JP3438764B2 - Leveling zero adjustment method of hot rolling finishing mill - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for zeroing the leveling of a finishing mill for rolling a hot-rolled steel sheet. 2. Description of the Related Art FIG. 1 shows a mechanism of a general hot rolling finishing mill. In the figure, Op indicates the operator side,
Dr indicates the drive side. Reference numeral 1 denotes a hydraulic pressure reduction cylinder on the operator side, and reference numeral 2 denotes a hydraulic pressure reduction cylinder on the drive side. 5 is an upper backup roll, 6 is an upper work roll, 7 is a lower work roll, and 8 is a lower backup roll. Reference numeral 3 denotes an operator-side load cell, and reference numeral 4 denotes a drive-side load cell. In hot rolling, it is necessary to set the opening of the gap between the upper and lower work rolls 6 and 7 of the finishing mill in order to roll to a target thickness. The opening degree setting is set by the operator side and the hydraulic pressure Siri Sunda 1,2 on the drive side of the normal on the backup roll 5. The positions (oil column positions) of the hydraulic pressure lowering cylinders 1 and 2 are recognized by a magnescale in the cylinder. At this time, if the shape of the work rolls 6 and 7 changes due to thermal deformation, wear, or replacement of the rolls, the position of the oil column (the value of the magnescale) at which the opening between the rolls becomes zero changes. For this reason, the position of the oil column at which the inter-roll opening of the work rolls 6 and 7 becomes zero is stored, the position of the hydraulic pressure reduction cylinders 1 and 2 is adjusted based on the stored value, and the inter-roll opening is adjusted. I am making adjustments. The operation of storing the oil column position of the roll-to-roll opening serving as this reference (the operation of associating the roll-to-roll opening with the oil column position) is referred to as a roll-down position zero adjustment. As described above, when the roll changes, the oil column position at which the inter-roll opening becomes zero changes, so when the work rolls 6 and 7 are rearranged,
It is necessary to perform the rolling position zero adjustment. If the roll opening is not parallel (uniform) in the roll width direction (barrel direction), there is a difference in the amount of reduction between the operator side and the drive side, and there is a possibility that the rolled material may meander. Therefore, at the same time as the above-described zero adjustment of the rolling position, the oil column difference in which the roll opening is parallel in the roll barrel direction is also stored. This work is called leveling zero. In the normal leveling zero adjustment, the hydraulic pressure on the operator side and the drive side is adjusted so that the difference load (the difference between the load on the operator side load cell 3 and the load on the drive side load cell 4) at the time of 1500 [t] reduction matches the target difference load. The positions of the pressing cylinders 1 and 2 are adjusted, and the values are stored. At this time, generally, the work rolls 6 and 7 are rotating, but if the rolls cross between the work rolls and the backup roll, a thrust force is generated in the axial direction of each roll. This thrust force is determined by a thrust coefficient representing the magnitude of the thrust force with respect to the actual load. FIG. 2 shows the relationship between the roll cross angle and the thrust coefficient. At the time of zero adjustment, a water-cooled state as shown by a symbol W in the drawing is shown, and the thrust coefficient changes greatly even at a small cross angle. Therefore, even if the cross angle is slightly increased, a large thrust force is generated. FIG. 3 is a plan view of the roll 10. As shown in FIG. 3, the rolling mill has a housing (crosshead).
9 and the roll chock 11 have a clearance d, and the cross angle θ changes accordingly. The change in the cross angle θ due to the clearance d is usually uncontrollable.
For example, in the example shown in FIG. 3, a minute cross angle of θ = 0.04 ° may occur. FIG. 4 shows the relationship between the cross angle, the difference load, and the thrust force when the lower work roll 7 and the lower backup roll 8 cross each other. As shown in FIG.
120 [t] even at a small cross angle of 0.04 °
Thrust force is generated. This thrust force changes the differential load between the operator side and the drive side by 60 [t] due to the moment balance. As a result, the leveling amount is 60
