JPH0459112A - Method for controlling crown on cold rolling of reverse mill - Google Patents

Abstract

PURPOSE:To improve the working efficiency for controlling the crown by specifying the shifting position of the work roll and setting it on the cold rolling of the reverse mill. CONSTITUTION:The taper effect quantity ( h) displaying the good state at each pass of the cold rolling of the reverse mill is caluculated with the equation. Here, (ah+b) is the constant decided with the roll dimension of the rolling mill, WRT is the value decide with the taper angle (theta) of the work roll, WRdelta is the shifting position of the work roll. By moving the work roll to its axial direction in the range that this taper effect quantity is made respectively to be under than 1% of the outlet side sheet thickness (h), the shifting is distributed and decided. Therefore, the taper effect quantity of each pass can be easily controlled and the working efficiency is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves cold rolling a metal strip by reciprocating the strip through a rolling mill equipped with a work roll having a tapered end at one end of the body. When rolling the metal strip, it is possible to uniformly control the thickness distribution in the width direction of the rolled metal strip, and to grasp the amount of control, thereby making it possible to roll the metal strip with high thickness accuracy in the width direction and with a good shape. The present invention relates to a crown control method in cold rolling using a reverse mill.

[Conventional technology]

In general, metal strips such as hot-rolled steel strips, which are raw sheets for cold rolling, have a thickness distribution in which the thickness decreases from the center in the width direction toward the edges, that is, a convex crown shape, especially at the edges in the width direction. The plate thickness decreases rapidly in the vicinity. This is because in the conventional cold rolling method in which a metal strip is rolled by opposing cylindrical work rolls, an external force is applied to bend the work rolls in the axial direction in order to maintain a constant thickness of the metal strip at the center of the width of the strip. Because the metal strip is rolled by roll bending, the work roll comes into strong contact with the metal strip, especially near the edges in the width direction, resulting in the strip being rolled into a shape in which the thickness of the strip is sharply reduced near the edges in the width direction. Because it will be done.

However, in cold rolling a metal strip, it is required to roll such a convex crown-shaped metal strip so that it has a good rolled shape and a uniform thickness distribution with a rectangular cross section.

Therefore, a tapered part is formed at one end of the right and left opposite sides of the body of each of the opposing work rolls, and the edge of the metal strip to be rolled is formed between the taper start point and the end point of the taper part. A rolling method has been proposed that suppresses the decrease in the thickness of the metal strip in the vicinity of the edges in the width direction by cold rolling the metal strip and increases the precision of the thickness of the metal strip. This is because when a metal strip is cold-rolled using this rolling method, the distance between opposing work rolls at the tapered part of the work roll increases, so the thickness of the metal strip at the tapered part decreases in the width direction of the metal strip. This is because the thickness is suppressed compared to the central portion, and the thickness shape of the metal strip as a whole becomes better.

However, when reverse rolling is performed by passing a metal strip back and forth through a rolling mill equipped with a work roll having such a tapered portion, the taper of the work roll is removed from the widthwise edge of the metal strip in each pass. If the set value of the distance to the starting point is not appropriate, the shape of the cold-rolled metal strip will be poor, and the metal strip as a whole will not have a good thickness shape. In addition, when a metal strip that has been rolled in a poor shape in the previous pass is passed through the rolling mill again, the shape deteriorates further and the metal strip sometimes breaks from the edge.

Therefore, it is necessary to set the distance from the widthwise edge of the metal strip to the taper start point of the work roll to an appropriate value. Since the distance from the edge to the start point of the work roll's taper was set, the extent to which the thickness of the widthwise edge of the metal strip passed through the rolling mill had improved could only be confirmed after rolling. In reverse rolling, it is difficult to accurately preset the distance from the widthwise edge of the metal strip to the taper start point of the work roll in order to obtain the target thickness accuracy. As the shape of the metal strip further deteriorates, it becomes more difficult to set the distance from the widthwise edge of the metal strip to the taper start point of the work roll to an appropriate value. There was a drawback that the shape could not be grasped, resulting in lower yield and lower work efficiency.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of the prior art, and the work roll is tapered from the taper start point to one end of the body in each pass before the final pass. By making it possible to set the distance to the edge of the rolled metal strip in advance to a value that allows the desired thickness accuracy, it is possible to grasp the thickness accuracy of the metal strip rolled in the final pass. An object of the present invention is to provide a method for controlling crown in cold rolling using a reverse mill, which improves yield and has excellent work efficiency.

