JPS6054214A - Method for setting pass schedule in continuous cold rolling mill - Google Patents

Abstract

PURPOSE:To make operation stable by setting the rolling reduction at a final stand by a table interpolation and setting the draft schedules of other stands so as to determine the distribution of the electric currents of respective driving motors to a prescribed ratio. CONSTITUTION:In a continuous cold rolling mill consisting of plural stands; the target inlet sheet-thickness of a final stand of plural ones is set by a table interpolation, and the target interstand sheet-thickness are set so as to determine the distribution of the currents of respective driving motors of said stands excluding the final one to a prescribed ratio, to decide the draft schedules. In this way, the optimum rolling speed at the final stand is decided, and also the generation of heat scratch at other rolls is prevented, to make the stable operation possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for setting a bus schedule when rolling a strip from a predetermined plain thickness to a finished thickness in a continuous cold rolling mill having a plurality of stands.

When rolling a strip in a continuous cold rolling mill with multiple stands, the raw thickness (inlet thickness) and finished thickness (exit thickness) of the strip are given in advance, but the amount of thickness reduction between each stand is conventionally determined. This was determined by the operator selecting appropriate values for the rolling load distribution, motor power distribution, etc. of each stand based on experience.

In recent years, with the spread of computers, it has become possible to automatically set roll gears using computers, but even in this case, appropriate draft schedules obtained through experience can be used as table values. The method used is to use the collected data and use an interpolation method to determine a draft schedule that corresponds to the target finished thickness.

As an example of the conventional method as described above, a table interpolation method for a five-stand continuous cold rolling mill will now be described with reference to FIG. FIG. 1 is a plot of outlet plate thickness values at each stand.

Broken line 1 is an example of a draft schedule with the minimum rolling reduction for the plain thickness he. Line 2 shows an example of the draft schedule with the maximum rolling reduction for plain thickness. The total rolling reduction rTA of the target draft schedule for the broken line 3 determined by the table interpolation method of the prior art is expressed by equation +11 from the pre-given plain thickness and target finished thickness hss.

Flow to rrA=l- (1) )'LO The total reduction rate rT of the draft schedule of broken line 1 is similarly expressed by equation (2).

1'TB=1-chi...(2) Similar to the above, the total reduction rate r"r of the draft schedule of broken line 2
c is expressed by formula (3).

I'Tc, = 1-j &... (3) Next, the target exit plate thickness at each stand, that is, the target draft schedule h-LA (L = 1.2.3.4), is expressed by the following formula using proportional allocation. Ru.

From the above two equations, the schedule h-=A (L=1.2.3.4) is calculated by the broken line 1
It can be determined from the draft schedule of 2 and 2 and the target finish thickness and iris.

Here we have explained the case where there is actually a raw thickness in the table value that matches the given strip thickness, but if there is no raw thickness in the table value that matches the given raw thickness. calculates the thickness before and after the given thickness ho as shown by hop and hOE in Figure 1, and calculates the proportional distribution method based on the thickness based on the two draft schedules obtained. Determine a target draft schedule based on.

If a draft schedule corresponding to the target finished thickness is determined according to such a table interpolation method and the strip is rolled based on this, the motor current value of a particular stand may become abnormally high during strip rolling.

It is known from experience that when such a situation occurs, minute burn-in scratches called heat scratches are formed on the roll surface of this particular stand. Once these heat scratches occur, they gradually grow and print on the strip surface, necessitating roll changes.

When such heat scratches are about to occur on the roll surface of the stand, there is a method to prevent the growth of heat scratches by lowering the rolling speed, but in this case, the productivity of the mill is significantly reduced.

Therefore, as a method for determining a draft schedule to prevent such heat scratches from occurring on the roll surface, a method for determining a draft schedule in which the distribution of motor current of each stand is set at a predetermined ratio was proposed in 1972. This is proposed in Japanese Patent No. 106951.

However, when trying to set the motor current distribution ratio of all stands constituting a continuous rolling mill to a target value as in the method for determining the draft schedule described in this publication, the draft schedule for the last stand cannot be determined for the reasons explained below. This is often difficult, and there are many problems in putting it into practical use.

The strip coming out of the final stand of the continuous cold rolling mill is subjected to an annealing treatment as the next step, but there is a risk of seizure between the coil strips.

