Method for setting work roll balance force, method for operating a rolling mill, method for switching between rolling mill operations, and rolling mill

Abstract

In the method for setting the work roll balance force of the rolling mill, the kiss roll load Pk, rolling load Pr, and rolling torque Tr of the work rolls 610, 611 for the work roll angle θx at the tip position of the rolled material 5 from the start of biting the rolled material 5 to the end of biting are obtained using the mill vertical stiffness coefficient K and the rolling conditions. Then, in a state where a hypothetical work roll balance force Pb is applied, the traction coefficient μrt between the work rolls 610, 611 and the intermediate rolls 620, 621 for θx and the maximum value μrtmax of μrt are obtained from the total P and Tr of Pk, Pr, and Pb from the start of biting the rolled material 5 to the end of biting. Then, the allowable value μrtcr of μrt is compared with μrtmax, and if μrtcr is equal to or greater than μrtmax, the work roll balance force at the start of biting the rolled material 5 is reset to a value equal to or greater than the value when the maximum value μrtmax of μrt is shown and equal to or less than the limit value due to the constraints on the strength of the rolling mill.

Description

[Technical field]

[0001] The present invention relates to a work roll balance force setting method, a rolling mill operating method, a rolling mill operation switching method, and a rolling mill. [Background technology]

[0002] As an example of hot rolling equipment that prevents poor biting of a plate material by small-diameter work rolls, Patent Document 1 describes the following technology. An entry-side plate guide and an exit-side plate guide are arranged on the entry side and exit side of the rolling mill to guide the hot plate material to the work rolls. Since the hot plate material that advances bends upward due to a reaction force, the plate material is held down by a liftable hold-down roll to prevent the plate material from floating up. The plate material has a pressing force that is greater than the reaction force received from the work rolls, and the hot plate material is reliably bitten by the work rolls. In addition, in order to transmit the torque required for the work rolls, the roll balance force or roll bending force of the work rolls is controlled when biting the rolled material, and the contact force between the rolls and the intermediate rolls is increased. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3067589 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to roll thinner plates, it is effective to reduce the radius of the work rolls, but this reduces the load capacity of the drive spindles of the work rolls. Therefore, intermediate roll drive or backup roll drive using the drive spindles of intermediate rolls or backup rolls, which have a higher load capacity, is sometimes used.

[0005] Here, in the case of intermediate roll drive or backup roll drive, the rolling torque is transmitted to the work rolls at the contact area between the rolls, so if a large slip occurs between the rolls, the necessary rolling torque cannot be transmitted.

[0006] For example, Patent Document 1 discloses that the roll balance force or bending force during biting is set as large as possible within the range permitted by the strength of the roll neck, thereby preventing poor biting.

[0007] However, the above-mentioned technique does not take into consideration the fact that the roll balance force becomes excessive when kiss rolls occur during rolling to a thin plate thickness, and there is room for improvement.

[0008] The present invention provides a method for setting a work roll balance force that is capable of suppressing slippage between rolls without damaging components such as bearings even if kiss rolls occur during biting, a method for operating a rolling mill, a method for switching between rolling mill operations, and a rolling mill. [Means for solving the problem]

[0009] The present invention includes a plurality of means for solving the above-mentioned problems. One example of such a method is a method for setting a work roll balance force of a rolling mill which includes a pair of upper and lower work rolls and one or more pairs of upper and lower rolls provided on the opposite side of the work rolls to the material to be rolled, and which supplies a rolling torque Tr to the work rolls to drive the work rolls, the method comprising the steps of: obtaining a mill longitudinal stiffness coefficient K of the rolling mill; calculating a kiss roll load Pk of the work rolls relative to a work roll angle θx at the tip position of the rolled material from the start of biting the rolled material to the completion of biting using the obtained mill longitudinal stiffness coefficient K and rolling conditions; calculating a rolling load Pr and the rolling torque Tr relative to the work roll angle θx at the tip position of the rolled material from the start of biting the rolled material to the completion of biting; and calculating a rolling torque Tr and a rolling load Pr and a rolling torque Tr ... a step of calculating a traction coefficient μrt between the work rolls and the rolls for the work roll angle θx at the tip position and a maximum value μrtmax of the traction coefficient from the sum P of the kiss roll load Pk, the rolling load Pr, and the hypothetical work roll balance force Pb up to the tip position and the rolling torque Tr; a step of obtaining an allowable value μrtcr of the traction coefficient μrt of the rolling mill; a step of comparing the maximum value μrtmax calculated in the step of calculating the traction coefficient μrt with the allowable value μrtcr; and a step of resetting, when the allowable value μrtcr is equal to or greater than the maximum value μrtmax, the work roll balance force at the start of biting of the rolled material to a value equal to or greater than the work roll balance force when the traction coefficient μrt indicates the maximum value μrtmax and equal to or less than the work roll balance force that is the limit due to restrictions on the strength of the rolling mill. Effect of the Invention

[0010] According to the present invention, even if kiss rolls occur during biting, slippage between rolls can be suppressed without damaging components such as bearings. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] FIG. 13 is a diagram showing an example of a change in spindle torque when the leading end is bitten. [Diagram 2] FIG. 13 is a diagram showing an example of a horizontal force acting on each roll when the intermediate roll is engaged. [Diagram 3] FIG. 13 is a diagram showing an example of a horizontal force acting on each roll when the intermediate roll is engaged. [Figure 4] FIG. 13 is a diagram showing an example of a comparison of the total horizontal force acting on each roll during meshing when the drive roll is changed and the torque amplification factor is 3. [Diagram 5] FIG. 4 is a diagram showing the process of change in the gap between the work rolls during the biting process. [Figure 6] A diagram showing the definition of kiss roll. [Figure 7] A diagram showing the definition of kiss roll. [Figure 8] FIG. 4 is a diagram showing the relationship of kiss roll loads set before the start of rolling. [Figure 9] FIG. 4 is a diagram showing the relationship of kiss roll loads set before the start of rolling. [Figure 10] FIG. 1 is a diagram showing the relationship between the plate tip position in the roll bite and the traction coefficient between the intermediate roll and the work roll. [Figure 11] FIG. 1 is a diagram showing the relationship between the plate tip position in the roll bite and the traction coefficient between the intermediate roll and the work roll. [Figure 12] FIG. 4 is a diagram showing the relationship between the plate tip position in the roll bite and the load between the intermediate roll and the work roll. [Figure 13] FIG. 1 is a diagram showing the relationship between the plate tip position in the roll bite and the traction coefficient between the intermediate roll and the work roll. [Figure 14] FIG. 1 is a diagram showing the relationship between the plate tip position in the roll bite and the maximum value of the traction coefficient between the intermediate roll and the work roll. [Figure 15] FIG. 1 is a diagram showing the relationship between the thickness of the plate on the exit side in the roll bite and the work roll balance force. [Figure 16] 1 is a diagram showing an outline of a finishing rolling mill to which the rolling mill of the present invention is applied; [Figure 17] FIG. 4 is a diagram showing another outline of a finishing mill to which the rolling mill of the present invention is applied. [Figure 18] FIG. 4 is a diagram showing another outline of a finishing mill to which the rolling mill of the present invention is applied. [Figure 19] FIG. 4 is a diagram showing another outline of a finishing mill to which the rolling mill of the present invention is applied. [Figure 20] FIG. 2 is a front view of an example of a rolling mill of the present invention. [Figure 21] 21A and 21B are diagrams showing modified examples of the entrance side fixing member and the exit side fixing member in FIG. 20. [Figure 22] FIG. 4 is a front view of another example of a rolling mill according to the present invention. [Diagram 23] 23 is a diagram showing modified examples of the entrance side fixing member and the exit side fixing member of FIG. 22. [Figure 24] 21 is a view taken along the line A-A' in FIG. 20. [Diagram 25] 21 is a view taken along the line B-B' in FIG. 20. [Figure 26] 23 is a view taken along the line CC' in FIG. 22. [Figure 27] 23 is a view taken along the line D-D' in FIG. 22. [Figure 28] FIG. 2 is a diagram showing a state in which a driving spindle is shared in the rolling mill of the present invention. [Figure 29] FIG. 2 is a diagram showing a state in which a driving spindle is shared in the rolling mill of the present invention. [Diagram 30] FIG. 2 is a diagram showing a state in which a driving spindle is shared in the rolling mill of the present invention. [Diagram 31] FIG. 2 is a diagram showing a state in which a driving spindle is shared in the rolling mill of the present invention. [Diagram 32] 4 is a flowchart showing a flow of determining a set work roll balance force Pbact according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A method for setting a work roll balance force, a method for operating a rolling mill, a method for switching between rolling mill operations, and an embodiment of the rolling mill according to the present invention will be described with reference to Figs. 1 to 32.

[0013] In the drawings used in this specification, the same or corresponding components are denoted by the same or similar reference numerals, and repeated description of these components may be omitted.

[0014] First, the background that has led to the method for setting the work roll balance force, the method for operating the rolling mill, the method for switching between rolling mill operations, and the configuration of the rolling mill according to the present invention will be described with reference to Figs.

[0015] Figure 1 shows an example of the measurement results of the change in spindle torque when the tip of a finishing mill with an intermediate shaft bites. As shown in Figure 1, the spindle torque fluctuates with the period of the natural frequency of torsion. From Figure 1, the rise time Δt1 of the rolling torque Tr is expected to be about 0.01 [sec].

[0016] At Δt1 when the rolling torque Tr rises, the spindle torque is still only Ts, so the shortage Tr1 of the rolling torque Tr is supplied by the change in the inertia force of the roll. The shortage Tr1 of the rolling torque Tr is mainly supplied by the change in inertia caused by the slight deceleration of the backup roll.

[0017] After that, at Δt2, the maximum spindle torque acts. At this time, a torque larger than the rolling torque Tr by Tr2 acts on the spindle. Tr2 balances the change in the inertia force of the roll, and mainly balances the change in inertia caused by a slight increase in the speed of the backup roll.

[0018] Figure 2 is a diagram showing an example of the horizontal force acting on each roll when the rolls are biting when the intermediate rolls are driven, where (a) is before the rolled material is bitten, (b) is when Tr1 is in operation, (c) is when Tr2 is in operation, and (d) is during normal rolling when the spindle torque fluctuation at the beginning of biting has disappeared. Figure 3 is a diagram showing the total horizontal force acting on each roll when the rolls are biting when the intermediate rolls are driven. Here, the force in the rolling direction is + and the force in the opposite rolling direction is -.

