JP3327212B2 - Cold rolling method with reduced edge drop - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolling method which suppresses edge drop during cold rolling of a cold rolled metal sheet such as a cold rolled steel sheet.

[0002]

2. Description of the Related Art As is well known, a cold-rolled metal sheet (hereinafter, a cold-rolled steel sheet is taken as an example of a cold-rolled metal sheet in this specification) is used.
It is manufactured using hot rolled sheets as cold rolled materials. FIG. 8 schematically shows the profile of the hot rolled sheet. In the figure, reference numeral H _C
Represents the thickness at the center of the plate width direction of the hot-rolled sheet 1, reference numeral H _DX denotes the thickness at the site of X (mm) from the drive side DS side plate end, code H _DY from the drive side DS side plate end Y (mm) indicates the plate thickness at a position, and the symbol H _WX indicates the plate thickness at a position of X (mm) from the work side WS side plate end,
Further, the symbol H _WY indicates the plate thickness at a position Y (mm) from the plate end on the work side WS side. Here, X> Y.

[0003] As shown in the figure, the profile of the hot rolled sheet 1 usually has an edge drop E _DX-Y in which the sheet thickness sharply decreases in the vicinity of 30 to 50 mm from the end in the sheet width direction to the center side,
E _WX-Y (where E _DX-Y = H _DX -H _DY , E _WX-Y = H _WX −
H _WY ) and the sheet crowns C _DX , C _wx (where C _DX = H _C −H) in which the sheet thickness gradually decreases on the center side.
_DX and C _wx = H _C −H _wx ).

[0004] For example, the Iron and Steel Handbook Volume III (1)
As described in page 507 of the steel sheet (edited by the Iron and Steel Institute of Japan), there has been an almost linear correlation between the sheet crown of a hot-rolled sheet and the sheet crown of a cold-rolled sheet. It is known that there is a relationship. That is, the sheet crown of the cold-rolled steel sheet is almost uniquely determined by the sheet crown of the hot-rolled sheet, and it has been considered that sheet crown control in the cold rolling stage is impossible. On the other hand, it has been considered that edge drop is governed by cold rolling conditions such as rolling reduction and tension.

Japanese Patent Publication No. Hei 7-14526 discloses a so-called work roll shift mill, in which a work roll having a tapered end is shifted in the sheet width direction to perform cold rolling. An invention that determines the shift amount of the work roll based on the edge drop of the sheet and performs cold rolling to suppress the edge drop and the sheet crown of the cold-rolled steel sheet is disclosed in Japanese Patent Publication No. 63-35325. Using a so-called pair cross mill in which an upper work roll and a backup roll pair and a lower work roll and a backup roll pair intersect by an arbitrary amount according to a set value in a four-high rolling mill, a cold rolled steel sheet crown is formed. Each of the inventions for suppressing is proposed.

[0006]

Meanwhile [0007], the hot rolled plate 1 showing the profile in Figure 8, in most cases, the wedge (single crown) is a profile of asymmetrical W _X exists. The wedge W _X refers strip crown C _wx in the sheet width direction end sides of the hot-rolled sheet 1, the deviation of the C _DX, in FIG _{8, W X = C wx -C} DX = (H C -H wx) − (H _C −
H _DX ) = H _DX −H _WX .

The aforementioned Japanese Patent Publication No. Hei 7-14526 and Japanese Patent Publication No.
The conventional cold rolling technology represented by JP-A-63-35325 is based on the premise that this wedge W _X does not exist in a hot rolled sheet, that is, W _X = 0, and the sheet crown control is performed. This is performed in cold rolling. In other words, in the conventional cold rolling technology, the average value (C _wx + C _DX ) of the sheet crowns C _wx and C _DX at both ends in the sheet width direction of the hot-rolled sheet 1 is used.
/ 2, the crown control is performed in cold rolling.

Therefore, according to this conventional cold rolling technique, even if cold rolling is performed using the hot rolled sheet 1 on which the wedges W _X are present as a cold rolled material, the hot rolled sheet 1 at both ends in the sheet width direction can be used. On the side where the sheet crown is large, the edge drop after cold rolling is further larger than on the side where the sheet crown is small. For this reason, the crown of the sheet remains as it is on the cold rolled steel sheet as a product, resulting in a defective product due to the deviation of the thickness tolerance, lowering the yield and causing a serious problem in operation.

