JPH0451245B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention is directed to a meandering correction control method for a rolling mill, which prevents the occurrence of plate bending in a plate rolled by a rolling mill. [Prior Art] In hot finish rolling, etc., the tension applied to the strip becomes zero when the strip is inserted into the plate or when the strip is pulled out, so that meandering of the strip is likely to occur. If such bending of the strip, which results in a meandering strip, is left unaddressed, problems such as the rolled material not being able to be caught in the rolling mill, bumping against the side guide device, or end bending occur frequently. In addition, in the case of rolled material that is wound into a coil shape, if plate bending occurs during hot finish rolling, for example, the appearance of the coil during winding will deteriorate, significantly reducing the product value of the coil. be. By the way, when observing the causes of plate bending in rolled materials, it is generally known that plate bending is less likely to occur when the plate crown is convex, and conversely, plate bending is more likely to occur when the plate crown is concave. That is, considering the roll deflection during rolling and the cross-sectional shape of the rolled material, the following results are obtained. That is, as shown in FIG. 1, in an example where the plate crown of the rolled material 5 is convex, for some reason the rolling reduction ratio on the operating side WS of the rolling roll 6 becomes larger than the rolling reduction ratio on the driving side DS, and the rolling material 5 Consider the state where it has moved to the drive side. When the rolled material 5 shifts toward the drive side in this way, in the case of a convex plate crown, the roll gap on the drive side becomes smaller as the plate shifts toward the drive side. Therefore,
The rolling reduction ratio on the driving side increases, and eventually the rolling reduction ratio on the driving side becomes larger than that on the operating side, and the rolled material 5 returns to the operating side. In this way, the rolled material 5
However, when the crown is convex, an effect is produced that returns the rolled material to the center of the rolling mill. On the other hand, when the rolled material 5 has a concave crown, the opposite phenomenon occurs, resulting in a divergence phenomenon. Next, the relationship between such plate deviation and plate bending caused by this will be explained with reference to FIGS. 2 and 3. Figure 2a shows a part of the rolling mill.
A state in which a rolled material 5 having a width B is rolled by an upper roll 6 and a lower roll 6, which are rolling rolls, is shifted by δ toward the drive side. The roll gap on the operation side and the drive side is operated by a hydraulic jack consisting of a reduction ram 1, a reduction ram 2, a hydraulic cylinder 3, and a hydraulic cylinder 4. Symbols S _w , (S _d ) and Pw,
(P _d ) indicates the unloaded roll gap and rolling load on the operation side (drive side). Furthermore, h _{w and} (h _d ) indicate the outlet side plate thickness on the operation side (drive side). As shown in Fig. 2a, when the rolled material 5 is shifted toward the drive side, the rolling load P _w acting on the rolled material 5 is
The center Q of the resultant force P of P _d shifts from the center of the rolling mill to the driving side, and as a result, the relationship between P _w and P _d becomes P _w <P _d .
Therefore, the spring K _d on the side where the load is greater is the spring K _W
Since it bends excessively from the side, the thickness distribution of the inclined rolled material 5 as shown in Fig. 1 is h _w as shown in Fig. 2 a.
