JPH10296303A - Method for rolling metallic strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rolling method with a strip mill excellent in productivity by elevating the limit of rolling load (the limit of draft) due to the max. Hertz stress. SOLUTION: In this rolling method of metallic strips 6, the metallic strips 6 are rolled by taking the circumferential speed ratio of an upper and lower work rolls 1, 2 as >=1.1 with the rolling mill in at least either upper or lower roll assembly of which has a mechanism in which the work roll 1 is supported with divided back-up rolls 3, 4 which are divided into three or more divisions in the axial direction, in which an independent load detecting device and screw down device are arranged on each divided back-up roll 3, 4, the roll diameter Dwr of the work roll 1 supported with the divided back-up rolls 3, 4 is taken as <=400 mm and the ratios Dbur/Dwr of the roll diameters Dbur of the divided back-up rolls 3, 4 to the diameter of the work roll Dwr are taken as <=3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism in which at least one of upper and lower roll assemblies supports a work roll by a split backup roll divided into three or more in an axial direction. The present invention relates to a method for rolling a metal strip by a plate rolling mill in which an independent load detecting device and a rolling-down device are arranged.

[0002]

2. Description of the Related Art In recent years, a load distribution of a split backup roll is detected and a load distribution between a rolled material and a work roll is estimated as in a plate rolling mill described in Japanese Patent Application Laid-Open No. 05-48375. A rolling mill capable of estimating a later sheet crown and sheet shape with high accuracy has been attracting attention.

In this rolling mill, Japanese Patent Application Laid-Open No. 06-2622
No. 11 discloses a cluster type rolling mill having a vertically asymmetric roll arrangement as shown in FIG. Such a rolling mill is capable of controlling a sheet crown, a sheet shape, and the like with high accuracy, and is therefore extremely advantageous for producing a sheet rolled material requiring strict shape quality. It is known that, in a rolling mill provided with a backup roll and a work roll, a Hertzian stress acts between the backup roll and the work roll.
Japanese Patent Application Laid-Open No. 7-108303 discloses that the position of each split backup roll and the roll diameter of the split backup roll are set such that the maximum Hertz stress between the split backup roll and the work roll is equal on the entrance side and the exit side of the rolling mill. Are disclosed.

[0004]

As described above, a rolling mill having split backup rolls can control a sheet crown, a sheet shape, and the like with high accuracy. If it is provided, a great deal of expense is required. On the other hand, it is also possible to divert the housing of the existing 4Hi rolling mill and incorporate a roll assembly having split backup rolls into the housing to form a vertically asymmetric rolling mill as shown in FIG. 1, for example. .

When a metal strip having a thickness of several mm to several tens of mm is rolled, a work roll of a 4Hi rolling mill has conventionally used a roll diameter of 500 to 700 mm. Compared with the case of using a work roll having a roll diameter of 400 mm or less, the control accuracy of the plate thickness and shape is remarkably inferior. Therefore, in order to accurately roll a metal strip having a thickness of several mm to several tens of mm, the work roll diameter must be a small diameter roll of 400 mm or less, but a work roll having a roll diameter of 400 mm or less is required. If a roll roll is used, the horizontal deflection of the work roll becomes a problem as in a conventional 4Hi rolling mill, so it is necessary to support a small-diameter work roll with a plurality of backup rolls.

On the other hand, when the above configuration is incorporated in an existing housing, the roll diameter of the split backup roll is limited by the size of the existing housing as shown in FIG. 1, that is, the roll diameter of the backup roll in the existing housing. It must be less than half the diameter. Normal,
The roll diameter of the backup roll of the 4Hi rolling mill for rolling the metal strip having the above-mentioned thickness range is 1500 to 180.
Since it is 0 mm, the roll diameter of the split backup roll is 750 to 900 mm or less. Therefore, when the existing housing is diverted as described above, the ratio between the roll diameter of the divided backup roll and the roll diameter of the work roll supported by the divided backup roll is 3 or less.

