Patent Application
20240416402
The present invention relates to a work roll balance force setting method and a rolling mill running method, a rolling mill running switching method, and a rolling mill.
As an example of a hot rolling facility that prevents biting failure of strip materials by small-diameter work rolls, Japanese Patent No. 3067589 describes a technology like the one below. An entry-side strip passing guide and an exit-side strip passing guide that guide a hot-rolled strip material to work rolls are arranged on the entry side and exit side of a rolling mill. Since the advancing hot-rolled strip material warps upward due to reaction force, by holding down the strip material by using hold-down rolls that can be lifted and lowered so as to prevent the strip material from floating, the strip material gets to have pressing force which is larger than the reaction force received from the work rolls, and the work rolls surely bite the hot-rolled strip material. In addition, in order to transfer necessary torque to the work rolls, roll balance force or roll bending force of the work rolls is controlled when the rolled material is bitten, and inter-roll contact force between the work rolls and intermediate rolls is increased.
A strip can be rolled to have a thinner strip thickness effectively by using work rolls with a smaller radius, but this accompanies a decline in the load capacity of a drive spindle of the work rolls. In view of this, intermediate roll driving or backup roll driving that uses a drive spindle of intermediate rolls or backup rolls with higher load capacity is adopted in some cases.
Here, in a case of intermediate roll driving or backup roll driving, since rolling torque is transferred to work rolls at inter-roll contact portions, if a significant slide occurs between rolls, it becomes not possible to transfer necessary rolling torque.
For example, Japanese Patent No. 3067589 discloses that biting failure is prevented by increasing roll balance force or bending force as much as possible only to the extent allowed by the strength of roll necks at the time of biting.
However, there is room for improvement in the technology described above because it does not take into consideration the fact that roll balance force becomes excessive in a case where kiss roll occurs when rolling is performed to attain a thin strip thickness.
The present invention provides a work roll balance force setting method and a rolling mill running method, a rolling mill running switching method, and a rolling mill that enable suppression of an inter-roll slide without damaging components such as bearings even if kiss roll occurs at the time of biting.
The present invention includes a plurality of means for solving the problems described above, and an example thereof is a work roll balance force setting method of a rolling mill that includes a pair of upper and lower work rolls, and one or more pairs of upper and lower rolls that are provided on sides of the work rolls that are opposite to a rolled material, the rolling mill driving the work rolls by supplying rolling torque Tr from the rolls to the work rolls, the work roll balance force setting method including the steps of: obtaining a mill longitudinal rigidity coefficient K of the rolling mill; determining a kiss roll load Pk of the work rolls in relation to a work roll angle θx of a tip position of the rolled material between a start of biting of the rolled material and completion of the biting, the kiss roll load Pk being determined by using the obtained mill longitudinal rigidity coefficient K and a rolling condition; determining a rolling load Pr and the rolling torque Tr in relation to the work roll angle θx of the tip position of the rolled material between a start of biting of the rolled material and completion of the biting; determining a traction coefficient μrt between the work rolls and the rolls, and a maximum value μrtmax of the traction coefficient in relation to the work roll angle θx of the tip position in a state in which hypothetical work roll balance force Pb is applied, the traction coefficient μrt between the work rolls and the rolls, and the maximum value μrtmax of the traction coefficient being determined from a sum P of the kiss roll load Pk, the rolling load Pr, and the hypothetical work roll balance force Pb, and the rolling torque Tr between a start of biting of the rolled material and completion of the biting; obtaining a tolerated value μrter of the traction coefficient μrt of the rolling mill; comparing the maximum value μrtmax determined at the step of determining the traction coefficient μrt with the tolerated value μrter; and resetting work roll balance force at a start of biting of the rolled material to a value which is equal to or larger than the work roll balance force that is required when the traction coefficient μrt assumes the maximum value μrtmax, and equal to or smaller than the work roll balance force that is a limit based on a constraint in terms of strength of the rolling mill, when the tolerated value μrter is equal to or larger than the maximum value μrtmax.
According to the present invention, it is possible to suppress an inter-roll slide without damaging components such as bearings even if kiss roll occurs at the time of biting. Problems, configurations, and advantages other than those described above are made clear by the following explanation of an embodiment.
An embodiment of a work roll balance force setting method, and a rolling mill running method, a rolling mill running switching method, and a rolling mill according to the present invention is explained by using
Hereinafter, identical or corresponding constituent elements in the figures used in the present specification are given identical or similar reference characters, and repetitive explanations about these constituent elements are omitted in some cases.
First, the background that has led to the configurations of the work roll balance force setting method and the rolling mill running method, the rolling mill running switching method, and the rolling mill in the present invention is explained by using
At the moment when Δt1 has elapsed, and the rolling torque Tr has risen, applied spindle torque is only Ts yet, and thus an amount of torque Tr1 required in addition to the rolling torque Tr is supplied by a change in the inertial force of a roll. Mainly, an inertial change that accompanies slight deceleration of a backup roll supplies the amount of torque Tr1 required in addition to the rolling torque Tr.
Thereafter, at the moment when Δt2 has elapsed, the largest spindle torque is applied. At this time, torque which is Tr2 larger than the rolling torque Tr is applied onto the spindle. Tr2 and a change in the inertial force of the roll balance out, and mainly Tr2 and an inertial change that accompanies slight acceleration of the backup roll balance out.
In
In addition, it is assumed in
As depicted in (a) in
As depicted in
In addition, in a case of backup roll driving, if a kiss roll load is applied, the sum Fit of horizontal force applied onto the intermediate roll during mill idle running before biting becomes −1.4Fr, which is a little large value. Note that at the timings of Tr1 and Tr2, the sum Fbt of horizontal force applied onto the backup roll, the sum Fit of horizontal force applied onto the intermediate roll, and the sum Fwt of horizontal force applied onto the work roll become small.