[0019] In Fig. 2, δiw is the offset between the intermediate roll and the work roll, δbi is the offset between the backup roll and the intermediate roll, Fobi is the offset force component of the rolling load Pr acting between the backup roll and the intermediate roll, Foiw is the offset force component of the rolling load Pr acting between the intermediate roll and the work roll, Fbi is the tangential force acting between the backup roll and the intermediate roll, Fiw is the tangential force acting between the intermediate roll and the work roll, Fbt is the total horizontal force acting on the backup roll, Fit is the total horizontal force acting on the intermediate roll, and Fwt is the total horizontal force acting on the work roll. In addition, Fr is the rolling torque / work roll radius, Fbb is the resistance of the backup roll bearing, Fii is the resistance of the intermediate roll bearing, Fww is the resistance of the work roll bearing, and Fbb, Fii, and Fww are treated as ≒0 because they are smaller than Fr.

[0020] In addition, in Fig. 3, the offset force component Foiw during normal rolling is set to be equal to the driving tangential force Fiw, the kiss roll load during mill idling is set to rolling load Pr x 0.7, and when Tr1 is applied, the tangential force generated by the change in inertia of the backup roll accounts for most of the force at Tr1, and when Tr2 is applied, the over torque = (TAF-1)Tr generated in the driving spindle at Tr2 is mainly balanced by the increase in inertia of the backup roll. Note that "TAF" means torque amplification factor, and is the ratio of maximum shaft torque to steady-state rolling torque, and in Fig. 1, TAF is calculated as 7.5kNm / 3.3kNm = 2.27.

[0021] As shown in Figures 2(a), 2(b), and 3, the change in inertia of the backup roll when the rolled material is bitten compensates for the rolling torque until the spindle torque starts up. After that, as shown in Figure 2(c), the over-torque of the driving spindle of the work roll balances with the change in inertia of the backup roll. Furthermore, as shown in Figure 2(d), when the spindle torque fluctuation at the beginning of biting disappears, the tangential force Fbi acting between the backup roll and the intermediate roll becomes 0 because the frictional resistance of the backup roll is treated as 0 here. The tangential force Fiw acting between the intermediate roll and the work roll becomes Fr.

[0022] Fig. 4 is a diagram showing an example of a comparison of the total horizontal force acting on each roll during meshing when the torque amplification factor is 3. Fig. 4 shows the total horizontal force acting on each roll when the spindle torque fluctuates from the mill idling to the initial stage of meshing and Tr1 or Tr2 acts under the condition that the offset component force is adjusted so that the total horizontal force acting on each roll (the sum of the offset component force of the rolling load Pr and the roll interlinear force) becomes almost 0 when the spindle torque fluctuation at the initial stage of meshing disappears (corresponding to (d) normal rolling).

[0023] As shown in Fig. 4, when the torque amplification factor is set to 3, the total horizontal force Fit acting on the intermediate roll during Tr2 action in the work roll drive becomes -4Fr, which is a problem in that the force supporting the intermediate roll in the rolling direction becomes large.

[0024] In addition, in the case of backup roll drive, if a kiss roll load is applied, the total horizontal force Fit acting on the intermediate rolls during mill idling before engagement is -1.4Fr, a slightly large value. Note that at the timings of Tr1 and Tr2, the total horizontal force Fbt acting on the backup rolls, the total horizontal force Fit acting on the intermediate rolls, and the total horizontal force Fwt acting on the work rolls are small.

[0025] In contrast, when the intermediate rolls are driven, the total horizontal force Fit acting on the intermediate rolls when Tr2 is applied is a horizontal force of -2Fr, half that when the work rolls are driven. Also, the total horizontal force Fwt acting on the work rolls is smaller than that when the work rolls are driven, both when Tr1 and Tr2 are applied.

[0026] Here, the characteristics of the torque amplification factor will be described. The torque amplification factor is expressed as (Tr2+Tr) / Tr, and tends to become smaller as the rolling torque Tr increases. The maximum value of the peak torque tends to occur at the rated torque, and is expressed as torque amplification factor x rated torque. In this case, the torque amplification factor at the rated torque is about 2.0. Furthermore, when the rolling torque Tr is smaller than the rated torque, the torque amplification factor becomes a large value. For example, when the rolling torque Tr is 50% of the rated torque, the torque amplification factor becomes a value of about 2.0 to 4.0. Here, the rated torque means the rolling torque when the drive motor output is 100%.

[0027] According to "Kawasaki Steel Technical Report Vol. 33 (2001) No. 1, P. 37-42, Clarification of the mechanism of non-steady load generation in the rolling process and measures to suppress it," when the roll receives horizontal force F at the roll body and the roll bearing box and housing collide, the resultant force Pt acting on the collision part in the rolling direction is Pt = horizontal force F + impact force P (= (2KhFδ) 0.5 ), where Kh is the elastic coefficient of the housing's deformation in the rolling direction, and δ is the distance the roll bearing box moves when horizontal force F is applied, which corresponds to the distance between the roll bearing box and the housing. It has been reported that when F = 80 tons, P = 220 to 280 tons, so Pt = 300 to 360 = (3.8 to 4.5) x F, and when F = 20 tons, P = 90 to 100 tons, so Pt = 110 to 120 = (5.5 to 6.0) x F.

[0028] When the rolls move in the rolling direction and the bearing box collides with the housing, Pt becomes as large as 3.8 to 6.0 times F, depending on the gap between the housing and the bearing box.

[0029] The backlash-reducing cylinder can eliminate the gap between the housing and the bearing box, which has the effect of reducing P and bringing Pt closer to F.

[0030] Incidentally, inside the bearing, there is a radial clearance of the bearing itself and a small gap between the roll shaft and the inner diameter of the bearing, so even if the bearing housing does not move, a small impact force acts.

[0031] Next, the traction coefficient μrt between the intermediate roll and the work roll in the intermediate roll drive will be explained. Figure 5 shows the change in the gap between the upper and lower work rolls and the forces acting on each part during the biting process with and without a kiss roll.

[0032] As shown in FIG. 5, when there are kiss rolls, the vertical pushing force P between the intermediate rolls and the work rolls is the rolling load Pr + kiss roll load Pk + work roll balance force Pb, and when there are no kiss rolls, the vertical pushing force P between the intermediate rolls and the work rolls is Pr + Pb.

[0033] Here, the traction coefficient μrt means the necessary coefficient of friction between the work roll and the intermediate roll, and a small necessary coefficient of friction means that large slippage is less likely to occur. Since the traction coefficient μrt is expressed as μrt=F / P, if P is large, the traction coefficient μrt will be small. When there is a kiss roll, P is larger by the kiss roll load Pk than when there is no kiss roll, so the traction coefficient μrt will be small.

[0034] In Fig. 5, angle θi is the bite angle, angle θx is the angle at the tip position of the rolled material, angle θn is the angle at the neutral point, and exit thickness hoa is the gap between the upper and lower work rolls when biting, which is set to 0 when there is a kiss roll. If hi is the entry thickness, ho is the exit thickness, and μm is the friction coefficient between the work roll and the material during the biting process, at the position of angle θn, the traveling speed of the rolled material and the peripheral speed of the roll are equal. In addition, in the range of angles θi to θn, the traveling speed of the material is slower than the peripheral speed of the roll, and in the range of angles θn to θx, the traveling speed of the material is faster than the peripheral speed of the roll.

[0035] Figure 6 shows the change in the gap between the work rolls and the forces acting on each part during the bite process when there is a kiss roll, and Figure 7 shows the change in the gap between the work rolls and the forces acting on each part when there is no kiss roll.

[0036] Usually, the roll gap is tightened before the strip is threaded by an amount equal to the elastic deformation caused by the rolling load Pr, which is smaller than the desired strip thickness. Then, as the strip is bitten, a roll load is generated, which expands the roll gap and allows the desired strip thickness to be obtained.

[0037] Pr is the rolling load, K is the spring constant of the rolling mill, hereafter referred to as the mill vertical stiffness coefficient K, and R is the work roll radius.

[0038] Pr / K corresponds to the amount of tightening that is equal to the elastic deformation of the rolling load Pr. When the maximum reduction amount becomes negative, it means that the upper and lower work rolls are in contact with each other before threading, and this state is called kiss roll. The load acting between the upper and lower work rolls during kiss roll is called kiss roll load.

[0039] If the plate thickness is h, the roll gap before rolling is hog, and M is the plasticity coefficient, then the elastic characteristic curve can be approximated by a straight line as Pr = K (exit plate thickness ho-hog), and the plastic characteristic curve of the material can be approximated by a straight line as Pr = M (ho-entry plate thickness hi).

[0040] Here, the roll gap hog before rolling indicates the value obtained by subtracting the amount of elastic deformation of the rolling mill when the kiss roll load Pk acts further by pressing in from the state when the upper and lower work rolls have just started to come into contact and the kiss roll load Pk is still 0 and no elastic deformation is occurring. Note that although the upper and lower work rolls each elastically deform and bring their axes closer together, the gap between the upper and lower work rolls remains 0 (gap between the upper and lower work rolls when biting hoa=0), and is not a negative value.

[0041] As shown in Figures 5 and 6, when there are kiss rolls, the vertical pushing force P between the intermediate roll and the work roll at the start of biting is Pr+Pk+Pb. As biting starts, Pr rises and Pk decreases, and when a gap occurs between the upper and lower work rolls, Pk becomes 0. When θx=0, it means that biting is complete, and the thickness at the tip of the strip becomes the delivery thickness ho.

[0042] In contrast, as shown in Figures 5 and 7, when there is no kiss roll, P = Pr + Pb at the start of biting, during biting, and completion of biting, and Pr is maximum at the completion of biting.

[0043] Figures 8 and 9 show the relationship between the finished strip thickness in the final stand of the finishing mill and the unit width kiss roll load, which is set before rolling begins. Figure 8 shows the case when the mill longitudinal stiffness coefficient K is 4000 [kN / mm], and Figure 9 shows the case when the mill longitudinal stiffness coefficient K is 6000 [kN / mm]. The numbers in Figures 8 and 9 indicate the strip width [mm], and the unit width kiss roll load was obtained under several rolling conditions assumed for the finishing mill in question.

[0044] As shown in Fig. 8 and Fig. 9, the kiss roll load per unit width varies depending on rolling conditions such as the assumed entry and exit thicknesses, width and hardness of the rolled material, and so is distributed within a certain range.

[0045] Furthermore, when the mill longitudinal stiffness coefficient K is relatively small as shown in Fig. 8, the kiss roll load per unit width is larger than when it is large as shown in Fig. 9. Furthermore, when the mill longitudinal stiffness coefficient K is 4000 [kN / mm], Pk occurs when the finished delivery thickness ho is about 2.6 [mm], whereas when the mill longitudinal stiffness coefficient K is 6000 [kN / mm], Pk occurs when the delivery thickness ho is about 2.2 [mm] as shown in Fig. 9. Therefore, the smaller the mill longitudinal stiffness coefficient K, the greater the tendency for the kiss roll load Pk to occur.

