JP6733396B2 - Rolling mill - Google Patents

Description

The present invention relates to a rolling mill capable of preventing a defective shape such as a cross back ring or a vertical buck ring that occurs in a material to be rolled during temper rolling.

Temper rolling is the final production of cold-rolled steel sheets, where the thin steel sheets after cold-rolling and annealing are subjected to light reduction rolling with a rolling reduction of several% or less to adjust surface roughness, mechanical properties such as strength and elongation, and shape. It is a process. As a product manufactured through such temper rolling, there is a thin steel plate such as a container steel plate (for example, tin plate) used for beverage cans and the like. In such temper rolling of a thin steel sheet, shape defects such as a cross buckling phenomenon and a vertical buckling phenomenon occur depending on the physical properties of the steel sheet.

In order to suppress a shape defect such as crossback ring in temper rolling, various studies have been conventionally made on the cause of occurrence and the influence of rolling conditions on the occurrence of crossback ring and the like. As such a study, for example, in Non-Patent Document 1, the occurrence of crossback rings is prevented by adjusting operating conditions of temper rolling such as tension on the outlet side of the rolling mill and outlet angle of the steel sheet on the outlet side. A method is disclosed. According to Non-Patent Document 1, the occurrence of crossback rings can be prevented by increasing the tension on the delivery side of the rolling mill to the same level as the yield stress or increasing the outflow angle on the delivery side.

Further, for example, in Patent Document 1, in a plate rolling machine in which upper and lower work rolls are horizontally offset with respect to a backup roll, a roll offset adjusting device capable of adjusting a roll offset amount is used as at least a work roll and an intermediate roll. The technique of providing one roll is disclosed. According to the technique of Patent Document 1, it is said that the plate shape controllability is excellent and the jumping phenomenon in skin pass rolling can be suppressed.

JP-A-3-146205

Hideo Kijima CAMP-ISIJ Vol. 23 (2010)-662 "Problem of shape control in temper rolling of thin steel sheet"

However, although Non-Patent Document 1 discloses an example of operating conditions for preventing the occurrence of crossback rings, how does a defective shape such as crossback rings occur? The mechanism of occurrence) is not mentioned. Therefore, the method of Non-Patent Document 1 may not be able to prevent the occurrence of crossback ring. Further, in the method of Non-Patent Document 1, it is necessary to provide an auxiliary roll for adjusting the outgoing angle of the steel plate on the outgoing side of the rolling mill, and a new cost for providing the auxiliary roll is required. Further, in the method of Non-Patent Document 1, when the exit side outflow angle of the steel sheet is increased in order to prevent the occurrence of crossback ring, L warp is likely to occur.

Further, Patent Document 1 does not mention the occurrence of a defective shape such as a cross back ring, and does not disclose a method for preventing the defective shape. In particular, specific conditions (for example, horizontal roll bending force, roll offset amount, etc.) when the technique of Patent Document 1 is used to prevent the occurrence of shape defects such as crossback rings are as follows: Neither disclosed nor suggested.

The present invention has been made in view of the above points, and a cross back ring, a vertical buckling, and the like that occur in a material to be rolled during temper rolling at a minimum cost and while suppressing the occurrence of L warp. It is an object of the present invention to provide a rolling mill capable of preventing the defective shape of the rolling mill.

In order to achieve the above-mentioned object, the present invention is provided with a first stand having a pair of upper and lower work rolls having an upper work roll and a lower work roll having the same roll diameter, and rolling for temper rolling a material to be rolled. In the machine, the pair of upper and lower work rolls are offset forward and backward with respect to the sheet passing direction, and the offset amount of the pair of upper and lower work rolls in the sheet passing direction is the plate thickness of the material to be rolled. against 20 times or more, the upper Ri 0.1 times less der the work roll average of diameter of the lower work roll, the pair of upper and lower work rolls, the material to be rolled in the first stand Is characterized by being temper-rolled only once .
The present invention according to another aspect is a rolling mill that temper-rolls a material to be rolled, comprising a first stand having a pair of upper and lower work rolls each having an upper work roll and a lower work roll having different roll diameters, The pair of upper and lower work rolls are offset forward and backward with respect to the sheet passing direction, and the offset amount of the pair of upper and lower work rolls in the sheet passing direction is 20 times the sheet thickness of the material to be rolled. As described above, the average value of the diameters of the upper work roll and the lower work roll is less than 0.1 times, and the pair of upper and lower work rolls tempers the material to be rolled only once in the first stand. Characterized by rolling.