In contrast to this, in a case of intermediate roll driving, the sum Fit of horizontal force applied onto the intermediate roll when Tr2 is applied includes horizontal force of −2Fr which is half the horizontal force applied in a case of work roll driving. In addition, the sum Fwt of horizontal force applied onto the work roll both when Tr1 is applied and when Tr2 is applied is small as compared to that in a case of work roll driving.
Here, features of the torque amplification factor are explained. The torque amplification factor is expressed as (Tr2+Tr)/Tr. The larger the rolling torque Tr is, the smaller the torque amplification factor tends to be. In addition, the maximum value of peak torque tends to be generated at the time of rated torque, and is (torque amplification factor)×(rated torque). In this case, the torque amplification factor at the time of the rated torque is approximately 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 is approximately a value of 2.0 to 4.0. Here, the rated torque means rolling torque that is generated when output power of a drive motor is 100%.
According to “KAWASAKI STEEL TECHNICAL REPORT Vol. 33 (2001) No. 1, P. 37-42, Analysis of Unsteady Load Mechanism in Strip Rolling Processes and Its Control in Commercial Line,” when a roll receives horizontal force F at its roll body section, and a bearing housing of the roll collides with a housing, resultant force Pt that is applied to the colliding section in the rolling direction is expressed by Pt=(horizontal force F)+(impact force P) (=(2KhFδ)0.5). Here, Kh is an elasticity coefficient of deformation of the housing in the rolling direction, and δ is a distance over which the roll bearing housing moves during the application of the horizontal force F, and is equivalent to the distance between the roll bearing housing and the housing. It has been reported that when F=80 tons, P=220 to 280 tons, and Pt=300 to 360=(3.8 to 4.5)×F, and when F=20 tons, P=90 to 100 tons, and thus Pt=110 to 120=(5.5 to 6.0)×F.
When the roll moves in the rolling direction, and the bearing housing collides with the housing, Pt inevitably becomes a large value which is 3.8 to 6.0 times larger than F, although this depends on the gap between the housing and the bearing housing.
An anti-backlash cylinder can remove the gap between the housing and the bearing housing, and thus can reduce P, and this provides an advantage of making Pt close to F.
Note that since there are a radial gap in a bearing itself and a slight gap between the roll axis and the internal diameter in the bearing inside the bearing, slight impact force is applied even in a case where the bearing housing does not move.
Next, the traction coefficient μrt between an intermediate roll and a work roll in a case of intermediate roll driving is explained.
As depicted in
Here, the traction coefficient μrt means a required coefficient of friction between the work roll and the intermediate roll, and a small required coefficient of friction means making a significant slide unlikely to occur. Since the traction coefficient μrt is represented as F/P, if P is large, the traction coefficient μrt becomes small. When there is kiss roll, P becomes large by an amount corresponding to the kiss roll load Pk as compared to when there is not kiss roll, and thus the traction coefficient μrt becomes small.
In
Typically, the roll gap is narrowed in advance by an amount corresponding to elastic deformation caused by the rolling load Pr relative to a desired strip thickness before a strip passes therethrough. Then, by biting the strip, the roll load is generated, the roll gap is enlarged and the desired strip thickness can be attained.
Pr is the rolling load, K is the spring constant of the rolling mill, and hereinafter is a mill longitudinal rigidity coefficient K, and R is the work roll radius.
Pr/K is equivalent to an amount to be narrowed, and is the amount corresponding to elastic deformation caused by the rolling load Pr. Here, when the maximum rolling reduction becomes negative inevitably, this means that the upper and lower work rolls have come into contact before the strip passes therethrough, and this state is expressed as kiss roll. The load that is applied between the upper and lower work rolls at the time of kiss roll is defined as a kiss roll load.
If the strip thickness is h, the roll gap before rolling is hog, and M is the coefficient of plasticity, the elastic characteristic curve, when approximately represented by a straight line, can be represented as Pr=K((exit-side strip thickness ho)−hog), and the plasticity characteristic curve of a material, when approximately represented by a straight line, can be represented as Pr=M(ho−(entry-side strip thickness hi)).
Here, the roll gap hog before rolling represents a value obtained by subtracting an elastic deformation amount of the rolling mill that is observed when the strip is pressed further and the kiss roll load Pk is applied, from an amount in a state where the upper and lower work rolls just started contacting, the kiss roll load Pk is 0 yet, and an elastic deformation is not generated. Note that although the upper and lower work rolls are elastically deformed, and their axial centers have come close to each other, the gap between the upper and lower work rolls remains 0 (the gap hoa between the upper and lower work rolls at the time of biting is 0), and is not a negative value.
As depicted in
In contrast to this, as depicted in
As depicted in
In addition, as depicted in
In this manner, as the mill longitudinal rigidity coefficient K changes, the state of kiss roll before the start of rolling in certain rolling changes. That is, the traction coefficient μrt (a required coefficient of inter-roll friction) changes depending on the work roll balance force Pb and the state of kiss roll before the start of rolling that changes depending on the value of the mill longitudinal rigidity coefficient K.
In
As depicted in
In addition, whereas the traction coefficient μrt changes in the process after the strip tip starts being bitten until the strip advances to the work roll exit side, the maximum value μrtmax of the traction coefficient μrt when the strip tip is in the roll bite is approximately 0.070 when the mill longitudinal rigidity coefficient K is 6000 [kN/mm], approximately 0.060 when the mill longitudinal rigidity coefficient K is 4000 [kN/mm], and approximately 0.060 when the mill longitudinal rigidity coefficient K is 3000 [kN/mm].