[Means to solve the problem]

As a result of intensive research in order to solve this problem, the present inventors have found that, for the reasons explained below with some speculation,
A predetermined value near the edge of the metal strip in the width direction when the rolled metal strip is cold-rolled by a cylindrical work roll and when it is cold-rolled by a work roll with a taper tapered at one end of the body. The thickness difference at the position (hereinafter referred to as the taper effect amount) is the exit side plate thickness of the rolled metal strip, and the distance from the widthwise edge of the rolled metal strip to the taper start point of the work roll (hereinafter referred to as the shift of the work roll) They completed the present invention by discovering that it is proportional to the taper angle (referred to as position) and the taper angle of the taper attached to the work roll.

■ In a rolling mill in which a tapered part is formed at one end of the opposite left and right sides of the body of each of the opposing work rolls, the edge positions in the width direction of the rolled metal strip are opposite when no load is applied. The amount of increase in the distance between the work rolls is determined from the tangent tan θ of the taper angle θ of the work rolls WRT (the amount of decrease in the diameter of the work rolls per 100++ a of the length of the tapered part in the roll axis direction) W
RT = 100 /1
It can be approximated as a value of 00.

■ The influence of the tapered part of the work roll on the elastic deformation of the work roll during cold rolling is that the tapered part is locally formed so that it is located near the widthwise edge of the rolled metal strip. This mainly affects the roll flatness of the work roll, which has a small effect on the fine deflection of the roll. Therefore, at a predetermined position near the edge in the width direction of the rolled metal strip located at the tapered portion of the work roll, the rolling load is reduced due to an increase in the tension of the rolled metal strip, so that the amount of flattening of the work roll is reduced.

■ Work roll flattening reduction amount and rolling load reduction amount.

Since the amount of reduction in rolling load and the amount of increase in tension, and the amount of increase in tension and amount of increase in thickness on the exit side are each approximately proportional to each other, the amount of decrease in flatness of the work roll and the amount of increase in thickness on the exit side are approximately proportional to each other. Ignoring the influence of the taper section on the deflection of the work roll axis, the increase in thickness at the exit side is calculated from the increase in the gap between the opposing work rolls at the edge position in the width direction of the rolled metal strip under no load. This is obtained by subtracting the amount of flattening of the work rolls, and the amount of increase in thickness on the exit side is approximately proportional to the amount of increase in the distance between the work rolls.

■ When the thickness of the rolled metal strip near the edge in the width direction increases due to the work roll being tapered, the elongation rate with respect to the center of the width of the metal strip near this edge decreases, and this elongation rate increases. The amount of decrease increases or decreases depending on the thickness of the exit side plate, and is almost proportional to the amount of increase in tension described above, and has almost no relation to other rolling conditions.

From the knowledge of the above 0 to 0 terms, the value a h + b derived from the exit side plate thickness at the widthwise center of the rolled metal strip and the constants a and b determined by the roll dimensions of the rolling mill,
The taper effect amount is calculated by multiplying the value WRT obtained from the tangent tanθ of the taper angle θ of the work roll and the work roll shift position [WRδ, which indicates the distance from the edge of the metal strip to be rolled to the taper start point of the work roll. The present invention was completed by discovering that Δh, that is, Δh=(ah+b)×WRT×WRδ, can be estimated.

Hereinafter, the method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is an explanatory side view showing an example of a reverse mill suitable for carrying out the method of the present invention, and FIG.
-A cross-sectional explanatory view, Fig. 3 is an enlarged explanatory view of B part in Fig. 2, and Fig. 4 is the amount of taper effect at a predetermined position from the width direction edge when a metal strip to be reverse rolled is made one pass. FIG. 5 is a diagram showing the relationship between measured values and values obtained from formulas, and FIG. 5 is a diagram showing the relationship between measured values and values obtained from formulas. Figure 6 shows the distribution of sheet thickness deviation with respect to the widthwise center of a cold-rolled metal strip that is reciprocally passed through a rolling mill. Figure 7 shows the relationship between the taper effect amount and the shift position of the work roll when a metal strip that is reverse-rolled is passed through one pass while keeping the rolled metal strip constant. A diagram showing the relationship between the taper effect amount and the tangent of the taper angle of the work roll when a metal strip that is reverse-rolled at a constant position is passed through one pass. FIG. 12 is a diagram showing the relationship between the taper effect amount and the exit side plate thickness when a metal strip that is reverse rolled is passed through one pass while keeping the shift position of the work roll constant.