According to the present invention, the pair of upper and lower work rolls are offset forward and backward in the sheet passing direction by 20 times or more with respect to the plate thickness of the material to be rolled. Can be wrapped. In this way, by winding the rolled material around the work roll on the roll bite exit side, it becomes possible to automatically restrain the displacement of the rolled material on the roll bite exit side. As a result, it is possible to prevent the tension distribution in the width direction and the rolling direction, which originates from the vertical buckling generated after temper rolling, from being transmitted to the roll bite exit side. Therefore, it is possible to prevent a defective shape such as a cross back ring or a vertical back ring that occurs in the material to be rolled during temper rolling.

In such a case, the roll diameter difference between the upper work roll and the lower work roll may be 0.2 times or less the diameter of the lower work roll. Further, the diameter of the lower work roll may be larger than the diameter of the upper work roll.

Further, the rolling mill may further include a second stand having a pair of upper and lower work rolls on the exit side of the first stand. Furthermore, in the second stand, the material to be rolled may be rolled at an elongation rate of more than 0 to 0.3%.

Further, the rolled material may be a steel plate having a plate thickness of 0.6 mm or less.

According to the present invention, it is possible to provide a rolling mill capable of preventing a defective shape such as a cross back ring or a vertical buckling that occurs in a material to be rolled during temper rolling by a method based on the mechanism of occurrence. It will be possible. Further, according to the rolling mill of the present invention, the improvement cost of the rolling equipment can be minimized, the occurrence of L warpage can be suppressed, and the defective shape of the material to be rolled can be prevented.

It is a schematic diagram for explaining the mechanism of generation of a vertical buckling wave on the roll bite exit side. It is a schematic diagram for explaining the mechanism of generation of a vertical buckling wave on the roll bite exit side. It is a schematic diagram for demonstrating the generation mechanism of a vertical buckling and a cross buckling. It is a schematic diagram for demonstrating the generation mechanism of a vertical buckling and a cross buckling. It is a side view which shows the structure of the rolling mill concerning 1st Embodiment. It is a side view which shows the structure of the rolling mill concerning 2nd Embodiment. It is a side view which shows the structure of the rolling mill concerning 3rd Embodiment. It is a graph for demonstrating the basis of the proper range of the offset amount of a pair of upper and lower work rolls in 1st-3rd embodiment. It is a graph for demonstrating the basis of the suitable range of the roll diameter difference of a pair of upper and lower work rolls in 2nd Embodiment. It is a graph for demonstrating the basis of the suitable range of the elongation rate at the time of rolling in the 2nd stand in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and duplicate description is omitted.

<Cross-buckling phenomenon occurrence mechanism>
The present inventor estimated the mechanism of occurrence of the crossback ring phenomenon in order to suppress the occurrence of crossback ring based on the mechanism of occurrence thereof. The mechanism of occurrence of the crossback ring phenomenon estimated by the present inventors will be described below with reference to FIGS. 1 to 4. 1 and 2 are schematic diagrams for explaining the mechanism of generation of a vertical buckling wave on the roll bite exit side. 3 and 4 are schematic diagrams for explaining the generation mechanism of the vertical buckling and the cross buckling.

As shown in FIG. 1, in temper rolling, a steel sheet S, which is a material to be rolled, is rolled by being sandwiched between a pair of upper and lower work rolls 1 provided in a rolling mill and passed. At this time, a predetermined tension T is applied in the rolling direction of the steel sheet S from both the inlet side and the outlet side of the rolling mill. When the steel sheet S is rolled, a plastic region (region indicated by diagonal lines in FIG. 1) is formed in the roll bite RB, so that plastic deformation occurs in the width direction and the sheet passing direction of the steel plate S, and the steel plate is provided on the delivery side of the rolling mill. Widening of S occurs. On the other hand, in the steel plate S on the delivery side of the rolling mill, width reduction due to elastic deformation also occurs due to the effect of the Poisson's ratio of the tension T1 (exit side tension) applied to the delivery side of the rolling mill. Since the steel sheet S is trying to shrink while being constrained by the work roll 1, it receives a stress (tensile stress) T2 in the width-spreading direction from the work roll 1 that contacts in the roll bite RB. The tensile stress T2 in the roll bite RB is in a state of being balanced with the stress T3 due to the contraction of the width of the steel plate S due to the effect of the Poisson's ratio on the delivery side of the rolling mill. Further, since the tensile stress T2 is determined according to the magnitude of the tension T1, the steel plate S on the rolling-out side has a plastic elongation in the width direction depending on the magnitude of the tension T1.