[0046] In this way, when the mill longitudinal stiffness coefficient K changes, the state of the kiss rolls before the start of rolling in any rolling operation changes. In other words, the traction coefficient μrt (required coefficient of friction between rolls) changes depending on the state of the kiss rolls before the start of rolling, which changes depending on the value of the mill longitudinal stiffness coefficient K, and the work roll balance force Pb.

[0047] Figure 10 shows the relationship between the work roll angle θx at the tip position of the rolled material in the roll bite and the traction coefficient μrt between the intermediate roll and the work roll, and was simulated under the conditions of an exit plate thickness of 1.2 [mm] x width of 1300 [mm], with no lubricant oil on the rolls and cooling water on the rolls. In Figure 10, △ indicates the case where the mill longitudinal stiffness coefficient K = 6000 [kN / mm], ◇ indicates the case where the mill longitudinal stiffness coefficient K = 4000 [kN / mm], and ○ indicates the case where the mill longitudinal stiffness coefficient K = 3000 [kN / mm].

[0048] In Figure 10, θx = 0.11 [radian] corresponds to the angle when the tip of the strip is bitten, which corresponds to the biting angle θi. θx = 0.00 [radian] indicates the time when the tip of the strip reaches the exit of the work roll.

[0049] As shown in FIG. 10, a kiss roll load exists from the beginning of engagement until θx=0.020 to 0.040 [radians], and the traction coefficient μrt is suppressed to a low value due to the presence of the kiss roll load.

[0050] In addition, the traction coefficient μrt changes as the plate tip advances to the exit side of the work roll after being bitten, but the maximum value μrtmax of the traction coefficient μrt when the plate tip is within the roll bite is approximately 0.070 when the mill longitudinal stiffness coefficient K = 6000 [kN / mm], approximately 0.060 when the mill longitudinal stiffness coefficient K = 4000 [kN / mm], and approximately 0.060 when the mill longitudinal stiffness coefficient K = 3000 [kN / mm].

[0051] As the work roll balance force Pb increases, the traction coefficient μrt tends to decrease. However, when the delivery thickness ho is 1.2 mm, which is the condition in FIG. 10, the effect of the work roll balance force Pb on the maximum value μrtmax is small.

[0052] Fig. 11 shows the relationship between the work roll angle θx at the tip position of the rolled material in the roll bite and the traction coefficient μrt between the intermediate roll and the work roll, assuming an exit plate thickness of 2.0 mm and a width of 1250 mm. In Fig. 11, θx = 0.135 radians corresponds to the bite angle θi.

[0053] As shown in FIG. 11, when the mill longitudinal stiffness coefficient K = 6000 [kN / mm], a kiss roll load exists from the beginning of engagement until around θx = 0.120 [radians], but the traction coefficient μrt increases rapidly and reaches a maximum value μrtmax of about 0.120 at around θx = 0.120 [radians] where the kiss roll load disappears.

[0054] In addition, when the mill longitudinal stiffness coefficient K=4000 [kN / mm], a kiss roll load exists from the beginning of engagement until θx=0.080 [radian], and the presence of this kiss roll load keeps the traction coefficient μrt at a low value. The maximum value μrtmax of the traction coefficient μrt is about 0.105, which occurs at about θx=0.080 [radian].

[0055] When the mill longitudinal stiffness coefficient K=3000 [kN / mm], a kiss roll load exists from the beginning of engagement until θx=0.050 [radian], and the presence of this kiss roll load keeps the traction coefficient μrt at a low value. The maximum value μrtmax of the traction coefficient μrt is about 0.090, which occurs at θx=0.050 [radian].

[0056] Thus, the smaller the mill longitudinal stiffness coefficient K, the wider the range in which the kiss roll load exists. It is also possible to reduce the maximum value μrtmax by the work roll balance force Pb, and it can be seen that the effect of the work roll balance force Pb is greater when the delivery thickness is ho=2.0 [mm] than when the delivery thickness is ho=1.2 [mm].

[0057] FIG. 12 shows the relationship between θx and each load, assuming that the thickness of the rolled material is 2.0 [mm] × width is 1250 [mm], the mill vertical stiffness coefficient K is 4000 [kN / mm], and the work roll balance force Pb is 0 [kN / roll].

[0058] As shown in Fig. 12, when kiss rolls are present, the kiss roll load is already acting when the leading edge of the strip is bitten by the work rolls, and the kiss roll load decreases as the leading edge of the strip enters the roll bite. On the other hand, the rolling load Pr gradually increases as the leading edge of the strip enters the roll bite.

[0059] Therefore, it is understood that within the kiss roll load acting range, even if the rolling load Pr is a relatively small value, the load P (≒Pr+Pk+Pb) between the intermediate roll and the work roll can be maintained at a high state, making it possible to reduce the traction coefficient μrt.

[0060] FIG. 13 is a diagram showing the relationship between the work roll angle θx at the tip position of the rolled material in the roll bite and the traction coefficient μrt between the intermediate roll and the work roll, and is based on the conditions of an exit plate thickness of 3.0 [mm] × width of 1600 [mm].

[0061] As shown in Figure 13, when the mill longitudinal stiffness coefficient K = 6000 [kN / mm], the bite angle θi corresponds to θx = 0.133 [radian]. The kiss roll load does not exist from the beginning of the bite. The maximum value μrtmax of the traction coefficient μrt is about 0.130, and occurs at the bite angle of θx = 0.133 [radian].

[0062] In addition, when the mill longitudinal stiffness coefficient K = 4000 [kN / mm], the bite angle θi corresponds to θx = 0.155 [radian]. The kiss roll load is only present at the beginning of the bite, and the maximum value μrt of the traction coefficient μrt is about 0.150, which occurs at the bite angle of θx = 0.151 [radian].

[0063] When the mill longitudinal stiffness coefficient K = 3000 [kN / mm], θx = 0.155 [radians] corresponds to the bite angle. Kiss roll load exists up to θx = 0.090 [radians], and the maximum value μrt of the traction coefficient μrt is about 0.110, which occurs at the bite angle of θx = 0.090 [radians].

[0064] In addition, the maximum value μrtmax can be reduced by the work roll balance force Pb. When the delivery thickness ho=3.0 [mm], the effect of the work roll balance force Pb is greater than when the delivery thickness ho=1.2 [mm] or ho=2.0 [mm].

[0065] Fig. 14 is a diagram showing the relationship between the work roll balance force Pb and the maximum value μrtmax of the traction coefficient between the intermediate roll and the work roll. As shown in Fig. 14, the influence of the work roll balance force Pb on the maximum value μrtmax is as follows.

[0066] When the delivery plate thickness ho is 3.0 mm, the maximum value μrtmax can be further reduced by increasing the work roll balance force Pb. On the other hand, when the delivery plate thickness ho is 1.2 mm, the effect of the work roll balance force Pb on the maximum value μrtmax is small.

[0067] In addition, the effect of the mill longitudinal stiffness coefficient K on the maximum value μrtmax is as follows: The effect of the mill longitudinal stiffness coefficient K on the maximum value μrtmax differs depending on the delivery plate thickness ho, and when the delivery plate thickness ho is thin at 1.2 [mm], the smaller the mill longitudinal stiffness coefficient K, the smaller the maximum value μrtmax becomes, but when the delivery plate thickness ho is thick at 3.0 [mm], the relationship between the mill longitudinal stiffness coefficient K and the maximum value μrtmax becomes complicated.

[0068] Thus, it can be seen that both the work roll balance force Pb and the mill longitudinal stiffness coefficient K affect the maximum value μrtmax.

[0069] Here, the limit value μrtcr of the maximum value μrtmax differs depending on the state between the two contacting rolls. It is believed that in most cases, if the traction coefficient μrt is 0.10 or less, there will be no significant slippage. Here, the work roll balance force at the maximum value μrtmax is defined as Pbcr1. If the limit value μrtcr of the maximum value μrtmax is 0.10, then the work roll balance force at which the maximum value μrtmax reaches the limit value μrtcr0.10 is defined as Pbcr1cr. Let Pbcr1cr be the required limit work roll balance force. By setting Pbcr1 to be equal to or greater than Pbcr1cr, the maximum value μrtmax will be equal to or less than the limit value μrtcr0.10.

[0070] Fig. 15 is a diagram showing the relationship between the delivery plate thickness ho and the required limit work roll balance force Pbcr1cr, and shows the limit work roll balance force Pbcr1cr when the limit value μrtcr of the maximum value μrtmax is 0.10. By setting the work roll balance force Pb larger than Pbcr1cr, the maximum value μrtmax≦limit value μrtcr is satisfied, and rolling can be continued without causing large slippage.

[0071] As shown in FIG. 15, the relationship between the delivery plate thickness ho and the critical work roll balance force Pbcr1cr varies depending on the mill longitudinal rigidity coefficient K, and the critical work roll balance force Pbcr1cr is affected by the mill longitudinal rigidity coefficient K.

[0072] For example, when the mill vertical stiffness coefficient K is 3000 [kN / mm], the critical work roll balance force Pbcr1cr is 0 [kN / roll] when the delivery plate thickness ho is from 1.2 [mm] to 2.0 [mm], but when the delivery plate thickness ho increases from 2.0 [mm] to 3.0 [mm], the critical work roll balance force Pbcr1cr increases rapidly.

[0073] In addition, when the mill vertical stiffness coefficient K is 4000 [kN / mm], the limit work roll balance force Pbcr1cr increases gradually when the delivery plate thickness ho changes from 1.2 [mm] to 2.0 [mm], whereas the limit work roll balance force Pbcr1cr increases rapidly when the delivery plate thickness ho increases from 2.0 [mm] to 3.0 [mm].

[0074] Furthermore, when the mill vertical stiffness coefficient K is 6000 [kN / mm], the critical work roll balance force Pbcr1cr remains flat when the delivery plate thickness ho increases from 2.0 [mm] to 3.0 [mm].

[0075] In addition to the limit work roll balance force Pbcr1cr, there is a limit to the work roll balance force. When the work roll diameter is small, the work roll balance force Pb cannot be increased due to the strength of the bearings and roll neck, so there is a limit work roll balance force Pbcr2 due to the constraints of the strength.

[0076] When the required critical work roll balance force Pbcr1cr is greater than the critical work roll balance force Pbcr2 due to strength restrictions, it is preferable to use work rolls with a relatively large diameter for work roll drive.