＜h _d , and it becomes the closest. For this purpose, the operating side
The rolling reduction rate (elongation rate) of the WS becomes larger than that on the drive side, and as a result, the rolled material 5 meanders toward the drive side. Here, the advancing speed of the rolled material 5 during rolling is not equal to the circumferential speed V _R of the rolling roll 6, the advancing speed V _p of the exit side rolled material is faster than the roll circumferential speed V _R , and the advancing speed V of the incoming rolled material _I is the roll peripheral speed V _R
slower. The advancing rate F indicates the ratio of the advancing speed V _p of the exit side rolled material to the circumferential speed V _R of the rolling roll, and the backward advancement rate B indicates the ratio of the incoming rolled material V _i to this, as follows. These values are widely used as one parameter indicating the rolling phenomenon. F = (V _p - V _R ) / V _R × 100 (%) B = (V _R - V _i ) / V _R × 100 (%) The above advance rate F and backward rate B change depending on the rolling reduction rate γ do. FIG. 3 shows the relationship between the advance rate F and the backward rate B with respect to the rolling reduction rate μ. Third
As shown in the figure, the change in the backward movement rate B with respect to the change in the rolling reduction rate γ is generally much larger than the change in the advance rate F. Therefore, when a difference occurs in the rolling reduction rate, the resulting left and right backward movement rate difference B _df is Left and right advanced rate difference F _df
It will be much larger than. As a result, the rolled material is in a rolled state in which it bends more on the entry side than on the exit side. Here, the curve on the entry side acts in a direction that promotes the difference in rolling reduction γ _df between the left and right sides, so it has the property of increasing the meandering phenomenon. In other words, when a rolling reduction difference γ _df occurs, the rolled material on the entry side will have a difference in the left and right advance amount and will be bent, so the rolled material will be bitten diagonally by the rolling rolls, causing the rolling material to be bitten. A shift occurs in the insertion position. The direction of deviation of this biting position is the direction that increases the rolling reduction difference γ _df between the left and right sides, so the rolling reduction difference γ _df gradually increases as time passes, and as a result, the degree of diagonal biting of the rolled material increases. Since this also increases, the speed of displacement of the biting position also increases. FIG. 4 systematically shows the relationship of the above-mentioned meandering phenomenon, and symbols a, b, and c in the figure show the situation over time. [Object of the Invention] An object of the present invention is to provide a novel meandering correction control method for a rolling mill that prevents the occurrence of the meandering phenomenon in a rolled material. [Summary of the Invention] In order to achieve the above object, the present invention calculates the roll opening difference to be compensated for from the roll inclination rigidity based on the rolling load difference between the operating side and the driving side of the rolling mill, and In the meandering correction control method for a rolling mill that prevents meandering, the rolling load difference is multiplied by a control constant determined according to the state of tension applied to the rolled material to determine the roll opening on the operating side and the driving side. This is to perform feedback compensation control. In other words, by changing the control constant according to the state of tension applied to the rolled material and changing the amount of rolling load difference incorporated into meandering correction control, the apparent rigidity of the rolling mill in the width direction can be changed. , it is possible to provide centripetal properties in the width direction of the rolled material,
Optimal meandering correction control becomes possible. [Embodiments of the Invention] Next, in describing embodiments of the present invention, the functions of the meandering correction control of the present invention will be explained. In Fig. 2, K indicates the spring constant on one side of the rolling mill, and the outlet side plate thickness is the sum of the elongation of the rolling mill due to the rolling load and the roll gap at no load, so the outlet side plate thicknesses h _w and h _d are respectively It can be expressed by the following formula. h _w =S _W +P _W /K (1) h _d =S _d +P _d /K (2) From equations (1) and (2), the left and right plate thickness difference h _df is shown below. h _df = h _w − h _d = (S _W − S _d ) + (P _W − P _d )・1/K …(3) Here, S _df = S _W − S _d , P _df = P _W −P _d , h _df = S _df + P _df /K (4) By detecting the difference S _df in the roll gap at no load between the operating side WS and the driving side DS and the rolling load P _df , the operating side WS and the driving side DS are You can know the thickness difference h _df of DS. Equation (4) expresses that it is possible to control the thickness of the rolled material in the width direction, and by controlling the roll gap difference S _df so that S _df + P _df /K = 0 (5) , the plate thickness difference h _df on the drive side can be made zero. Furthermore, the rolling load signal taken into the control is multiplied by a constant α _l S _df +P _df /K・α _l =0...(6) According to changes in the rolling load difference P _df so that equation (6) is always satisfied. If you control the roll gap difference S _df ,
By changing the value of α _l and the amount of load difference P _df taken into control, the apparent stiffness of the rolling mill in the width direction can be changed, and by setting α _l ≧1, the width direction of the rolled material can be changed. It is possible to provide centripetal property against positional deviation. In an actual machine, the mill parallel rigidity Kl is set for the conventional mill constant K, taking into account the spring element of the rolling mill's rigid roll bias, which causes a difference in roll opening due to a load difference. Next, let's consider an actual rolling mill. In actual rolling, the following four types can be distinguished depending on the tension state on the input and output sides of the rolling mill. In other words, as shown in Fig. 4, when there is no tension in the strip width direction at the entrance and exit side of the rolling mill, when there is tension on the exit side of a tandem rolling mill, etc., when there is tension on the entry side, This is the case where there is tension on the input and output sides. Hereinafter, among these four states, phenomena will be explained when there is tension on the exit side of the rolling mill, when there is tension on the entry side, and when there is tension on the entry and exit sides. For convenience of explanation, a case where there is tension on the entry side of the rolling mill is shown, but the same can be said in other situations. Figure 5 shows a state where there is tension on the entry side of rolling.