As shown in FIG. 2, when the steel plate S comes out of the roll bite RB after rolling, the tensile stress T2 in the width expanding direction from the work roll 1 to the steel plate S is no longer constrained, so that elastic recovery (compressive stress) occurs. As a result, elongation occurs in the width direction of the steel plate S. Due to this elongation, a vertical buckling wave (longitudinal wave) BW is generated in the width direction of the steel plate S in the vicinity of the exit side of the roll bite RB (a region shown by a dot in FIG. 2) where displacement constraint is severe.

Next, the present inventor considers how the vertical buckling and the cross buckling are generated after the occurrence of the above-described vertical buckling wave BW on the exit side of the roll bite RB, as follows. It was

As described above, due to the elongation in the width direction due to the elastic recovery after the steel plate S comes out of the roll bite RB, the completely restrained state in the vicinity of the roll bite RB, and the tension T1 in the rolling direction of the steel plate S, the roll steel is near the roll bite RB. Buckling wave BW is generated. The stress deviation distribution in the plate width direction and the plate thickness direction of the steel plate S caused by the occurrence of this buckling wave (for example, when an upward convex longitudinal wave is generated, the upper surface of the steel plate S corresponds to the compression side as compared with the lower surface in the compression side. Is applied as a tension distribution near the exit side of the roll bite RB, which is a plastic region. The steel plate S is pulled in the rolling direction with the above tension distribution on the exit side of the roll bite RB, so that vertical (flow) buckling occurs as shown in FIGS. 3 and 4. In addition, the cross back ring is generated by longitudinal waves or seismic waves at the free ends of both edge portions of the steel sheet S each accompanied by periodic fluctuations in the rolling direction, and the longitudinal wave profile generated in the width direction is periodically inverted. Thought to be a thing. More specifically, in the buckling profile, when the seismic buckling shape profile of the free ends of both edge portions of the steel plate S is large, when it changes by half a cycle in the rolling direction, the buckling profile in the width direction is 180 degrees. The phases are out of phase. It is considered that crossback ring occurs due to the phenomenon and the tension distribution (tension variation) of the steel plate S on the exit side of the roll bite RB interlocking with each other.

The present inventor has diligently studied in order to prevent shape defects such as the vertical buckling and the crossback ring based on the mechanism of occurrence of the vertical buckling and the crossback ring estimated as described above. As a result, they have found that it is not necessary to transmit the tension distribution in the width direction and the rolling direction starting from the vertical buckling generated after temper rolling to the exit side of the roll bite RB. Since the roll bite RB exit side is in the plastic region, if the stress distribution in the width direction and rolling direction due to the out-of-plane deformation can be prevented from being transmitted to this plastic region, the occurrence of the buckling wave BW will be elastic. Since it can be stopped in the region, it is considered that it is possible to suppress or prevent the occurrence of defective shapes such as the vertical buckling and the cross buckling.

Based on the above findings, as a result of further studying means for preventing shape defects such as vertical buckling and cross buckling, by arranging a pair of upper and lower work rolls 1 with a predetermined offset, the roll bite RB exit side Thus, the steel plate S can be wound around the work roll 1. As described above, by winding the steel plate S around the work roll 1 on the roll bite RB exit side, the displacement of the steel plate S can be automatically restrained on the roll bite RB exit side. That is, even if a buckling wave BW is generated near the exit side of the roll bite RB, the steel plate S is wound around the work roll 1 on the exit side of the roll bite RB to constrain the displacement, thereby suppressing the vertical buckling that occurs after temper rolling. It is possible not to transmit the tension distribution in the width direction and the rolling direction, which is the starting point, to the exit side of the roll bite RB, and prevent the out-of-plane deformation in the range of the length equal to or more than the predetermined ratio with respect to the plate thickness of the steel plate S. Therefore, the plate thickness and the stress deviation in the plate width direction generated in the steel plate S due to the occurrence of the buckling wave are also made uniform. As a result, the influence of the tension distribution on the exit side of the roll bite RB is reduced, and the shape of the steel plate S can be flattened.

At this time, since an auxiliary roll installed on the delivery side of the rolling mill as described in Non-Patent Document 1 is not required separately, the cost for improving the rolling equipment can be minimized. Further, in Non-Patent Document 1, since the outflow angle of the steel plate on the delivery side of the rolling mill is increased by using the auxiliary roll, the L warp is likely to occur, while the above When the pair of work rolls 1 is offset, the steel plate S can be wound around the work roll 1 without increasing the outflow angle of the steel plate on the delivery side of the rolling mill, and thus L warpage is unlikely to occur.

