TW201603904A - Method for rolling metal strip - Google Patents

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[Delta]CR) 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 hot rolling method for a metal strip (rolled material), and more particularly to a hot rolling method in which a plurality of rolled materials in a rolling cycle are provided A rolling mill for shifting a work roll in the axial direction, shifting the work rolls for each of the rolled materials at a predetermined pitch while reciprocating between predetermined folding positions .

In the metal strip rolling, friction occurs at a portion where the work roll is in contact with the metal strip (rolled material) (hereinafter referred to as "the track"), and the wear corresponding to the portion of the work path of the work roll is continuously developed. Further, in the hot rolling, since the material to be rolled is at a high temperature of about 800 ° C to 1,100 ° C, thermal expansion occurs in a portion corresponding to the land of the work roll called a thermal crown.

Therefore, as the number of rolling increases, the profile of the work roll changes due to local wear and thermal expansion of the work roll, whereby the thickness distribution or shape of the rolled material in the width direction is deteriorated, thereby causing the quality of the product. Or the problem of reduced plate stability. For example, in the case of continuously rolling a narrow roll of the material to be rolled, the local plate wear is progressed, so that the thickness distribution of the wide rolled material to be subsequently rolled is abnormal. In order to avoid this abnormality, it is necessary to carry out the engineering management of limiting the width of the material to be rolled in the rolling cycle, such as rolling from the wide portion to the narrow portion of the material to be rolled (rolling opportunity (rolling opportunity) Chance) limit).

In order to suppress this phenomenon, for example, as described in Patent Document 1 and Patent Document 2, a cyclic shift method is used in which the axial direction of the work roll is made each time the rolled material is rolled. The fixed pitch (hereinafter referred to as "shift pitch") is shifted by a millimeter (mm) every time, and after the amount of displacement in the axial direction of the work roll reaches the maximum or minimum, it is folded back and continues to be displaced. Further, in Patent Document 3, a rolling method or the like is designed in which an error of a predicted calculation value of a work roll profile and a target value is obtained for all the materials to be rolled in a rolling cycle, and an error is made using an evaluation function. It is the smallest for all rolled materials in one rolling cycle. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei.

However, in Patent Document 3, "the amount of change in the displacement position of each of the rolled materials is fixed in the rolling cycle, and the rolled material is obtained for all the rolled materials scheduled for rolling in the rolling cycle. The error between the predicted calculated value of the work roll profile of the contact portion of the work roll and the target value of the work roll profile is determined by changing the value of the error of all the rolled materials in the rolling cycle to the minimum. The amount and the folding position in which the shifting direction is reversed." Therefore, for example, in a special case where a plurality of narrow-rolled materials to be rolled are continuously rolled as a preceding rolled material, only one width wider than the material, for example, 200 mm or more is rolled. The rolled material and then the subsequent rolling of a plurality of narrow-sized rolled materials, there is a case where even a large number of narrow-sized rolled materials have small errors in rolling, and a wide rolled material is rolled. The error in the system will also increase, and the error is out of tolerance. Alternatively, if the shift position is set such that the error of the wide rolled material is minimized, there is a case where a narrow rolled material before and after the wide rolled material is wasted. As described above, in the technique of Patent Document 3, in the width recovery rolling, there is a problem that a good contour of the material to be rolled cannot be obtained, and in the width recovery rolling, a narrow rolling material to be rolled is continuously used as the leading one. After the rolled material, only a wide rolled material having a width larger than the material is rolled, and then the narrow rolled material is subsequently rolled again.

[Problems to be solved by the invention]

An object of the present invention is to provide a rolling method in which rolling is performed in a rolling cycle in a cyclic shift rolling of a metal belt of a rolling mill including a shifting mechanism that shifts a work roll in the axial direction. In the case where the order is a narrow-rolled material to be rolled → a wide rolled material of a material to be rolled having a width larger than a narrow width, in particular, a narrow rolled material → a wide rolled material → a narrow width In the case of a material to be rolled (hereinafter referred to as "width recovery rolling"), a metal strip having a good profile in the width direction is obtained when a wide rolled material is rolled. Here, "narrow" and "wide" refer to a relationship in which the width of the wide rolled material is larger than the width of the narrow rolled material, and does not mean that the width is a few millimeters or more or a few millimeters or more. Value. In the width recovery rolling, the narrow rolled material before and after the wide rolled material is not necessarily the same width dimension.