Therefore, in order to prevent seizure during the annealing process, a dull roll with a high surface roughness is often used as a work roll in the final stand, and a cloak is attached to the strip surface. In this case, the coefficient of friction between the roll and the rolled material increases.

On the other hand, it is necessary to maintain a good finished plate shape in the final stand, and for this purpose it is necessary to set the rolling load of the final stand to a desired value. However, as mentioned above, the friction coefficient between the rolls and the rolled material is high, so the rolling reduction that can be achieved at the final stand is very small, 1 to 5%, and it is difficult to delicately determine the rolling reduction within this range. becomes.

Furthermore, considering the rolling power, the total tension on the input side of the final stand of a continuous rolling mill is high, and the tension cannot be increased too much on the exit side because the strip is wound up, so the difference in tension before and after the final stand is The proportion of torque caused by rolling is large, and the proportion of rolling torque is relatively small. Under these circumstances, the target value of the motor current (corresponding to the tension torque plus the rolling torque) at the final stand is set to a certain value.
If the amount of rolling is calculated, the amount of rolling will vary, causing a problem that the rolling load at the final stand will vary. This is because it is actually difficult to determine such a small rolling reduction amount from the motor current target value.

On the other hand, based on the empirical knowledge that heat scratches do not occur at all in the final stand using such a dull roll, it was decided to determine the draft schedule for the final stand by a method different from the draft schedules for other stands. This makes it possible to optimally determine the rolling speed, etc. at the final stand, and to prevent heat scratches from occurring on other rolls.

In other words, in the present invention, the drafting amount of the final stand is determined by the table interpolation method shown in FIG. It is determined as follows. By combining the two draft schedule determination methods in this way, the inconveniences that were unavoidable in each draft schedule determination method can be rationally resolved, and as a result, the above-mentioned effects can be achieved. .

Here, a pass schedule setting method according to the present invention will be explained using a 5-stand continuous rolling mill as an example.

First, using the table interpolation method described in detail with reference to FIG.
, 4). This draft schedule has more F than Lk.
The target exit thickness of stand 4 (target inlet thickness of stand F5) L4A is expressed as follows.

Autumn to k4A= (5) Next, using the tentative draft schedule kLk, F1~
F4 stand motor current value ApL<L=1.2.3.
4) Predict. At this time, the roll circumferential speed is the maximum roll circumferential speed VmaxL (i
=1.2.3.4.5). In addition, for the tension values on the entry and exit sides, for example, make a table of the tensile stress values calculated empirically for each finished thickness and plate width of the rolled material, and multiply these tension stress values by multiplying the plate thicknesses on the entry and exit sides. Then, the total tension per unit width can be determined.

Various theoretical formulas are known for the motor current prediction formula in this case, and for example, the unit sheet width roll torque G (for one roll) can be calculated using the old-11 approximation formula shown below. (Refer to Chapter 2, p. 54 of “Rolling Theory and Its Applications” edited by the Japan Iron and Steel Institute) G = −R・δ(1,05
+ (0,07+ 1.32 and)C-0,85F) ・
...(6) Where: Two-dimensional deformation resistance of rolled material R: Work roll radius δ: Reduction amount t: Reduction rate ・= μ J t R ": Flattened work roll radius H Two-person plate thickness μ: Rolling Coefficient of friction between the material and the rolls Once the roll torque G is determined by the above formula, the motor current A (for two rolls) can be determined according to the following formula.

A=η(2GjR(Tb-10,000)) KbN/E...(
7) Here, b: Plate width N: Roll rotation speed E: Motor voltage: Unit conversion factor η: Mechanical efficiency Tb Two unit width input side total tension T: Unit width output side total tension Next, the exit of the second stand If the influence coefficient on the change in the motor current value of the L-th stand is ~Y when only the thickness is changed by Δbi, then the changes ΔΔ1 to ΔA+ in the motor current value in the L-th stand are expressed as follows.

ΔA1=CuΔ.

ΔAz=C−pΔ++cnΔk.

ΔHallerCj□Δhλ+CBΔto8 ΔAto=C4,Δ)La...(8) As is clear from the above equation (8), the influence coefficient cμ changes the exit thickness by a small amount of zft in the tentative draft schedule. It can be obtained by calculating the amount of change in motor current of the stands before and after that time using equation (7).