[0077] In contrast, when a relatively large diameter work roll is used and the work roll is directly driven, a large rolling torque Tr can be transmitted. For example, when the delivery thickness ho is 3.0 [mm] or more, the required limit work roll balance force Pbcr1cr becomes large when K is 3000 [kN / mm] or 4000 [kN / mm], but by setting the condition of driving the work rolls as a relatively large diameter work roll, the rolling torque Tr is not transmitted between the rolls, and the restrictions on the traction coefficient μrt and the maximum value μrtmax can be eliminated.

[0078] Here, we will explain the mill vertical stiffness coefficient K. The mill vertical stiffness coefficient K is expressed as P / δ, where P is the rolling load Pr and δ is the elastic deformation amount of each part of the rolling mill when P acts.

[0079] This mill vertical stiffness coefficient K is determined by the stiffness of the rolls that make up the rolling mill, the housing, the reduction gear, the bearing housing of each roll, etc. The mill vertical stiffness coefficient K at the beginning of operation is an arbitrary value, and as the mill is used, the mill vertical stiffness coefficient K decreases. This is thought to be because the housing, reduction gear, bearing housing, and other equipment wears out over the course of use, causing changes in the way each part contacts, resulting in a decrease in the mill vertical stiffness coefficient K.

[0080] As the mill longitudinal stiffness coefficient K decreases, a difference in the amount of elastic deformation between the working side and the driving side occurs, causing rolling to become unstable, and repairs are therefore carried out. This repair restores the mill longitudinal stiffness coefficient K to a value close to that at the beginning of operation. However, it will never recover to the same value as the mill longitudinal stiffness coefficient K at the beginning of operation.

[0081] In this way, the mill longitudinal stiffness coefficient K changes with use, and in order to continue stable rolling, the mill longitudinal stiffness coefficient K is monitored at regular intervals and repairs are made depending on the situation. Note that the mill longitudinal stiffness coefficient K is generally not adjustable.

[0082] In addition, the mill longitudinal stiffness coefficient K differs depending on the equipment. For example, the mill longitudinal stiffness coefficient K of a four-high rolling mill is greater than that of a six-high rolling mill, and the greater the number of rolls, the smaller the mill longitudinal stiffness coefficient K becomes.

[0083] On the other hand, when the intermediate rolls or backup rolls are driven, the maximum value μrtmax changes depending on the mill vertical stiffness coefficient K. If the maximum value μrtmax exceeds the limit value μrtcr and large slippage occurs between the rolls, rolling cannot be continued.

[0084] Therefore, the inventors of the present invention came up with the idea that it is possible to suppress large slippage between rolls by confirming the mill longitudinal stiffness coefficient K, determining the critical work roll balance force Pbcr1cr required from the mill longitudinal stiffness coefficient K and the rolling conditions, and setting the work roll balance force Pb to Pbcr1cr or more to bite the front end of the strip. This led to the idea that even if the diameter of the work rolls is made small and the work rolls themselves cannot be used as drive rolls, rolling can be performed by driving the intermediate rolls or the backup rolls.

[0085] The present invention was made based on these findings.

[0086] Next, an outline of a rolling facility equipped with the rolling mill of this embodiment will be described with reference to Figures 16 to 19. Figures 16 to 19 are diagrams showing an outline of a finishing mill to which the rolling mill of the present invention is applied.

[0087] The rolling equipment 1 shown in Figure 16 is equipped with multiple rolling mills that hot roll the rolled material 5 into strips, and has a control device 80 and six stands, from the entrance side of the rolled material 5, namely, F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, and F6 stand 60.

[0088] Of these, each of F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, and F6 stand 60, and the portion of the control device 80 that controls each stand, correspond to the rolling mill as defined in the present invention, but here the above-mentioned knowledge is applied only to F6 stand 60.

[0089] In FIG. 16, F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, and F5 stand 50 are four-stage rolling mills, and only the final stand F6 stand 60 is a six-stage rolling mill equipped with small diameter work rolls.

[0090] The rolling equipment 1A shown in FIG. 17 is a four-stage rolling mill including an F1 stand 10, an F2 stand 20, an F3 stand 30, an F4 stand 40, an F5 stand 50, and an F6 stand 60A equipped with large diameter work rolls.

[0091] Furthermore, in the rolling equipment 1B shown in Fig. 18, the F1 stand 10, the F2 stand 20, the F3 stand 30, the F4 stand 40, and the F5 stand 50 are four-stage rolling mills, and only the final stand F6 stand 60B is a six-stage rolling mill equipped with large diameter work rolls. In Fig. 18, the above-mentioned knowledge is applied to the F6 stand 60B.

[0092] In the rolling facility 1C shown in Fig. 19, the F1 stand 10, the F2 stand 20, the F3 stand 30, and the F4 stand 40 are four-high rolling mills, whereas the F5 stand 50C and the F6 stand 60C are six-high rolling mills equipped with small diameter work rolls. In Fig. 19, the above-mentioned knowledge is applied to the F5 stand 50C and the F6 stand 60C.

[0093] The rolling equipment 1, 1A, 1B, 1C is not limited to six stands as shown in Figs. 16 to 19, but may be one having at least two stands.

[0094] In addition, in the above-mentioned Figures 16 to 19, the case of a four-high rolling mill in which only backup rolls, which will be described later, are used as one or more pairs of upper and lower rolls provided on the opposite side of the work rolls to the rolled material, or a six-high rolling mill in which intermediate rolls and backup rolls are used, has been described. However, the rolling mills to which the work roll balance force setting method, rolling mill operating method, and rolling mill operation switching method of the present invention apply are not limited to the above-mentioned four-high rolling mills or six-high rolling mills, and are also suitable targets for application to rolling mills equipped with side support rolls that directly contact the work rolls.

[0095] In addition, in the embodiment, a hot rolling mill having a biting process will be described as an example, but the present invention is not limited to this.

[0096] Next, an outline of the rolling mill of the present invention will be described with reference to Fig. 20 to Fig. 29. Fig. 20 is a front view of an example of a rolling mill in the rolling facility shown in Fig. 16, Fig. 21 is a view showing a modified example of the entry side fixed member and the exit side fixed member in Fig. 20, Fig. 22 is a front view of another example of a rolling mill in the rolling facility shown in Fig. 17, Fig. 23 is a view showing a modified example of the entry side fixed member and the exit side fixed member in Fig. 22, Fig. 24 is a view taken along the arrows A-A' in Fig. 20, Fig. 25 is a view taken along the arrows B-B' in Fig. 20, Fig. 26 is a view taken along the arrows C-C' in Fig. 22, and Fig. 27 is a view taken along the arrows D-D' in Fig. 22. Figs. 28 and 29 are views showing a state in which a drive spindle is shared.

[0097] 20 to 29, the rolling equipment 1 shown in FIG. 16 or the rolling equipment 1A shown in FIG. 17 will be described using the F6 stands 60, 60A as an example, but the rolling mill of the present invention can be applied to any of the F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, 50C, and F6 stand 60B, 60C shown in FIG. 16 etc., and further to other stands.

[0098] Further, although the case of intermediate roll drive will be described, the present invention is also applicable to backup roll drive.

[0099] As shown in Figures 20 and 21, the F6 stand 60, which is an example of a rolling mill in this embodiment, is a six-stage rolling mill that rolls the rolled material 5, and has a housing 600, a control device 80, and a hydraulic device 90, although not shown.

[0100] The housing 600 is provided with an upper and lower pair of upper work rolls 610 and lower work rolls 611, and an upper and lower pair of upper intermediate rolls 620 and lower intermediate rolls 621 which are provided on the opposite side of the rolled material 5 to the upper work rolls 610 and lower work rolls 611 and support the rolled material 5 by contacting each other. The housing 600 further includes an upper and lower pair of upper backup rolls 630 and lower backup rolls 631 which support the upper intermediate roll 620 and lower intermediate roll 621 by contacting each other.

[0101] In contrast, the F6 stand 60A, which is another example of the rolling mill of this embodiment shown in FIGS. 22 and 23, is a four-stage rolling mill for rolling the strip 5.

[0102] As shown in Figure 22, the F6 stand 60A is equipped with a pair of upper and lower work rolls 610A and 611A, which have a larger diameter than the work rolls 610, 611, and a pair of upper and lower backup rolls 630 and 631, which are provided on the opposite side of the rolled material 5 from the upper work roll 610A and lower work roll 611A and support the rolled material 5 by contacting each other.

[0103] The work rolls 610, 611 and intermediate rolls 620, 621 are configured to be interchangeable with the work rolls 610A, 611A. When the equipment associated with the work rolls 610, 611 and intermediate rolls 620, 621 in FIG. 20 is replaced with equipment associated with the work rolls 610A, 611A, the F6 stand 60A shown in FIG. 22 is obtained. When the equipment associated with the work rolls 610A, 611A in FIG. 22 is replaced with equipment associated with the work rolls 610, 611 and intermediate rolls 620, 621, the F6 stand 60 shown in FIG. 20 is obtained.

[0104] In the F6 stand 60A shown in Figure 22, a direct drive system in which the work rolls 610A, 611A themselves are driven is preferably used, and in the F6 stand 60 shown in Figure 20, an indirect drive system in which the rolling torque Tr of the upper intermediate roll 620 and the lower intermediate roll 621 is supplied to the upper work roll 610 and the lower work roll 611 to drive the upper work roll 610 and the lower work roll 611 is preferably used, so that the systems are swapped when switching operations.

[0105] As a result, the positions of the upper backup roll 630 and the lower backup roll 631 do not require significant movement in the vertical direction, making it possible to switch between the small diameter work rolls 610, 611 and the large diameter work rolls 610A, 611A without changing the hydraulic pressure reduction devices or pass line adjustment devices above and below the upper backup roll 630 and the lower backup roll 631.

[0106] Returning to Fig. 20, of the rolls, a bearing 610A1 (see Fig. 25) which shifts in the axial direction of the roll together with the upper work roll 610 and receives the load from the roll is provided on the operation side of the axial end of the upper work roll 610, and these bearings 610A1 are supported by an upper work roll bearing box 612 on the work side. Similarly, a bearing 610A1 (see Fig. 25) which shifts in the axial direction of the roll together with the upper work roll 610 and receives the load from the roll is provided on the drive side, and these bearings 610A1 are supported by an upper work roll bearing box 612 on the drive side.

[0107] Similarly, the lower work roll 611 is provided with bearings 611A1 at its axial end on both the drive side and the operation side, and these bearings are supported by lower work roll bearing boxes 613 on the operation side and drive side, respectively.

[0108] In this embodiment, the upper work roll 610 is configured to be shiftable in the roll axis direction by a shift cylinder 615 as shown in Fig. 25 via an upper work roll bearing housing 612 on the operation side. Similarly, the lower work roll 611 is configured to be shiftable in the roll axis direction by a shift cylinder 616 as shown in Fig. 25 via a lower work roll bearing housing 613A on the operation side.