To carry out the method of the present invention, first, as shown in FIGS. 1 to 3, a work roll 3 having a tapered portion 3a formed at one end of each body portion 3b is first prepared. , a reverse mill consisting of rolling mills 2 facing each other with their tapered portions 3a located on opposite left and right sides is prepared. In this rolling mill 2, the metal strip 1 to be rolled is passed back and forth, and the work roll 3 on which the tapered portion 3a is formed has a taper starting point which is the boundary point between the body portion 3b and the tapered portion 3a having the same diameter. The distance from T0 to the edge of the rolled metal strip 1 in the width direction, that is, the shift position WR of the work roll 3
It is installed movably in the axial direction so that δ can be set to a predetermined value.

A rolling mill 2 equipped with such work rolls 3 has work rolls 3 on both sides sandwiching the metal strip 1 to be rolled, as shown in FIGS. In addition to a six-high rolling mill in which a set of rolls 4 and a set of backup rolls 5 are installed on the outside thereof, various rolling mills such as a cluster mill and a Sendzimya mill can be used.

Then, the thickness of the rolled metal strip 1 near the edge in the width direction is measured on the exit side and/or the entry side of the rolling mill 2, and based on this measurement value, the work roll 3 is It is preferable to modify the shift position WRδ.

[For production]

When carrying out the method of the present invention using such a reverse mill, the rolled metal strip 1 is passed back and forth through the rolling mill 2, and in each pass from the first pass to the previous pass of the final pass, the rolled metal strip 1 is passed back and forth through the rolling mill 2. 1 is positioned at the tapered portion 3a of the work roll 3, and the shift position WRδ of the work roll 3 is set as explained below.6 First, each pass from the first pass to the previous pass of the final pass. The taper effect amount Δh to be improved is determined, and the taper effect amount Δh is a constant a determined by the thickness of the exit side plate at the widthwise center of the rolled metal strip 1 and the roll dimensions of the rolling mill 2, as described above.

b and the value W obtained from the tangent tanθ of the taper angle θ of the work roll 3.
It is estimated by the product of RT WRT=100X 2 Xtanθ and the shift position WRδ of the work roll 3, that is, Δh = (ah + b)XWRT XWRδ. That is, in the rolling mill 2, the rolled metal strip 1
When the metal strip 1 to be rolled is cold-rolled with the thickness of the outlet plate at the center in the width direction and the taper angle θ of the work roll 3 being constant, the taper effect amount Δh is determined by the shift of the work roll 3 as shown in FIG. The taper effect amount increases in direct proportion to the increase in the position WRδ, and when the metal strip 1 to be rolled is rolled with the exit side plate thickness at the center in the width direction of the metal strip 1 to be rolled and the shift position WRδ of the work roll 3 constant. Δh is the tangent tanθ of the taper angle θ of the work roll 3 as shown in FIG.
The taper effect amount Δ increases when the metal strip 1 to be rolled is rolled while keeping the taper angle θ of the work roll 3 and the shift position WRδ of the work roll 3 constant.
It has been confirmed through experiments that h increases in direct proportion to the increase in thickness of the exit side plate at the widthwise center of the rolled metal strip 1, as shown in FIG. Furthermore, the value a h+b derived from constants a and b determined by the exit side plate thickness at the widthwise center of the rolled metal strip 1 and the roll dimensions of the rolling mill 2 and the tangent tan θ of the taper angle θ of the work roll 3 is obtained. The taper effect amount Δh obtained from the product of the value WRT and the shift position WRδ of the work roll 3 was compared with the measured value of the rolled metal strip 1 on the exit side of the rolling mill 2, as shown in FIG. It was confirmed that they almost matched. At this time, the amount of increase in the interval between the work rolls 3 at a predetermined position near the edge in the width direction of the rolled metal strip 1 is WRTXWR
It is approximated as δ/100, and the thickness of the cold-rolled metal strip 1 gradually decreases in a quadratic curve from the center in the width direction of the metal strip to the edge, and 20 mm from the edge.
Normally, the plate thickness decreases rapidly on the edge side from the position of
The taper effect amount Δh at a position 20 mm from the edge is set. In addition, the taper effect amount Δh is calculated between the rolled metal strip 1 cold-rolled by the cylindrical work roll 3 and the taper portion 3.
This is the thickness difference near the edge in the width direction with the rolled metal strip 1 cold-rolled by the work roll 3 formed with a cylindrical work roll 3. The taper effect amount Δh to be improved is set from the crown amount at a position 20 m+ from the edge. This taper effect amount Δh is set to an appropriate value depending on the rolling ratio, plate thickness, etc., and is set to 1% or less of the exit side plate thickness in order to prevent plate breakage due to increased tension near the plate edge. Set within the range of values.