[0007] As described above, a metal strip having a thickness of several mm to several tens of mm is formed with high precision in the thickness and shape of the existing 4Hi.
In order to perform rolling in a rolling mill using the housing of the rolling mill, the roll diameter of the work roll needs to be 400 mm or less, and the roll diameter of the split backup roll and the roll diameter of the work roll supported by the split backup roll Must be 3 or less.

A vertically asymmetric rolling mill having a split backup roll disclosed in the above-mentioned Japanese Patent Application Laid-Open No. H06-262111 rolls a metal strip of several mm or less. Is also as small as 80 mm, and the ratio of the roll diameter of the split backup roll to the roll diameter of the work roll supported by the split backup roll is as small as 1.6.

As described above, when rolling a metal strip in a rolling mill having a backup roll and a work roll, a Hertzian stress acts between the backup roll and the work roll. In a rolling mill having a configuration as shown in FIG. 1, a rolling load is generally P, a plate width is W, a work roll diameter is Dwr, a divided backup roll diameter is Dbur, a line passing through the center of the divided backup roll and the work roll, and a horizontal line. Let θ be the angle formed by the following equation, the Hertz stress σHZmax is given by the following equation.

[0010]

(Equation 1)

As is clear from the above equation, the Hertz stress can be reduced by increasing the diameter ratio between the work roll and the split backup roll. However, as described above, especially when the existing housing is diverted, Its value cannot be made large. For example, a normal 4Hi rolling mill has a work roll diameter of about 600 mm and a backup roll diameter of 150 mm.
It is about 0 mm, and the roll diameter ratio between the work roll and the backup roll is 2.5. However, as described above, when a rolling mill having a split backup roll using an existing housing is used, for example, a work roll diameter of 30 mm is used.
0 mm, split backup roll diameter 600 mm, θ = 45
Degree, the work roll diameter is 1 compared to a normal rolling mill.
/ 2 times, the diameter of the divided backup roll becomes 1 / 2.5 times, and the roll diameter ratio between the work roll and the backup roll becomes 2.0. When the rolling load is the same, when calculated based on the above equation, the Hertz stress of the rolling mill to which the above technique is applied is increased about 1.74 times as much as the Hertz stress of the conventional 4Hi rolling mill.

From the above, in such a rolling mill, the diameter ratio of the small-diameter work roll to the divided backup roll cannot be sufficiently increased, and the work roll diameter must be reduced as described above. In this situation, the Hertz stress between the work roll and the split backup roll is greatly increased. If the Hertz stress exceeds a certain limit value during rolling, surface fatigue defects of the roll called spalling and surface flaws where the end of the divided reinforcing roll called a roll mark is transferred to the rolled sheet occur.
The limit value of the Hertz stress varies depending on the material of the roll and the like, but is generally a value of 180 to 220 kgf / mm ² . In order to avoid the above-mentioned problems, rolling is usually performed at or below the Hertz stress limit. For this reason, in the above-mentioned vertically asymmetric cluster-type rolling mill, when the rolling reduction is increased, the rolling load increases and the Hertz stress increases, and thus there is a problem that it is difficult to increase the rolling reduction.

As a method for solving such a problem, there is a technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 07-108303. However, in this method, since the work roll diameter is the same, the rolling load itself does not change. For this reason, there is a limit to the rolling reduction that can be taken by the rolling mill, and there is a problem that productivity is sometimes hindered. The present invention is such a cluster type of vertically asymmetric roll arrangement, comprising a small-diameter work roll, and in a rolling mill having a small roll diameter ratio between the backup roll and the work roll, when rolling the metal strip, the rolling mill An object of the present invention is to provide a rolling method that improves the restriction of the draft due to the Hertz stress. Thereby, for example, even when a rolling mill of a cluster type is configured by diverting the housing of an existing rolling mill, it is possible to provide a method that enables rolling without being restricted by the rolling reduction.