[0109] 24 and 25, the upper intermediate roll 620 has a tapered portion at its drive side end, and the lower intermediate roll 621 has a tapered portion at its operation side end, so that the upper intermediate roll 620 and the lower intermediate roll 621 are point symmetrical vertically. The upper intermediate roll 620 is configured to be shiftable in the roll axis direction by a shift cylinder 617 as shown in Fig. 25, and the lower intermediate roll 621 is configured to be shiftable by a shift cylinder 618 as shown in Fig. 25.

[0110] 20, the exit side fixed member 602 is fixed to a housing 600 on the exit side of the rolled material 5. An entry side fixed member 603 is fixed to the housing 600 on the entry side of the rolled material 5 so as to face the exit side fixed member 602.

[0111] 20 and 24, in the F6 stand 60, on both the operation side and the drive side, the upper work roll bearing box 612 is supported by upper work roll bending cylinders 640 provided in the axial direction of the roll on the exit side fixed member 602, and upper work roll bending cylinders 641 provided in the axial direction of the roll on the entry side fixed member 603. By appropriately driving these cylinders, a bending force is applied in the vertical direction to the bearing 610A1 of the upper work roll 610.

[0112] Similarly, on both the operating side and the driving side, the lower work roll bearing box 613 is supported by a lower work roll bending cylinder 644 provided on the exit side fixed member 602 and a lower work roll bending cylinder 645 provided on the entry side fixed member 603, and by appropriately driving these cylinders, a bending force is applied vertically to the bearing of the lower work roll 611.

[0113] Furthermore, as shown in Figures 20 and 24, for the purpose of removing backlash, an upper work roll bearing box backlash removing cylinder 660 is provided in the axial direction of the roll on the inlet side of the rolled material 5, and this cylinder applies a horizontal force, specifically a pressing force in the rolling direction, to the upper work roll 610 via a liner (not shown) of the upper work roll bearing box 612, thereby pressing the bearing 610A1 against the housing 600.

[0114] Similarly, the inlet side fixed member 603 is provided with a lower work roll bearing box clearance cylinder 662 which applies a pressing force in the rolling direction to the lower work roll 611 via the liner of the lower work roll bearing box 613 to press the bearing 611A1 against the housing 600.

[0115] These cylinders can apply a desired force to the upper work roll 610 etc. in a direction perpendicular to the roll axial direction.

[0116] 20, 24, and 25, bearings 620A1 are provided at both the driving side and the operating side of the axial end of the upper intermediate roll 620, and these bearings are supported by an upper intermediate roll bearing box 622. Similarly, bearings 621A1 are provided at both the driving side and the operating side of the lower intermediate roll 621, and these bearings are supported by a lower intermediate roll bearing box 623.

[0117] On both the operating side and the driving side, the upper intermediate roll 620 supports the upper intermediate roll bearing box 622 by an upper intermediate roll bending cylinder 650 provided on the exit side fixed member 602 and an upper intermediate roll bending cylinder 651 provided on the entry side fixed member 603, and by appropriately driving these cylinders, a bending force is applied to the bearing in the vertical increase side.

[0118] The lower intermediate roll 621, on both the operating side and the driving side, supports the lower intermediate roll bearing box 623 by a lower intermediate roll bending cylinder 652 provided on the exit side fixed member 602 and a lower intermediate roll bending cylinder 653 provided on the entry side fixed member 603, and by appropriately driving these cylinders, a bending force is applied to the bearing in the vertical increase side.

[0119] A work roll balance force Pb is applied to the work rolls 610 and 611 by each of these bending cylinders 640, 641, 644, and 645.

[0120] As shown in Figures 20 and 24, an upper intermediate roll bearing box clearance adjustment cylinder 672 is provided on the entry side fixed member 603 so as to apply a horizontal force to the upper intermediate roll 620 via the upper intermediate roll bearing box 622, and an upper intermediate roll bearing box clearance adjustment cylinder 671 is provided on the exit side fixed member 602 so as to apply a horizontal force to the upper intermediate roll 620 via the upper intermediate roll bearing box 622.

[0121] Similarly, a lower intermediate roll bearing box clearance adjustment cylinder 674 is provided on the entry side fixed member 603 so as to apply a horizontal force to the lower intermediate roll 621 via the lower intermediate roll bearing box 623, and a lower intermediate roll bearing box clearance adjustment cylinder 673 is provided on the exit side fixed member 602 so as to apply a horizontal force to the lower intermediate roll 621 via the lower intermediate roll bearing box 623.

[0122] Here, in the indirect drive that drives the intermediate rolls 620, 621, the maximum load acts on the intermediate rolls 620, 621 in the entry direction during overtorque action. At that time, the load is received on the entry side of the housing 600, and an overload of the torque amplification factor is prevented from acting on the upper intermediate roll bearing box clearance removing cylinder 671 and the lower intermediate roll bearing box clearance removing cylinder 673 on the exit side. In Fig. 20, the upper intermediate roll bearing box clearance removing cylinder 672 and the lower intermediate roll bearing box clearance removing cylinder 674 are not used, but the upper intermediate roll bearing box clearance removing cylinder 672 and the lower intermediate roll bearing box clearance removing cylinder 674 can also be used instead of the upper intermediate roll bearing box clearance removing cylinder 671 and the lower intermediate roll bearing box clearance removing cylinder 673. FIG. 4 shows the case where the torque amplification factor is 3, but when the torque amplification factor is 2 or less, (b) the sum of the horizontal forces when Tr1 acts may be greater than (c) the sum of the horizontal forces when Tr2 acts. In such a case, by using the upper intermediate roll bearing box clearance removing cylinder 672 or the lower intermediate roll bearing box clearance removing cylinder 674, it is possible to reduce the output of the intermediate roll bearing box clearance removing cylinders. Therefore, taking into consideration the magnitude of Tr1 and Tr2, it is possible to select either the use of the upper intermediate roll bearing box clearance removing cylinder 671 and the lower intermediate roll bearing box clearance removing cylinder 673, or the use of the upper intermediate roll bearing box clearance removing cylinder 672 and the lower intermediate roll bearing box clearance removing cylinder 674.

[0123] In addition, the upper work roll bearing housing clearance cylinder 660 and the lower work roll bearing housing clearance cylinder 662 act to push the bearing housings 612, 613 of the small diameter work rolls 610, 611, respectively, supporting the small diameter work rolls 610, 611 so as not to move in the rolling direction. Figure 4 shows the total horizontal forces acting on each roll when Tr1 is applied (b) and Tr2 is applied (c) under the condition that the offset amount is set so that the sum of the offset component force of the rolling load Pr and the roll interline force (total horizontal force) is almost 0 during normal rolling (d). When the intermediate rolls are driven, the total horizontal force acting on the work rolls is 0 in all of (b), (c), and (d), but it is difficult to make the offset component force and the roll interline force all the same in actual operations and facilities, and the torque amplification factor also varies within a certain range depending on the rolling conditions, so the total horizontal force is not 0. In this way, even when the sum of horizontal forces caused by changes in rolling conditions, etc., acts, the small diameter work rolls 610, 611 can be prevented from moving in the rolling direction. Here, the upper work roll bearing box clearance removing cylinder 660 and the lower work roll bearing box clearance removing cylinder 662 are installed on the entry side in the rolling direction, but they can also be installed on the exit side. Furthermore, the entry side intermediate roll bearing box clearance removing cylinders 672, 674, together with the upper work roll bearing box clearance removing cylinder 660 and the lower work roll bearing box clearance removing cylinder 662, can also be used as large diameter work roll bearing box clearance removing cylinders for the large diameter work rolls 610A, 611A.

[0124] In the case of the large diameter work rolls 610A, 611A, the rolling torque Tr may be larger than that of the small diameter work rolls 610, 611. Also, as shown in FIG. 4, in the case of the work roll drive, the total horizontal force when (b) Tr1 acts and (c) Tr2 acts may be larger than that when the intermediate roll is driven, so that the output of the clearance removing cylinder may be required to be larger than that of the clearance removing cylinder for the small diameter. In addition, it is preferable that the clearance removing cylinder supports the vicinity of the center of the roll in the vertical direction. Therefore, in the case where the work roll bearing box clearance removing cylinder 660 and the lower work roll bearing box clearance removing cylinder 662 cannot support the roll, the upper intermediate roll bearing box clearance removing cylinder (upper large diameter work roll bearing box clearance removing cylinder) 672 and the lower intermediate roll bearing box clearance removing cylinder (lower large diameter work roll bearing box clearance removing cylinder) 674 can also be used as clearance removing cylinders for the large diameter work rolls 610A, 611A. Furthermore, the rolling equipment 1B shown in FIG. 18 shows a six-high rolling mill equipped with large diameter work rolls, but in this case too, it is possible to use the intermediate roll bearing housing clearance removing cylinder and the work roll bearing housing clearance removing cylinder shown in FIG. 20, making it possible to use the equipment for both small diameter work rolls and large diameter work rolls.

[0125] Furthermore, bearings (not shown) are provided on both the drive side and the operation side at the axial end of the upper backup roll 630, and these bearings are supported by an upper backup roll bearing box 632. Similarly, bearings (not shown) are provided on both the drive side and the operation side at the axial end of the lower backup roll 631, and these bearings are supported by a lower backup roll bearing box 633.

[0126] 20, an upper backup roll bearing box clearance cylinder 680 is provided in the outlet housing 600 so as to apply a horizontal force to the upper backup roll 630 via the upper backup roll bearing box 632. Similarly, a lower backup roll bearing box clearance cylinder 682 is provided in the outlet housing 600 so as to apply a horizontal force to the lower backup roll 631 via the lower backup roll bearing box 633.

[0127] The hydraulic unit 90 is connected to each hydraulic cylinder, such as the above-mentioned bending cylinders, the gap removing cylinders, the shift cylinders 615, 617, or a rolling device (not shown) that applies a rolling force to the upper work roll 610 and the lower work roll 611 to roll the rolled material 5, and this hydraulic unit 90 is connected to the control device 80.

[0128] In contrast, in the four-high rolling mill shown in Fig. 22, a bearing 610A2 (see Fig. 27) that shifts in the axial direction of the roll together with the upper work roll 610A and receives the load from the roll is provided on the operation side of the axial end of the upper work roll 610A among the rolls, and these bearings 610A2 are supported by a top work roll bearing box 612A on the work side. Similarly, a bearing 610A2 (see Fig. 27) that shifts in the axial direction of the roll together with the upper work roll 610A and receives the load from the roll is provided on the drive side, and this bearing 610A2 is supported by a top work roll bearing box 612A on the drive side.