Next, the value ah+b is derived from the exit plate thickness at the widthwise center of the rolled metal strip 1, that is, the distance between the bodies 3b of the opposing work rolls 3 and the constants a and b determined by the roll dimensions of the rolling mill 2. Deduce. Constants a and b determined by the roll dimensions of this rolling mill 2 are the roll diameter,
Although it differs depending on the roll body length and the distance between roll chokes, the variation in these roll dimensions is small in the same rolling mill. Therefore, for the roll dimensions consisting of WRδ and WR
It can be determined by conducting an experiment in which T is kept constant and the thickness of the exit side plate is varied, and the taper effect amount Δh is measured at that time.For example, in the example described later, a is 0.
225, the above values were determined with b as o and oso.

From the values obtained above, the shift position of work roll 3 is 11.
The above relationship for WRδ, that is, the taper effect amount Δh is a value derived from constants a and b determined by the outlet thickness of the metal strip 1 to be rolled and the roll dimensions of the rolling mill 2. h + the taper of the work roll 3 The value WRT obtained from the tangent tan θ of the angle θ and the taper start point T of the work roll 3 from the edge of the metal strip 1 to be rolled. WR
It is determined and set from δ=Δh/((a h+b)XWRT).

In this setting, since the deformation resistance of the rolled metal strip 1 is low in the first pass, Δh/h (this value is approximately proportional to the amount of increase in tension near the strip edge) is made small, and Δ
It is preferable to distribute the taper effect amount Δh so that h/h increases sequentially.

At this time, if the shift position WRδ of the work roll 3 cannot be set to a predetermined value due to reasons such as when the width of the rolled metal strip 1 is wide or when the movement range of the work roll 3 in the axial direction is small, etc. In this case, it is sufficient to replace the work roll 3 with a tapered portion 3a having a large taper angle θ, set the taper angle θ of the work roll 3, and then set the shift position WRδ of the work roll 3 as described above. .

In this way, the shift position WRδ of the work roll 3 is set in each pass up to the pass before the final pass, but in order to reduce the influence of medium elongation on the metal strip, in the final pass, the shift position WRδ of the work roll 3 is Since rolling is performed only by the body 3b having a diameter, the target thickness improvement of the final rolled metal strip is not the sum of the taper effect amounts Δh obtained by each pass up to the previous pass of the final pass. , the target plate thickness improvement amount by a value that takes into account the decrease in plate thickness near the width direction edge of the metal strip in the final pass, which is the sum of the taper effect amounts Δh obtained from each pass up to the previous pass of the final pass. In order to increase the taper effect amount Δh obtained by each pass up to the pass before the final pass, the taper effect amount Δh is distributed within a range that is 1% or less of the exit side plate thickness.

Furthermore, if the plate thickness near the width direction edge on the exit side of the rolled metal strip 1 is measured and the work roll shift position 11WRδ of each pass up to the previous pass of the final pass is corrected based on this measurement value, it is possible to It is possible to effectively obtain plate thickness accuracy, and the plate thickness near the width direction edge on the entry side of the rolled metal strip 1 can be measured, and based on this measurement value, the thickness of each pass up to the previous pass of the final pass can be measured. By correcting the work roll shift position 11 (WRδ), plate thickness accuracy can be obtained more effectively.

