the board at the exit of the stand 6, that is, the amount of change in the width of the finished product ΔbF is as follows.

Next, the amount of current change Δli of the i-th stand is as follows.

Furthermore, the volume velocity change at the exit of the i-th stand. 3*Amount △ui becomes.

However, ui: the volume velocity before change in the i-th stand', i.e. ui=(・tenfi) static Ri・Ni・hi
●bi nose:: Rate of change in advanced rate due to change in inlet thickness (1/
) The above formulas '6} to '9- can be summarized as the following formula 00, using row examples.

However, matrix A is a matrix with 17 columns of 1 nail, and its rank is 1.
It is 4.

Next, △Sj, △Ni, △ satisfy the condition that △hF, △bF, △uj are zero, and also make it possible to set △li to a desired change amount.

Find i. Since the rank of matrix A is 14, there exists a generalized inverse matrix B of A as shown in equation (11). B=A'(
AAt)-1...(11) However, A
t: layer inversion matrix of A-1: inverse matrix of A, and △Sio, △Ni〇, △ given by the following equation (12).

i. satisfies equation (10), and furthermore, this △S
i○, △Nio, △.

i〇 are other △Sj, △Ni, △ that satisfy equation (10).
Among the combinations of i, the value of L given by the following equation (13) is minimized. That is, the above △Si〇,
△Nio, △. io changes the current of each stand by △li, even if the roll gap, roll rotation speed, and inter-stand tension are simultaneously varied, it does not cause fluctuations in finished plate thickness, finished plate width, and volume velocity. △Si, △Ni, △
. The combination of values of i is 6 5 L=i heat. △920i≧. △Ni20i≧・△.

i2. ．．・(13) In other words, assuming 4・matrix C from the 3rd column to the 8th column of matrix B with 17 rows and 14 columns, the desired ASj, △Ni, △hii are expressed by the following equation (15) It will be given by

That is, by generalizing equation (15) to the case of a continuous hot rolling facility having n stands, equation (1) can be obtained.

Note that bj, i (j=1,2...Yoichi 1, i=1,2・
...n) is clear from the above, [6}~{
It is an element determined by the coefficient in formula 9), that is, the material information such as steel type and the individual values of the rolling schedule of each stand. Therefore, the present invention causes a computer to perform the calculation of the above-mentioned formula (1) based on fixed information such as Mi given in advance and variable information such as Ni that is read every moment, and sets △li to a desired value. Therefore, △Si, △Ni, △.

i is automatically changed and adjusted. Next, examples of the method of the present invention will be described.

In a 6-stand continuous rolling mill with a rated current of 6000 A for each motor, the inlet thickness (to) is 25 mm, the product thickness (h6 or hF) is 1.6 side, and the product width (b6 or bF) is 125 mm.
It is assumed that the rolling current value of each stand detected by the current detector during rolling in the case of 0 skin is as follows.
1,=8 cycles OA 12=5640A 13=5170A L=5100A Chi=5290A Chi=6010A Therefore, when the rolling current exceeds 125% of the rated current in any stand, the current control according to the present invention is performed. If you do it, 1. =8380A satisfies this condition.

Therefore, the current of each stand is the average current in this case 1^vE
Each rolling current is changed so that =5930A. That is, the current variables at each stand are △1,2 - 2450A △122 290A △13 = 760A △L = 83 mountains A △ et al = IOA △k = -80A.

Then, △Si, △Ni, and △oi are found to realize this. However, in this embodiment, the value of L in equation (13) is not minimized, but - in equation (16) below is minimized for ΔSi, ΔNi, and A. We decided to find i. This is to satisfy the conditions required when actually applying the method of the present invention, such as not wanting to change the roll gaps S4, S5, and S6 of the latter rolls 4, 5, and 6. . 6 -: Old, Zhi. Kago i) 20i≧, (way/obi i) 10 stars, (large/etc.) 2. ．．・(I6) However, W, i, W2i, W
3j is a weighting coefficient of each term on the right side.

Then, matrix B in equation (12) changes as shown in equation (17) below. B=RRAt(ARRAt)-1
...(17) However, R is a diagonal matrix of 17 rows and 17 columns shown by equation (18).

Now, W. i,=1000,W2i,=1000,W3i
, = 1, the C matrix of equation (15) is as shown in Table 1.

(However, all units are per 100M) According to Table 1, the current change values in the examples △1, △12...AI
In order to realize 6, △Sj, △Ni, △hii become as shown in Table 2.

Table 2: Roll gap Si, roll rotation speed Ni, and tension between adjacent stands for each stand according to these values.

By changing i, △hF, △bF and △ui can be set to zero and △li can be controlled as desired, and as mentioned above, △S4, Ami is smaller than △S, , △S2, △S3. , ΔS6 can be satisfied as much as possible. As described above, in the case of the method of the present invention, the rolling current can be changed without changing the product thickness during rolling, so some stands where the current exceeds the allowable value occur.
6...Rolling current detector.

As a result, accidents such as mill stoppage troubles can be reliably prevented, and there are practical benefits such as improving product quality, improving production efficiency, and reducing unnecessary maintenance man-hours. Brief explanation of the drawings - Figure 1 is a schematic diagram of a 6-stand type continuous hot rolling mill.
FIG. 2 is a graph showing the time course of the temperature of the rolled material.

1, 2...6...stand, 11,12...15. ．．・Loopa, 21, 22...26...Electric motor, 31
, Figure 2 Sphere

Claims (1)

[Claims] 1. In order to eliminate the difference ΔIi between the rolling current of each stand of a continuous hot rolling mill having n stands (n is a plurality of stands) and the rolling current target value of each stand, each stand is 1. A current control method for a continuous rolling mill, comprising simultaneously changing and welding the roll gap, the number of roll rotations per unit time in each stand, and the tension between adjacent stands based on the following equation (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼However, ΔIi: Difference between the rolling current at the i-th stand (i = 1, 2...n) from the rolling material entry side and the same target value ΔSi: Similarly, the i-th stand Amount of change in roll gap ΔNi in the ith stand: Amount of change in roll rotation speed per unit time Δσi in the ith stand: Amount of tension change bj between the ith stand and the i+1th stand, i: matrix R with (3n-4) rows and (2n+2) columns
RA^t(ARRA^t)^-^1 from the third column to the (n
+2) The element in the jth row and i-th column of (3n-1) rows and n columns (j = 1, 2...3n- 1, i = 1, 2...n) A: Rolled material It is determined from material information such as steel type and reduction schedule of each stand, etc., and has a (2n + 2) row by (3n - 1) column matrix that has the relationship of formula (II) below ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Δh_F: Amount of plate thickness change Δb at the exit of the final stand
_F: Amount of plate width change Δui at the exit of the final stand:
Amount of change in volume velocity at the i-th stand from the rolling material entry side (i = 1, 2...n) A^t: Transposed matrix R of A: represents the weight of the (3n-1) row and (3n-1) column In the diagonal row example and below, Δh_F, Δb_F, and Δui are set to 0.