Then, whereas
As depicted in
In addition, when the mill longitudinal rigidity coefficient K is 4000 [kN/mm], there is a kiss roll load from the initial period of biting to θx which is approximately 0.080 [radian], and the traction coefficient μrt is kept low at a small value due to the presence of the kiss roll load. The maximum value μrtmax of the traction coefficient μrt is approximately 0.105, and is generated at θx which is approximately 0.080 [radian].
When the mill longitudinal rigidity coefficient K is 3000 [kN/mm], there is a kiss roll load from the initial period of biting to θx which is approximately 0.050 [radian], and the traction coefficient μrt is kept low at a small value due to the presence of the kiss roll load. The maximum value μrtmax of the traction coefficient μrt is approximately 0.090, and is generated at θx which is approximately 0.050 [radian].
In this manner, the range within which there is a kiss roll load widens as the mill longitudinal rigidity coefficient K decreases. In addition, it can be known that it is possible to make the maximum value μrtmax smaller depending on the work roll balance force Pb, and the influence of the work roll balance force Pb is more significant in a case where the exit-side strip thickness ho is 2.0 [mm] as compared to a case where exit-side strip thickness ho is 1.2 [mm].
As depicted in
Accordingly, it can be known that in the kiss roll load application range, the load P (≈Pr+Pk+Pb) between the intermediate roll and the work roll can be kept large even if the rolling load Pr is a relatively small value, and thus it becomes possible to lower the traction coefficient μrt.
As depicted in
In addition, when the mill longitudinal rigidity coefficient K is 4000 [kN/mm], θx which is approximately 0.155 [radian] is equivalent to the biting angle θi. There is a slight kiss roll load only in the initial period of biting, and the maximum value μrtmax of the traction coefficient μrt is approximately 0.150, and is generated at θx of biting which is approximately 0.151 [radian].
When the mill longitudinal rigidity coefficient K is 3000 [kN/mm], θx which is approximately 0.155 [radian] is equivalent to the biting angle. There is a kiss roll load until θx which is approximately 0.090 [radian], and the maximum value μrtmax of the traction coefficient μrt is approximately 0.110, and is generated at θx of biting which is approximately 0.090 [radian].
In addition, the maximum value μrtmax can be lowered depending on the work roll balance force Pb. In a case where the exit-side strip thickness ho is 3.0 [mm], there is greater influence of the work roll balance force Pb as compared to a case where the exit-side strip thickness ho is 1.2 [mm] or the exit-side strip thickness ho is 2.0 [mm].
When the exit-side strip thickness ho is thick, and is 3.0 [mm], it becomes possible to further lower the maximum value μrtmax by increasing the work roll balance force Pb. On the other hand, when the exit-side strip thickness ho is thin, and is 1.2 [mm], there is less influence of the work roll balance force Pb on the maximum value μrtmax.
In addition, the influence of the mill longitudinal rigidity coefficient K on the maximum value μrtmax is as follows. How the mill longitudinal rigidity coefficient K influences the maximum value μrtmax differs depending on the exit-side strip thickness ho. When the exit-side strip thickness ho is thin, and is 1.2 [mm], the maximum value μrtmax lowers as the mill longitudinal rigidity coefficient K lowers, but when the exit-side strip thickness ho is thick, and is 3.0 [mm], the relation between the mill longitudinal rigidity coefficient K and the maximum value μrtmax becomes complicated.
It can be known that both the work roll balance force Pb and the mill longitudinal rigidity coefficient K influence the maximum value μrtmax in this manner.
Here, a limit value μrter of the maximum value μrtmax differs depending on the state of two contacting rolls. It is considered that if the traction coefficient μrt is equal to or smaller than 0.10, a significant slide does not occur in most cases. Here, work roll balance force at the time of the maximum value μrtmax is defined as Pbcr1. If it is supposed that the limit value μrter of the maximum value μrtmax is 0.10, the work roll balance force when the maximum value μrtmax becomes the limit value μrter 0.10 is defined as Pbcr1cr. Pbcr1cr is treated as required limit work roll balance force. By making Pbcr1 equal to or larger than Pbcr1cr, the maximum value μrtmax becomes equal to or smaller than limit value μrter 0.10.
As depicted in
For example, whereas when the mill longitudinal rigidity coefficient K is 3000 [kN/mm], the limit work roll balance force Pbcr1cr is 0 [kN/roll] within the range of the exit-side strip thickness ho from 1.2 [mm] to 2.0 [mm], the limit work roll balance force Pbcr1cr increases suddenly when the exit-side strip thickness ho increases from 2.0 [mm] to 3.0 [mm].
In addition, whereas when the mill longitudinal rigidity coefficient K is 4000 [kN/mm], the limit work roll balance force Pbcr1cr gradually increases when the exit-side strip thickness ho changes from 1.2 [mm] to 2.0 [mm], the limit work roll balance force Pbcr1cr increases suddenly when the exit-side strip thickness ho increases from 2.0 [mm] to 3.0 [mm].
Furthermore, when the mill longitudinal rigidity coefficient K is 6000 [kN/mm], the limit work roll balance force Pbcr1cr remains constant when the exit-side strip thickness ho increases from 2.0 [mm] to 3.0 [mm].
Other than the limit work roll balance force Pbcr1cr, there is a limit of the work roll balance force. When the diameter of work rolls is small, the work roll balance force Pb cannot be increased due to the strength of the bearings or the roll necks, and thus there is limit work roll balance force Pbcr2 that is determined from a constraint in terms of the strength.
When the required limit work roll balance force Pbcr1cr is a value larger than the limit work roll balance force Pbcr2 that is determined from the constraint in terms of the strength, work roll driving by using work rolls with a relatively large diameter is adopted preferably. In contrast to this, when work rolls with a relatively large diameter are used, and the work rolls are driven directly, it is possible to transfer large rolling torque Tr. For example, when the exit-side strip thickness ho is equal to or larger than 3.0 [mm], the required limit work roll balance force Pbcr1cr increases when K is 3000 [kN/mm] or 4000 [kN/mm], but by adopting a condition of work roll driving in which work rolls with a relatively large diameter are used, there is not inter-roll transfer of the rolling torque Tr, and thus it is possible to eliminate constraints of the traction coefficient μrt and the maximum value μrtmax.
