JPH0573486B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a rolling mill plate that predicts the displacement amount of the rolling mill from the mill rigidity coefficient and rolling load, and controls the rolling position based on this predicted value. This invention relates to a thickness control method.

(Prior art) The roll gap during rolling, that is, the rolled plate thickness h, is
It is given by the sum of the rolling position S and the displacement amount δ caused by the rolling load. : h=S+δ+ _ΔSO ...(1) This displacement amount δ is given by rolling load P and mill rigidity coefficient M as follows: δ=P/M...(2). Therefore, the plate thickness h is calculated as h=S+(P/M)+ΔS _O (3) (here, ΔS _O is the zero point correction value of the roll gap).

In rolling mill control, from the initial plate thickness value h, etc.
The plate thickness is controlled by calculating the rolling position S using equation (3). Therefore, calculating an accurate value of the mill stiffness coefficient M is a key point in plate thickness control.

As the value of the mill rigidity coefficient M, an actual value M _O of the mill rigidity coefficient calculated from the relationship between the tightening amount and the load in the roll kiss state can be used.
However, the value of the mill stiffness coefficient M depends not only on the elastic properties of the rolling mill during rolling but also on the strip width. Therefore, conventionally, the actually measured value M _O of the mill stiffness coefficient determined by the tightening method is corrected for the plate width W, and M is calculated using, for example, the following equation (4).

M=M _O +m(W _B −W) (4) Here, W _B is a constant constant in each rolling mill, and m is a strip width coefficient determined in advance from rolling etc.

(Problem to be solved by the invention) The calculation of the mill stiffness coefficient M using the conventional formula (4) etc. is as follows.
Even if the influence of the plate width W is considered, the relationship between M and the plate width W is not accurately given. Therefore, M used in equation (3) becomes inaccurate. As a result,
In places where the sheet width changes greatly in the roll pattern and cannot be corrected by feedback, the accuracy of the gauge meter thickness h calculated using the gauge meter formulas (3) and (4) deteriorates.

Therefore, an object of the present invention is to calculate an accurate value of the mill rigidity coefficient for any plate thickness, and to make it possible to control the plate thickness by using a gauge meter formula that calculates the amount of displacement of the rolling mill based on this. An object of the present invention is to provide a method for controlling plate thickness in a rolling mill. In particular, to provide a strip thickness control method for a rolling mill that accurately reflects the dependence of the mill stiffness coefficient on the strip width and can control the strip thickness to a predetermined value with high precision even when the strip width changes suddenly during a roll pattern. The purpose is to

(Means for Solving the Problems) In order to achieve this objective, the inventor of the present invention focused on the importance of facts while continuing research. In other words, the displacement amount δ of the rolling mill is decomposed into the sum of the roll system displacement amount δ _R and the housing system displacement amount δ _H : δ = δ _R + δ _H …(5) Here, what is the displacement amount of the roll system? This is the amount of displacement due to deflection and flattening of the work roll and back-up roll, and the amount of displacement of the housing system is the amount of displacement due to deformation other than the roll system, such as deformation of the housing and shrinkage of the screw. Of these displacement amounts δ _R and δ _H , only δ _R changes depending on the plate width W, and δ _H does not depend on the plate width W. Furthermore, the amount of displacement δ _R that depends on the sheet width W can be theoretically calculated with high accuracy from the roll dimensions and sheet thickness using a roll division model. On the other hand, the plate width W
δ _H, which does not depend on , can also be calculated with high accuracy from the measured value M _O.

By the way, the mill stiffness coefficient M can be calculated from equations (2) and (5) as follows: M=dP/dδ = dP/(dδ _R + dδ _H ) = 1/(dδ _R /dP+dδ _H /dP)...(6) . Therefore, if we calculate the displacements d _R and d _H of δ _R and δ _H per predetermined rolling load and then calculate M using equation (6), the obtained values are extremely high for each plate thickness. Have precision.

Thus, the gist of the present invention is to provide a plate thickness control method in which the displacement P/M of the rolling mill is calculated from the mill rigidity coefficient M and the rolling load P, and the rolling position of the rolling mill is controlled thereby. Calculate the roll system displacement d _R per rolling load from the roll dimensions and sheet width, and (b) the housing system displacement d _H per given rolling load.
is the actual value of the mill stiffness coefficient using the tightening method.
( _c ) Calculating the mill rigidity coefficient M from the roll system displacement d _R and the housing system displacement d _H calculated in steps (a) and (b), respectively; This is a method for controlling plate thickness of a rolling mill, which is characterized by the following.