〔Example〕

Example 1 Tapered with a taper angle θ of 5,00 x 10-'rad, body diameter 135 mm, and body 3b length 85 mm.
0 m and a distance between chocks of 1075+m+, an intermediate roll 4 having a body diameter of 300 mm, a body length of 850 mm, and a distance between chocks of 1660 nm, and a body diameter of 630 nm. The length of the body is 850m and the distance between chocks is 1475m++
A 6-high rolling mill 2 consisting of a back-up roll 5 and a tapered body 3b as shown in FIG. When rolling a stainless steel strip 5US304 of Kaku in a reciprocating manner so that the exit side plate thickness is 1.01 mm, the taper effect amount Δh is adjusted to the exit side plate thickness 2 in the first pass.
, the amount of reduction WR per 100 mm in the diameter of the work roll 3 in order to make it 4.38 ta, which is 1% or less of the value of 21.
Since T is 0.10 mm, the shift position WRδ of the work roll 3 is set to 80 mm, and in the second pass, the taper effect amount Δh is set to 6,38-, which is a value of 1% or less of the exit side plate thickness of 1.55 m+. 100 of the diameter of work roll 3 to
Since the reduction amount WRT per mm is 0.10 mm, the shift position WRδ of the work roll 3 is set to 160 m, and in the third pass, the taper effect amount Δh is set to 1.
Since the reduction amount WRT per 100 diameters of the work roll 3 is 0.10 m in order to make the value 7,304 which is less than 1% of 13 on, the shift position WR of the work roll 3 is
δ is set to 240 mm, and in the final pass, the work roll 3 is moved in the axial direction so that the edge in the width direction of the metal strip l to be rolled is located on the body 3b having the same diameter of the work roll 3, and the work roll 3 is moved in the axial direction. As a result of cold rolling with the interval between the rolls 3 set to 1.01 m, the thickness of the stainless steel strip at a position 20 mm from the edge in the width direction to the center side changes from the first pass to the final thickness as shown in Figure 5. The roll diameter up to the pass is 135
It was possible to roll the stainless steel strip about 94 mm thicker than when the stainless steel strip was rolled using the ++a cylindrical work roll 3 under the same conditions.

Example 2 The taper angle θ is 8.00 x 10-'rad, the diameter of the body is 135I, and the length of the body 3b is 850.
A work roll 3 having a body diameter of 300 wn and a body length of 8501 mm and a distance between chocks of 1075 m+ and a distance between chocks of 1660 m+.
The intermediate roll 4 has a trunk diameter of 630I, a trunk length of 850m++, and a distance between chocks of 1475m.
As shown in FIG. 2, a six-high rolling mill 2 consisting of a back-up roll 5 and a tapered body 3b with one end of the tapered body 3b located on the opposite left and right side is equipped with a 6-high rolling mill 2 having a width of 1420a and a thickness of 2.36 mm. When rolling a stainless steel strip 5US430 in a reciprocating manner so that the exit side plate thickness becomes 0.77mm, the taper effect amount Δh in the first pass is set to a value of 1% or less of the exit side plate thickness of 1.66 m4. , 0? , the reduction amount WR per 100 mm of the diameter of the work roll 3 is
Since T is 0.16 m, the shift position WRδ of the work roll 3 is set to 60 m, and in the second pass, the taper effect amount Δh is set to a value of 1% or less of the exit side plate thickness of 1.16 m5.
Since the reduction amount WRT per 100 mm in the diameter of the work roll 3 is 0.16 m in order to make 97 hot water, the shift position WRδ of the work roll 3 is set to 120 m, and the third
In order to make the taper effect amount Δh in the pass to 6,9511 m, which is less than 1% of the exit side plate thickness of 0.85 mm, the reduction amount WRT per 100 m+ of the diameter of the work roll 3 is 0.
Since it is 16na, the shift position WRδ of the work roll 3 is
is set to 180I, and in the final pass, the work roll 3 is moved in the axial direction so that the edge in the width direction of the metal strip 1 to be rolled is located on the body 3b having the same diameter of the work roll 3, and the work roll 3 is As a result of cold rolling with the interval set to 0.77 mm, the plate thickness at a position 20 mm from the edge in the width direction to the center side of the stainless steel strip from the first pass to the final pass is as shown in Figure 5. Roll diameter is 135
It was possible to roll the stainless steel strip about 8p thicker than when the stainless steel strip was rolled using the ++w cylindrical work roll 3 under the same conditions.

〔Effect of the invention〕

When the method of the present invention is carried out as detailed above, the taper effect, which indicates that the rolled metal strip cold-rolled by the reverse mill has a good shape in each pass, can be achieved only by moving the work roll in the axial direction. The desired value can be set by setting the shift position of the work roll through a simple operation, and the shift position of the work roll can be set appropriately before rolling, so the thickness at the exit side can be adjusted for each pass. In cold rolling with a reverse mill, which varies in the width of the strip, the taper effect of each pass can be easily controlled, greatly improving work efficiency, and it is also possible to easily accommodate changes in strip width. be. In addition, if the work roll shift position cannot be set to a predetermined value due to reasons such as when the width of the metal strip to be rolled is wide or when the movement range of the work roll in the axial direction is small, the taper angle may be changed. By replacing the work roll with a different work roll, setting the taper angle of the work roll, and then setting the shift position of the work roll to a predetermined value, it is possible to easily correspond to various rolling mills.