Here, the mill longitudinal rigidity coefficient K is explained. The mill longitudinal rigidity coefficient K is expressed as P/δ when the rolling load Pr is P, and an elastic deformation amount of each section of the rolling mill when P is applied is δ.
The mill longitudinal rigidity coefficient K is determined by the rigidity of a group of rolls, housings, rolling devices, bearing housings of rolls, and the like that are included in the rolling mill. The mill longitudinal rigidity coefficient K in the initial period of activation is a certain value, and as the use period of the rolling mill becomes longer, the mill longitudinal rigidity coefficient K lowers. It is considered that this is due to the fact that in the process of use, devices such as the housings, the rolling devices, and the bearing housings are worn, changes occur in the abutting condition of each section, and the mill longitudinal rigidity coefficient K lowers.
Repairs are carried out because, simultaneously with the lowering of the mill longitudinal rigidity coefficient K, differences between elastic deformation amounts on the work side and the drive side occur to make rolling unstable. Due to the repairs, the mill longitudinal rigidity coefficient K returns to a value close to the one in the initial period of activation. It should be noted however that the mill longitudinal rigidity coefficient K cannot recover to reach the one in the initial period of activation.
In this manner, the mill longitudinal rigidity coefficient K changes along with the use, the mill longitudinal rigidity coefficient K is monitored at predetermined intervals in order to continue stable rolling, and repairs are carried out depending on situations. Note that the mill longitudinal rigidity coefficient K cannot typically be adjustment.
In addition, different facilities have different mill longitudinal rigidity coefficients K. For example, the mill longitudinal rigidity coefficient K of a four-stage rolling mill is a value larger than the mill longitudinal rigidity coefficient K of a six-stage rolling mill. The larger the number of rolls is, the smaller the value of the mill longitudinal rigidity coefficient K is.
On the other hand, in a case of intermediate roll driving or backup roll driving, the maximum value μrtmax changes depending on the mill longitudinal rigidity coefficient K. In a case where the maximum value μrtmax inevitably exceeds and becomes larger than the limit value μrter, and a significant inter-roll slide occurs inevitably, it becomes not possible to continue rolling.
In view of this, the present inventors have conceived of the idea that by checking the mill longitudinal rigidity coefficient K, determining the required limit work roll balance force Pbcr1cr from the mill longitudinal rigidity coefficient K and rolling conditions, and setting the work roll balance force Pb to a value equal to or larger than Pbcr1cr to perform biting of a strip tip, it becomes possible to suppress a significant inter-roll slide. Thereby, the present inventors have conceived of the idea that even when work rolls have a small diameter, and the work rolls themselves cannot be used as driving rolls, rolling becomes possible by intermediate roll driving or backup roll driving.
The present invention has been made on the basis of such findings.
Next, an overview of a rolling facility including a rolling mill of the present embodiment is explained by using
A rolling facility 1 depicted in
Among these, each of the F1 stand 10, the F2 stand 20, the F3 stand 30, the F4 stand 40, the F5 stand 50, and the F6 stand 60, and a portion of the controller 80 that controls a corresponding one of the stands are equivalent to what is called a rolling mill in the present invention, but it is assumed here that the findings mentioned above are applied only to the F6 stand 60.
In
A rolling facility 1A depicted in
Furthermore, a rolling facility 1B depicted in
In a rolling facility 1C depicted in
Note that the numbers of stands included in the rolling facilities 1, 1A, 1B, and 1C are not limited to six like the one depicted in
In addition, whereas four-stage rolling mills in which only backup rolls mentioned below are used as one or more pairs of upper and lower rolls provided on sides of the work rolls that are opposite to a rolled material, or six-stage rolling mills in which intermediate rolls and backup rolls mentioned below are used as such one or more pairs of upper and lower rolls are explained in cases of
In addition, whereas hot rolling mills at a biting step are explained as examples in the embodiment, these are not the sole examples.
Next, an overview of the rolling mill according to the present invention is explained by using
Note that whereas the F6 stands 60 and 60A in the rolling facility 1 depicted in
In addition, whereas a case of intermediate roll driving is explained, the present invention can be applied also to backup roll driving.
As depicted in
The housings 600 include: a pair of an upper work roll 610 and a lower work roll 611; and a pair of an upper intermediate roll 620 and a lower intermediate roll 621 that are provided on sides of the upper work roll 610 and the lower work roll 611 that are opposite to the rolled material 5, and support the upper work roll 610 and the lower work roll 611 by contacting them. Furthermore, the housings 600 include a pair of an upper backup roll 630 and a lower backup roll 631 that support the upper intermediate roll 620 and the lower intermediate roll 621 by contacting them.
In contrast to this, the F6 stand 60A which is another example of the rolling mill according to the present embodiment depicted in
As depicted in
The work rolls 610 and 611 and the intermediate rolls 620 and 621, and the work rolls 610A and 611A can be replaced with each other. If equipment related the work rolls 610 and 611 and the intermediate rolls 620 and 621 in
In the F6 stand 60A depicted in
Thereby, it is made possible to switch between the small-diameter work rolls 610 and 611 and the large-diameter work rolls 610A and 611A without changing hydraulic rolling devices, passage line adjusting devices, or the like that are located on or under the upper backup roll 630 and the lower backup roll 631 because such replacement does not accompany significant positional shifts of the upper backup roll 630 and the lower backup roll 631 in the upward/downward direction.