For example, 1000 tons is taken as the predetermined rolling load P _O in step (a), and the value d _R of the roll system displacement amount δ _R per this load is first calculated. Since the dimensions of the work roll and back-up roll are known, if the load and plate width are given, _dR can be calculated theoretically using a split model as the sum of the roll deflection amount and the contact flattening amount. Note that to calculate _dR in actual operation, it is preferable to use an approximation of the calculation formula based on the split model.

In process (b), the rolling load is the same as in process (a).
Since the housing system displacement amount δ _H per P _O does not depend on the plate width, _the predetermined rolling load is calculated using the following formula:
Amount of housing displacement when the P _O area is in a roll kiss state
It is approximated by d _HO (d _H ≒ d _HO ).

d _HO = (P _O / M _O ) − d _RO (7) where d _RO is the roll system displacement amount per load P _O in the roll kiss state, and as in step (a), the split model ( or its approximate formula). Moreover, M _O is an actual value of mill rigidity measured by the tightening method, and is measured for each roll chance.

It is also possible to use the value of d _HO obtained by equation (7) as is as the value of d _H. However, it is preferable to calculate _dH as follows. That is, the actual measured value (average value) of d _H for the rolling mill is determined in advance for each roll chance, and compared with d _HO calculated from equation (7) for each corresponding roll chance.
As a result, we find the relational expression d _H = a + b・d _HO (8) that holds between d _H and d _HO (a and b are constants), and use equations (7) and (8) to calculate d _H Calculate.

Next, in step (c), M is calculated as follows: M=P _O /(d _R +d _H ) (9).

The plate thickness is accurately controlled by using the value of M calculated by equation (9) for M in equation (3) above.

(Example) Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

The rolling mill position control is based on equation (3) above. Calculation of M in formula (3) is performed in steps (a), (b), and (c) as described above. Each step will be explained separately below.

(a) Calculation of dR _dR is the load in the relevant rolling load range _.
The amount of roll displacement at the center of the roll per 1000 tons is used. The amount of roll system displacement δ _R is the component of the deflection of the back-up roll axis δ _R1 , the contact flatness of the back-up roll and the work roll δ _R2 , and the contact flatness of the work roll and the rolled material δ _R3 (δ _R = δ _R1 + δ _R2 + δ _R3 ). These displacement amounts δ _R1 ,
δ _R2 and δ _R3 are the plate width W, the roll diameter of the work roll and back-up roll, the roll barrel length,
It can be calculated accurately from the network length using a well-known partitioning model. Regarding this split model, for example, KNShohet and NATownsend: JISI
(1968), Nov., p. 1088. d _R is the value of δ _R at the center of the roll per 1000 tons: d _R = δ _R /1000 [mm/ton] …(10) However, in calculating d _R in actual operation,
Preferably, an approximation of equation (10) as a function of plate width and roll dimensions is used to simplify the calculation.

In other words, d _R = d _R ′+{a+b(c-W)}(d-D _B ) (a, b, c, d: constant, D _B : Backup roll diameter, mm) However, d _R ′ is It varies depending on the plate width W (mm),
For example, when 3500<W≦4000, it can be determined as follows.

d _R ′=e+{1000−D _W )×f+g} +{(1000−D _W )×h+i}×(4000−W) (e, f, g, h, i: constant D _W : work roll diameter, mm) (b) Calculation of d _H d _H is the load in the relevant rolling load range.
The displacement of the housing system per 1000 tons is used (d _H = δ _H /1000 [mm/ton]).

The amount of displacement of the housing system does not depend on the plate width, but there are many factors such as elongation of the housing, contraction of the rolling screw, deformation of the liner, etc., and it is also affected by the contact status of each of these factors. It is something. Therefore, its value differs depending on the daily roll chance.

However, d _H can be predicted from the mill stiffness coefficient M _O measured by the roll tightening method. That is, by using the measured value M _O of roll tightening, it is possible to accurately calculate the rigidity of the mill housing system, which varies for each roll chance.

