JPH0123204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the crown of a strip, particularly a hot strip, and more particularly, to a method for controlling the crown of a strip, which is useful when rolling a plate using a four-high rolling mill having work rolls movable in the roll axis direction. This paper proposes a crown control rolling method, which attempts to effectively control the crown of the strip by skillfully linking the width change of the material to be rolled during rolling with the deformation characteristics of the roll barrel.

As shown in Figure 1, the plate crowns of rolled plate products are: (a) Body crown due to thickness deviation in the width direction of the remaining part excluding both edges, (b) Unique metal crown only at both edges. It is roughly divided into three types: edge drop due to flow, and (c) local protrusion (center build-up, edge build-up, etc.). Edge drops are flattening of the work roll surface due to contact with the rolled material, and local protrusions are local wear of the work roll, and strict limits are required for all three.

In order to suppress body crown and reduce edge drop in conventional 4-high rolling mills,
There was no better way than to pay close attention to the operation from hot rolling to cold rolling under a careful rolling schedule, and roll bending equipment was used exclusively as a control means. This method is only slightly effective in correcting the shape of the rolled material (ear wave, belly elongation, etc.), but has little effect on controlling the body crown or reducing edge drop, which is the current situation. In order to increase the effectiveness of the roll bending device, it is disclosed in Japanese Patent Application Laid-Open No. 53-48047 and US Pat. It is virtually useless in reducing local protrusions.

By the way, in the case of a 6-high rolling mill, the intermediate roll is moved in the axial direction according to the width of the material to be rolled, and the axial deflection deformation of the work roll is reduced, thereby strongly suppressing and controlling the body crown. However, since the edge drop reduction control is controlled by the axial deflection of the work roll, its effect is small as it is determined by the mechanical deformation characteristics of the work roll, and its effectiveness in preventing local protrusions is small. It is completely powerless, and in addition, modifying a regular 4-high rolling mill to create a 6-high rolling mill is not only very complicated and difficult, but also has the significant disadvantage of high modification costs. Note that if a work roll with a so-called trapezoidal crown in which both ends of the roll body are tapered and ground is used, the body crown of the rolled material corresponding to the tapered and ground portions is suppressed, and the surface shape of the work roll is can be arbitrarily determined without depending on the mechanical deformation characteristics, which has a great effect in reducing edge drops. However, if the width of the material to be rolled changes, the effect changes accordingly, and the Similarly, there was a problem in that it did not help prevent local protrusions.

In other words, local protrusions such as center build-up and edge build-up are caused by abnormal wear of the work roll, but since such abnormal wear occurs at a fixed position in the width direction of the rolled plate,
This is difficult to avoid in rolling mills with fixed work rolls. In particular, edge build-up occurs when abnormal wear progresses in the tapered grinding area that comes into contact with the edge of the rolled plate, where the temperature drop is greater than in the center and the deformation resistance is higher. Where it is likely to occur if width rolling is continued,
In this regard, in rolling using work rolls with trapezoidal crowns, it is necessary to keep the width of the plate to be rolled constant, so the contact position in the tapered grinding area of the edge is approximately the same. The occurrence of edge build-up was even more significant.

Furthermore, when the trapezoidal crown roll is used, if the material (hardness) changes, the occurrence of edge build-up and edge drop as described above tends to be further promoted.

The present invention completely solves the problems of the prior art as described above, and proposes a rolling method that can strongly control the crown of the rolled material, such as body crown control, edge drop reduction control, and prevention of local protrusions. .

This invention reduces body crowns and edge drops by moving a work roll with a special initial crown in the roll axis direction, and prevents the occurrence of local protrusions. The body crown is reduced by back-up roll.

In other words, a pair of work rolls each having a convex initial crown formed by tapering grinding over a length of less than half of one side of the roll barrel are stacked one on top of the other with the crowns arranged alternately, and are movable in the roll axis direction. At the same time, on the side opposite to the tapered grinding area of each of the upper and lower work rolls, a convex initial crown was formed on one side of the roll body of the back-up roll corresponding to each of these work rolls by tapering grinding over less than half the length in the axial direction. Using a four-high rolling mill built into the mill housing along with the back-up roll, the upper and lower work rolls are moved in the roll axis direction according to the width of the material to be rolled, and both edges of the material to be rolled are tapered to the upper and lower work rolls. Rolling is performed by positioning it in the grinding zone to achieve crown control.