Returning to
Similarly, the lower work roll 611 also has bearings 611A1 provided at its axial end sections on both the drive side and the work side, and these bearings are supported by the work-side and drive-side lower work roll bearing housings 613, respectively.
In the present embodiment, the upper work roll 610 is configured to be able to shift in the roll-axis direction due to a shift cylinder 615 like the one depicted in
In addition, as depicted in
Returning to
As depicted in
Similarly, on both the work side and the drive side, a lower work roll bending cylinder 644 provided to the exit-side fixation member 602, and a lower work roll bending cylinder 645 provided to the entry-side fixation member 603 support the lower work roll bearing housings 613, and by driving these cylinders as appropriate, bending force is applied to the bearings of the lower work roll 611 vertically.
Furthermore, as depicted in
Similarly, one lower-work-roll bearing-housing anti-backlash cylinder 662 that applies pressing force in the rolling direction to the lower work roll 611 via liners of the lower work roll bearing housings 613, and presses the bearings 611A1 against the housings 600 are provided to the entry-side fixation member 603.
These cylinders allow application of desired force to the upper work roll 610 and the like in a direction orthogonal to the roll-axis direction.
As depicted in
Regarding the upper intermediate roll 620, on both the work side and the drive side, an upper intermediate roll bending cylinder 650 provided to the exit-side fixation member 602, and an upper intermediate roll bending cylinder 651 provided to the entry-side fixation member 603 support the upper intermediate roll bearing housing 622, and by driving these cylinders as appropriate, bending force is applied to the bearings vertically toward the increase side.
Regarding the lower intermediate roll 621 also, on both the work side and the drive side, a lower intermediate roll bending cylinder 652 provided to the exit-side fixation member 602, and a lower intermediate roll bending cylinder 653 provided to the entry-side fixation member 603 support the lower intermediate roll bearing housing 623, and by driving these cylinders as appropriate, bending force is applied to the bearings vertically toward the increase side.
These bending cylinders 640, 641, 644, and 645 apply the work roll balance force Pb to the work rolls 610 and 611.
In addition, as depicted in
Similarly, a lower-intermediate-roll bearing-housing anti-backlash cylinder 674 is provided to the entry-side fixation member 603 such that the lower-intermediate-roll bearing-housing anti-backlash cylinder 674 applies horizontal force to the lower intermediate roll 621 via the lower intermediate roll bearing housing 623, and a lower-intermediate-roll bearing-housing anti-backlash cylinder 673 is provided to the exit-side fixation member 602 such that the lower-intermediate-roll bearing-housing anti-backlash cylinder 673 applies horizontal force to the lower intermediate roll 621 via the lower intermediate roll bearing housing 623.
Here, in indirect driving in which the intermediate rolls 620 and 621 are driven, the largest load is applied in the entry side direction when overtorque is applied to the intermediate rolls 620 and 621. At that time, the load is received on the entry-side housing 600, and overload according to the torque amplification factor is prevented from being applied to the exit-side upper-intermediate-roll bearing-housing anti-backlash cylinder 671 and lower-intermediate-roll bearing-housing anti-backlash cylinder 673. Whereas the upper-intermediate-roll bearing-housing anti-backlash cylinder 672 and the lower-intermediate-roll bearing-housing anti-backlash cylinder 674 are not used in
In addition, the upper-work-roll bearing-housing anti-backlash cylinder 660 and the lower-work-roll bearing-housing anti-backlash cylinder 662 apply force to press the bearing housings 612 and 613 of the small-diameter work rolls 610 and 611, and support the small-diameter work rolls 610 and 611 to prevent them from moving in the rolling direction.
In a case of the large-diameter work rolls 610A and 611A, the rolling torque Tr becomes larger than that at the time when the small-diameter work rolls 610 and 611 are used in some cases, and also the sum of horizontal force (b) when Tr1 is applied and (c) when Tr2 is applied in a case of work roll driving becomes large as compared to that in a case of intermediate roll driving as depicted in
Furthermore, bearings (not depicted in figures) are provided at axial end sections of the upper backup roll 630 on both the drive side and the work side, and these bearings are supported by an upper backup roll bearing housing 632. Similarly, bearings (not depicted in figures) are also provided at axial end sections of the lower backup roll 631 on both the drive side and the work side, and these bearings are supported by a lower backup roll bearing housing 633.
In addition, as depicted in
The hydraulic device 90 is connected to each hydraulic cylinder such as each bending cylinder or anti-backlash cylinder mentioned above, the shift cylinders 615 and 617, or rolling devices (not depicted in figures) that apply roll force for rolling the rolled material 5 to the upper work roll 610 and the lower work roll 611, and the hydraulic device 90 is connected to the controller 80.
In contrast to this, in the four-stage rolling mill depicted in
Similarly, the lower work roll 611A also has bearings 611A2 provided at its axial end sections on both the drive side and the work side, and these bearings are supported by the work-side and drive-side lower work roll bearing housings 613A, respectively.
In the present embodiment, the upper work roll 610A is configured to be able to shift in the roll-axis direction due to the shift cylinder 615 like the one depicted in
As depicted in
Similarly, on both the work side and the drive side, the lower intermediate roll bending cylinder 652 provided to the exit-side fixation member 602, and the lower intermediate roll bending cylinder 653 provided to the entry-side fixation member 603 support the lower work roll bearing housings 613A, and by driving these cylinders as appropriate, bending force is applied to the bearings of the lower work roll 611A vertically.
These bending cylinders 650, 651, 652, and 653 apply the roll balance force to the work rolls 610A and 611A.
Furthermore, as depicted in
Similarly, the lower-work-roll bearing-housing anti-backlash cylinder 662 and the lower large-diameter work-roll bearing-housing anti-backlash cylinder 674 apply pressing force in the rolling direction to the lower work roll 611A via liners of the lower work roll bearing housings 613A, and press the bearings 611A2 to the housings 600.
