JPH08252621A - Method for preventing meandering in cross-roll rolling - Google Patents

Abstract

PURPOSE: To prevent meandering in cross roll rolling in a cold rolling mill by adjusting the roll roughness of an upper work roll and roll roughness of a lower work roll. CONSTITUTION: The roll roughness of the upper work roll 11u which is arranged in the crossed state in a plane view in the cold rolling mill and the roll roughness of the lower work roll 11d are adjusted. The work roll having the roll roughness lower than that of the upper work roll 11u is used as the lower work roll 11d. It is desirable that difference in roll roughness is 0.05-0.10μm. In this way, the thrust force which acts on between the lower work roll 11d and a metal plate and the thrust force which acts on between the upper work roll 11u and the metal plate are uniformized and the meandering of the metal plate is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called cross, in which a plate material is passed between an upper work roll and a lower work roll, which are arranged in a crossed state when viewed in plan, to perform cold rolling. The present invention relates to a meandering prevention method in roll rolling.

[0002]

2. Description of the Related Art In recent years, the quality of rolled products by cold rolling,
In particular, the demand for shape accuracy has become extremely strict. Rolling of plate material is generally performed by passing between upper and lower work rolls, but rolling with the axis of the upper work roll and the axis of the lower work roll arranged in parallel When rolling with rolls, the initial crown of the work roll must be changed as appropriate depending on the plate width and material of the plate to be rolled, and therefore, when performing such rolling, work rolls with different crown amounts must be prepared. There was a problem that had to be kept. In order to solve this problem, so-called cross roll rolling is performed, in which a plate material is passed between an upper work roll and a lower work roll which are arranged in a crossed state when viewed in plan, and rolling is performed.

However, in this cross roll rolling, since the plate material is passed between the upper work roll and the lower work roll which are arranged in a crossed state in a plan view, the plate material is passed from the upper work roll. The thrust force received by
There is a problem that the plate material easily meanders because the balance of the thrust force received by the plate material from the lower work roll is lost. To address this problem, for example, the following method is disclosed.

In Japanese Patent Laid-Open No. 57-4314,
A method of controlling the meandering of the plate material by appropriately selecting and supplying the type and amount of the lubricant applied between the upper and lower work rolls and the plate material is disclosed.

Further, in Japanese Unexamined Patent Publication No. 60-72605, the upper and lower work rolls are rolled at different peripheral speeds. At this time, a work roll having a low peripheral speed is in a horizontal plane as compared with a work roll having a high peripheral speed. There is disclosed a meandering control rolling method in which a predetermined angle is inclined largely with respect to a direction orthogonal to the rolling direction.

[0006]

However, the above-mentioned conventional techniques have the following problems, respectively. That is, the former method is intended to prevent meandering by applying a lubricant between the upper and lower work rolls and the plate material.
During cross roll rolling, characteristics such as iron content, particle size, viscosity, and temperature in the lubricant are usually different depending on the operating conditions. Therefore, it is very difficult to select the type and amount of the lubricant to be applied according to the operating condition at the time of application. If the selected lubricant concentration is too low, plate contamination or heat streak occurs due to poor lubrication, and if the lubricant concentration is too high, slippage occurs between the work roll and the plate material.

On the other hand, the latter method requires equipment for rotating the upper and lower work rolls at different peripheral velocities and equipment for horizontally rotating at least one of the upper and lower work rolls. Will be a big deal.

[0008] Therefore, an object of the present invention is to provide a meandering prevention method in cross roll rolling which can always expect a certain meandering prevention effect irrespective of changes in operating conditions and does not require any large-scale equipment at all. .

[0009]

A meandering prevention method according to the present invention, which has solved the above-mentioned problems, is to arrange an upper work roll and a lower work roll in a cold rolling mill in a state of intersecting in plan view, In the meandering prevention method in cross roll rolling in which a plate material is rolled between the upper work roll and the lower work roll, adjusting the roll roughness of the upper work roll and the roll roughness of the lower work roll. By so doing, the thrust forces acting on the upper and lower surfaces of the plate member can be made uniform.

Specifically, for example, when the lubrication characteristics of the lower surface of the plate material are poor due to the difference in the plate-out property of the lubricating oil, the lower work roll has a lower roll roughness than the upper work roll. Is used, the thrust forces acting on the upper and lower surfaces of the plate material are made uniform. In this case, it is desirable that the difference in roll roughness between the upper and lower work rolls be 0.05 μm or more and 0.10 μm or less.