The rolling cycle is referred to as a constituent unit in which a plurality of (50 to 100 or so) rolled materials are arranged in a rolling order, and the rolled material is replaced by a roll replacement. The rolling mill that has entered the work roll starts rolling, and the plurality of rolled materials (about 50 to 100) are rolled, and the rolling is carried out by using the next roll replacement. The rolled material until the machine starts rolling. [Means for solving the problem]

In order to achieve the above problems, the present invention employs the following means. [1] A hot rolling method for a metal strip, wherein a rolling mill having a shifting mechanism for displacing a work roll in an axial direction is reciprocated at a predetermined folding position with a fixed pitch for each In a rolling method of a metal strip in which a work roll is displaced by a rolled material, when a rolled material having a wide width of a preceding rolled material is rolled, between predetermined return positions of the work rolls are displaced. By rolling the work roll shift position so that the evaluation function J _{Δ CR} obtained by the following formula (1) is minimized, the rolled material in the rolling cycle is rolled: [Number 1] CR _i : predicted value of roll crown CR _i *: target value of roll crown subscript i: an integer (1, ..., n) indicating the roll crown calculation point in the width direction. [2] The hot rolling method of the metal strip according to [1], wherein a width dimension of the wide rolled material is 10% or more larger than a width dimension of the preceding rolled material, and the preceding The material to be rolled is continuously rolled at a total rolling length of 5 km or more. [3] The hot rolling method of the metal strip according to [1], wherein the rolling mill including the shifting mechanism for shifting the work roll in the axial direction is provided in a tandem type. More than one stand of the rolling mill. [4] The hot rolling method of the metal strip according to any one of [1] to [3] wherein the work roll of the rolling mill including the shift mechanism for shifting the work roll in the axial direction is High speed roller. [Effects of the Invention]

According to the metal strip rolling method of the present invention, in the cyclic shift rolling method by the rolling mill including the shift mechanism for shifting the work roll in the axial direction, the rolled material having a larger width than the preceding one can be improved. The outline of the wide rolled material, whereby the restriction of the rolling opportunity can be alleviated, and the step management of the rolling operation can be easily performed.

Using a simulator, the mechanism of the poor profile of the wide rolled material during rolling in the rolling cycle was examined in the following manner, and the width of the wide rolled material was smaller than that of the preceding narrow The rolled material of the rolled material has a width of 200 mm or more. The case of hot rolling was performed by a 7-stand tandem rolling mill including an F1 frame to an F7 frame. The cyclic shift rolling is performed on the F5 frame to the F7 frame, and the work rolls are made of one piece of the material to be rolled as a metal strip (hereinafter sometimes referred to as "WR"). Displace in the direction of the roller axis at a fixed pitch. Regarding the work roll material, a high speed roller is used in each of the F1 to F6 frames, and a nickel die roll is used in the F7 frame. High-speed rolls have high surface hardness and wear resistance, but they are not normally used in the final F7 frame due to their high coefficient of thermal expansion. This is because if a work roll having a high coefficient of thermal expansion is used in the final frame, the profile of the material to be rolled is unstable.

Fig. 1 shows a simulation condition in which, in a rolling cycle in which 100 materials are rolled, width-recovery rolling is performed five times (in which the frame is applied in Fig. 1), that is, a rolling width of 1000 mm is obtained. After a narrow strip of rolled material (steel strip), a wide strip of rolled material having a width of 200 mm and a width of 1200 mm is rolled, and then the width is restored to a narrow width of 1000 mm. Rolling of the rolled material.

Fig. 2 shows the outline (convexity distribution in the width direction) of the F7 frame exit side of the wide rolled material in the width recovery rolling as a result of the simulation. The "one" indicated by the mark means that a narrow rolled material having a width of 1000 mm is first rolled before rolling of a wide rolled material having a width of 1200 mm. ■ "15" indicated by the mark is the 15th piece of the rolled material which is rolled from the "1" wide rolled material before the wide rolling is performed. Rolled material. In the same way, before the rolling of the wide rolled material, the 17 pieces of the rolled material having a narrow width are rolled in the same manner, and the "rolled material" having a width of "1" is rolled. The 34th root counted. In addition, the "50" shown in the figure is similarly the first to roll a narrow rolling material 19 before the wide-rolling, and the first to be measured from the "one" wide rolled material. 54 roots.