In addition, in the rolling mill of the present embodiment, as depicted in
As depicted in
In particular, the roll speed is higher at a latter stage of a finishing rolling mill, and the rotational speed of rolls becomes higher. If it is possible to increase the diameter of the drive spindle, the natural frequency of deflection vibration of the drive spindle can be increased, and even if the rotational speed of rolls increases, the natural frequency of deflection vibration can be made higher than the rotational speed of the rolls, and resonance with the deflection vibration can be suppressed.
In addition, as depicted in
Here, when it is made possible to switch between a four-stage rolling mill including the large-diameter work rolls 610A and 611A and a six-stage rolling mill including the small-diameter work rolls 610 and 611 and the intermediate rolls 620 and 621, a diameter Di2 of the intermediate rolls 620 and 621 is desirably made larger than a diameter Dw2 of the work rolls 610 and 611.
Horizontal force applied onto the intermediate rolls 620 and 621 is larger than horizontal force applied onto the work rolls 610 and 611. This is for avoiding a situation where this horizontal force inevitably warps the rolls horizontally, an inter-roll offset amount that is set in the initial period increases due to the warping, the horizontal force increases further, the resultant force of the horizontal force and an offset component of the rolling load Pr is applied onto the rolls, and a problem in terms of strength occurs.
In addition, when the direction of horizontal force changes in a transitional period, and the rolls move in the rolling direction, this gives rise to a problem that local slides occur between the work rolls 610 and 611 and the intermediate rolls 620 and 621, and the rolls are damaged.
In view of this, desirably, the diameter Di2 of the intermediate rolls 620 and 621 is made larger than the diameter Dw2 of the work rolls 610 and 611, and warping of the intermediate rolls 620 and 621 is reduced.
The drive spindle depicted in
The angles of the universal joints 760 are preferably equal to or smaller than 3 degree. If the distance between the universal joints 760 at two locations is defined as L1, the relation of Di2 max=2 (2L1 min×tan 3°+Dw1 min/2−Dw2 max)) holds true. Here, L1 min is the minimum value that L1 can be.
In a case where the diameter Di2 of the intermediate rolls 620 and 621 is set such that it does not exceed the largest diameter Di2 max that the intermediate rolls 620 and 621 can have, the angles of the universal joints 760 relative to the spindle that drives the large-diameter work rolls 610A and 611A, and the spindle that drives the intermediate rolls 620 and 621 when the small-diameter work rolls 610 and 611 can be made equal to or smaller than 3° without shifting the position of the drive spindle on the side opposite to the rolls, and a simple driving device 750 can be realized.
Note that in a case where the diameter Di2 of the intermediate rolls 620 and 621 is set such that it exceeds the largest diameter Di2 max that the intermediate rolls 620 and 621 can have, it becomes possible to make the angles of the universal joint 760 equal to or smaller than 3° by shifting the position of the drive spindle in the upward/downward direction on the side opposite to the rolls. In this case, the structure of the driving device 750 becomes complicated to some extent, but the same type of drive spindle can be used.
The universal joints 760 may be cross pin type universal joints, gear type universal joints or another type of universal joints, and their type is not limited.
The outer diameters of roll axial end sections are made smaller than at least bearing internal diameters such that bearing housings and bearings can be incorporated into rolls together.
When the diameter of the upper intermediate roll 620 and the lower intermediate roll 621 is smaller than the diameter of the upper work roll 610A and the lower work roll 611A, the internal diameter of roll axial end sections coupled with roll-side couplings of the universal joints 760 as in
In order to solve this, in
In a case of work roll driving, the outer diameter of the roll-side couplings 761a of the universal joints 761 cannot be made larger than the diameter of body sections of the work rolls in order to avoid interference in the upward/downward direction. On the other hand, in a case of intermediate roll driving, the outer diameter of the roll-side couplings 761a of the universal joints 761 can be made larger than the diameter of body sections of the intermediate rolls, and thus the diameter of the body sections of the intermediate rolls does not constrain the outer diameter of the roll-side couplings 761a of the universal joints 761.
The gap filling members 800 are attached at the roll axial end sections of the upper intermediate roll 620′ and the lower intermediate roll 621′ after bearing housings and bearings are incorporated into the rolls together. When the mode of rolling is switched from rolling depicted in
Here, it is also possible to attach the gap filling members 800 on the side of the roll-side couplings 761a, and this provides similar advantages. When it is relatively easy to attach the gap filling members 800 on the side of the roll-side couplings 761a in the rolling mill, this manner can be selected also.
When the mode of rolling is switched from the rolling depicted in
The controller 80 is a device that controls operation of each piece of equipment in the rolling facilities 1, 1A, 1B, and 1C, and suitably includes a computer or the like including a CPU, a storage medium, a display device, or the like.
For example, the controller 80 controls actuation of the hydraulic device 90, and causes a hydraulic fluid to be supplied to each bending cylinder or the like mentioned above or to be discharged from each bending cylinder or the like mentioned above to thereby controls driving of each cylinder.
In addition, at the time of direct driving, the controller 80 performs driving control of the upper work roll 610A and the lower work roll 611A, and, at the time of indirect driving, the controller 80 performs driving control of the upper intermediate roll 620 and the lower intermediate roll 621 such that drive 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, and the upper work roll 610 and the lower work roll 611 are driven.
As depicted in
The first acquiring section 80a is a portion that obtains the mill longitudinal rigidity coefficient K of the rolling mill, and suitably is a portion that acquires the latest value of mill longitudinal rigidity coefficients K of the relevant rolling mill that are recorded in advance on the storage section 80h or the like.