0 [μm]. [0010] However, in the method of adjusting the leveling so that the difference load becomes a target difference load in a state where the difference load changes due to such a thrust force, the thrust force due to the cross angle is increased. The value changes from the true leveling value (a state in which the gap between the rolls is parallel). Therefore, when rolling is performed in this state, there is a problem that a meandering occurs in the steel sheet, which may cause a line trouble and reduce the operation rate. The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide a technique for improving the accuracy of a roll-down position zero adjustment and a leveling zero adjustment. According to the present invention, there is provided a leveling zero adjustment method for a hot rolling finish rolling mill, wherein when performing a leveling zero adjustment of a rolling-down position, the rotation of a work roll is stopped to stop the thrust. This problem has been solved by reducing the force and reducing the variation of the leveling zero difference load. According to the present invention, the rotation of the work roll is stopped at the time of zero leveling, so that it is not affected by the change in the difference load due to the thrust force caused by the cross angle between the rolls, and the accuracy is improved. The gap between the rolls can be set in a parallel state. Embodiments of the present invention will be described below in detail with reference to the drawings. This embodiment is applied to a general hot rolling finish rolling mill as shown in FIG. As described above, when the work rolls 6 and 7 are rearranged, zero leveling is performed. At this time, the work rolls 6 and 7 are normally in a rotating state. This is because the backup rolls 5 and 8 have heat, and when the rotation of the work rolls 6 and 7 is stopped, a temperature difference occurs between a portion that is in contact with the backup rolls 5 and 8 and a portion that is not. This is to prevent the rolls 6 and 7 from being thermally deformed. However, in this embodiment, the rotation of the work rolls 6 and 7 is stopped after taking measures such as spraying cooling water to prevent thermal deformation. FIG. 5 shows the variation in oil column difference (leveling zero adjustment value) between the drive side and the operator side in each of the stands F1 to F7 of the finishing mill at this time. As shown in FIG. 5, the variation in the oil column difference is smaller when the rotation of the work rolls 6 and 7 is stopped than when the rotation is not stopped. FIG. 6 shows the results obtained when the rotation of the work rolls 6 and 7 and the rotation of the work rolls 6 and 7 are stopped when the gap between the rolls is parallel in the actual rolling in the hot finishing mill. The oil column difference at the time of zero adjustment is shown in comparison. As shown in FIG. 6, the dispersion of the oil column difference at the time of zero adjustment is small and coincides with the oil column difference at the time of rolling by adjusting the target differential load. in this way,
By stopping the rotation of the work roll roll in the zeroing of the leveling at the time of changing the work roll, the accuracy of the zeroing of the leveling can be improved. As described above, according to the present invention,
At the time of zero leveling, the rotation of the work rolls is stopped, so there is no effect of the change in the difference load due to the thrust force caused by the cross angle between the rolls. And the accuracy of leveling zero adjustment can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing a general hot rolling finish rolling mill. FIG. 2 is a diagram showing a relationship between a roll cross angle and a thrust coefficient. FIG. 3 is a minute cross generated by clearance. FIG. 4 is a plan view of a work roll showing an angle state. FIG. 4 is a diagram showing a relationship between a thrust force generated by a minute cross angle and a difference load. FIG. 5 is a graph showing a variation in leveling null. FIG. Graph comparing oil column differences during rolling [Explanation of symbols] 1 ... operator side hydraulic pressure reduction cylinder 2 ... drive side hydraulic pressure reduction cylinder 3 ... operator side load cell 4 ... drive side load cell 5 ... upper backup roll 6 ... upper work roll 7 ... Lower work roll 8 ... Lower backup roll 9 ... Housing 10 ... Roll 11 ... Roll chock

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsu Takeguchi 4-72-22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Hirofumi Aratani Hiroshi Kannon, Nishi-ku, Hiroshima-shi, Hiroshima No. 6-22, Mitsubishi Heavy Industries, Ltd. Hiroshima Works (56) References JP-A-5-138220 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37/00-37 / 78 B21B 35/00

Claims (1)

(57) [Claims 1] In a leveling zero adjustment method for a hot rolling finishing mill, the thrust force is reduced by stopping the rotation of a work roll when performing a leveling zero adjustment of a rolling position. A leveling zero adjustment method for a hot-rolling finishing mill, wherein the leveling zero difference load variation is reduced.