[0011]

First, the principle of meandering from the viewpoint of mechanical structure will be briefly described with reference to FIG. Note that, here, the description will be made on the premise that the peripheral speeds of the upper work roll 11u and the lower work roll 11d in the cross roll rolling machine 1 are the same. Plate material, for example steel plate M
Direction perpendicular to the transport direction of each work roll 11
The angle formed by the center lines of u and 11d (hereinafter, "cross angle")
Is denoted by θ, the thrust force (extrusion force) received by the steel plate M from the upper work roll 11u is Vu, and the thrust force received by the lower work roll 11d is Vd.

Further, the description will be continued assuming that the vertical upward direction (arrow + direction) with respect to the conveying direction of the steel sheet M is positive. The magnitude of the positive component of the total sum Vf of the thrust forces received by the steel sheet M from both work rolls 11u and 11d is determined by the magnitudes of the sine component of Vu and the sine component of Vd. Are the same in θ and are substantially determined by the magnitudes of Vu and Vd. Specifically, since the sine component of Vu is in the negative direction and the sine component of Vd is in the positive direction, it meanders in the positive direction if Vd> Vu and in the negative direction if Vd <Vu. Occurs, and if Vd = Vu, the meandering does not occur.

FIG. 3 shows an example of Vd> Vu, which is a general tendency in the prior art. That is, generally, the lower surface side of the plate material that is passed between the work rolls has a lower plate-out property of the lubricating oil than the upper surface side. Therefore, the lubrication characteristics are poor, and the coefficient of friction between the work roll and the plate during rolling increases accordingly.
Therefore, the thrust force applied to the plate material by the lower work roll is larger than the thrust force applied by the upper work roll, and the relationship of Vd> Vu is established.
Meander occurs.

In view of the principle of meandering described above, the present inventors have paid attention to the point that the meandering of the plate material is prevented by making the coefficient of friction between both work rolls and the plate material uniform.

That is, the coefficient of friction between the work roll and the plate is determined by the roll roughness of the work roll, the surface roughness of the plate, the property of the lubricant interposed between them, and the peripheral speed of the work roll. It Of these, the surface roughness of the plate material has already been determined, and since the properties of the lubricant change depending on the operating conditions as described above,
It is very difficult to handle, and in addition, in order to change the peripheral speed of the work roll, large-scale equipment is required as described above.

Therefore, in the present invention, by adjusting the roll roughness of the upper and lower work rolls, the thrust force acting between both work rolls and the plate material is made uniform. In a normal example, the coefficient of friction between the lower work roll and the plate is larger than the coefficient of friction between the upper work roll and the plate due to the difference in the plate-out property (water separation and spreading property) of the lubricating oil as described above, By using a work roll having a lower roll roughness than the upper work roll as the roll, it is possible to make the thrust force generated as a result uniform. In this case, as will be apparent from Examples described later, a remarkable meandering prevention effect can be expected by setting the roll roughness difference between the upper and lower work rolls to 0.05 μm or more. However, if the difference in roll roughness between the upper and lower work rolls is too large, meandering occurs in the opposite direction. Therefore, it is desirable that the difference in roll roughness between the upper and lower work rolls be 0.20 μm or less. Particularly, when the thickness is 0.10 μm or less, a remarkable effect of preventing meandering can be expected. Of course, in the case where the upper surface of the plate material has a higher frictional resistance, conversely, by setting the roll roughness of the lower work roll higher than that of the upper work roll, the generated thrust force Uniformity can be achieved.

Thus, the thrust force acting between the lower work roll and the plate material and the thrust force acting between the lower work roll and the plate material can be made uniform, and the meandering of the plate material can be prevented.

As described above, in the case of preventing the meandering by adjusting the roll roughness according to the present invention, it is possible to stably and continuously prevent the meandering because it is not affected by the change of the operating condition as in the conventional case. .

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments.
FIG. 1 is a plan view of a cross roll rolling mill 1 during rolling,
FIG. 2 is a view taken along the line 2-2. The cross roll rolling mill 1 includes an upper work roll 11u and an upper backup roll 12 arranged on the upper side of a plate material to be rolled, for example, a steel plate M.
u and the lower work roll 11 arranged below the steel plate M
d, the lower backup roll 12d. The upper work roll 11u, the upper backup roll 12u, the lower work roll 11d, and the lower backup roll 12d are arranged in parallel. When rolling the steel sheet M, a lubricant is supplied by a lubricant supply device (not shown).

In such a cross roll rolling machine 1, the upper backup roll 11 is used as the lower work roll 11d.
A roll having a lower roll roughness than the roll used for u is used. In the actual rolling operation, the lubricant is continuously supplied, and the plate-out property is different between the upper surface and the lower surface of the steel plate M, so the remaining amount of the lubricant (spreading amount)
Of course, there will be more on the upper surface. Therefore, the thrust force generated by the lower work roll 11d becomes larger than the thrust force generated by the upper work roll 11u.
In the positive direction, and meanders to the place where the force of the widthwise component of the steel plate M is balanced, and then stabilizes.