The simulation result based on Fig. 2 in Fig. 3 indicates a high point amount (maximum convexity difference ΔCR). "◆", "■", "▲" and "●" in the figure correspond to the "1", "15", "30" and "50" respectively.

According to FIG. 2 and FIG. 3, in the case of continuously rolling a narrow rolled material and rolling a wide rolled material, "15" and "30" except "1" are used. In the case of "50", a local protrusion (high spot) having a large ΔCR is formed in the vicinity of the width end portion of the wide rolled material, and the ΔCR increases as the number of rolling increases. Increase. In this case, it is considered that in the case where a wide rolled material is continuously rolled after continuously rolling a narrow rolled material, the contour of the work roll is transferred to a wide rolled material, and at the width end of the rolled material. A locally thickened protrusion called edge build up is produced, which may result in deterioration of the profile of the material to be rolled (refer to Fig. 19 for edge projection).

In order to find out the formation mechanism of the high point, the roll crown and wear profile formed by the upper and lower work rolls in the F7 frame are obtained, and the respective roll crown and wear profile are respectively shown in FIG. 4 and FIG. . The term "roll crown" refers to the roll crown of the work roll obtained by summing the amount of thermal expansion and the amount of wear of the work roll to the initial value of the work roll radius. In addition, the amount of thermal expansion and the amount of wear of the work rolls can be predicted and calculated based on the rolling history of the simulation conditions.

4 and 5, the number of rolling of the material to be rolled with a narrow width increases, and the wear of the work rolls also increases. This is the reason why the roll crown is biased to the negative side, and the roll crown in the F7 frame is dominated by the roll wear, and the roll crown is not biased toward the positive side as it is near the width end as shown in FIG. There are no elements formed by edge protrusions.

On the other hand, in Fig. 6, the roll crown of each of the F5 racks to the F7 racks when the number of rolling is "50" is shown, and the roll crown of the F5 rack and the F6 rack is to the side. And increase. The thermal crown (the amount of thermal expansion) which is one of the constituent elements is shown in Fig. 7. According to Fig. 7, the thermal crown (the amount of thermal expansion) of the work rolls of the F5 frame and the F6 frame is higher than that of the F7 frame. The thermal crown of the roller is large (in addition, the curves of F5 and F6 in Fig. 7 almost overlap). This is because, in the F7 frame of the final frame, a nickel die roll is used in the work roll, and a high-speed roll having a relatively large thermal expansion rate is used in the F5 frame and the F6 frame.

That is, it is considered that the cause of the deterioration of the profile of the wide rolled material in the width recovery rolling is caused by the mechanism that the edge projection generated on the outlet side of the F5 frame or the F6 frame passes through the F7 frame. The worn work rolls in the square box mold are rolled to form a wavy edge. Therefore, based on the above-described mechanism for restoring rolling, the following simulation was carried out, and means for reducing the influence of thermal expansion of the work rolls of the F5 frame and the F6 frame were sought.

Under the rolling conditions shown in Fig. 8, as in the case shown in Fig. 1, the upper limit of the work rolls of the rear frame of F5 to F7 is shifted by the 7-stand tandem rolling mill. The value is +150 mm, the lower limit value is -150 mm, and the shifting pitch is 30 mm. The rolling is performed on 50 pre-rolled narrow-width rolled materials with a width of 1000 mm, and then the number is 67. Root) Rolling of a wide rolled material having a width of 1200 mm. In the rolling of a wide rolled material having a width of 1200 mm, which is the 67th root, as shown in FIG. 8, the shift position of the work rolls of the F5 frame and the F6 frame is kept at a fixed pitch. The continuation shifts the rolling of 0 (the current set value) (indicated by the ▲ mark), and sets the shift position to the shift position +150 mm (indicated by the ◆ mark), +60 mm (marked by ■) The five types of rolling conditions in which the shift position was changed by -40 mm (indicated by the mark) and -150 mm (indicated by the mark ○) were simulated.

In the five cases in which the shift positions of the work rolls are different, the outline of the outlet side of the F7 rack is shown in FIG. Moreover, the maximum value of the amount of thermal expansion of the work rolls of the F5 frame in the five cases is shown in FIG. As can be seen from Fig. 9, the contour is most improved in the case where the period shift position is -150 mm. This is because, as shown in FIG. 10, the thermal crown of the shift position F5 is the smallest.