The first calculating section 80b is a portion that uses the acquired mill longitudinal rigidity coefficient K and rolling conditions to determine the kiss roll load Pk of the upper work roll 610 and the lower work roll 611 at the angle θx of the tip position of the rolled material 5 relative to the upper work roll 610 and the lower work roll 611 between the start of biting of the rolled material 5 and completion of the biting.
The second calculating section 80c is a portion that determines the rolling load Pr and the drive torque Tr in relation to the angle θx of the tip position of the rolled material 5 relative to the upper work roll 610 and the lower work roll 611 between the start of biting of the rolled material 5 and completion of the biting.
The traction coefficient calculating section 80d is a portion that determines the traction coefficient μrt between the upper work roll 610 and the upper intermediate roll 620, and between the lower work roll 611 and the lower intermediate roll 621 in relation to the angle θx of the tip position relative to the upper work roll 610 and the lower work roll 611 from the sum P of the kiss roll load Pk, the rolling load Pr, and hypothetical work roll balance force Pb, and the drive torque Tr between the start of biting of the rolled material 5 and completion of the biting in a state in which the hypothetical work roll balance force Pb is applied.
The second acquiring section 80e is a portion that obtains the tolerated value μrter of the traction coefficient μrt of the rolling mill.
Here, the tolerated value μrter is the tolerated maximum value of the traction coefficient μrt, and is such a value that when a traction coefficient equal to or larger than this value is necessary, a significant slide is caused between an intermediate roll and a work roll, and rolling becomes difficult.
The step comparing section 80f is a portion that compares the maximum value μrtmax of the traction coefficient μrt determined by the traction coefficient calculating section 80d with the tolerated value μrter of the traction coefficient μrt.
The setting section 80g is a portion that resets the work roll balance force at the start of biting of the rolled material 5 to a value which is equal to or larger than the required limit work roll balance force Pbcr1cr that is required when the traction coefficient μrt assumes the maximum value μrtmax, and is equal to or smaller than the limit work roll balance force Pbcr2 that is determined from a constraint in terms of the strength of the rolling mill when the tolerated value μrter of the traction coefficient μrt becomes equal to or larger than the maximum value μrtmax of the traction coefficient μrt.
The storage section 80h is a storage device of a computer included in the controller 80, and suitably includes an SSD or an HDD.
Control of operation of each piece of equipment, and control of operation of the first acquiring section 80a, the first calculating section 80b, the second calculating section 80c, the traction coefficient calculating section 80d, the second acquiring section 80e, the step comparing section 80f, the setting section 80g, and the like by the controller 80 are executed on the basis of various types of program recorded on the storage section 80h.
Note that operation control processes executed by the controller 80 may be integrated into one program, may be a plurality of separate programs, or may be a combination of these.
In addition, some or all of the programs may be realized by dedicated hardware or may be formed as modules.
Next, a work roll balance force setting method and a rolling mill running switching method of the rolling mill according to the present embodiment are explained with reference to
First, as depicted in
More specifically, the mill longitudinal rigidity coefficient K may be calculated for work roll balance force setting, or an existing numerical value (a value at the time of the delivery of the rolling mill, a value after several years of activation, etc.) that is recorded on the storage section 80h or the like may be read in as the mill longitudinal rigidity coefficient K. As the existing numerical value, any of values that a manufacturer who is actually activating the rolling mill has obtained by measurement and computation at each predetermined timing like at the time of the delivery of the rolling mill, one year after, two years after . . . , and so on for management of the rolling mill can be used as is.
Here, at the step of obtaining the mill longitudinal rigidity coefficient K, when the mill longitudinal rigidity coefficient K has been obtained twice or more about the rolling mill, the latest mill longitudinal rigidity coefficient K is desirably used.
Next, the rolling load Pr and the rolling torque Tr are calculated from rolling conditions (Step S102). This Step S102 is equivalent to a step of determining the rolling load Pr and the rolling torque Tr.
At this step, the moment of biting means a timing just before the start and at the start of biting, and completion of the biting is a timing at which the angle θx of the tip position becomes 0. Since there can be cases where the kiss roll load Pk changes before the start and just before the start, it is sufficient if there is at least data of the kiss roll load Pk from the moment when biting occurs, there is little necessity for use of the kiss roll load Pk “before the start” when a rolled material is apart from rolls, and thus the rolling load Pr and the rolling torque Tr are desirably determined from the start of biting.
Here, the rolling conditions are information such as an entry-side thickness, an exit-side thickness, the width of the rolled material, or the hardness of the rolled material in the relevant rolling mill, and the rolling torque is determined by using a known computation method.
Next, the rolling load Pr and a kiss roll load at the strip tip position in a roll bite are calculated by using the mill longitudinal rigidity coefficient K (Step S103). This Step S103 is equivalent to a step of determining the kiss roll load Pk.
Next, the maximum value μrtmax is determined supposing that the work roll balance force Pb is the upper limit work roll balance force Pbcr2, and the maximum value μrtmax is compared with the tolerated value μrter (Step S104). This step is equivalent to a step of determining the traction coefficient μrt and the maximum value μrtmax of the traction coefficient, a step of obtaining the tolerated value μrter of the traction coefficient μrt of the rolling mill, and a step of comparing the maximum value μrtmax with the tolerated value μrter.
Here, it is supposed that hypothetical work roll balance force is applied, for example the work roll balance force Pb is 0, 350, and 700 [kN/roll], and 0.15 is used as a constant when water is used as a coolant, 0.10 is used as a constant when an oil is used or another value is used as a constant because the tolerated value μrter of the traction coefficient is difficult to measure. In addition, at this Step S104, the traction coefficient μrt that is observed when the kiss roll load Pk becomes 0, that is, local maximums depicted in
Next, when it is decided at Step S104 mentioned earlier that the maximum value μrtmax is equal to or smaller than the tolerated value μrter, the work roll balance force Pb that produces the maximum value μrtmax is determined. This work roll balance force Pb is set as the lower limit work roll balance force Pbcr1 (Step S105).
