JPS6055201B2 - Rolling method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rolling method using rolls.

In the rolling method, in which the material to be rolled is rolled by running it between rotating rolls, there is a strong demand for uniformity in the thickness of the rolled product in the width direction, and various methods have been used to meet this demand. It is being When rolling, a rolling load is applied only to both ends of the roll, so the central part of the roll to which no load is applied is deflected, and this deflection causes the thickness of the product to be uneven in the width direction.

In other words, the center portion in the width direction is thicker. Therefore, the following method is used to prevent uneven plate thickness due to roll deflection. The first rolling method involves applying an initial crown to the roll.

This changes the outside diameter of the roll along its length. For example, if the center of the roll bends as described above, the outside diameter of the roll at the center is made larger to make the thickness uniform. It is something. However, this method not only requires rolls with a wide variety of initial crowns to accommodate changes in rolling conditions such as strip width, strip thickness, and strip temperature, but also reduces the operating rate of the rolling mill due to roll replacement. There is a drawback that it does. The second rolling method involves adding a bending force to the rolls.

This applies a bending force to the roll. For example, if the center of the roll is deflected as described above, the bending force is applied in a direction to cancel out this deflection and make the board thickness uniform, making it necessary to replace the roll. The thickness distribution can be controlled without any problems. However, with this method, there is a limit to the bending force that can be applied to the roll due to the strength of the roll neck, and therefore, the plate thickness cannot be adequately controlled. In addition, there is a third rolling method in which rolls are crossed with each other.

This is achieved by rotating the axes of the upper work roll 1 and the lower work roll 2 by θ in a horizontal plane, as shown in FIG. 1 and FIG.
While detecting the thickness of the rolled material 3, the cross angle θ is changed according to the detected value to control the thickness distribution in the width direction. Further, as a fourth rolling method similar to this, as shown in the front view in FIG. 3 and in the side view in FIG. There is a method in which the rolls 4 are provided and the upper and lower parts constitute bare rolls, and the method is carried out in the same manner as rolling method 3. In this way, rolling methods 3 and 4 in which the work rolls are crossed are effective for the purpose of correcting the thickness distribution in the width direction of the sheet. However, in the roll cross rolling method in which the work rolls are crossed, a thrust force (a force applied parallel to the work roll) is generated on the work roll, and the bearings that receive this thrust force must be made large, which increases the manufacturing cost of the rolling mill. Become.

Further, depending on the rolling conditions, the generation of thrust force may damage the bearing, resulting in a major equipment accident, or generate heat in the bearing, making it impossible to perform high-speed rolling. On the other hand, in addition to the above-mentioned rolling method for sheet thickness control, a different circumferential speed rolling method has been developed for the purpose of reducing the rolling load applied to the rolls and the energy required for rolling, and has already been put into practical use.

However, when this different circumferential speed rolling method is applied to hot rolling, the following restrictions arise. Already, in the latter stage of the finishing mill, the upper and lower work rolls come into contact (roll kiss), so if there is a circumferential speed difference between the upper and lower work rolls, the frictional resistance caused by the opposing edges will cause a ζ driving force to be applied to the work rolls. It acts on the drive shaft as a transmission torque. If this transmitted torque exceeds the strength of the drive shaft, the drive shaft will be destroyed, resulting in a scratch load (
The rolling conditions such as the rolling load during roll kissing and the circumferential speed ratio of the upper and lower rolls are limited, and as a result, the thickness of the plate that can be rolled is limited. FIG. 5 shows the results of an experiment using the different circumferential speed rolling method and measuring the scratch load during roll kissing and the transmitted torque acting on the drive shaft.

In this experiment, the diameter of the upper and lower work rolls is 3? This is an actual measurement of the transmitted torque applied to the drive shaft when the work rolls are rotated in a roll-kiss state with a circumferential speed difference given by a certain degree of diameter difference. As shown in the figure, the transmitted torque increases approximately in proportion to the flaw load, and since the allowable torque limit of the work roll is 60T0N-tile in this rolling mill, the flaw load is limited to 70mCN or less. In addition, due to the capacity of the rolling mill, it is actually 300
A scratch load of up to 0T'0N can be applied. The present invention alleviates the drawbacks of such a rolling method, and makes it possible to make the thickness of the sheet uniform in the width direction with a small rolling load and low rolling energy.
Moreover, it is an object of the present invention to provide a rolling method that generates less thrust force and less transmitted torque than the conventional method.

The structure of the present invention which achieves this object is characterized in that upper and lower work rolls intersect and a material to be rolled is rolled by giving a peripheral speed difference between the upper and lower work rolls. Hereinafter, the present invention will be explained in detail based on examples.

It has been found that when upper and lower parallel work rolls with different circumferential speeds are crossed, the generated transmitted torque is reduced, and when a circumferential speed difference is given to the crossed upper and lower work rolls, the generated thrust force is reduced. is a combination of roll cross rolling method and different circumferential speed rolling method.

First, the thrust force generated by the roll cross rolling method and the transmitted torque generated by the different circumferential speed rolling method will be explained.

Figure 6 shows the results of measuring the thrust force FT generated when a steel plate is hot rolled using the upper and lower bare rolls shown in Figures 3 and 4 and changing the cross angle θ and rolling reduction γ. It is expressed by the coefficient μT (thrust force FT/reducing blade P). From this figure, it can be seen that the larger the cross angle 0 is, the larger the thrust coefficient μT is, and the larger the reduction rate γ is, the smaller the thrust coefficient μ7 is. Coefficient μ
τ is 2% to 6%. On the other hand, when the material to be rolled becomes thinner, the work rolls are in a roll kiss state when they idle before and after rolling, and at this time, unlike during rolling, a thrust force is generated on the work rolls. Figure 7 shows a cross angle of 0 in the roll kiss state.
This is a graph obtained through experiments to determine the relationship between the thrust coefficient μ and the thrust coefficient μ. From this figure, the thrust coefficient μa increases as the cross angle θ increases, and remains constant above 0=0j degrees (μ7=3
0%). The reason why the thrust coefficient is large during rolling relative to rolling is that the direction of the thrust force is changed or the size is suppressed by retarding, advancing, or shearing the rolled material due to the work roll pressure. Regarding the transmitted torque, the following formula holds true when rolling is performed using normal parallel rolls at different circumferential speeds.