Furthermore, during rolling in the final pass, the influence of elongation during elongation on the metal strip is reduced by rolling with the edge of the rolled metal strip in the width direction positioned on the body of the work roll having the same diameter. As a result, the metal strip to be rolled can be rolled into a good shape.

In addition, if the thickness of the rolled metal strip near the widthwise edge on the exit or entry side is measured, the shift position of the work roll can be easily adjusted to accommodate changes in the thickness of the rolled metal strip. Rolling can be effectively performed with excellent plate thickness accuracy.

The method of the present invention, which allows metal strips with excellent plate thickness accuracy to be efficiently rolled using various rolling mills, makes a major contribution to the field of steel manufacturing, and has great industrial value. It is.

[Brief explanation of the drawing]

FIG. 1 is an explanatory side view showing an example of a reverse mill suitable for carrying out the method of the present invention, and FIG.
-A cross-sectional explanatory view, Fig. 3 is an enlarged explanatory view of B part in Fig. 2, and Fig. 4 is the amount of taper effect at a predetermined position from the width direction edge when a metal strip to be reverse rolled is made one pass. FIG. 5 is a diagram showing the relationship between measured values and values obtained from formulas, and FIG. 5 is a diagram showing the relationship between measured values and values obtained from formulas. Figure 6 shows the distribution of sheet thickness deviation with respect to the widthwise center of a cold-rolled metal strip that is reciprocally passed through a rolling mill. Figure 7 shows the relationship between the taper effect amount and the shift position of the work roll when a metal strip that is reverse-rolled is passed through one pass while keeping the rolled metal strip constant. A diagram showing the relationship between the taper effect amount and the tangent of the taper angle of the work roll when a metal strip that is reverse-rolled at a constant position is passed through one pass. FIG. 12 is a diagram showing the relationship between the taper effect amount and the exit side plate thickness when a metal strip that is reverse rolled is passed through one pass while keeping the shift position of the work roll constant. In the drawings 1... Rolled metal strip 2... Rolling mill 3... Work roll 3a... Taper section 3b... Body section 4... Intermediate roll 5...・Backup roll T,... Taper starting point θ... Work roll theno (angle WRδ...
Work roll shift position WRT... Work roll taper (diameter reduction amount per 100 mm Patent applicant Nisshin Steel Co., Ltd. 1゛) , ↑ Taper effect amount t 1 obtained from the diagram 1 Figure, - A L-Yame 2 Plate thickness deviation with respect to the center in the axial direction ↑ Shift position diagram of the checking work roll Tangent of the taper angle of the work roll

Claims (1)

[Scope of Claims] 1. A pair of work rolls each having a tapered portion formed at one end of its body, facing each other with the tapered portions located on left and right opposite sides, and facing each other in the axial direction. When performing reverse rolling by reciprocating a rolled metal strip through a rolling mill that is movably installed at and the value (ah+b) derived from the outlet thickness (h) of the metal strip to be rolled and constants (a, b) determined by the roll dimensions of the rolling mill and the tapered part of the work roll. The value (W
RT) WRT=100×2×tanθ and the shift position of the work roll (WRδ), which indicates the distance from the edge of the metal strip to be rolled to the taper start point of the work roll.
The shift position (WRδ) of the work roll is set within a range where the taper effect amount (Δh) expressed as the product of Δh=(ah+b)×WRT×WRδ is 1% or less of the exit side plate thickness (h). A crown control method in cold rolling using a reverse mill, which is characterized by moving a work roll in its axial direction to set the distribution. 2. When setting the shift position (WRδ) of the work roll, the work roll is moved in the axial direction after setting the taper angle (θ) of the work roll to set the shift position (WRδ) of the work roll. Crown control method in cold rolling using a reverse mill described in . 3. Claim 1 or 2, wherein the thickness of the rolled metal strip near the edge in the width direction on the exit side is measured, and the shift position (WRδ) of the work roll up to the previous pass of the final pass is corrected based on the measured value. Crown control method in cold rolling using a reverse mill described in . 4. Claims 1 to 3, wherein the plate thickness near the widthwise edge on the entry side of the rolled metal strip is measured, and the shift position (WRδ) of the work roll up to the previous pass of the final pass is corrected based on this measurement value. The crown control method in cold rolling using a reverse mill according to any one of the preceding items.