The reason is expressed as follows based on FIGS. 11A to 11C. 11A to 11C are diagrams for the rolling of the F5 frame, and the thermal crown of the work roll and its maximum value (Peak point) are shown together with the strip to be rolled. Fig. 11A shows a case where the peak point at which the amount of thermal expansion (thermal crown) is the largest is located near the center of the plate reference, and the narrow rolled material (width: 800 mm) is rolled. Fig. 11B shows a case where a wide rolled material (width: 1000 mm) which is displaced by a cyclic shift of one pitch amount and a rolling width is widened, and Fig. 11C shows a shift position of the work roll. The case where the rolling of FIG. 11B is performed by shifting to the maximum shift amount.

In the case of Fig. 11A, the peak point at which the amount of thermal expansion is the largest is located at the center of the plate reference (the portion where the width is 1/2), and when the narrow rolled material is rolled, the convex metric caused by the thermal crown is almost Does not affect the profile of the material being rolled. However, in the case of FIG. 11B in which a wide rolled material is rolled, the position of the peak point is hardly changed, and the thermal crown is directly transferred to the wide rolled material by the amount of thermal crown growth. The end of the width becomes an edge protrusion.

On the other hand, in the rolling of the wide rolled material, the displacement position of the work roll is not the predetermined position of the cyclic shift of FIG. 11B, and in the case of FIG. 11C of the portion moved to the maximum shift amount, The peak point can be moved from the width center portion to the vicinity of the end portion during rolling, and as a result, it is considered that the transfer of the heat crown can be suppressed to a minimum. In the case where the displacement is +150 mm in Fig. 9, the edge projection is not improved, and the shifting action of the work roll before the shift is +150 ⇒ + 120 ⇒ + 90 ⇒ + 60 ⇒ + 30, Therefore, there is more heat convexity in the positive side region of the shift position than the negative side region of the shift position, and thus the effect is poor.

According to the above analysis, in the present invention, when rolling a wide rolled material after rolling of a narrow-width rolled material in width recovery rolling or the like, steps (1) to (steps) shown in Fig. 12 are used. (8) The evaluation function J _{Δ CR is} calculated and the optimum work roll shift position capable of minimizing the influence of the thermal crown is determined. The decision method will be described below. (1) Calculation of displacement limit of work roll The displacement limit value of the work roll is calculated in consideration of the width of the material to be rolled or the equipment limit in the rolling cycle. (2) The determination of the shifting pitch of the work rolls determines the shift pitch of the cyclic shift of the work rolls in the rolling cycle and the limit from the start of the cyclic shift. (3) Changing the work roll shift position (shift lower limit to shift upper limit) The shift position of the work roll is determined between the shift lower limit value and the shift upper limit value. Further, the shift lower limit value and the shift upper limit value are determined in consideration of the following values. Shift upper limit value = MIN (cyclic shift upper limit, first material position + upper and lower limit values) Shift lower limit value = MAX (cyclic shift lower limit, first material position - upper and lower limit values) (4) For wide width The calculation of the roll crown prediction value at the time of rolling the rolled material is based on the rolling history of the rolling cycle, and the predicted value CR of the roll crown is calculated from the amount of thermal expansion of the work roll and the amount of wear. (5) The calculation of the roll crown target value when rolling a wide rolled material is based on the rolling history of the rolling cycle, and the roll crown target value CR* is calculated by setting a predetermined number formula. (6) Calculating the evaluation function J _{Δ CR} (error with the target) The evaluation function J _{Δ CR} is the predicted value and the target value of the roll crown obtained in the above (4) and (5), and the width Several parts of the side portion (for example, three points of 25 mm, 75 mm, and 150 mm from the end of the width) are obtained by the following formula. [Number 2] CR _i : predicted value of roll crown CR _i *: target value of roll crown subscript i: indicates several parts of the side (in the example, three points of 25, 75, and 150, i = 1 to Any one of 3). Further, the target value CR _i * of the roll crown is set, for example, as a quadratic function in the width direction, and can be calculated and calculated (see FIG. 13). CR0 in Fig. 13 is a value that changes due to the shift position of the work rolls, and Wid is the width of the material to be rolled. (7) The evaluation function J _{Δ CR is} calculated at all shift positions to calculate an evaluation function for all shift positions. Further, the shift position is calculated by a pitch width (for example, 5 mm) smaller than the pitch width of the cyclic shift rolling. In addition, "No" in "calculation at all shift positions" in Fig. 12 means that there is a portion where the J _{Δ CR} is not calculated in the range of the shiftable stroke of the work roll, and similarly, "Yes" is Refers to the case where all J _{Δ CRs} are calculated within the range of the shift stroke of the work rolls. (8) Setting the evaluation function J _{Δ CR} to the minimum shift position → End When the set cyclic shift stroke is less than ±150 mm, the shift position is determined within the set range.

In this way, it is possible to determine the position of the work roll displaced by which the evaluation function J _{Δ CR} is the smallest, that is, the position at which the edge protrusion is the smallest. The simulation result of calculating the optimum position of the work roll shift using this logic is shown in Fig. 14 and Figs. 15A and 15B. As shown in Fig. 14, in the schedule in which 35 rolled materials are rolled by the cyclic shift method with a shift amount of 30 mm, 19 rolled materials having a width of 1000 mm are continuously rolled. In the rolling of the 20th rolled material, a sheet having a width of 1200 mm, that is, a wide rolled material having a width of 200 mm was rolled, and then 15 sheets of a material having a width of 1000 mm were continuously rolled.

Fig. 15A shows a simulation result of the evaluation function J _{Δ CR} at the displacement position (-150 mm to +150 mm) in the rolling of the 20th rolled material. As can be seen from Fig. 15A, J _{Δ CR} is the smallest at the displacement position +130 mm on the positive side. 15B shows the thickness profile of the width end portion of the F7 frame exit side after rolling in the simulation result of the logic to which the present invention is applied, and the cyclic shift rolling method based on the application of the conventional unaltered shift pitch. The outline of the thickness of the actual performance. It can be seen that in the width direction profile of the wide rolled material to which the logic of the present invention is applied, the edge projection is improved as compared with the case where the conventional rolling method is applied (conventional example).

The type of the roll of the work roll which is most effective in applying the present invention is a roll which is a problem in which the heat crown which is a problem in rolling of a wide rolled material is dominant, and the roll wear is small. Therefore, in general, it is most effective to implement the present invention in a frame using a high-speed roll having a large coefficient of thermal expansion and low wear, for the use of nickel crystals which are used in the final frame of the finishing mill. In the case of the work rolls of the rolls, the amount of wear is large and the effect is reduced.

According to the determination method of the present invention, the present invention can be applied not only to the rolling of a wide rolled material in the width recovery rolling but also to the rolling after the rolling of the narrow rolled material. In the case of rolling of the material to be rolled, it is more effective in the case of continuously rolling a plurality of narrow rolled material to be rolled and then rolling a wide rolled material. 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, and a narrow width, which is larger than the width of the first narrow rolled material. The rolling of the material to be rolled is more effective when the total rolling length is 5 km 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. Moreover, it can be seen that the simulation is applied to the F5 rack and the F6 rack of the tandem rolling mill including the F1 rack to the F7 rack, but the present invention can be applied to the tandem rolling of any rack. The machine can be applied to a single-stand rolling mill including one. The embodiment of the present invention was applied to a tandem rolling mill of a real machine in the following manner, and the effect thereof was confirmed. [Examples]

The present invention was carried out using a hot rolling line having a tandem finishing mill comprising an F1 frame to an F7 frame. The work roll shifting mechanism is set in the F5 rack to the F7 rack. The equipment specifications of each rack of the F5 rack to the F7 rack are shown in Table 1. In addition, high-speed rolls are used in the work rolls of the F5 frame and F6 frame, and nickel die rolls are used in the final F7 frame. Moreover, normal convexity control is performed in the F1 rack to the F4 rack.

In the three frames F5 to F7, cyclic shift rolling was performed, that is, the work rolls were displaced for each of the rolled materials at a fixed shift pitch of 30 mm. Further, the work roll shift position change of the present invention was carried out in the F5 frame and the F6 frame. In addition, since the work rolls of the F7 frame are worn out, they are set as in the case of a cyclic shift.

The material to be rolled is a medium carbon grade steel strip, and the thickness and width of the material to be rolled in the rolling cycle are shown in Fig. 16 . The work roll shift position change of the present invention is carried out for the 139th rolled material (the frame is marked with a mark in FIG. 16), that is, a wide rolled material having a width larger than the front material by 240 mm. . Before the wide rolled material is rolled, 30 narrow rolling of the material to be rolled is continuously performed. Figure 17 shows the amount of displacement of the work rolls of the F5 frame.

Fig. 18 shows the thickness profile of the outlet side of the F7 frame in the example of the present invention to which the present invention is applied, and the results of the conventional example. In the conventional example, the work rolls of the F5 rack to the F7 rack are set as in the case of a cyclic shift. In the case of the material to be rolled after rolling, the ΔCR of the edge portion is about 30 μm in excess of 25 μm in the conventional example, whereas in the example of the invention of the present invention, ΔCR is about 10 μm below 25 μm. . As described above, according to the present invention, the amount of formation of the edge portion of the material to be rolled after rolling can be reduced.

F1～F7‧‧‧Rack

Fig. 1 shows simulation conditions of a material to be rolled in a rolling cycle. Fig. 2 shows a profile (convexity distribution in the width direction) after rolling of a wide rolled material in width recovery rolling. Fig. 3 shows the relationship between the number of rolling of the narrow rolled material and the amount of high spot (maximum convexity difference ΔCR). Figure 4 shows the roll crown in the width direction of the work rolls formed in the F7 frame. Figure 5 shows the wear profile in the width direction of the work rolls formed in the F7 frame. Fig. 6 shows the roll crown in the width direction of each of the F5 frame to the F7 frame after rolling a narrow roll of the material to be rolled. Fig. 7 shows the thermal crown in the width direction of each of the F5 frame to the F7 frame after rolling a narrow roll of the material to be rolled. Fig. 8 is a view showing simulation conditions for shifting displacement during rolling of a wide rolled material in width-recovery rolling in cyclic shift rolling in which the shift pitch is fixed. Fig. 9 shows a profile (convexity distribution in the width direction) after rolling of a wide rolled material in width recovery rolling in five cases in which the shift positions of the work rolls are different. Figure 10 shows the maximum amount of thermal crown of the work rolls of the F5 frame. Fig. 11A shows the relationship between the width direction distribution of the thermal crown and the width of the material to be rolled of the material to be rolled (a narrow rolled material and a wide rolled material). Fig. 11B shows the relationship between the width direction distribution of the thermal crown and the width of the material to be rolled (a narrow rolled material and a wide rolled material). Fig. 11C shows the relationship between the width direction distribution of the thermal crown and the width of the material to be rolled (a narrow rolled material and a wide rolled material). Fig. 12 shows a rolling method of the present invention. Fig. 13 shows a calculation method of the evaluation function. Fig. 14 shows the simulation conditions of the rolling method to which the present invention is applied. Fig. 15A shows an evaluation function at the displacement position of the work roll at the time of width recovery rolling under the condition shown in Fig. 14. Fig. 15B shows the thickness distribution of the end portion in the width direction under the condition shown in Fig. 14. Fig. 16 shows the rolling cycle of the embodiment. Fig. 17 shows the displacement position of the work rolls of the F5 frame of each of the material to be rolled. Fig. 18 shows the thickness distribution of the material to be rolled in the end portion in the width direction on the outlet side of the F7 frame. Fig. 19 shows the width direction profile of the material to be rolled in which the edge projections are formed.

Claims (4)

A metal strip hot rolling method in which a rolling mill having a shifting mechanism for displacing a work roll in an axial direction is rolled at a fixed pitch while reciprocating between predetermined folding positions In the rolling method of the metal strip in which the work rolls are displaced, when the rolled material having a wide width of the preceding rolled material is rolled, between the folded positions of the predetermined work rolls being displaced, The evaluation function J _{Δ CR} obtained by the following formula (1) is the smallest, and the workpiece roll displacement position is changed to roll the material to be rolled in the rolling cycle: [Number 3] CR _i : predicted value of roll crown CR _i *: target value of roll crown subscript i: an integer (1, ..., n) indicating a roll crown calculation point in the width direction. The metal strip hot rolling method according to claim 1, wherein the wide rolled material has a width dimension that is 10% or more larger than a width dimension of the preceding rolled material, and the advanced The material to be rolled is continuously rolled at a total rolling length of 5 km or more. The metal strip hot rolling method according to the first or second aspect of the invention, wherein the rack having the shifting mechanism for shifting the work roll in the axial direction is provided in one of the tandem rolling mills. Above the rack. The metal strip hot rolling method according to any one of claims 1 to 3, wherein the work roll having the frame of the shift mechanism for shifting the work roll in the axial direction is a high speed roll .