Therefore, as described above, by predicting these situations, the roll roughness of the lower work roll 11d is reduced in advance to reduce the frictional force, so that the thrust acting on each of the upper and lower surfaces of the steel plate M is reduced. The force can be made uniform, and thus the meandering of the steel sheet M can be prevented.

Since the magnitude of the thrust force received from the work roll is also affected by the physical properties of the lubricant,
It is desirable to determine the difference in roll roughness between both work rolls in consideration of these factors. Considering this point, the lower work roll 11d and the upper work roll 11u
Even when the peripheral velocities are not constant but different peripheral velocities, the meandering prevention method according to the present invention can be applied.

<Experimental Example 1> As a rolled material, a thickness of 3.0 m
An experiment of cross roll rolling was conducted using a general cold-rolled material having m, a width of 150 mm and a finished thickness of 0.6 mm. In the cross roll rolling machine used here, the roll roughness Ra of the upper work roll 11u is Ra = 0.25 μm, and the roll roughness Ra of the lower work roll 11d in the present invention is Ra = 0.2.
The lower work roll 11d in the comparative example has a roll roughness Ra of 0.25 μm. The work roll diameter of each work roll is 460 mm, and the rolling speed is 300 mpm.
Further, rolling was performed while appropriately changing the cross angle θ shown in FIG. The meandering amount generated at that time is shown in FIG.

As can be seen from FIG. 4, in the comparative example (roll roughness difference = 0 μm), the meandering amount increases as the cross angle θ increases, whereas the invention example ( According to the rolling according to the roll roughness difference = 0.05 μm, the meandering amount could be reduced as the roll roughness difference was increased.

<Experimental Example 2> Further, in order to compare the influence of the roughness difference between the upper work roll and the lower work roll, the roughness difference between the upper work roll and the lower work roll was changed stepwise so that the sheet material was rolled. An experiment was conducted. The conditions other than the roll roughness were the same as in Experimental Example 1. The result is shown in FIG.

As can be seen from FIG. 5, the result is that the meandering amount of the upper work roll and the lower work roll becomes smaller as the roughness difference becomes larger up to a certain roughness difference. Especially, the roughness difference between the upper and lower work rolls is 0.05 μm
From the above, it was found that the meandering amount hardly increased even when the cross angle θ was increased, and the effect of preventing the meandering was remarkably exhibited. However, conversely, if the roughness difference is too large, specifically, if the roughness difference exceeds 0.10 μm, meandering will occur in the negative direction, which is not preferable. In particular, it was found that when the thickness exceeds 0.20 μm, remarkable meandering occurs. From this result, the difference between the upper work roll and the lower work roll is 0.05 μm or more and 0.10 μm or more.
The following range is desirable.

[0027]

As is apparent from the above description, according to the present invention, in the cross roll rolling, the meandering of the plate material is performed without using the elements that change depending on the operating condition and without requiring large-scale equipment. Can be prevented.

[Brief description of drawings]

FIG. 1 is a conceptual plan view showing cross roll rolling.

FIG. 2 is a view taken along line 2-2.

FIG. 3 is an explanatory diagram showing a principle of occurrence of meandering.

FIG. 4 is a graph showing a difference in meandering amount between a case where a roughness difference is provided between an upper work roll and a lower work roll and a case where no roughness difference is provided.

FIG. 5 is a graph showing a change in meandering amount when the roughness difference between the upper work roll and the lower work roll is changed stepwise.

[Explanation of symbols]

1 ... Cross roll rolling machine, 11u ... Upper work roll, 1
1d ... lower work roll, 12u ... upper backup roll, 12d ... lower backup roll, M ... steel plate.

Claims (3)

[Claims] 1. An upper work roll and a lower work roll in a cold rolling mill are arranged so as to intersect each other when viewed in plan, and a plate material is passed between the upper work roll and the lower work roll for rolling. In the meandering prevention method in cross roll rolling, in order to achieve uniform thrust forces acting on the upper and lower surfaces of the plate material by adjusting the roll roughness of the upper work roll and the roll roughness of the lower work roll. A method for preventing meandering in cross roll rolling, comprising: 2. The method of preventing meandering in cross roll rolling according to claim 1, wherein a work roll having a roll roughness lower than that of the upper work roll is used as the lower work roll. 3. The method for preventing meandering in cross roll rolling according to claim 2, wherein the difference in roll roughness between the upper and lower work rolls is 0.05 μm or more and 0.10 μm or less.