When the rolled material 5 is also being rolled in the preceding rolling mill,
Since the force that tends to bend the rolled material 5 in the width direction is restrained by the rolling mill in the previous stage, the backward movement rate difference B _df appears as the backward tension forces σ _w and σ _d of the rolled material 5 . Here, the rolling state is shown with reference to FIG. 6. With respect to the rolling mill, the front tension is σ _f and the rear tension is σ _b , the biting angle α, the peripheral side V _R of the rolling roll 6, and the rolled material 5. If the angle of the neutral point where the velocities of φ=α/2−F ₁ (γ)−F ₂ (σ _b )+F ₃ (σ _f ) (7) Expression (7) can be specifically expressed as follows. φ=α/2−(1+F)・h ₂・γ/4μR・k ₁ −(
1-B)・h ₁・σ _b /4μR・k ₂ + (1+F) h ₂ σ _f /4μR
・k ₂ (8) Here, k ₁ : Inlet side plate thickness k ₂ : Outlet side plate thickness F: Advance rate B: Reverse rate μ: Friction coefficient k ₁ , k ₂ : Coefficient R: Roll radius. In other words, F ₁ and F ₃ are F ₂
is expressed as a function of the backward movement rate B. Table 1 shows the changes in the angle φ of the neutral point, the backward movement rate B, and the forward movement rate F, among the parameters in (8) above, when the rolled material 5 is misaligned in the DS on the drive side. .

[Table] When the rolled material 5 is misaligned on the driving side DS, a difference in backward movement rate occurs, but since the rolled material is restrained in the preceding rolling mill, there is a tension difference on the entry side of the rolling mill, that is, a backward movement rate difference occurs. The tension difference appears as θ _bw <θ _bd . Also, the angle θ of the neutral point in equation (8), the backward movement rate B
and the advanced rate F change as shown in Table 1. As can be seen from Table 1, the backward movement rate B on the side where the rolling reduction rate γ is large changes to decrease, so when there is a rolling mill in the previous stage, that is, when there is tension, the meandering phenomenon works in the direction of decreasing. That's why it happens. In Fig. 5, when there is tension and there is a positional deviation amount δ, the rolling reduction ratio of the operating side WS and the driving side DS is γ _w
＞γ _d , the tension σ _w , σ _d and the entrance speed
V _HW and V _Hd are as shown by the solid line in Figure 5. Here, as time passes, as shown in equation (7) and Table 1, the backward movement rate B decreases on the operation side and increases on the drive side, so the input side speed on the operation side V _HW and the input side speed on the drive side V _Hd changes as shown by the broken line, and from this, the operating side tension σ _w ,
The driving side tension σ _d also becomes as shown by the broken line, and the tension decreases in a self-balancing manner. As a result, just as it is known that increasing the control constant in plate thickness control causes a vibration phenomenon because it applies a large correction amount to a minute deviation, the control constant α also changes depending on the tension condition in meandering correction control. Optimal meandering control is possible by switching _l . The amount of positional deviation δ (mm) is taken, and the horizontal axis is the advance amount L, which is the rolling length from the roll bite to the tip of the advanced rate material, and the solid line is the advance amount L toward the side where there is tension on the input and output side. indicates a state where there is tension on the input and output sides,
The broken line indicates the state of tension on the input and output sides. In FIG. 7, when there is no tension and the control constant α _l =0, it indicates an uncontrolled state, and when there is no tension and α _l =0.75, the meandering phenomenon becomes weak but diverges. On the other hand, when there is tension on the input and output sides, there is a weak divergence even when the control constant α _l = 0, and the control constant α _l
It converges even when <1. Based on the above facts, the present invention changes the control constant α _l for plate bending control by changing the tension conditions during rolling, and FIG. 9 shows the change in the constant α _l during rolling.