Mill stiffness coefficient M _O determined by tightening method
The total displacement of the mill in the roll-kiss state can be found from . Therefore, by subtracting the displacement amount d _RO of the roll system in the roll kiss state from this value, the deformation amount of the housing system in the roll kiss state d _HO can be found: d _HO = (1000/M _O ) − d _RO …(11 ) However, d _RO uses a value calculated using the approximation formula of the split model in the same way as the calculation of d _R in step (a) above.

The approximate expression at this time is expressed by the following expression.

d _RO = _j + _K The average value _H of d _H is calculated for each time, and this is compared with d _HO calculated by equation (11).

The circles in FIG. 1 plot the points corresponding to (d _HO , _H ) in each roll chance. As can be seen from the figure, d _HO and d _H are almost equal. However, in order to accurately calculate the value of the housing system displacement amount d _H , it is preferable to obtain a relational expression expressing _H by d _HO from FIG. 1 and calculate d _H using this relational expression. In the case of FIG. 1, for example, the following relationship holds: d _H =0.23+0.88·d _HO (12). (The solid line graph in the figure shows this relationship.) Therefore, in this case, calculate d _H using d _HO in equation (11) as d _H = 0.23 + 0.88・d _HO …(13) The value of d _H can be calculated with extremely high accuracy.

(c) Calculation of M M, which should be used to calculate the gauge meter thickness h using equation (3) above, is calculated using the following equation using d _R and d _H calculated in (a) and (b) above. .

M=1000/(d _R +d _H )...(14) (Effect of the invention) In the present invention, the displacement amount of the mill is changed from the roll system displacement amount d _R that depends on the plate width to the housing system displacement amount d _H that does not depend on the sheet width. The mill stiffness coefficient M can be calculated extremely accurately by dividing these values into 2 and calculating these values individually using an appropriate method.

Figure 2 shows the mill stiffness coefficient M actually measured at a constant roll change (the rolled plate is marked with a circle for each case W) and the mill stiffness coefficient M calculated by the method of the present invention (calculated in (14) above). The values are shown in solid line graphs). On the other hand, the chain line graph in the figure shows the value of M calculated using the conventional equation (4). As can be seen from this appendix, M calculated by the formula (14) according to the present invention matches the actually measured value extremely well throughout each plate width W.

As described above, according to the present invention, the value of M can be accurately determined for all plate widths W. Therefore, the accuracy of the gauge meter thickness does not deteriorate even at a point where the sheet width W suddenly changes during the roll change.

The upper graph in FIG. 3 shows a portion of the change in finished sheet width W within a constant roll chance. The lower graph shows the deviation of the gauge meter thickness calculated by the present invention (○ and solid line graph)
This figure compares the deviation of the gauge meter thickness calculated by the conventional method (● and the dashed line graph).
(The deviation here is the difference between the actual measured value of the finished plate thickness and the gauge meter thickness, and deviation = 0 indicates that the gauge meter thickness matches the actual measured value.) As can be seen from the figure, conventional The gauge meter thickness calculated by the method deviates significantly from the actual thickness at locations A and B where the board width W suddenly changes. On the other hand, the gauge meter thickness calculated according to the present invention also agrees well with the measured thickness at these locations A and B.

As described above, according to the present invention, it is possible to maintain the accuracy of the gauge meter thickness even when the sheet width suddenly changes, and to control the rolling thickness to a desired value with high accuracy.

[Brief explanation of the drawing]

Figure 1 is a graph for determining the relational expression used to calculate the displacement of the housing system used in calculating the mill stiffness coefficient according to the present invention; A graph comparing the calculated mill stiffness coefficient with the measured value; and Fig. 3 compares the variation in gauge meter thickness deviation due to changes in plate width within the roll chance between the case of the present invention and the case of the conventional method. This is a graph.

Claims (1)

[Claims] 1. In a plate thickness control method in which the displacement P/M of the rolling mill is calculated from the mill rigidity coefficient M and the rolling load P, and the rolling position of the rolling mill is controlled based on this, (a) per predetermined rolling load. Calculate the roll system displacement d _R from the roll dimensions and plate width, and (b) the housing system displacement d _H per given rolling load.
is the actual value of the mill stiffness coefficient using the tightening method.
( _c ) Calculating the mill rigidity coefficient M from the roll system displacement d _R and the housing system displacement d _H calculated in steps (a) and (b), respectively; A method for controlling plate thickness in a rolling mill, characterized by: