WO2015174075A1

WO2015174075A1 - Method for rolling metal strip

Info

Publication number: WO2015174075A1
Application number: PCT/JP2015/002401
Authority: WO
Inventors: 英介住田; 慎也山口; 舘野　純一
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2014-05-15
Filing date: 2015-05-12
Publication date: 2015-11-19
Also published as: JP2015217405A; TW201603904A; JP6044589B2

Abstract

　The present invention provides a hot-rolling method for a metal strip by a cyclic shift method in which the work rolls are shifted in the axial direction, wherein the rolling method affords a metal strip having a good profile in the width direction, in instances in which the rolled material currently in the rolling cycle is a wide rolled material following a narrow rolled material. According to this hot-rolling method for a metal strip, for a rolled material currently in the rolling cycle, the work rolls are shifted by a constant pitch for each single rolled material while reciprocating between predetermined folding locations, by means of a rolling machine equipped with a shift mechanism for shifting the work rolls in the axial direction. When a rolled material wider than the preceding rolled material is to be rolled, rolling is carried out at a work roll shift position modified such that an evaluation function (J_ΔCR) calculated from the difference between the predicted value and the target value of the roll crown is minimized.

Description

Metal strip rolling method

The present invention relates to a method of hot rolling a metal strip (rolled material), and more specifically, with respect to a plurality of rolled materials in a rolling cycle, by a rolling mill equipped with a shift mechanism that shifts a work roll in the axial direction in advance. The present invention relates to a hot rolling method in which a work roll is shifted for each material to be rolled at a predetermined pitch while reciprocating between predetermined turning positions.

In rolling a metal strip, friction occurs at the contact portion between the work roll and the metal strip (rolled material) (hereinafter referred to as “plate path”), and wear of the portion corresponding to the plate path of the work roll proceeds. go. Furthermore, in hot rolling, the material to be rolled becomes a high temperature of about 800 ° C. to 1100 ° C., and therefore thermal expansion occurs in a portion corresponding to the plate path of the work roll called a thermal crown.

For this reason, as the number of rolling rolls increases, the work roll profile changes due to partial wear and thermal expansion of the work rolls, so that the thickness distribution and shape in the width direction of the material to be rolled deteriorates, resulting in product quality and threading. There was a problem that the stability was lowered.
For example, in the case where a narrow material to be rolled is continuously rolled, wear of a partial plate path progresses, so that an abnormality occurs in the thickness distribution of a wide material to be rolled subsequently. In order to avoid this, process management (roll chance regulation) for restricting the width of the material to be rolled in a rolling cycle, such as rolling in a stepwise manner from a wide material to a narrow material, has been forced.

In order to suppress these, as described in, for example, Patent Document 1 and Patent Document 2, each time the material to be rolled is rolled, the axial position of the work roll is called a constant pitch (hereinafter referred to as “shift pitch”). ), A cyclic shift method is widely used in which the shift is continued when the amount of axial shift of the work roll reaches the maximum or minimum, and the shift is continued.
Further, in Patent Document 3, an error between a predicted calculation value of a work roll profile and a target value is obtained for all rolled materials in a rolling cycle, and this error is minimized for all rolled materials in one rolling cycle using an evaluation function. A rolling method has been devised.

Japanese Patent Laid-Open No. 06-154823 Japanese Patent Laid-Open No. 11-254015 JP 2013-111649 A

However, in Patent Document 3, “the shift position change amount for each material to be rolled is made constant in the rolling cycle, and the shift position change amount and the turn-back position that reverses the shift movement direction are determined to be rolled in the rolling cycle. For all rolled materials, find the error between the predicted calculated value of the work roll profile and the work roll profile target value at the contact part of the rolled material and the work roll, and sum the error for all the rolled material in the rolling cycle. Is determined to be minimal. For this reason, for example, after a large number of narrow materials as the preceding material to be rolled continue, only one wide material to be rolled having a width of, for example, 200 mm or more larger than this material is rolled. In special cases followed by the material to be rolled, even if the error is small when rolling a large number of narrow materials, the error is large when rolling a single wide material, and this error is outside the allowable range. There are cases where Alternatively, if the shift position is set so as to minimize the error of one wide rolled material, the narrow rolled material before and after the wide rolled material may be sacrificed. As described above, in the technique of Patent Document 3, after a narrow material is continued as the preceding material to be rolled, only one wide material to be rolled having a width larger than this material is rolled, and then the width is again narrowed. In the width return rolling in which the material to be rolled follows, there is a problem that a good profile of the material to be rolled cannot be obtained.

In the present invention, in the cyclic shift rolling of a metal strip by a rolling mill equipped with a shift mechanism for shifting a work roll in the axial direction, the rolling order in a rolling cycle is narrow material to be rolled → narrow material to be rolled. In the case of a wide rolled material having a width dimension larger than that of the material, in particular, a narrow rolled material → a wide rolled material → a narrow rolled material (hereinafter referred to as “reverse rolling”). In some cases, an object of the present invention is to provide a rolling method for obtaining a metal band having a good profile in the width direction when rolling a wide material to be rolled.
Here, “narrow” and “wide” refer to a relative relationship in which the width of the wide rolled material is larger than the width of the narrow rolled material. It is not an absolute one. In the above-described width return rolling, the narrow rolled materials before and after the wide rolled material need not have the same width dimension.

The rolling cycle starts rolling with a rolling mill in which work rolls are incorporated by roll exchange, rolls several (50 to 100 inside / outside) materials to be rolled, and incorporates work rolls by next roll exchange. A group of the above-mentioned several (about 50 to 100) materials to be rolled in order to start rolling by the rolling mill is referred to as one constituent unit.

In order to achieve the above object, the present invention employs the following means.
[1] For each material to be rolled in a rolling cycle, the material is rolled at a constant pitch while reciprocating between predetermined folding positions by a rolling mill having a shift mechanism for shifting the work roll in the axial direction. In the rolling method of the metal strip for shifting the work roll, when rolling a material to be rolled that is wider than the preceding material to be rolled, the following formula (1) is used between the predetermined roll-back positions of the work roll shift. A hot rolling method for a metal strip, in which the work roll shift position is changed and rolled so as to minimize the obtained evaluation function J _ΔCR .

[2] The width of the wide rolled material is 10% or more larger than the width of the preceding rolled material, and the preceding rolled material is continuously rolled to a total rolling length of 5 km or more. The method for hot rolling a metal strip according to [1].
[3] The hot strip of the metal strip according to [1] or [2], wherein a rolling mill provided with a shift mechanism for shifting the work roll in the axial direction is provided on one or more stands of a tandem rolling mill. Rolling method.
[4] The method for hot rolling a metal strip according to any one of [1] to [3], wherein a work roll of a rolling mill provided with a shift mechanism that shifts the work roll in the axial direction is a high-speed roll.

In the cyclic shift rolling method using a rolling mill equipped with a shift mechanism that shifts the work roll in the axial direction by the metal strip rolling method of the present invention, the width of the material to be rolled is larger than that of the preceding material to be rolled. The profile can be improved, which makes it possible to relax the roll chance regulation and facilitate the process management of the rolling operation.

FIG. 1 shows simulation conditions for a material to be rolled in a rolling cycle. FIG. 2 shows the profile (crown distribution in the width direction) after rolling of a wide material to be rolled in width return rolling. FIG. 3 shows the relationship between the number of rolled materials with a narrow width and the high spot amount (maximum crown difference ΔCR). FIG. 4 shows the roll crown in the width direction formed on the work roll of the F7 stand. FIG. 5 shows the wear profile in the width direction formed on the work roll of the F7 stand. FIG. 6 shows the roll crown in the width direction of each stand of the F5 to F7 stands after rolling a narrow material to be rolled. FIG. 7 shows the thermal crown in the width direction of each stand of the F5 to F7 stands after rolling a narrow material to be rolled. FIG. 8 shows the width-return rolling in the cyclic shift rolling with a constant shift pitch.シミュレーション Shows the simulation conditions for shift change when rolling a wide workpiece. FIG. 9 shows a profile (crown distribution in the width direction) after rolling of a wide material to be rolled in the width return rolling in five cases where the shift positions of the work rolls are different. FIG. 10 shows the thermal crown maximum amount of the F5 stand work roll. FIG. 11A shows the relationship between the distribution in the width direction of the thermal crown and the width of the material to be rolled (the material to be rolled and the material to be rolled). FIG. 11B shows the relationship between the distribution in the width direction of the thermal crown and the width of the material to be rolled (the material to be rolled to be narrow and the material to be rolled to be wide). FIG. 11C shows the relationship between the distribution in the width direction of the thermal crown and the width of the material to be rolled (the narrow material to be rolled and the wide material to be rolled). FIG. 12 shows the rolling method of the present invention. FIG. 13 shows an evaluation function calculation method. FIG. 14 shows simulation conditions for applying the rolling method of the present invention. FIG. 15A shows an evaluation function at the shift position of the work roll during the width return rolling under the conditions shown in FIG. FIG. 15B shows the thickness distribution at the end in the width direction under the conditions shown in FIG. FIG. 16 shows the rolling cycle of the example. FIG. 17 shows the shift position of the work roll of the F5 stand for each material to be rolled. FIG. 18 shows the thickness distribution of the material to be rolled at the end in the width direction on the F7 stand exit side. FIG. 19 shows the width direction profile of the material to be rolled on which the edge buildup is formed.

Using the simulator, in the rolling cycle, the mechanism of the profile failure that occurs during rolling of a wide rolled material having a width of 200 mm or more larger than the width of the rolled material of the preceding narrow rolled material is described below. Consider.
A simulation was performed for hot rolling with a 7-stand tandem rolling mill composed of F1 to F7 stands.
Cyclic shift rolling, in which work rolls (hereinafter sometimes referred to as “WR”) of each material to be rolled, which is a metal strip, are shifted in the roll axis direction at a constant pitch, was performed at the F5 to F7 stands. .
As work roll materials, high-speed rolls were used for the stands F1 to F6, and nickel grain rolls were used for the F7 stand. High-speed rolls have high surface hardness and wear resistance, but are generally not used in the final F7 stand because of their high coefficient of thermal expansion. This is because when a work roll having a high thermal expansion coefficient is used in the final stand, the profile of the material to be rolled is not stable.

FIG. 1 shows a rolling cycle in which 100 materials are rolled, five times (with circled circles in FIG. 1) of width return rolling, that is, a material to be rolled (steel strip) having a width of 1000 mm. After rolling, a simulation is performed in which a wide rolled material having a width of 1200 mm, in which one width dimension is enlarged by 200 mm, is rolled, and then rolling of a narrow rolled material in which the width dimension is returned to 1000 mm is followed. Conditions are indicated.

FIG. 2 shows a profile (crown distribution in the width direction) on the F7 stand exit side of a wide material to be rolled in width return rolling as a result of the simulation.
In “1” indicated by a mark, a material to be rolled having a width of 1000 mm is rolled in advance immediately before rolling a material to be rolled having a width of 1200 mm. In the case of “15” indicated by the mark (1), 14 narrow rolled materials are rolled in advance, just before the wide rolling, and counted from the “1” wide rolled material. This is the 15th material to be rolled. The “30” indicated by the ▲ mark is also rolled with 17 narrow rolled materials immediately before rolling the wide rolled material. From “1” wide rolled material, The 34th is counted.
In addition, “50” indicated by ● is also rolled with 19 narrow materials to be rolled immediately before the wide rolling, and 54 from the “1” wide material to be rolled. This is true.

FIG. 3 shows the high spot amount (maximum crown difference ΔCR) based on the simulation result of FIG. “♦”, “■”, “▲”, and “●” in the figure correspond to “1”, “15”, “30”, and “50”, respectively.

As can be seen from FIG. 2 and FIG. 3, when rolling the wide rolled material after continuously rolling the narrow rolled material, except for “1”, “15”, “30” and In the case of “50”, a local protrusion (high spot) having a large ΔCR is formed in the vicinity of the wide end of the wide material to be rolled, and the ΔCR increases as the number of rolling increases. .
In this way, when the wide rolled material is rolled after continuously performing the narrow rolled material, the work roll profile is transferred to the wide rolled material, and the wide edge of the rolled material is transferred. It is considered that a protrusion called edge buildup that locally increases in thickness occurs at the part, which causes deterioration of the profile of the material to be rolled (see FIG. 19 for edge buildup).

In order to investigate the formation mechanism of this high spot, the roll crown and the wear profile formed by the upper and lower work rolls on the F7 stand were obtained, and these are shown in FIGS. 4 and 5, respectively.
Here, the “roll crown” is a roll crown of the work roll obtained by adding the thermal expansion amount and the wear amount of the work roll to the initial value of the work roll radius.
The amount of thermal expansion and wear of the work roll can be predicted and calculated based on the rolling history under the simulation conditions described above.

4 and 5, it can be seen that the wear of the work rolls increases with an increase in the number of rolled materials having a narrow width. This is the cause of the roll crown swinging to the minus side. The roll crown at the F7 stand is dominated by roll wear, and as shown in FIG. 6, the roll crown swings to the plus side as it approaches the width end. There is almost no element of edge buildup formation.

On the other hand, FIG. 6 shows the roll crowns of the respective stands of the F5 to F7 stands when the number of rolling is “50”. The roll crowns of the F5 and F6 stands increase toward the edge.
FIG. 7 shows a thermal crown (thermal expansion amount) which is one of the constituent elements. From FIG. 7, the thermal crown (thermal expansion amount) of the work rolls of the F5 and F6 stands is compared with that of the work roll of the F7 stand. (In FIG. 7, the curves of F5 and F6 almost overlap).
This is because a nickel grain roll is used as a work roll in the F7 stand as the final stand, whereas a high-speed roll having a relatively high thermal expansion coefficient is used in the F5 and F6 stands.

In other words, the cause of the deterioration of the profile of the wide material to be rolled in the roll-back rolling is that the edge build-up generated on the exit side of the F5 stand or F6 stand is rolled by the work roll worn on the box shape of the F7 stand, and has an edge extension shape. It is thought that it was generated by the mechanism.
Therefore, based on the mechanism at the time of the width return rolling, the following simulation was performed to search for means for reducing the influence of thermal expansion of the work rolls of the F5 and F6 stands.

Also in the rolling conditions shown in FIG. 8, in the same way as shown in FIG. 1, the work rolls of the subsequent stands of F5 to F7 are shifted to the upper limit value +150 mm, the lower limit value −150 mm, and the shift pitch 30 mm. Then, 50 rolls of the narrow rolled material having a width of 1000 mm were performed, followed by rolling of the wide rolled material having a width of 1200 mm (at the 67th number).
As shown in FIG. 8, in the rolling of the 67-th wide 1200 mm wide workpiece, as shown in FIG. 8, “0 (current setting value)” in which the shift position of the work rolls of the F5 and F6 stands was continued at a constant pitch. Rolling (displayed with ▲ mark) and shift position + 150mm (displayed with ♦ mark), + 60mm (displayed with ■ mark), -40mm (displayed with ● mark), -150mm (displayed with ◯ mark) respectively. Shaking and changing the shift position, simulations were performed for five cases of rolling.

FIG. 9 shows the profiles on the F7 stand exit side for the above five cases with different work roll shift positions. FIG. 10 shows the maximum thermal expansion amount of the work roll of the F5 stand for these five cases.
As can be seen from FIG. 9, the profile is most improved in the case where the cycle shift position is −150 mm. This is because the thermal crown of F5 at this shift position is minimized as shown in FIG.

The reason is as follows based on FIGS. 11A to 11C.
FIGS. 11A to 11C show the thermal crown of the work roll and its maximum value (peak point) together with the material to be rolled (strip) in the case assumed in the rolling of the F5 stand.
FIG. 11A shows a case where a peak point at which the thermal expansion amount (thermal crown) is maximized exists near the center of the plate reference and a narrow material to be rolled (width 800 mm) is rolled. FIG. 11B shows a case where a wide material to be rolled (width: 1000 mm) is rolled by shifting one pitch of the cyclic shift from there, and FIG. 11C shows the rolling of FIG. A case where the shift position is shifted to the maximum shift amount is shown.

In the case of FIG. 11A, the peak point at which the amount of thermal expansion is the maximum is at the center of the plate (1/2 of the width), but when rolling a narrow material to be rolled, the crown amount by the thermal crown is Almost does not affect the rolled material profile. However, in the case of FIG. 11B in which a wide rolled material is rolled, the position of the peak point is not substantially changed, and the thermal crown is transferred to the wide end of the wide rolled material as much as the thermal crown grows. Edge build up.

On the other hand, in the case of FIG. 11C in which the shift position of the work roll is moved not to the position where the cyclic shift is planned in FIG. 11B but to the portion of the maximum shift amount when rolling a wide material to be rolled, the peak point is set to the width center at the time of rolling. It is considered that the transfer of the thermal crown can be suppressed to the minimum as a result.
When the shift is set to +150 mm in FIG. 9, the edge buildup is not improved, but this is because the last work roll shift operation is + 150⇒ + 120⇒ + 90⇒ + 60⇒ + 30. In comparison, the effect was weakened by the presence of a larger thermal crown in the positive side region of the shift position.

Based on the above analysis, in the present invention, the steps (1) to (8) shown in FIG. 12 are performed when rolling the wide rolled material subsequent to the rolling of the narrow rolled material in the width return rolling or the like. To calculate the evaluation function J _ΔCR and determine the optimum work roll shift position at which the influence of the thermal crown can be _minimized . This determination method will be described below.
(1) Calculation of work roll shift limit The work roll shift limit value is calculated in consideration of the width of the material to be rolled and the equipment limit in the rolling cycle.
(2) Determination of work roll shift pitch The shift pitch of the work roll in the rolling cycle and the change limit from the cyclic shift are determined.
(3) Change work roll shift position (shift lower limit to shift upper limit)
A shift position of the work roll is determined between the shift lower limit value and the shift upper limit value.
The shift lower limit value and the shift upper limit value are determined in consideration of the following values.
Shift upper limit = MIN (cyclic shift upper limit, preceding material position + upper and lower limit values)
Shift lower limit = MAX (cyclic shift lower limit, preceding material position-upper and lower limit)
(4) Calculation of roll crown predicted value when rolling a wide material to be rolled Based on the rolling history of the rolling cycle, the roll crown predicted value CR is calculated from the thermal expansion amount and wear amount of the work roll.
(5) Calculation of roll crown target value when rolling a wide material to be rolled Based on the rolling history of the rolling cycle, a roll crown target value CR * is calculated by setting a predetermined formula.
(6) _{Calculate the} evaluation function J _ΔCR (error with _{respect to the} target) The evaluation function J _ΔCR is calculated from the roll crown predicted value and the target value obtained in the above (4) and (5). For example, it is obtained from the following formula for three points of 25 mm, 75 mm, and 150 mm from the width end.

The roll crown target value CRi * can be calculated and set to be a quadratic function in the width direction, for example (see FIG. 13). In FIG. 13, CR0 is a value that varies depending on the work roll shift position, and Wid is the width of the material to be rolled.
(7) Calculate evaluation functions _JΔCR at all shift positions. Calculate evaluation functions at all shift positions. The shift position is calculated with a pitch width (for example, 5 mm) smaller than the pitch width of cyclic shift rolling.
Note that “No” in “Calculate at all shift positions” in FIG. 12 _indicates that there is a part where J _ΔCR is not calculated within the possible range of the work roll shift stroke, and “Yes” similarly indicates the work roll shift stroke. This _indicates the case where all J _ΔCR are calculated within the possible range.
(8) The evaluation function J _ΔCR is set to the minimum shift position → End (End)
When the cyclic shift stroke is set to be less than ± 150 mm, the shift position is determined within the setting range.

In this way, it is possible to determine the work roll shift position where the evaluation function J _ΔCR is minimized, that is, the position where the edge buildup is minimized.
FIG. 14 and FIG. 15 show simulation results of calculating the work roll shift shift optimum position using this logic.
As shown in FIG. 14, the simulation conditions are as follows. In the schedule for rolling 35 rolled materials by a cyclic shift method with a shift amount of 30 mm, 19 rolled materials with a width of 1000 mm are continuously rolled, and the 20th In rolling the material to be rolled, a plate material having a width of 1200 mm, that is, a wide material to be rolled having a width of 200 mm was rolled, and then 15 materials having a plate width of 1000 mm were continuously rolled.

FIG. 15A shows the simulation result of the evaluation function J _{ΔCR at} the shift position (−150 mm to +150 mm) in the rolling of the 20th rolled material.
As can be seen from FIG. 15A, J _ΔCR is minimized at the plus shift position ₊₁₃₀ mm.
FIG. 15B shows a thickness profile based on the results of applying the conventional cyclic shift rolling method without changing the shift pitch and the thickness profile of the width end portion on the F7 stand exit side after rolling according to the simulation result of applying the logic of the present invention to FIG. And showed.
It can be seen that the edge buildup is improved in the profile in the width direction of the wide material to be rolled to which the logic of the present invention is applied, as compared with the conventional rolling method applied (conventional example).