[0009] Here, an object of the present invention is to provide a cold rolled steel sheet in which edge drop is suppressed or eliminated even when cold rolling is performed using a hot rolled sheet having wedges having different sheet crowns at both ends in the sheet width direction as a cold rolled material. An object of the present invention is to provide a cold rolling method capable of obtaining a rolled metal plate and suppressing edge drop.

[0010]

As described above with reference to FIG. 8, in general, the difference between the sheet crowns C _DX and C _wx existing in the hot-rolled sheet 1, that is, the wedge W _X is cold-rolled. It has been considered that it cannot be changed. However, the present inventor has determined that the sheet crown C _{DX of} the hot-rolled sheet 1,
As a result of re-examining the relationship between C _wx and the strip crown after cold rolling in detail, the following items 1 to 4 were newly found.

FIG. 1 is a graph showing an example of the relationship of the size of the wedge W _X (= H _DX −H _WX ) with respect to the position in the longitudinal direction of the hot-rolled sheet 1. As shown by the graph in the figure, the wedge W _X generated in the hot-rolled sheet 1, in the same hot-rolled plate 1 occurs only on one side of one of both ends in the plate width direction. That is, in the same hot-rolled sheet 1, the magnitude relation between the sheet crowns C _wx and C _DX does not reverse.

FIG. 2 shows a case where a hot-rolled steel sheet 1 having a thickness of 3.8 mm is cold-rolled to obtain a cold-rolled steel sheet having a thickness of 1.0 mm. H _W −H _D ) /
6 is a graph showing an example of a relationship with H. The symbol H
Means the thickness of the hot-rolled sheet 1 at the center in the sheet width direction. From this graph, the wedge ratio decreases with decreasing the thickness at the position where the distance from the plate edge is 50 mm, 100 mm or 150 mm, but the thickness decreases at the position where the distance from the plate edge is 15 mm or 25 mm. It can also be seen that the wedge ratio is substantially constant, that is, the wedge amount changes. Therefore, contrary to the conventional technical common sense, wedge W _X of the hot-rolled sheet 1, for the range distance is within about 7 times the thickness of the hot rolled plate 1 in the plate width direction end portion side of the plate end is It can be seen that it can be corrected by cold rolling. That is, for this range, the cold rolling, the left and right strip crown C _wx, it is possible to control the wedge W _X which is the difference between C _DX.

FIG. 3A shows a drive side side DS.
Difference between the sheet crown on the work side and the work side WS side (C _wx −
FIG. 9 is a graph showing an example of a relationship between a distance from an end portion in the sheet width direction and a sheet thickness deviation with respect to a sheet thickness in a center portion in the sheet width direction of the hot rolled sheet 1 for the hot rolled sheet 1 having a large C _DX ). 3
(b) shows the distance from the end in the width direction of the hot-rolled sheet 1 to the cold-rolled steel sheet obtained by performing cold rolling on the hot rolled sheet 1 under the rolling conditions in which the edge drop on the side where the sheet crown is large is small. 4 is a graph showing an example of a relationship between a plate thickness and a plate thickness deviation at a center portion of the plate 1 in the plate width direction. As shown in the graph of FIG. 3 (a), the difference between the sheet crowns on the DS side and the WS side (C _wx −
If the hot rolled sheet 1 having a large sheet crown (C _DX ) is used as a cold-rolled material and cold rolling is performed under the rolling conditions in which the edge drop on the WS side having a large sheet crown is small, the DS side having a small sheet crown of the hot rolled sheet 1 is obtained Significant edge-up does not occur, and a cold-rolled steel sheet in which the sheet crowns C _wx and C _{DX at} both ends in the sheet width direction are equal or suppressed within an allowable range can be manufactured.

The present inventor has further studied based on these new findings and completed the present invention. Here, the gist of the present invention is that, for a hot-rolled sheet having wedges having different plate crowns at both ends in the plate width direction, a plate crown based on a value larger than an average value of the two plate crowns. This is a cold rolling method in which edge drop is suppressed, characterized in that a cold rolled metal sheet in which edge drop is suppressed is produced by performing cold rolling while performing control.