Set the motor current distribution target value of F1 to F4 stands to ξ1. Noon (however, ξλ1 is based on the third stand (0g = 1.0
), and expressed as a ratio thereto), then equation (9) shown below needs to hold in order to obtain the motor current distribution of this target value.

Aj 汀, = Apl + ΔAL = ξゎ (Aps 1ΔAδ
)...+91 However, j=l, 2.4 As mentioned above, APL is a provisional draft schedule)
It is assumed that the target distribution ratios ξ1 to ξ4 can be obtained by correcting the motor current values predicted by LLK by 9 kg, Δ, . . . 6 kg, respectively.

When Δhi is solved from equations (8) and (9), the amount of change in the exit thickness of each stand is as follows.

"'=f("rz"az"4B-C1z・C4s"94
゛exz゛ejρAp+-(1・CJ,・C44・Ap
xt noon 1・ko 1.・Ca・/4/) J-shi'rayu, c,
j-, Ap< J / λ2 (C + (C4)-
f4・e, API eu (C4a-q, -63)Δ
P5-(5+ ・exI-I?, ,, e, θ(-1A
ps→(Fj+ "x+-L"'n) Cas・A(p4
J /Ah4 kx = rca+ · et al. 2 · Now. 'A
PI't"caz'r, -Ap-c+CII-(,n
-4+ HAP' - (kidney CλVe4x-9:L' C++ 'K320C
Koichi °Cμ] ΔP4 (/Mutrust?', "L, 4=ηI・C Etorayu・Ci, -jin・C++ "j knee" 43+0II゛ko) λ-e,, ~ 小吟゛C ,,゛koλλ° kobe3 . . . QO) In this way, when the correction amount Δ of the plate thickness between stands is 1 to Δ, the target draft schedule can be calculated.

IL=A= )L4K +Δ'rbi, ^=1.2.3
...(11) To further improve accuracy, use the kLA determined by equation (11) as a temporary draft schedule instead of FL swimming using equations (6), (7), (8), and (9) above. It is sufficient to recalculate the APL using the equation 0Φ and calculate 3 for the plate thickness correction amount ΔIt, to Δ. This makes it possible to further improve the accuracy of the target draft schedule.

By repeating the above calculation two or three times, the target motor current distribution ratio can be achieved with sufficient accuracy and draft schedules h and L can be created.
A is determined. Check whether each stand motor current predicted by this draft schedule is within the allowable motor current range and satisfies the speed cone of each motor, and if not, modify the maximum rolling speed V maxb proportionally. By correcting each stand motor current within the above tolerance range.

Once the draft schedule is determined, the rolling load PL of each stand is predicted using the entry side and exit side plate thicknesses, target tension stress values, etc., and when this rolling load PL is generated, the roll at the time of loading on the roll exit side is predicted. Determine the roll gap at no load so that the gap matches the target plate thickness. Generally well-known methods may be used for these determination methods.

In other words, the roll gap when no load is to be claimed is βo
If L, /5ob=FLi-A'+ΔSoL +A67i −
...(12)i However, = 1.2.3.4.5 where kL: Mill rigidity of the third stand Δ56L: Zero point fluctuation amount of the third sword stand ΔS rod: Offset amount at zero adjustment of the Lth stand ΔSo is the difference between the mass flow plate thickness at the exit side of each stand, the rolling load, and the gauge meter plate thickness predicted from the mill rigidity, and is learned (adaptive) sequentially from roll change to each rolling coil by exponential smoothing, etc. It is something. The value is a correction value determined by the zero point adjustment (operation in which the upper and lower rolls are brought into contact with each other under a predetermined reference load, for example, 500 tonf, and the rolling position at this time is set as a predetermined reference value) performed after changing the rolls.

In addition, as for the target distribution ratio of motor current for each stand, the optimal distribution values obtained empirically for each dimension of the rolled material (plain thickness, finished thickness, sheet width) are given in advance in a table. Alternatively, the operator can give a distribution ratio to each rolled material depending on the rolling situation at that time.

A more specific embodiment of the present invention will now be described.

Comparison of the draft schedule, maximum rolling speed, etc. of the conventional method (draft schedule setting method using table interpolation method) and the method of the present invention when cold rolled coils of the sizes shown in Table 1 are rolled in a 5-stand continuous cold rolling mill. Shown in Table 2.

In the conventional method, the motor current value of the F2 stand is high and is limited by the motor allowable current (1290OA), so the maximum roll circumferential speed Vmax of the F5 stand! ; is 1340m and can be covered in 7 minutes. - In the second invention method, we determined a draft schedule in which the value (ξ2) of the F2 stand out of the motor current distribution value (ξi) of the Fl-F4 stand is slightly smaller using the method of the present invention, as shown in Table 2. Therefore, there is no need to worry about the occurrence of heat waves at the F2 stand, and Vmaxr = 1406m.
/min, and V maxr of the conventional method = 1340 m
The maximum rolling speed could be increased by about 5% compared to 7 minutes.

By adopting such a pass schedule setting method, all stands can operate stably and productivity can be improved.

[Brief explanation of drawings]

The attached drawing is a diagram for explaining the table interpolation method, and plots the exit plate thickness values at each stand. Hayashi stand procedural amendment January 176, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of case Patent Application No. 161621, 1982 2
4 Name of the invention Bus schedule setting method for continuous cold rolling mill 3, relationship with the case of the person making the amendment Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (211) Sumitomo Metal Industries Co., Ltd. Representative Kumagaya
Mibun 4, agent address ■3-3 Kojimachi, Chiyoda-ku, Tokyo 6.? @Correct Object The Claims column of the specification, Detailed Description of the Invention column 7, Contents of Amendment 1, and the Claims of the Specification are amended as shown in the attached sheet. 2゜ (Delete “11.” in the first line of page 3 of the specification. (2) Amend lines 3 to 10 of page 6 of the specification as follows: “Continuous cold rolling.” The strip from the final stand of the machine is often annealed in the form of a coil as the next step, but at this time there is a risk of seizure between the coil strips.Therefore, seizure during the annealing process is prevented. In order to
A dull roll with a high surface roughness (Shot Plus Tor) is often used as a work roll for the final stand, and a mantle (irregular pattern) is often applied to the strip surface. In this case, the coefficient of friction between the roll and the rolled material increases. (3) "It will be difficult to determine." on page 6, line 17 of the specification should be determined. ” he corrected. (4) "Tension torque" on page 7, line 4 of the specification is corrected to "tension torque." (5) "Equivalent amount added" in lines 4 and 5 of page 7 of the specification is amended to "equivalent to the amount added." (6) Insert "as a result" after "variations," on page 7, line 6 of the specification. (7) "1 because" on page 7, line 7 of the specification is amended to "that is." (8) In the specification box, page 7, line q, change “because it is difficult” to “
It is difficult.'' (9) "Drafter" in the last line of page 8 to the first line of page 9 of the specification is corrected to "1 drafter." Formula (7) on page 10 of the aφ specification is corrected as follows. A= (2G+R(Tb-Tchi))l(bN/E snout・
・ ・(7) (11) “Represented” in the third line from the bottom on page 10 of the specification
is corrected to be "represented." (12) 1 on page 11, line 3 of the specification As is clear from the above equation (8), "" is deleted. (13) "3rd stand" on page 11, line 9 of the specification is r
"F3 stand," he corrected. (14) Correct "motor current distribution value of value" in line 11 of page 11 of the specification to "motor current distribution value of value." (15) Formula (11) on page 12 of the specification is corrected as follows. LA = kbk + ΔJLQ,”, i = 1.2.3
・ ・ ・ (11) (16) Specification page 13 No. 10
Correct the line ``may be satisfied'' to ``may be satisfied by 1.'' (17) [Correct each stand motor current] on page 13, lines 12 to 13 of the specification. ” should be corrected to include “each stand motor current and roll speed.” (18) Correct "3rd stand" in lines 5, 6, and 7 of page 14 of the specification to "F^stand." Claims: In a continuous cold rolling mill consisting of a plurality of stands, a target inlet plate thickness of the last stand among the plurality of stands is determined by a table interpolation method, A method for setting a pass schedule for a continuous cold rolling mill, characterized in that a draft schedule is determined by determining a target plate thickness between stands so that the distribution of drive morph current for each stand is a predetermined ratio.

Claims (1)

[Claims] In a continuous cold rolling mill consisting of a plurality of stands, a target inlet thickness of the last stand among the plurality of stands is determined by a table interpolation method, and each of the stands other than the last stand among the plurality of stands is determined. 1. A pass schedule setting method for a continuous cold rolling mill, comprising determining a draft schedule by determining a target plate thickness between stands so that the distribution of drive motor current is at a predetermined ratio.