[0129] Similarly, the lower work roll 611A is provided with bearings 611A2 at its axial ends on both the drive side and the operation side, and these bearings are supported by lower work roll bearing boxes 613A on the operation side and drive side, respectively.

[0130] In this embodiment, the upper work roll 610A is configured so as to be shiftable in the roll axial direction by a shift cylinder 615 as shown in Fig. 27 via an upper work roll bearing housing 612A on the operation side. Similarly, the lower work roll 611A is configured so as to be shiftable in the roll axial direction by a shift cylinder 616 as shown in Fig. 27 via a lower work roll bearing housing 613A on the operation side.

[0131] 22 and 26, in the F6 stand 60A, on both the operation side and the drive side, the upper work roll bearing housing 612A is supported by two upper intermediate roll bending cylinders 650 provided in the axial direction of the roll of the exit side fixed member 602 and two upper intermediate roll bending cylinders 651 provided in the axial direction of the roll of the entry side fixed member 603. By appropriately driving these cylinders, a bending force is applied in the vertical direction to the bearing 610A2 of the upper work roll 610A.

[0132] Similarly, on both the operating side and the driving side, the lower work roll bearing box 613A is supported by a lower intermediate roll bending cylinder 652 provided on the exit side fixed member 602 and a lower intermediate roll bending cylinder 653 provided on the entry side fixed member 603, and by driving these cylinders appropriately, a bending force is applied vertically to the bearing of the lower work roll 611A.

[0133] These bending cylinders 650, 651, 652, and 653 apply roll balance forces to the work rolls 610A and 611A.

[0134] Furthermore, as shown in Figures 22 and 26, for the purpose of removing the backlash, the upper work roll bearing box backlash removing cylinder 660 and the upper large diameter work roll bearing box backlash removing cylinder 672 apply a horizontal force, specifically a pressing force in the rolling direction, to the upper work roll 610A through the liner (not shown) of the upper work roll bearing box 612A to press the bearing 610A2 against the housing 600.

[0135] Similarly, the lower work roll bearing box clearance taking cylinder 662 and the lower large diameter work roll bearing box clearance taking cylinder 674 apply a pressing force in the rolling direction to the lower work roll 611A through the liner of the lower work roll bearing box 613A, pressing the bearing 611A2 against the housing 600.

[0136] In the rolling mill of this embodiment, it is desirable to share a drive spindle for driving the large diameter work rolls 610A, 611A and for driving the intermediate rolls 620, 621 for driving the small diameter work rolls 610, 611, as shown in Figures 28 and 29.

[0137] 28, the drive spindle is connected to the intermediate rolls 620, 621 to drive the intermediate rolls 620, 621. By driving the intermediate rolls 620, 621 in this manner, the diameter of the drive spindle can be made larger than the diameter of the intermediate rolls 620, 621, so that a drive spindle with high strength can be used even if the intermediate rolls 620, 621 have a small diameter.

[0138] In particular, the rolling speed is increased in the latter stages of the finishing mill, and the number of rotations of the rolls is increased. If the diameter of the driving spindle can be increased, the natural frequency of the flexural vibration of the driving spindle can be increased, and even if the number of rotations of the rolls is increased, the natural frequency of the flexural vibration can be made greater than the number of rotations of the rolls, and resonance with the flexural vibration can be suppressed.

[0139] Also, as shown in Fig. 29, the drive spindle is connected to large diameter work rolls 610A, 611A, making it possible to drive the work rolls 610A, 611A. In the case of large diameter work rolls 610A, 611A, the diameter of the drive spindle can also be made large, and the load capacity is high. If there is a concern about slip between the rolls when driving the intermediate rolls 620, 621, driving the work rolls 610A, 611A makes it possible to perform rolling with a larger rolling torque Tr.

[0140] Here, when it is possible to switch between a four-high rolling mill with large diameter work rolls 610A, 611A and a six-high rolling mill with small diameter work rolls 610, 611 + intermediate rolls 620, 621, it is desirable to make the diameter Di2 of the intermediate rolls 620, 621 larger than the diameter Dw2 of the work rolls 610, 611.

[0141] The horizontal force acting on the intermediate rolls 620, 621 is larger than the horizontal force acting on the work rolls 610, 611. This is to avoid a problem in strength caused by the horizontal force, which causes the rolls to bend in the horizontal direction, and the initially set offset amount between the rolls to increase due to the deflection, which in turn causes the horizontal force to increase and the resultant force of the offset component force of the rolling load Pr and the horizontal force to act on the rolls.

[0142] Furthermore, during the transition period, the direction of the horizontal force changes and the rolls move in the rolling direction, causing localized slippage between the work rolls 610, 611 and the intermediate rolls 620, 621, resulting in damage to the rolls.

[0143] Therefore, it is desirable to make the diameter Di2 of the intermediate rolls 620, 621 larger than the diameter Dw2 of the work rolls 610, 611 to reduce the deflection of the intermediate rolls 620, 621.

[0144] 28 and 29 has a universal joint 760. In general work roll driving, the angle of the universal joint 760 changes in response to changes in the diameter of the work roll being used, but even when the universal joint 760 is shared between driving the large diameter work rolls 610A, 611A and driving the intermediate rolls 620, 621 of the small diameter work rolls 610, 611 as in this embodiment, the angle of the universal joint 760 is also changed.

[0145] The angle of the universal joint 760 is preferably 3° or less. If the distance between the two universal joints 760 is L1, then the relationship Di2max=2(2L1min×tan3°+Dw1min / 2−Dw2max) holds. Here, L1min is the minimum value that L1 can take.

[0146] If the diameter Di2 of the intermediate rolls 620, 621 is set so as not to exceed the maximum diameter Di2max that the intermediate rolls 620, 621 can have, the angle of the universal joint 760 between the spindle driving the large diameter work rolls 610A, 611A and the spindle driving the intermediate rolls 620, 621 when the small diameter work rolls 610, 611 are used can be kept within 3° without shifting the position of the anti-roll side of the driving spindle, and a simple drive unit 750 can be realized.

[0147] When the diameter Di2 of the intermediate rolls 620, 621 is set to exceed the maximum possible diameter Di2max of the intermediate rolls 620, 621, the angle of the universal joint 760 can be set to 3° or less by shifting the vertical position of the drive spindle on the side opposite to the roll. In this case, the structure of the drive device 750 becomes somewhat complicated, but the drive spindle can be shared.

[0148] The type of universal joint 760 is not limited to a cross pin type or a gear type.

[0149] The outside diameter of the roll shaft end is smaller than at least the inside diameter of the bearing so that the bearing housing and the bearing can be assembled together into the roll.

[0150] As shown in Figures 28 and 29, when the upper intermediate roll 620 and the lower intermediate roll 621 have a smaller diameter than the upper work roll 610A and the lower work roll 611A, the inner diameter of the roll shaft end of the upper intermediate roll 620 and the lower intermediate roll 621 is determined by the outer diameter of the roll shaft end of the upper intermediate roll 620 and the lower intermediate roll 621. Even if the outer diameter of the roll shaft end of the upper intermediate roll 620 and the lower intermediate roll 621 is made as large as possible, the outer diameter of the roll shaft end of the upper work roll 610A and the lower work roll 611A will be smaller than the inner diameter of the bearing of the upper and lower work rolls. Therefore, the rolling torque that can be transmitted when the work rolls are driven is restricted by the roll shaft end having low strength.

[0151] To solve this problem, in Fig. 31, the outer diameters of the roll shaft ends of the upper work roll 610A' and the lower work roll 611A' are made larger than those in Fig. 29, but within a range that is smaller than the inner diameter of the bearing. This makes it possible to increase the diameters of the universal joint 761, roll side coupling 761a, and drive device side coupling 761b connected to the drive device 751, and to increase the rolling torque that can be transmitted.

[0152] Figure 30 shows a case where the upper intermediate roll 620' and lower intermediate roll 621' have smaller diameters than the upper work roll 610A' and lower work roll 611A' in Figure 31, and the outer diameters of the roll shaft ends of the upper intermediate roll 620' and lower intermediate roll 621' are smaller than the outer diameters of the roll shaft ends of the upper work roll 610A' and lower work roll 611A'. However, in Figure 30, a removable gap filling member 800 is provided at the portion where the shaft ends of the upper intermediate roll 620' and lower intermediate roll 621' fit into the roll side coupling 761a, so that it can also be used as the universal joint 761 in Figure 31.

[0153] When driving the work rolls, the outer diameter of the roll-side coupling 761a of the universal joint 761 cannot be made larger than the diameter of the work roll barrel to avoid interference between above and below. On the other hand, when driving the intermediate rolls, the outer diameter of the roll-side coupling 761a of the universal joint 761 can be made larger than the diameter of the intermediate roll barrel, so the diameter of the intermediate roll barrel does not restrict the outer diameter of the roll-side coupling 761a of the universal joint 761.

[0154] The gap filling members 800 are attached to the roll shaft ends of the upper intermediate roll 620' and the lower intermediate roll 621' after the bearing housings and bearings are assembled together into the rolls. When switching from the rolling in FIG. 31 to the rolling in FIG. 30, the upper work roll 610A' and the lower work roll 611A' are pulled out of the rolling mill, and then the upper intermediate roll 620', the lower intermediate roll 621', the upper work roll 610, and the lower work roll 611, to which the gap filling members 800 are attached, are inserted into the rolling mill. It is possible to switch between driving the large-diameter upper work roll 610A' and the lower work roll 611A' and driving the small-diameter upper intermediate roll 620' and the lower intermediate roll 621' without changing the roll side coupling 761a.

[0155] Here, it is also possible to attach the void filling member 800 to the roll side coupling 761a side, and the same effect is obtained. If it is relatively easy to attach the void filling member 800 to the roll side coupling 761a side inside the rolling mill, this method can be selected.

[0156] When switching from rolling in Figure 30 to rolling in Figure 31, the upper intermediate roll 620', lower intermediate roll 621', upper work roll 610, and lower work roll 611 are pulled out of the rolling mill, and then, if the gap filling member 800 is attached to the roll side coupling 761a, the gap filling member 800 is removed before the upper work roll 610A' and lower work roll 611A' are inserted into the rolling mill.

[0157] The control device 80 is a device that controls the operation of each device in the rolling facilities 1, 1A, 1B, and 1C, and is preferably composed of a computer equipped with a CPU, a storage medium, a display device, and the like.

[0158] For example, the control device 80 controls the operation of a hydraulic device 90 to supply and discharge pressure oil to each of the bending cylinders and the like described above, thereby controlling the drive of each of these cylinders.