Figure 8 shows an example of application in a tandem rolling mill.
Figure 9 shows rolled material 1 of a rolling mill with a tandem rolling mill.
This figure shows changes in the control constant α _l and rolling load P when rolling a book. When the current rolling mill 10 bites the rolled material 5, the rolling load P rises. At this time, the constraint condition is that tension is generated in the rear and there is no tension in the front, so the optimal constant at that time is α _l 〓, and when the tip is bitten by the rolling mill 11 in the subsequent stage, the constraint condition is that the tension is generated in both the front and rear. exists, the optimal condition at that time is changed to α _l 〓. When the rear end of the rolled material passes through the rolling mill 9 in the previous stage, the constraint condition is the forward tension.
Since there is no tension at the rear, the optimum condition at that time is changed to α _l 〓. The above control constants are switched by experimentally creating the same rolling conditions as the expected rolling conditions based on changes in the rolling load P by the load cells 7 of the front and rear rolling mills, and under these experimentally created conditions. The control constants are changed according to predetermined rolling conditions determined during actual rolling. Here, the rolling conditions include the plate thickness and width of the rolled material, and the constraint conditions of the rolled material on the entrance and exit sides of the rolling machine. Table 2 shows an example of constant values determined as explained above.

〔Effect of the invention〕

According to the present invention, it is possible to always give the optimum control constant α _l to the plate bending control device according to the tension conditions applied to the rolled material, so it is possible to obtain a rolled material with less bending of the plate, and to prevent undesirable behavior. This has the effect of preventing

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram for explaining the state of plate bending of a rolled material, Figs. 2 to 10 are for explaining an embodiment of the present invention, and Figs. An explanatory diagram showing the behavior. Figures 5 and 6 are explanatory diagrams showing the behavior when restrained. Figure 7 is a characteristic showing the relationship between the control constant α _l and the positional deviation amount δ when there is no tension and when there is tension. 8 is a simplified diagram showing the outline of the meandering control device of the present invention, and FIG. 9 is a rolling load and control constant α _l
FIG. 10 is a partial block diagram of the control device shown in FIG. 8. DESCRIPTION OF SYMBOLS 1... Reduction ram (operation side), 2... Reduction ram (drive side), 3... Hydraulic jack (operation side), 4... Hydraulic jack (drive side), 5... Rolling material, 6... Rolling roll,
7...Load cell, 8...Control device, 9...Previous stage rolling mill, 10...Current rolling machine, 11...Late stage rolling machine,
12...α _l = changeover switch, 13...α _l = changeover switch, 14...α _l = changeover switch.

Claims (1)

[Scope of Claims] 1 Meandering of a rolling mill that prevents meandering of rolled material by calculating a difference in roll opening degree to be compensated and controlled from the rigidity against roll inclination based on the rolling load difference between the operating side and the driving side of the rolling mill. The corrective control method is characterized in that the rolling load difference is multiplied by a control constant determined according to the state of tension applied to the rolled material to perform feedback compensation control of the roll openings on the operating side and the driving side. A meandering correction control method for a rolling mill.