Here, on the cylinders of the upper and lower back-up rolls, on the side opposite to the tapered grinding area of each of the upper and lower work rolls, on one side of the roll cylinder of the back-up rolls corresponding to each of these work rolls, there is a tapered grinding process over a length of less than half in the axial direction. By applying this, the contact pressure with the back-up roll at the body end of the work roll is reduced, and as no extra oiling moment is applied to the work roll, the axial deflection deformation of the work roll is reduced, and the body The crown is suppressed, and by moving the upper and lower work rolls according to the width of the rolled material to position both edges of the rolled material in the tapered grinding areas of the upper and lower work rolls,
Since the control pressure between the work roll and both edges of the material to be rolled is reduced and sudden changes in roll flatness deformation at both edges can be alleviated, edge drops can be controlled to be reduced.

Furthermore, since both the upper and lower work rolls are movable in the axial direction, it is possible to reduce local abnormal wear that tends to occur in conventional work rolls, and advantageously prevent local protrusions.

In other words, regarding center build-up that occurs in the non-tapered grinding area, by moving the work roll in the axial direction, even if localized abnormal wear occurs on the roll surface, wear and tear on the roll surface caused by this can be prevented. Since it can be dispersed throughout the tapered grinding area, it can be effectively reduced. Also, regarding edge build-up, it is not necessary to limit the contact position in the tapered grinding area of the edge of the rolled plate to one point, and there is a certain tolerance range, so the set position of the edge part is set as appropriate within that tolerance range. This can be effectively prevented by changing the

On the other hand, even if the material of the rolled plate changes, for example from a hard one to a soft one, the length of the edge of the rolled plate rolled in the tapered grinding area will increase. In addition to adjusting for plate width changes, by finely adjusting the shift amount, you can effectively prevent edge drops and edge build-up. It can be prevented.

Furthermore, since the tapered grinding areas of the work roll and the back-up roll are in opposite halves, the contact pressure distribution between the work roll and the back-up roll changes greatly when the work roll is moved, resulting in a body crown. The suppressing effect of

To explain the four-high rolling mill used in the above rolling method, as shown in Fig. 2, 1 is the material to be rolled, 2,
3 are upper and lower work rolls, respectively.

The work rolls 2 and 3 have tapered grinding areas arranged alternately as shown, and both are pivoted so as to be movable in the roll axis direction. 4 and 5 are tapered grinding areas of the upper and lower work rolls 2 and 3, respectively, and the degree of grinding may be different between the upper and lower parts. 6 and 7 are bearing chokes for upper and lower work rolls, 8 and 9 are upper and lower work rolls 2 and 3, respectively.
The spindle has a spline structure for torque transmission. Although the device for moving the upper and lower work rolls 2, 3 in the axial direction is not shown in the figure, it may be installed around the work roll bearings 6, 7, or it can be installed around the extensions of the spindles 8, 9, for example around the gearbox. It may be equipped, and the movement method may be hydraulic, electric, or magnetic. 10 is a balance device for the work rolls 2 and 3 or a roll bending device for increasing, and 11 is a roll bending device for decreasing.

Reference numerals 12 and 13 are back-up rolls of the upper and lower work rolls 2 and 3, and 14 and 15 are tapered grinding regions of the upper and lower back-up rolls, respectively, and the degree of grinding may be different between the upper and lower parts. 1
6 and 17 are chock for backup roll, 18
are the bearings in the chock 16 and 17 for the back-up roll, 19 is the lowering screw, and 20 is the housing stand.Although this example shows the work roll drive system, the drive system may also be a back-up roll drive. Furthermore, the horizontal relationship of the tapered grinding areas of the upper and lower work rolls may be reversed from this example.

The thickness distribution in the width direction of a rolled material when rolling is performed using the rolling method according to the present invention is calculated using a split model, and the effects thereof will be described.

Here, the relative positions of the work rolls, back-up rolls, and material to be rolled used for rolling, as well as the grinding depths, are defined as shown in FIG. 3. In addition,
Both the work role and the backup role are defined in the same way, and are distinguished by adding the subscripts w and B, respectively.

The tapered grinding length L applied to the roll is the length from the position where the difference between the grinding amount at the center of the roll is 20μ to the end of the roll, and the grinding length H is the difference between the grinding amount between the center of the roll and the end of the roll.

In addition, the difference between the amount of grinding at the end of the rolled material and the amount of grinding at the center of the roll is defined as the effective grinding amount EH, and of the tapered grinding length L, the length inside the material to be rolled is the effective grinding length. It was set to EL.