[0159] In addition, during direct drive, the control device 80 controls the drive of the upper work roll 610A and the lower work roll 611A, and during indirect drive, controls the drive of the upper intermediate roll 620 and the lower intermediate roll 621 so as to supply a drive torque Tr of the upper intermediate roll 620 and the lower intermediate roll 621 to the upper work roll 610 and the lower work roll 611 to drive the upper work roll 610 and the lower work roll 611.

[0160] As shown in FIG. 16, the control device 80 has a first acquisition unit 80a, a first calculation unit 80b, a second calculation unit 80c, a traction coefficient calculation unit 80d, a second acquisition unit 80e, a process comparison unit 80f, a setting unit 80g, a memory unit 80h, and the like.

[0161] The first acquisition unit 80a is a part that acquires the mill longitudinal stiffness coefficient K of the rolling mill, and preferably is a part that acquires the latest value of the mill longitudinal stiffness coefficient K of the corresponding rolling mill that is pre-recorded in the memory unit 80h or the like.

[0162] The first calculation unit 80b is a part that uses the acquired mill vertical stiffness coefficient K and rolling conditions to calculate the kiss roll load Pk of the upper work roll 610 and the lower work roll 611 at the angle θx of the upper work roll 610 and the lower work roll 611 at the tip position of the rolled material 5 from the start of biting of the rolled material 5 to the completion of biting.

[0163] The second calculation unit 80c is a part that calculates the rolling load Pr and the driving torque Tr with respect to the angle θx of the upper work roll 610 and the lower work roll 611 at the tip position of the rolled material 5 from the start of biting of the rolled material 5 to the completion of biting.

[0164] The traction coefficient calculation unit 80d is a part that calculates the traction coefficient μrt between the upper work roll 610, the lower work roll 611 and the upper intermediate roll 620, and the lower intermediate roll 621 in relation to the angle θx of the upper work roll 610 and the lower work roll 611 at the tip position, from the kiss roll load Pk, the rolling load Pr, and the total P of the hypothetical work roll balance force Pb from the start of biting the rolled material 5 to the end of biting, and the drive torque Tr, when a hypothetical work roll balance force Pb is applied.

[0165] The second obtaining unit 80e is a part that obtains the allowable value μrtcr of the traction coefficient μrt of the rolling mill.

[0166] Here, the allowable value μrtcr is the maximum allowable value of the traction coefficient μrt, and when a traction coefficient of this value or more is required, a large slippage occurs between the intermediate rolls and the work rolls, making rolling difficult.

[0167] The step comparison section 80f is a section that compares the maximum value μrtmax of the traction coefficient μrt calculated by the traction coefficient calculation section 80d with the allowable value μrtcr of the traction coefficient μrt.

[0168] The setting unit 80g is a part that, when the allowable value μrtcr of the traction coefficient μrt becomes equal to or greater than the maximum value μrtmax of the traction coefficient μrt, resets the work roll balance force at the start of the bite of the rolled material 5 to a value equal to or greater than the limit work roll balance force Pbcr1cr required when the traction coefficient μrt indicates the maximum value μrtmax of the traction coefficient μrt, and equal to or less than the limit work roll balance force Pbcr2 due to the strength constraints of the rolling mill.

[0169] The storage unit 80h is a storage device of the computer constituting the control device 80, and is preferably configured with an SSD or HDD.

[0170] The control of the operation of each device by the control device 80 and the control of the operation of the first acquisition unit 80a, the first calculation unit 80b, the second calculation unit 80c, the traction coefficient calculation unit 80d, the second acquisition unit 80e, the process comparison unit 80f, the setting unit 80g, etc. are executed based on various programs recorded in the memory unit 80h.

[0171] The control processes for the operations executed by the control device 80 may be integrated into one program, or may be divided into multiple programs, or may be a combination of these. Also, some or all of the programs may be realized by dedicated hardware, or may be modularized.

[0172] Next, a method for setting the work roll balance force of the rolling mill and a method for switching the operation of the rolling mill according to this embodiment will be described with reference to Fig. 32. Fig. 32 is a flowchart showing a flow for determining the set work roll balance force Pbact.

[0173] First, as shown in Fig. 32, the mill longitudinal stiffness coefficient K is continuously monitored to identify the mill longitudinal stiffness coefficient K in the rolling (step S101). This step S101 corresponds to a step of obtaining the mill longitudinal stiffness coefficient K.

[0174] More specifically, calculation may be performed to set the work roll balance force, or existing values ​​(such as the value at the time of delivery of the rolling mill, or the value after a certain number of years of operation) recorded in the memory unit 80h or the like may be read in. The existing values ​​may be values ​​measured and calculated at predetermined intervals, such as at the time of delivery of the rolling mill, one year later, two years later, etc., by the manufacturer that actually operates the rolling mill for the purpose of managing the rolling mill, and these values ​​may be used as they are.

[0175] Here, in the step of obtaining the mill longitudinal stiffness coefficient K, if the mill longitudinal stiffness coefficient K has been obtained twice or more for the rolling mill, it is preferable to use the latest mill longitudinal stiffness coefficient K.

[0176] Next, the rolling load Pr and the rolling torque Tr are calculated from the rolling conditions (step S102). This step S102 corresponds to the step of determining the rolling load Pr and the rolling torque Tr.

[0177] In this process, the moment of biting refers to the start of biting just before the start, and the completion of biting refers to the time when the tip position angle θx = 0. Since there may be cases where the kiss roll load Pk changes before and just before the start, it is sufficient to have data on the kiss roll load Pk from at least the moment of biting, and there is little need to use the kiss roll load Pk "before the start" when the rolled material is separated from the rolls, so it is preferable to find the rolling load Pr and rolling torque Tr from the start of biting.

[0178] Here, the rolling conditions refer to information such as the inlet thickness, outlet thickness, rolled material width, and rolled material hardness of the rolling mill, and the rolling torque is determined using a known calculation method.

[0179] Next, the rolling load Pr at the strip tip position in the roll bite and the kiss roll load are calculated using the mill vertical stiffness coefficient K (step S103). This step S103 corresponds to the step of determining the kiss roll load Pk.

[0180] Next, the maximum value μrtmax when the work roll balance force Pb=the upper limit work roll balance force Pbcr2 is assumed, and the maximum value μrtmax is compared with the allowable value μrtcr (step S104). This process corresponds to the process of determining the traction coefficient μrt and the maximum value μrtmax of the traction coefficient, the process of obtaining the allowable value μrtcr of the traction coefficient μrt of the rolling mill, and the process of comparing the maximum value μrtmax with the allowable value μrtcr.

[0181] Here, a hypothetical work roll balance force is applied, for example, the work roll balance force Pb = 0,350,700 [kN / roll]. Since it is difficult to measure the allowable value μrtcr of the traction coefficient, a constant such as 0.15 is used when water is used as the coolant, and 0.10 is used when oil is used.

[0182] In addition, in step S104, when the kiss roll load Pk becomes 0 from the start of biting the rolled material 5 to the completion of biting, that is, the traction coefficient μrt of the maximum value shown in Figures 10, 11, and 13, is set to the maximum value μrtmax of the traction coefficient μrt.

[0183] Next, when it is determined in the previous step S104 that the maximum value μrtmax≦the allowable value μrtcr, the work roll balance force Pb that gives the maximum value μrtmax is obtained, and this work roll balance force Pb is set as the lower limit work roll balance force Pbcr1 (step S105).

[0184] Here, the lower limit work roll balance force Pbcr1 is the lower limit of the work roll balance force Pb to prevent slippage. If the work roll balance force Pb is equal to or greater than the lower limit work roll balance force Pbcr1, the maximum value μrtmax does not exceed the allowable value μrtcr, so that rolling can be continued without significant slippage occurring between the intermediate rolls and the work rolls.

[0185] Thereafter, the set work roll balance force Pbact is set to a value in the range that satisfies the condition of lower limit work roll balance force Pbcr1≦set work roll balance force Pbact≦upper limit work roll balance force Pbcr2 (step S106). This step S106 corresponds to a process of resetting the work roll balance force at the start of biting of the rolled material 5 to a value equal to or greater than the work roll balance force Pbcr1 when the traction coefficient μrt has the maximum value μrtmax of the traction coefficient μrt and equal to or less than the limit work roll balance force Pbcr2 due to the constraints of the strength of the rolling mill when the allowable value μrtcr of the traction coefficient μrt is equal to or greater than the maximum value μrtmax of the traction coefficient μrt (i.e., the indirect drive method is selected).

[0186] Here, the upper limit work roll balance force Pbcr2 is the limit work roll balance force due to the constraints of the strength of the rolling mill, and is the maximum value of the work roll balance force Pb that cannot be increased any further in order to avoid damage to the parts. This upper limit work roll balance force Pbcr2 is basically determined by the work roll bearing strength and the work roll neck strength.

[0187] The set work roll balance force Pbact is the value of the work roll balance force Pb that is actually set during rolling, and is an arbitrary set value between the lower limit work roll balance force Pbcr1 and the upper limit work roll balance force Pbcr2, and other factors are also taken into consideration.

[0188] On the other hand, if it is determined in the previous step S104 that the maximum value μrtmax is greater than the allowable value μrtcr, the large diameter work rolls 610A, 611A are used, and rolling is switched to driving the work rolls 610A, 611A (step S107).

[0189] In the method of operating the rolling mill, the work roll balance force is set according to each flow shown in Fig. 32 above, and then the operation of the rolling mill is started after the work roll balance force is set. Thereafter, before the rolling material 5 is bitten between the upper work roll 610 and the lower work roll 611, the control device 80 presses the bearings 610A1, 611A1 of the upper work roll 610 and the lower work roll 611 against the housing 600 of the rolling mill. Note that the timing to start pressing the bearings 610A1, 611A1 of the upper work roll 610 and the lower work roll 611 against the housing 600 of the rolling mill is preferably before the mill idles (before (a) in Fig. 2).

[0190] Next, the effects of this embodiment will be described.

[0191] According to the method for setting the work roll balance force of the rolling mill of this embodiment described above, the work roll balance force Pb is set taking into consideration the kiss roll load Pk, so that even if kiss rolls occur during biting, slip between the rolls can be prevented without damaging components such as bearings.

[0192] Furthermore, in the rolling mill operation switching method, when the allowable value μrtcr of the traction coefficient μrt is determined to be less than the maximum value μrtmax of the traction coefficient μrt, the direct drive method is selected, and when the allowable value μrtcr of the traction coefficient μrt is determined to be equal to or greater than the maximum value μrtmax of the traction coefficient μrt, the indirect drive method is selected. This allows the work roll balance force Pb to be set taking the kiss roll load into consideration, thereby preventing slippage between rolls without damaging components such as bearings. In addition, when the traction coefficient is too large, the problem of torque transmission can be solved by switching to direct drive instead of indirect drive. Note that, regardless of whether μrtmax is larger or smaller than μrtcr, if rolling is possible with large diameter work rolls, it is possible to select the large diameter work roll direct drive method.