[0014]

According to the present invention, at least one of the upper and lower roll assemblies is disposed in the axial direction.
This is a mechanism that supports a work roll by divided backup rolls divided into more than one. Each divided backup roll is provided with an independent load detection device and a reduction device, and the diameter of the work roll supported by the divided backup roll ( Dwr) is 400 mm or less, and the ratio (Dbur) of the roll diameter (Dbur) of the divided backup roll to the work roll diameter supported by the divided backup roll is
/ Dwr) is set to 3 or less, and the metal strip is rolled by setting the peripheral speed ratio of the upper and lower work rolls to 1.1 or more to roll the metal strip. Further, the present invention provides the above-mentioned invention,
This is achieved by a method for rolling a metal strip, wherein the peripheral speed ratio between the upper and lower work rolls is 1.1 or more and 1.3 or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. FIG. 1 is a schematic view showing one example of a rolling mill to which the method of the present invention is applied. FIG. 1 (a) is a side view thereof, and FIG. 1 (b).
Is a top view. In FIG. 1, the upper roll assembly is divided into seven backup rolls divided into seven in the axial direction.
A to 3C, a mechanism for supporting the work roll 1 by 4A to 4D, and each divided backup roll 3A to 3A
In C, 4A to 4D, a load detecting device and an independent split backup roll pressing device are arranged independently. The lower work roll 2 is supported by a lower backup roll 5. The roll diameter of the upper work roll 1 is 240 mm, the roll diameter of the split backup roll 3 is 500 mm, and the diameter ratio between the split backup roll and the work roll is about 2.1. The metal strip 6 is rolled by a rolling mill. The upper work roll 1 is rotating at a roll peripheral speed V _U , and the lower work roll is rotating at a roll peripheral speed _VL , and these are driven by two motors, respectively. In such a rolling mill, the metal strip was rolled while changing the peripheral speed ratio between the upper and lower work rolls, and the pressure distribution in the roll bite was investigated.

FIG. 2 is a conceptual diagram for explaining the pressure distribution in the roll bite and the position of the neutral point.
(A-2) is when the upper and lower work rolls have the same peripheral speed,
(B-1) and (b-2) of FIG. 2 show the case where the upper and lower rolls have different peripheral speeds. Normally, the peripheral velocity V _L of the upper work roll roll peripheral velocity V _U and the lower work rolls are speed controlled to be the same speed. That is, rolling is performed at a peripheral speed ratio of 1. At this time, the pressure distribution in the roll bite is, as shown in FIG. 2 (a-1), a neutral point position (a position where the moving speed of the metal strip rolled in the roll bite is equal to the circumferential speed of the roll, ie, FIG. (A-
Friction hills having rolling force peaks at E and F) in 2) are formed. The rolling load is obtained by integrating the friction hill.

In the method of the present invention, the peripheral speed ratio V _U / V
_L ≧ 1.1. Therefore, for example, when the upper work roll diameter is smaller than the lower work roll diameter as shown in (b-2) of FIG. 2, the upper work roll 1 rotates faster than the lower work roll 2. At this time, as shown in (b-2) of FIG. 2, the pressure distribution in the roll bite is such that the neutral point is located near the roll bite outlet G on the upper work roll (high peripheral speed roll) side and the lower work roll (low). On the peripheral speed roll) side, it is located near the roll bite entrance H. In (b-2) of FIG. 2, the direction of the friction shear stress is reversed at the neutral point as shown by the arrow, so that the friction shear stress is offset between the neutral point of the upper work roll and the neutral point of the lower work roll. Friction Hill is (if the peripheral speed is the same (a-
The friction hill of 1) is cut (indicated by a broken line in (b-1)), and the pressure distribution becomes a solid line as a result. As is clear from FIG. 2 (b-1), the rolling load is smaller under the conditions of the method of the present invention. Therefore, even at the same rolling reduction, the method of the present invention reduces the rolling load and reduces the Hertz stress between the upper work roll and the split backup roll. In other words, it can be seen that the rolling reduction until the maximum Hertz stress is reached can be increased by the method of the present invention.