From (1) and (2), FR: Transmitted torque FR: Frictional force between rolls Rw: Roll radius P: Kiss load μR: Coefficient of friction between rolls If μ8 and Rw are constant in (3), then TR is the drive of the rolls. The value of P is limited because it must be less than or equal to the strength of the shaft.

The present invention is illustrated in FIGS. 8 and 9.

FIG. 8 shows an upper work roll 6 and a lower work roll 7 having the same outer diameter dimensions intersecting each other, and the upper work roll 6
and the lower work roll 7 at different rotational speeds Vl and V2, respectively.
By doing so, a circumferential speed difference is given. FIG. 9 shows an upper work roll 8 and a lower work roll 9 having mutually different outer diameters Dl and D2 intersecting each other, and by rotating the upper work roll 8 and the lower work roll 9 at the same rotation speed. This gives a circumferential speed difference. Next, the effects of using the rolling method according to the present invention will be explained together with measured values.

FIG. 10 shows that when the work rolls are crossed, the inter-roll friction coefficient μm in the circumferential direction of roll rotation during roll kissing decreases.

In other words, when the cross angle 0 is 0 degrees (rolls are parallel)
Although μR=0.2 to 0.3, it can be reduced to μ8=0.05 by crossing θ=0.5 degrees. This means that μm in equation (2) or (3) above
This means that even though the value of TR is limited to less than the strength of the drive shaft, a larger scratch load P can be reduced.
can be added, expanding the range of sheet thickness that can be rolled. FIG. 11 shows that when the upper and lower work rolls are given a difference in circumferential speed, the thrust force generated on the work rolls during roll kissing is reduced.

That is, when the different circumferential ratio is 0% (the upper and lower work rolls have the same circumferential speed), μT=0.3, but by giving a different circumferential ratio of about α=5%, μT=0. It can be reduced to .1.

By combining the roll cross rolling method and the different circumferential speed rolling method in this way, the thrust card transmission torque that occurs when each method is used is simultaneously reduced.

The reason for this will be explained next.

In FIG. 12, which shows the combination of work rolls shown in FIG. The direction is at an angle β with respect to the central axis 10,
Frictional force F in this direction. works. The value of this FO is the scratch load P1 and the friction coefficient μ. Then VlVSIA
I, and the frictional force F.

The component forces Fτ and FR are applied to the upper work roll 6 as a thrust force and a transmitted torque in the rotational circumferential direction. This F
T and FR can be expressed as follows. On the other hand, the angle β is expressed as follows as a relationship between the cross angle θ and the different velocity rate α (=). Also, the thrust coefficient for the thrust force is expressed as μ
If the friction coefficient in the T1 roll rotation direction is μR, then equation (5)
~(9) to formula AIl(11), α=0.00
Figure 1)3 shows the values of the mortality x for the cross angle 0 when the cross angle is 0.2, 0.01, and 0.02.

For example, when a cross roll rolling method with a cross angle of 0 = 0.6 degrees and a different circumferential speed rolling method with a different speed ratio α = 0.02 are combined, what is the ratio of the thrust force generated by the cross roll rolling method to the frictional force? x is about 1.0 when there is almost no peripheral speed difference between work rolls (α=0.002), but when α=0.
When set to 02, it decreases to about 0.7.

On the other hand, what is the ratio of the transmitted torque to the frictional force generated by the different circumferential speed rolling method? x is 1.0 when cross angle 0=o, but O
=0. When used as a hoe, it decreases to about 0.7. As described above with reference to the embodiments and drawings, according to the present invention, it is possible to reduce both the thrust force and the transmission torque generated in the work roll. By selecting α, a rational equipment design of the rolling mill can be made, and as a result, the flaw load can be increased and the rolling conditions for thin products can be widened.

[Brief explanation of the drawing]

1 to 4 relate to a rolling mill using a conventional rolling method. Figure 4 is a front view and side view of a rolling mill in which the upper and lower work rolls and backup rolls cross each other, and Figure 5 is a graph showing the relationship between flaw load and transmitted torque when rolling is performed using the different circumferential speed rolling method. , Figures 6 and 7 are graphs showing the relationship between the thrust coefficient and the cross angle and reduction ratio when rolled by the roll cross rolling method, and the relationship between the thrust coefficient and the cross angle. Figures 8 and 9 are graphs showing the relationship between the thrust coefficient and the cross angle. Schematic diagrams showing the arrangement of work rolls, etc. in the rolling method according to FIGS. 10 and 11
The figure is a graph showing the relationship between the cross angle, roll rotation direction friction coefficient, different circumferential ratio, and thrust coefficient when rolled using the rolling method according to the present invention. Figure 12 explains the effects of the rolling method according to the present invention. FIG. 13 is a graph showing the relationship between the thrust force and the transmitted torque with respect to the cross angle and different speed ratio when the rolling method according to the present invention is used. In the drawing, 6 and 8 are upper work rolls, 7 and 9 are lower work rolls, and 10 is a central axis.

Claims (1)

[Claims] 1. A rolling method characterized by rolling a material to be rolled by intersecting upper and lower work rolls and giving a peripheral speed difference between the upper and lower work rolls.