[0193] In addition, in the step of obtaining the mill longitudinal stiffness coefficient K, if the mill longitudinal stiffness coefficient K has been obtained twice or more for the rolling mill, the latest mill longitudinal stiffness coefficient K is used. As the rolling mill is used, the mill longitudinal stiffness coefficient K becomes smaller, which tends to increase the kiss roll load. Therefore, by using the latest value of the mill longitudinal stiffness coefficient K, which has the smallest effect on the mill longitudinal stiffness coefficient K due to changes over time, the kiss roll load and the work roll balance force can be obtained with high accuracy.

[0194] Furthermore, in the process of obtaining the traction coefficient μrt, the traction coefficient μrt when the kiss roll load Pk becomes 0 from the start of biting the rolled material 5 to the end of biting is set as the maximum value μrtmax of the traction coefficient μrt. Since the traction coefficient μrt=F / P=F / (Pr+Pk+Pb), the traction coefficient μrt when Pk=0 is set as the maximum value μrtmax, which simplifies the derivation of the maximum value μrtmax.

[0195] The method of operating the rolling mill includes a step of setting the work roll balance force, and then starting the operation of the rolling mill after setting the work roll balance force, and a step of pressing the bearings 610A1, 611A1 of the upper work roll 610 and the lower work roll 611 against the housing 600 of the rolling mill before the rolled material 5 is bitten between the upper work roll 610 and the lower work roll 611. If a kiss roll load acts in a state where the axis of the roll is inclined with respect to the original axial direction, a thrust force is generated, for example, between the upper work roll 610 and the upper intermediate roll 620, between the upper and lower work rolls 610, 611, etc., and in the case of small diameter work rolls, bearings, etc. may be damaged. However, by pressing the bearings 610A1, 611A1 of the work rolls 610, 611 against the housing 600 in this way and not inclining the axis, it is possible to make it difficult for a thrust force to be generated, and it is possible to make it difficult for the bearings, etc. to be damaged even if a kiss roll load is generated between the work rolls 610, 611.

[0196] <Other> The present invention is not limited to the above-mentioned embodiment, and various modifications and applications are possible. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to having all of the described configurations. [Explanation of symbols]

[0197] 1, 1A, 1B, 1C...Rolling equipment 5...Rolled material 10...F1 stand (rolling mill) 20...F2 stand (rolling mill) 30...F3 stand (rolling mill) 40...F4 stand (rolling mill) 50,50C…F5 stand (rolling mill) 60, 60A, 60B, 60C...F6 stand (rolling mill) 80...Control device 80a…1st acquisition part 80b…1st calculation section 80c…Second calculation section 80d…Traction coefficient calculation section 80e…Second acquisition part 80f…Process comparison section 80g…Setting section 80h…Storage section 90...Hydraulic system 600…Housing 602…Outlet side fixing member 603...Inlet side fixing member 610...Upper work roll (first work roll) 610A, 610A': Upper work roll (second work roll) 610A1, 610A2, 611A1, 611A2, 620A1, 621A1...Bearings 611...Lower work roll (first work roll) 611A, 611A': Lower work roll (second work roll) 612, 612A...Upper work roll bearing box 613,613A…Lower work roll bearing box 615, 616, 617, 618...Shift cylinder 620,620'...Upper middle roll 621,621'...Lower middle roll 622...Upper intermediate roll bearing box 623...Lower intermediate roll bearing housing 630…Upper backup roll 631…Lower backup roll 632...Upper backup roll bearing box 633...Lower backup roll bearing box 640, 641...Upper work roll bending cylinder 644, 645...Lower work roll bending cylinder 650, 651...Upper intermediate roll bending cylinder 652, 653...Lower intermediate roll bending cylinder 660...Upper work roll bearing housing clearance cylinder (pressing device) 662...Lower work roll bearing housing backlash removal cylinder (pressing device) 671...Upper intermediate roll bearing housing backlash removal cylinder (pressing device) 672...Upper intermediate roll bearing housing backlash removing cylinder (Upper large diameter work roll bearing housing backlash removing cylinder, pressing device) 673... Lower intermediate roll bearing housing clearance cylinder (pressing device) 674...Lower intermediate roll bearing housing backlash removing cylinder (Lower large diameter work roll bearing housing backlash removing cylinder, pressing device) 680...Upper backup roll bearing housing clearance cylinder 682...Lower backup roll bearing housing backlash removal cylinder 750,751...Drive unit 760,761...Universal joint 761a...Roll side coupling 761b...Driver side coupling 800…Void filling material

Claims

1. The rolling mill comprises a pair of upper and lower work rolls and one or more pairs of upper and lower rolls provided on the opposite side of the work rolls to the rolled material, A method for setting a work roll balance force of a rolling mill that drives the work rolls by supplying a rolling torque Tr from the rolls to the work rolls, comprising the steps of: Obtaining a mill longitudinal stiffness coefficient K of the rolling mill; A step of calculating a kiss roll load Pk of the work roll with respect to a work roll angle θx at a tip position of the rolled material from a start time of biting of the rolled material to a completion time of biting by using the obtained mill vertical stiffness coefficient K and rolling conditions; A step of determining the rolling load Pr and the rolling torque Tr with respect to the work roll angle θx at the tip position of the rolled material from the start of biting of the rolled material to the completion of biting; a step of determining a traction coefficient μ between the work roll and the roll with respect to the work roll angle θ at the tip position and a maximum value μ of the traction coefficient from the kiss roll load Pk, the rolling load Pr, and the sum P of the hypothetical work roll balance force Pb from the start of biting the rolled material to the completion of biting, and the rolling torque Tr, in a state where a hypothetical work roll balance force Pb is applied; obtaining an allowable value μ of the traction coefficient μ of the rolling mill; a step of comparing the maximum value μ obtained in the step of obtaining the traction coefficient μ with the allowable value μ; When the allowable value μ is equal to or greater than the maximum value μ , the work roll balance force at the start of biting of the rolled material is reset to a value equal to or greater than the work roll balance force when the traction coefficient μ indicates the maximum value μ , and equal to or less than the work roll balance force that is the limit due to the strength constraints of the rolling mill. A method for setting a work roll balance force.

2. 2. The method for setting a work roll balance force according to claim 1, In the step of obtaining the mill longitudinal stiffness coefficient K, when the mill longitudinal stiffness coefficient K has been obtained twice or more for the rolling mill, the latest mill longitudinal stiffness coefficient K is used. A method for setting a work roll balance force.

3. 3. The method for setting a work roll balance force according to claim 1 or 2, In the step of obtaining the traction coefficient μrt, the traction coefficient μrt when the kiss roll load Pk becomes 0 from the start of biting the rolled material to the completion of biting is set as the maximum value μrtmax. A method for setting a work roll balance force.

4. A step of setting the work roll balance force by using the work roll balance force setting method according to any one of claims 1 to 3; starting operation of the rolling mill after setting the work roll balance force; and pressing a bearing of each of the work rolls against a housing of the rolling mill before the rolled material is engaged with the work rolls. A method for operating a rolling mill comprising the steps of:

5. A step of setting the work roll balance force by using the work roll balance force setting method according to any one of claims 1 to 3; determining whether the allowable value μ is equal to or greater than the maximum value μ; When it is determined that the allowable value μ is less than the maximum value μ, a direct drive method is selected for driving a pair of upper and lower second work rolls having a diameter larger than that of the work rolls, and when it is determined that the allowable value μ is equal to or greater than the maximum value μ, an indirect drive method is selected for supplying a rolling torque Tr from the rolls to the work rolls to drive the work rolls. A method for switching between rolling mill operations.

6. A rolling mill comprising a pair of upper and lower work rolls, one or more pairs of upper and lower rolls provided on the opposite side of the work rolls to a rolled material, and a control device that controls the drive of the rolls so as to supply a rolling torque Tr from the rolls to the work rolls to drive the work rolls, The control device includes: A first acquisition unit that acquires a mill vertical stiffness coefficient K of the rolling mill; A first calculation unit that calculates a kiss roll load Pk of the work roll with respect to a work roll angle θx at a tip position of the rolled material from a start time of biting of the rolled material to a completion time of biting by using the acquired mill vertical stiffness coefficient K and rolling conditions; A second calculation unit that calculates the rolling load Pr and the rolling torque Tr with respect to the work roll angle θx at the tip position of the rolled material from the start of biting of the rolled material to the completion of biting; a traction coefficient calculation unit which calculates a traction coefficient μ between the work roll and the roll with respect to the work roll angle θ at the tip position and a maximum value μ of the traction coefficient from the kiss roll load Pk, the rolling load Pr, and the sum P of the hypothetical work roll balance force Pb from the start of biting the rolled material to the end of biting, and the rolling torque Tr, in a state in which an assumed work roll balance force Pb is applied; A second acquisition unit that acquires an allowable value μ of the traction coefficient μ of the rolling mill; a process comparison unit that compares the maximum value μ obtained by the traction coefficient calculation unit with the allowable value μ; and a setting unit that resets the work roll balance force at the start of biting of the rolled material to a value equal to or greater than the work roll balance force when the traction coefficient μ indicates the maximum value μ and equal to or less than the work roll balance force that is the limit due to the strength constraints of the rolling mill, when the allowable value μ is equal to or greater than the maximum value μ. A rolling mill characterized by:

7. 7. The rolling mill according to claim 6, a bearing supporting each of the work rolls; a housing having the work roll and the bearing therein; a pressing device that presses the bearing against the housing, The control device presses the bearing against the housing before the rolled material is bitten by the work roll. A rolling mill characterized by:

8. In the rolling mill according to claim 6 or 7, The control device includes: a determination unit that determines whether the allowable value μ is equal to or greater than the maximum value μ; a selection unit which selects a direct drive method for driving a pair of upper and lower second work rolls having a diameter larger than that of the work rolls when the allowable value μ is determined to be less than the maximum value μ, and which selects an indirect drive method for supplying a rolling torque Tr from the rolls to the work rolls to drive the work rolls when the allowable value μ is determined to be equal to or greater than the maximum value μ. A rolling mill characterized by:

9. 9. The rolling mill according to claim 8, a roll-side coupling of a universal joint connected to a shaft end of the roll or the second work roll; and a shaft end portion of the roll having an outer diameter smaller than that of the shaft end portion of the second work roll, A gap filling member is provided which is detachably configured to be attached to a portion where the roll-side coupling and the shaft end portion of the roll are fitted together. A rolling mill characterized by:

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