In the above-described cold rolling method in which the edge drop is suppressed according to the present invention, (1) the sheet crown control is a control in which the edge drop at the end of the two sheet crowns on the larger value side is controlled. That (2) the sheet crown control is performed in the longitudinal direction based on the change of the wedge in the longitudinal direction of the hot-rolled sheet, and (3) the sheet crown controls the hot-rolled sheet in the hot rolling stage. Hot-rolled crown information obtained by actual measurement, or deviation from hot-rolled crown information and entrance-side measured crown information obtained by actually measuring hot-rolled sheet before cold rolling is performed at multiple positions in the length direction Or a value obtained by adding a wedge obtained by actually measuring a hot-rolled sheet in the hot rolling stage to the above, (4) sheet crown control is performed by performing cold rolling on a side having a larger value of the sheet crown. Target board after being broken It is preferable that the setting is performed by setting or controlling the crown of a work roll on which cold rolling is performed so that the crown becomes a crown.

In the above-described cold rolling method in which edge drop is suppressed according to the present invention, the crown adjusting mechanism of the cold rolling mill that performs cold rolling is a symmetric rolling mill symmetrical with respect to the width direction of the hot-rolled sheet. In this case, it is desirable that the crown control be performed by controlling the crown adjustment mechanism asymmetrically in the width direction.

As such a symmetrical rolling mill, a rolling mill having a roll bending, a work roll cross mechanism or a work roll shift mechanism (for example, UC (Universal)
al Crown) mill, HC (High Crown) mill, CVC (Conti
rolling mill (e.g., TP (Taper Piston)
Mill, etc.) . On the other hand, as the asymmetric rolling mill, leveling in which the roll axis is set to be inclined is exemplified.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of a cold rolling method according to the present invention for suppressing edge drop will be described in detail with reference to the accompanying drawings.

In this embodiment, for example, a right and left crown adjusting mechanism is symmetrical in the width direction of a cold rolled material, such as a normal four-high rolling mill or a rolling mill having a VC roll or a pair cloth system as a flat / crown control device. This is a case where cold rolling is performed using a symmetric rolling mill.

FIG. 4 is an explanatory diagram showing an outline of the control logic in this embodiment. In FIG.
(Hereinafter, abbreviated as “S”.) In step 1, hot rolled crown information that is crown information of a hot rolled coil that is a hot rolled sheet is obtained. The hot-rolled crown information is obtained from the above-described calculation formula (plate crown C) at an arbitrary point in the longitudinal direction of the hot-rolled coil from an actual value measured by a profile meter in a hot rolling step.
_DX = H _C −H _DX , sheet crown C _wx = H _C −H _wx ), which is obtained as a representative value of the crown of the hot-rolled coil. Thus, the wedge W _X having the hot-rolled coil is cold rolled material (= H _DX -H _WX) is, the strip crown C _DX for each plate width direction end sides, is determined as the deviation of C _wx.

In S2, the magnitudes of the two sheet crowns C _DX and C _wx of the hot-rolled coil calculated in S1 are compared, and the larger value C _DX or C _wx is obtained. In S3,
It is determined using a value C _DX or C _wx the larger determined in S2, while the strip crown control, the cold rolling is performed by symmetric rolling mill described above.

[0022] That is, the strip crown is large side C _DX or C _wx hot-rolled coils so edge drop is reduced, performs a cold rolling while setting or controlling the work roll crown. Thus, the strip crown is large side C _DX or C _wx hot rolled coils with edge drop is small, significant edge up to the small side C _wx or C _DX does not occur. In this way, a cold-rolled steel sheet in which the side with a large value of the sheet crown becomes the target sheet crown after cold rolling is performed, and edge drop at both ends in the sheet width direction is suppressed, is provided. . Therefore,
Product defects that deviate from product tolerances are eliminated, and a decrease in yield can be prevented.

As described above, in this embodiment, a symmetric rolling mill is used. Such a symmetric rolling mill includes a roll bending, a work roll cross mechanism, or a work roll shift mechanism as a crown adjusting mechanism. (For example, UC mill, HC mill, CV
C mill, etc.) and a rolling mill having a mechanism for expanding the diameter of the roll body as a crown adjusting mechanism (for example, a VC mill or TP
Mill etc.). To control S3 in FIG. 4 by such a symmetric rolling mill, the crown adjustment mechanism may be controlled asymmetrically in the width direction.