Figure 4 shows the effect of tapered grinding added to the back-up roll. L _B is 400mm, H _B is 0~
Calculations were made up to 1.0 mm, but when H _B is 0 to 0.5 mm, as the grinding depth increases, the body crown is greatly suppressed. However, even if H _B is increased to 1 mm, 0.5
Compared to the case of mm, the reduction effect of the body crown is small. Therefore, the appropriate grinding depth is between 0.1 and 0.5 mm.

Figure 5 shows the effect of tapered grinding of the work roll. Although the effect of tapered work roll grinding on the body crown is small, the edge drop is greatly reduced.

Incidentally, if the amount of tapering grinding of the work roll is excessively large, a plate thickness abnormality called edge build-up occurs, in which the plate thickness at the ends is extremely thicker than the plate thickness at the center. Furthermore, if the amount of tapering grinding of the work roll is small, the effect of reducing edge drops will be small.

The optimum amount of work roll grinding varies depending on rolling conditions such as rolling load, plate thickness, plate width, roll dimensions, etc., but is usually appropriate between 0.1 and 0.5 mm.

Figures 4 and 5 show that body crown is suppressed by tapering grinding of the back-up roll, and edge drop is reduced by moving the work roll to appropriate EH _w and EL _w according to the sheet width. It can be seen that by combining the effects of both, the thickness deviation in the width direction can be made extremely small.

FIG. 6 shows an example in which the thickness deviation in the width direction is reduced in this way.

Next, FIG. 7 shows the contact pressure distribution between the work roll and the back-up roll and the crown control ability in that case. (a) is a comparison case in which back-up roll is symmetrically tapered and ground;
(b) is a case in which the back-up roll is subjected to tapering grinding only on the opposite side of the work roll's tapering grinding. In case (a), the contact pressure distribution does not change much even if the work roll is moved in the axial direction, but in case (b)
In this case, the movement of the work roll greatly affects the contact pressure distribution, and as a result, the movement of the work roll increases the crown control effect.

As described above, the present invention is extremely effective for body crown control, edge drop reduction control, and prevention of local protrusions, and it is possible to produce a plate with almost no thickness change in the width direction.

The present invention can be applied to all conventional four-high rolling mills, such as plate rolling mills, hot rough rolling mills, hot finishing mills, cold rolling mills, and reverse rolling mills. Since it is easy to modify, there is no disadvantage of high equipment costs.

In addition, since the wear of the rolls during the rolling process is uniform, the number of coils in one cycle of rolling can be increased more than before, and there is no restriction on the width configuration of the rolled material at this time, which improves work efficiency and roll consumption. is significantly improved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the abnormal shape of a rolled plate product, Figure 2 is a front view of a four-high rolling mill used in the present invention, and Figure 3 is a diagram showing the relative positions of work rolls, back-up rolls, and rolled material. Explanatory drawings, Figures 4 and 5
The figure is a comparison graph comparing the profile in the width direction of a rolled material obtained by this invention with that of the conventional method, and Figure 6 shows that by this invention a plate with almost no thickness deviation in the width direction was obtained. An exemplary graph, FIG. 7, is a comparative graph illustrating the crown control capability of the method of the present invention as compared to using a double tapered back up roll. 1... Rolled material, 2... Upper work roll, 3...
...lower work roll, 4...upper work roll tapered grinding area, 5...lower work roll tapered grinding area, 6
...Bearing chock for upper work roll, 7...
...Bearing chock for lower work roll, 8...
Spindle for upper work roll, 9... Spindle for lower work roll, 10... Balance device or roll pending device for increase, 11
...Roll bending device for decrease, 12
...Upper back up roll, 13...Lower back up roll, 14...Upper back up roll tapered grinding area, 15...Lower back up roll tapered grinding area, 16...Bearing chock for upper back up roll, 17 ...Bearing chock for lower backup roll, 18 ...Bearing, 19
...Screw down, 20...Housing stand.

Claims (1)

[Claims] 1. When rolling a plate using a four-high rolling mill having work rolls movable in the roll axis direction, the work rolls have a length of 0.1 to 0.5 mm over half or less of one side in the axial direction. The crowns of the pair of rolls with convex initial crowns are overlapped in an alternating arrangement, and the back-up rolls that support these work rolls each have a length of less than half of the axial direction on the opposite side from the crown of the work roll. A strip crown control method characterized in that a convex initial crown of 0.1 to 0.5 mm is provided across the strip, and the plate crown is adjusted by shifting the work roll in the roll axis direction.