The most effective roll type of the work roll to which the present invention is applied is a roll in which the thermal crown which is a problem during rolling of a wide material to be rolled is dominant and roll wear is small.
Therefore, it is most effective to use a high-speed roll stand with a high coefficient of thermal expansion and low wear characteristics, and a work roll using a nickel grain roll, which is often used in the final stand of a finishing mill. The amount of wear is large and the above effect is reduced.

From the determination method of the present invention, the present invention is applicable not only to the rolling of a wide rolled material in the width return rolling, but also to the rolling in which the rolling subsequent to the rolling of the narrow rolled material is a wide rolled material. It is obvious that the present invention can be applied, but it is more effective in the case where a wide material to be rolled is rolled after a large number of rolling materials having a narrow width are continuously rolled.
When the material to be rolled is a steel strip, the width of the wide rolled material is 10 to 20% or more, preferably 20% or more larger than the width of the preceding narrow rolled material, and the narrow rolled material It is more effective when the rolling is continuously performed for a total rolling length of 5 to 10 km or more, preferably 10 km or more. The rolling length here is the length in the longitudinal direction (rolling direction) of the material to be rolled.
In the above simulation, the tandem type rolling mills F5 and F6 comprising F1 to F7 stands are applied. However, the present invention further includes one tandem type rolling mill having any number of stands. It is clear that the present invention can also be applied to a single stand rolling mill.
The effect of the embodiment of the present invention was confirmed by applying it to an actual tandem rolling mill as follows.

The present invention was carried out in a hot rolling line having a tandem finish rolling mill consisting of F1 to F7 stands. The work roll shift mechanism is provided in the F5 to F7 stands. Table 1 shows the equipment specifications for each of the F5 to F7 stands.
A high-speed roll was used for the work rolls of the F5 and F6 stands, and a nickel grain roll was used for the final F7 stand. Further, normal crown control is performed at the F1 to F4 stands.

In the three stands F5 to F7, cyclic shift rolling was performed in which the work roll was shifted at a constant shift pitch of 30 mm for each material to be rolled.
And the work roll shift position change of this invention was implemented in F5 and F6 stand. The work roll of the F7 stand is set according to the cyclic shift because of large wear.

The material to be rolled is a medium-carbon steel strip, and the thickness and width of the material to be rolled in the rolling cycle are shown in FIG.
The above-mentioned work roll shift position change of the present invention is carried out on the 139th rolled material (enclosed with a circle in FIG. 16), that is, a wide rolled material whose width dimension is 240 mm larger than the preceding material. did.
In front of the wide material to be rolled, 30 narrow materials to be rolled are continuously rolled.
FIG. 17 shows the shift amount of the work roll of the F5 stand.

FIG. 18 shows the thickness profile on the exit side of the F7 stand, together with the results of the conventional example, for the example of the present invention to which the present invention is applied.
In the conventional example, the work rolls of the F5 to F7 stands are set according to the cyclic shift.
Regarding the material to be rolled after rolling, ΔCR at the edge portion was about 30 μm exceeding 25 μm in the conventional example, whereas ΔCR was about 10 μm lower than 25 μm in the present invention example of the present invention.
Thus, according to the present invention, the build-up amount generated at the edge portion of the rolled material after rolling can be reduced.

Claims

About a material to be rolled in a rolling cycle, a work roll is provided for each material to be rolled at a constant pitch while reciprocating between predetermined folding positions by a rolling mill having a shift mechanism for shifting the work roll in the axial direction. In the rolling method of the metal strip to be shifted, when rolling a material to be rolled wider than the preceding material to be rolled, an evaluation function obtained by the following equation (1) between the turn-back positions of a predetermined work roll shift A hot rolling method for a metal strip that is rolled while changing the work roll shift position so as to minimize J ΔCR .
The width dimension of the wide rolled material is 10% or more larger than the width dimension of the preceding rolled material, and the preceding rolled material is continuously rolled to a total rolling length of 5 km or more. A method for hot rolling a metal strip as described in 1.
The method for hot rolling a metal strip according to claim 1 or 2, wherein a stand having a shift mechanism for shifting the work roll in the axial direction is provided on one or more stands of a tandem rolling mill.
The method of hot rolling a metal strip according to any one of claims 1 to 3, wherein a work roll of a stand provided with a shift mechanism for shifting the work roll in the axial direction is a high-speed roll.