As the left-right asymmetric rolling mill, there is a rolling mill having a leveling in which the roll axis is set to be inclined, and it is a matter of course that the present embodiment can be performed by the left-right asymmetric rolling mill.

(Second Embodiment) Next, a second embodiment of the cold rolling method in which edge drop is suppressed according to the present invention will be described.
This will be described in detail with reference to the accompanying drawings. In the following embodiments, portions different from those of the first embodiment will be described, and overlapping descriptions of common portions will be omitted.

FIG. 5 is an explanatory diagram showing an outline of the control logic in this embodiment. The control logic shown in FIG. 5 is similar to the control logic of the first embodiment shown in FIG. 4, after performing the sheet crown setting in the cold rolling using the hot-rolled crown information from the hot-rolled coil, First
By performing sheet crown measurement at a plurality of positions in the longitudinal direction of the hot-rolled coil on the entry side of the symmetric rolling mill similar to the embodiment,
This is an example of performing dynamic control of a sheet crown in the length direction of a hot-rolled sheet according to a change in a wedge in the length direction of the hot-rolled sheet.

At S1, hot rolled crown information is obtained as in the control logic shown in FIG. From the hot rolled crown information, the work side plate crown C _W = center plate thickness H _C −
The thickness H _W at the end of the work side plate, the drive side plate crown C _d = the center plate thickness H _C −the thickness H _d at the end of the drive side plate, and the plate crown C = (C _W + C _d ) / Two
And wedge W = C _d −C _W = H _W −H _d
Is required.

[0028] In S2, similarly to the control logic shown in FIG. 4, two strip crown C _D hot-rolled coil calculated in S1, the magnitude of C _w are compared. Here, assuming that wedge W <0, it is determined that C _W > C _D. In S3, the work side plate crown C
It is determined that _{W is} to be used, and the sheet crown control setting in the cold rolling is performed in S4 and subsequent steps.

At S4, the sheet crown of the hot-rolled coil, which is a cold-rolled material, is actually measured by a profile meter at a plurality of positions in the longitudinal direction of the hot-rolled coil on the inlet side of the cold rolling mill. Information is required. The measured values are C _d ′ (drive side) and C _W ′ (work side side). In order to simplify the description, it is assumed that the work side and the drive side of each of hot rolling and cold rolling are in the same direction.

In S5, the sheet crown deviation ΔC used for the dynamic control performed in the following S6 is:
(Incoming side actually measured crown information obtained in S4-hot rolled crown information obtained in S1) or (Incoming side actually measured crown information obtained in S4-hot rolled crown information obtained in S1 + wedge obtained in S1)
Is calculated.

Specifically, since the present example is a case where C _W > C _D , when a work side side sheet crown is measured by a cold rolling mill, ΔC = (C _W ′ −C _W ), And when measured on the drive side, ΔC =
The _{(C d '-C d) +} W.

In S6, since the sheet crown deviation ΔC is a deviation between the hot-rolled crown information and the actually measured crown information on the entry side, the side having a larger value of the sheet crown is subjected to cold rolling according to the sheet crown deviation ΔC. To set or control the crown of the work roll to be cold-rolled in the longitudinal direction of the hot-rolled sheet so that the target sheet crown is obtained after the processing, for example, symmetrically with respect to the width direction of the cold-rolled material. Strip crown control is performed by controlling a work roll bender, a pair cross angle, and the like of a certain cold rolling mill.

For example, when the work roll bender is changed by 1 ton, the change amount of the crown of the cold rolled steel sheet is α (μm
/ Ton), and the amount of change of the sheet crown of the cold-rolled steel sheet with respect to the cross angle of 1 degree is given by β (μm / de) since the sheet crown due to the change of the cross angle changes parabolically according to the cross angle.
g ² ), and the relationship of the sheet crown Ch of the cold-rolled steel sheet to the sheet crown CH of the hot-rolled sheet is expressed as Ch = ζ · CH ×
(1-red / 100), where red: reduction rate (%), Δ: coefficient.

Here, the sheet crown CH of the hot-rolled sheet is (CH
+ ΔC), the crown C of the cold-rolled steel sheet
h ′ is Ch ′ = ζ · (CH + ΔC) × (1-red / 100) = ζ · ΔC × (1-red / 100) + Ch That is, it is understood that the sheet crown Ch ′ of the cold-rolled steel sheet may be obtained by adding a change due to the sheet crown deviation ΔC to the sheet crown Ch of the cold-rolled steel sheet.

Therefore, the influence of the sheet crown deviation ΔC can be changed by changing the work roll bender or the cross angle. That is, if the sheet crown fluctuation after cold rolling is ΔCh = ζ · ΔC × (1-red / 100),
It can be seen that ΔCh / α should be operated for the work roll bender and ΔCh / β for the cross angle in order to prevent ΔCh.

[0036] Thus, according to the present embodiment shown in FIG. 5, the hot rolled crown information obtained in S1, the strip crown C of pre-hot-rolled sheet, strip crown C _D of the plate width direction end portion side, Knowing the size of C _w and the wedge W, S2
In step S3, the larger sheet crown _CD or _Cw is used. In step S4, the sheet crown is actually measured at the entry side of the cold rolling mill in the longitudinal direction of the hot-rolled sheet, and in step S5, the sheet crown deviation ΔC is obtained. In step S6, dynamic control of the sheet crown is performed based on the sheet crown deviation ΔC.

Here, in the present embodiment, in S4,
Even if only one side is measured without measuring the crowns on both sides, the correction based on the wedge information obtained in S1 can be performed in S5. That is, according to this embodiment, in S4, the profile of the hot rolled sheet is
There is no need to measure the entire board width, and the equipment cost required for the profile meter can be reduced.

As described above, according to the present embodiment, it is possible to manufacture a cold-rolled steel sheet with a small edge drop over the entire length by performing crown control such as feedforward control over the entire length of the hot-rolled sheet.

In this embodiment, as in the first embodiment,
Use a symmetric rolling mill. That is, most of the crown adjustment mechanisms of existing cold rolling mills are symmetrically controlled in the sheet width direction, and the asymmetrical control in the sheet width direction has hardly been performed until now. However, before cold rolling, based on the side of the hot rolled sheet having wedges in which the sheet crown in the sheet width direction is larger, the roll bending, work roll cross mechanism is performed so that the larger side becomes the target sheet crown after rolling. Alternatively, the work crown can be changed by controlling the work roll shift mechanism, the mechanism for expanding the diameter of the roll body, and the crown adjustment mechanism such as leveling in a bilaterally asymmetric manner. Thereby, the edge drop of the cold-rolled steel sheet is suppressed, the product defect out of the product tolerance is eliminated, and the decrease in the yield can be prevented.

(Third Embodiment) Next, a third embodiment of the cold rolling method according to the present invention in which edge drop is suppressed will be described in detail with reference to the accompanying drawings.

FIG. 6 is an explanatory diagram showing an outline of the control logic in this embodiment. This embodiment is an example in which a left-right asymmetric rolling mill such as a rolling mill having a roll shift mechanism or a left-right asymmetric roll bender is used.

FIG. 7 is an explanatory diagram showing a profile of the hot-rolled coil 1. As shown in FIG. In S1 in FIG. 6, the hot rolled crown information of the hot rolled coil 1 is obtained similarly to the control logic shown in FIGS.

In S2, the left and right sheet crown amounts C _d and C _w of the hot-rolled coil 1 are calculated as follows: C _d = W / 2 + C, C _w = C−W
Calculate as / 2. That is, the sheet crown average C is H
_C - is _{(H DX + H WX) /} 2, W = C d -C w.

In S3, the sheet crown setting in the cold rolling is calculated for the left and right sides (DS side, WS side) based on the left and right sheet crown amounts C _d and C _w obtained in S2. Specifically, C _d = W / 2 + C, C _w = C−W / 2
Then, the work roll bender shift amount and the work roll bender pressure are calculated in the same manner as in the first embodiment based on the sheet crown deviations ΔC _w and ΔC _d of each DS and WS.

Then, in S4, the work roll shift amount and the work roll bender pressure on the DS and WS sides are determined.
The change in the crown of the cold-rolled steel sheet due to the shift change is γ (μm / mm).

That is, in the case of a left-right symmetric rolling mill, it is often simplified by performing a setting calculation on only one side of the cold-rolled material in order to reduce the calculation time of the rolling setting. In the above, a cold rolled steel sheet with even less edge drop can be obtained by performing independent sheet crown control by individually setting the sheet crown in the cold rolling.

That is, the present embodiment is a case where the setting of the sheet crown in the cold rolling is performed independently on the large side and the small side of the sheet crown of the hot-rolled sheet. And
By setting the shift position or the left and right roll benders for each, the edge drop of the cold-rolled steel sheet can be reduced.

[0048]

[Variant] In each embodiment, is performed strip crown control based on the larger value C _DX or C _wx of the two strip crown obtained as hot rolled crown information, the present invention is to take the form Is not limited. Plate crown C _DX ,
By performing the plate crown control based also on the larger value than the average value of _{C wx (C DX + C wx} ) / 2, performs plate crown control based on the conventional average value as _{(C DX + C wx) /} 2 Edge drop can be suppressed as compared to the case where

In each embodiment, the case where the metal plate is a steel plate is described as an example. However, the present invention is not limited to this embodiment, and other cold-rolled metal plates such as a cold-rolled aluminum alloy plate may be used. Can be similarly applied.

[0050]

As described above in detail, according to the present invention, even if cold rolling is performed using a hot-rolled sheet having wedges having different sheet crowns at both ends in the sheet width direction as a cold-rolled material, substantially no edge drop occurs. Thus, it is possible to obtain a cold-rolled steel sheet that has been suppressed or eliminated. The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a relationship of a wedge size with respect to a position in a longitudinal direction of a hot-rolled sheet.

FIG. 2 shows an example of the relationship between the distance from the edge of the sheet and the wedge ratio when cold-rolling a hot-rolled sheet with a thickness of 3.8 mm to obtain a cold-rolled steel sheet with a thickness of 1.0 mm. FIG.

FIG. 3 (a) shows the distance from the end in the sheet width direction and the sheet thickness deviation with respect to a target value for a hot rolled sheet having a large difference in sheet crown between the drive side side DS side and the work side WS side. FIG. 3 (b) is a graph showing an example of the relationship of FIG. 3 (b). FIG. 3 (b) shows a cold-rolled steel sheet obtained by performing cold rolling on this hot-rolled sheet under the rolling condition in which the edge drop on the side where the sheet crown is large is small. It is a graph which shows an example of the relationship between the distance from the width direction end part, and the thickness deviation with respect to a target value.

FIG. 4 is an explanatory diagram showing an outline of control logic in the first embodiment.

FIG. 5 is an explanatory diagram showing an outline of control logic in a second embodiment.

FIG. 6 is an explanatory diagram showing an outline of control logic in a third embodiment.

FIG. 7 is an explanatory diagram showing a profile of a hot-rolled coil in a third embodiment.

FIG. 8 is an explanatory view schematically showing a profile of a hot-rolled sheet.

Claims (5)

(57) [Claims] 1. A hot rolled sheet having wedges having different sheet crowns at both ends in the sheet width direction while performing sheet crown control based on a value larger than an average value of the two sheet crowns. By performing rolling,
A cold rolling method in which edge drop is suppressed, wherein a cold-rolled metal sheet in which edge drop is suppressed is manufactured. 2. The cold rolling method according to claim 1, wherein the sheet crown control is control for suppressing the edge drop at an end of the two sheet crowns having a larger value. . 3. The cooling method according to claim 1, wherein the sheet crown control is performed in the length direction of the hot-rolled sheet based on a change in the wedge in the length direction. Rolling method. 4. The hot-rolled crown information obtained by actually measuring the hot-rolled sheet in a hot-rolling step, or the hot-rolled crown information and the hot-rolled roll before the cold rolling is performed. Deviation from the entrance-side measured crown information obtained by actually measuring the plate at a plurality of positions with respect to its length direction, or a value obtained by adding the wedge obtained by actually measuring the hot-rolled plate in the hot rolling step to them. Claim 1 obtained as
The cold rolling method according to any one of claims 1 to 3, wherein the edge drop is suppressed. 5. The work roll control according to claim 5, wherein the control is performed by setting a crown of a work roll for performing the cold rolling such that a side having a large value of the work crown becomes a target work crown after performing the cold rolling. The cold rolling method according to any one of claims 2 to 4, wherein the cold rolling is performed by controlling the edge drop.