FIG. 3 is a conceptual diagram showing the effect of the peripheral speed ratio on the rolling load and the rolling torque on the high peripheral speed roll side. As is clear from FIGS. 3 and 2, the load reduction effect has a larger speed ratio. When the speed ratio is smaller than 1.1, the effect is small, and when the speed ratio is 1.1 or more, the effect is increased. Further, when the neutral point position protrudes outside the roll bite (when the speed ratio is greater than 1.3), the load reduction effect is saturated. Further, the rolling torque on the high peripheral speed roll side increases as the peripheral speed ratio of the work roll increases, and rapidly increases when the speed ratio exceeds 1.3.
Therefore, in order to avoid an increase in the size of the motor of the rolling mill, the peripheral speed ratio of the work roll is 1.3 ≧ V _U / V
It has been found that _L ≧ 1.1 is preferred.

[0019]

FIG. 1 shows an embodiment of the present invention. FIG.
Is a plate rolling mill to which the present invention is applied, and its specifications are shown in Table 1. In FIG. 1, the upper roll assembly is divided into 7 divided backup rolls in the axial direction, 3A to 3A.
C, 4A to 4D, a mechanism for supporting the work roll 1, and each of the divided backup rolls 3A to 3C, 4
In each of A to 4D, a load detection device and an independent split backup roll pressing device are arranged independently.
Is an upper work roll, 2 is a lower work roll, 3 is an upper split backup roll (3 splits), 4 is an upper split backup roll (4 splits), 5 is a lower backup roll, and 6 is a metal strip. The angle θ of the upper divided backup roll is 45 degrees, and the body length of each divided backup roll is 130 mm.

When cold rolling is performed at a peripheral speed of the upper work roll and the lower work roll of 40 m / min using this mill, the rolling reduction from the maximum Hertz stress limit (200 kgf / mm ² ) of the split backup roll 3 is performed. The rate was 35% and the rolling load could only be taken up to about 970 TON. When applying the present invention and performing cold rolling at a peripheral speed of the upper work roll of 52 m / min and a peripheral speed of the lower work roll of 40 m / min, the maximum Hertz stress limit of the divided backup roll 3 (200 kgf / mm ² ). From this, it was possible to obtain a rolling reduction of 45% and a rolling load of about 970 TON. In the embodiment of the present invention, the case where the peripheral speed of the upper roll is faster than the peripheral speed of the lower roll has been described. However, the same effect can be obtained when the peripheral speed of the lower roll is faster than the peripheral speed of the upper roll. Needless to say, this is obtained.

[0021]

When the rolling mill of the present invention is used, the rolling load can be reduced by different peripheral speed rolling, so that high-pressure rolling can be performed, and the productivity of the rolling mill can be increased.

[0022]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of a rolling mill to which the method of the present invention is applied, where (a) is a side view and (b) is a top view.

FIGS. 2A and 2B are conceptual diagrams illustrating a pressure distribution in a roll bite and a position of a neutral point. FIGS. 2A and 2A illustrate a case where upper and lower work rolls have the same peripheral speed. (a-1) shows the pressure distribution, (a-2) shows the position of the neutral point, and (b-
1) and (b-2) show the case where the upper and lower rolls have different peripheral speeds, (b-1) shows the pressure distribution, and (b-2) shows the position of the neutral point.

FIG. 3 is a conceptual diagram showing the effect of a peripheral speed ratio on a rolling load and a rolling torque on a high peripheral speed roll side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Upper work roll 2 ... Lower work roll 3 ... Upper split backup roll (3 split) 4 ... Upper split backup roll (4 split) 5 ... Lower backup roll 6 ... Metal strip E, F, G, H ... Neutral point

Claims (2)

[Claims] 1. A mechanism in which at least one of the upper and lower roll assemblies supports a work roll by a split backup roll divided into three or more in an axial direction, and an independent load detecting device is provided for each split backup roll. And a roll-down device, and a roll diameter (Dwr) of a work roll supported by the divided backup roll.
And the ratio of the roll diameter (Dbur) of the divided backup roll to the work roll diameter supported by the divided backup roll (Dbur / Dwr) is 3 or less. A method for rolling a metal strip, wherein the metal strip is rolled at a speed ratio of 1.1 or more. 2. The peripheral speed ratio between upper and lower work rolls is set to 1.1.
2. The method for rolling a metal strip according to claim 1, wherein the value is not less than 1.3.