Here, the lower limit work roll balance force Pbcr1 is the lower limit value of the work roll balance force Pb for preventing a slide, and if the work roll balance force Pb is equal to or larger than the lower limit work roll balance force Pbcr1, the maximum value μrtmax does not exceed the tolerated value μrter, and thus rolling can be continued without occurrence of a significant slide between an intermediate roll and a work roll.
Thereafter, the set work roll balance force Pbact is set to a value within a range that satisfies the condition “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 is equivalent to a step of resetting the work roll balance force at the start of biting of the rolled material 5 to a value which is equal to or larger than the work roll balance force Pbcr1 that is required when the traction coefficient μrt assumes the maximum value μrtmax, and is equal to or smaller than the limit work roll balance force Pbcr2 that is determined from a constraint in terms of the strength of the rolling mill when the tolerated value μrter of the traction coefficient μrt becomes equal to or larger than the maximum value μrtmax of the traction coefficient μrt (i.e. an indirect driving mode is selected).
Here, the upper limit work roll balance force Pbcr2 is limit work roll balance force that is determined from a constraint in terms of the strength of the rolling mill, and is the maximum value of the work roll balance force Pb. The work roll balance force Pb beyond the maximum value can damage components, and thus cannot exceed the maxim value. Basically, the upper limit work roll balance force Pbcr2 is determined on the basis of the strength of work roll bearings and the strength of work roll necks.
The set work roll balance force Pbact is a value of the work roll balance force Pb that is actually set at the time of rolling, and is set to a certain setting 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.
In contrast to this, when it is decided at Step S104 mentioned earlier that the maximum value μrtmax is larger than the tolerated value μrter, the large-diameter work rolls 610A and 611A are used, and the mode of rolling is switched to rolling by driving the work rolls 610A and 611A (Step S107).
In the rolling mill running method, running of the rolling mill is started after the work roll balance force is set after the work roll balance force is set according to each flow depicted in
Next, advantages of the present embodiment are explained.
According to the work roll balance force setting method of the rolling mill according to the present embodiment mentioned above, the work roll balance force Pb is set taking also the kiss roll load Pk into consideration, and thus an inter-roll slide can be prevented without damaging components such as bearings even if kiss roll occurs at the time of biting.
Furthermore, in the rolling mill running switching method, a direct driving mode is selected when it is decided that the tolerated value μrter of the traction coefficient μrt is smaller than the maximum value μrtmax of the traction coefficient μrt, and an indirect driving mode is selected when it is decided that the tolerated value μrter of the traction coefficient μrt is equal to or larger than the maximum value μrtmax of the traction coefficient μrt. Thereby, the work roll balance force Pb is set taking also a kiss roll load into consideration, and thus an inter-roll slide can be prevented without damaging components such as bearings. In addition, when the traction coefficient is too large, a problem about torque transfer can be overcome by switching the driving mode not to indirect driving but to direct driving. Note that when large-diameter work rolls can be used for rolling regardless of whether μrtmax is larger than or smaller than μrter, it is possible to select the large-diameter-work-roll direct driving mode.
In addition, at the step of obtaining the mill longitudinal rigidity coefficient K, when the mill longitudinal rigidity coefficient K has been obtained twice or more about the rolling mill, the latest mill longitudinal rigidity coefficient K is used. There is a tendency that in the process of the use of the rolling mill, the mill longitudinal rigidity coefficient K becomes smaller, and thereby a kiss roll load increases. Accordingly, the latest value of the mill longitudinal rigidity coefficient K that has been influenced least by the mill longitudinal rigidity coefficient K due to temporal changes is used to thereby make it possible to more precisely determine a kiss roll load also, and precisely determine the work roll balance force also.
Furthermore, at the step of determining the traction coefficient μrt, the traction coefficient μrt that is observed when the kiss roll load Pk comes 0 between the start of biting of the rolled material 5 and completion of the biting is used as the maximum value μrtmax of the traction coefficient μrt. Since the traction coefficient μrt is F/P=F/(Pr+Pk+Pb), derivation of the maximum value μrtmax can be made simple by setting the traction coefficient μrt when Pk=0 as the maximum value μrtmax.
In addition, the rolling mill running method includes a step of starting running of the rolling mill after the work roll balance force is set after the work roll balance force is set, and a step of pressing the bearings 610A1 and 611A1 of the upper work roll 610 and the lower work roll 611 against the housings 600 of the rolling mill before the rolled material 5 is bitten by the upper work roll 610 and the lower work roll 611. If a kiss roll load is applied in a state in which the axial centers of the rolls are inclined relative to the original axial directions, for example, thrust force is generated between the upper work roll 610 and the upper intermediate roll 620, between the upper and lower work rolls 610 and 611, and so on, and there is a risk that bearings and the like are damaged in a case of small-diameter work rolls. However, by pressing the bearings 610A1 and 611A1 of the work rolls 610 and 611 against the housings 600, and preventing inclination of the axial centers in this manner, it is possible to make generation of thrust force unlikely, and it is possible to make damages of the bearings and the like unlikely even if a kiss roll load is generated between the work rolls 610 and 611.
Note that the present invention is not limited to the embodiment described above, but various modifications and applications are possible. The embodiment mentioned above is explained in detail for explaining the present invention in an easy-to-understand manner, and embodiments of the present invention are not necessarily limited to those including all the configurations explained.
The present application is a national phase application of PCT Application No. PCT/JP2021/040290, filed Nov. 1, 2021, entitled “WORK ROLL BALANCE FORCE SETTING METHOD AND ROLLING MILL RUNNING METHOD, ROLLING MILL RUNNING SWITCHING METHOD, AND ROLLING MILL”, which is incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/040290 | 11/1/2021 | WO |