Further, the roll offset in the present invention is merely an offset between the pair of upper and lower work rolls with respect to the backup roll. On the other hand, in Patent Document 1, the upper and lower work rolls are not offset from each other, but the work roll and the backup roll are offset, or the work roll and the intermediate roll are offset. Therefore, the offset in the present invention and the offset described in Patent Document 1 are completely different in meaning.

The first to third embodiments of the present invention made based on the above findings will be described below with reference to FIGS. 5 to 7. FIG. 5: is a side view which shows the structure of the rolling mill 10 concerning the 1st Embodiment of this invention. FIG. 6 is a side view showing the configuration of the rolling mill 20 according to the second embodiment of the present invention. FIG. 7: is a side view which shows the structure of the rolling mill 30 concerning the 3rd Embodiment of this invention.

<First Embodiment>
As shown in FIG. 5, the rolling mill 10 according to the first embodiment is a rolling mill that includes a single stand (first stand 11) and temper-rolls a steel sheet S that is a material to be rolled. The first stand 11 has a pair of upper and lower work rolls 110 including an upper work roll 111 and a lower work roll 112. The steel sheet S is rolled in a state of being pulled by the entrance tension T _EN and the exit tension T _EX .

The material and shape of the steel plate S that is the material to be rolled is not particularly limited, but in the case of a thin steel plate having a plate thickness of 0.6 mm or less, a vertical buckling or cross after temper rolling. Shape defects such as buckling are likely to occur. Therefore, in the case where the steel plate S is a thin steel plate having a plate thickness of 0.6 mm or less, temper rolling using the rolling mill 10 according to the present embodiment causes shape defects such as vertical buckling and crossback ring. Significance of suppression or prevention is great.

In the present embodiment, the pair of upper and lower work rolls 110 are offset by a predetermined amount in the front-back direction with respect to the sheet passing direction (rolling direction) as described above. In this way, the upper work roll 111 and the lower work roll 112 are offset by a predetermined amount in the rolling direction, so that the steel plate S can be wound around the upper and lower work rolls 110 on the roll bite exit side. Side, the displacement of the steel plate S can be automatically restrained. That is, even if a vertical buckling wave is generated near the exit side of the roll bite, the steel plate S is wrapped around the upper and lower work rolls 110 on the roll bite exit side to constrain the displacement, so that the steel plate S is wrapped around the upper and lower work rolls 110. It is possible to prevent out-of-plane deformation in the range (hereinafter referred to as a winding portion) B that is open. The length of the winding portion B can be increased as the offset amount L of the pair of upper and lower work rolls 110 is increased, and the larger the ratio of the steel plate S to the plate thickness d is, the higher the effect of displacement constraint is. The height of the vertical buckling, the cross buckling, etc. can be suppressed.

Specifically, in the present embodiment, the offset amount L of the pair of upper and lower work rolls 110 (the upper work roll 111 and the lower work roll 112) is equal to the plate thickness d of the steel plate S (before temper rolling). On the other hand, it is 20 times or more (Fig. 8). By setting the offset amount L to 20 times or more the plate thickness d of the steel plate S, the winding portion B can be made to have a sufficient length, and a sufficient displacement restraining effect of the steel plate S on the roll bite exit side can be obtained. Therefore, it is possible to prevent the tension fluctuation due to the buckling wave generated near the roll bite output side from being transmitted to the roll bite output side, and to suppress the height of the vertical buckling, the crossback ring, or the like. The offset amount L is preferably 30 times or more the plate thickness d of the steel plate S in order to more reliably prevent a defective shape such as a vertical buckling or a cross buckling. The “offset amount” in the present embodiment refers to the distance between the axis of the upper work roll 111 and the axis of the lower work roll 112 in the rolling direction (the same applies to the second and third embodiments described later). Is).

Further, when the offset amount L is 0.1 times or more the work roll diameter (when the upper and lower work roll diameters are different, the average value thereof), the roughness of the work roll surface is transferred to the steel plate. Is different between the upper and lower work rolls, which is not desirable especially for a steel sheet for containers in which the appearance (presence or absence of gloss by visual observation) is important. Therefore, the offset amount L is preferably less than 0.1 times the work roll diameter. ..

The rolling mill 10 according to the present embodiment does not require an auxiliary roll installed on the delivery side of the rolling mill as described in Non-Patent Document 1, so that the cost for improving rolling equipment can be minimized. As described above, it can be suppressed and the L warp is unlikely to occur.

<Second Embodiment>
As shown in FIG. 6, a rolling mill 20 according to the second embodiment is a rolling mill that includes a single stand (first stand 21) and temper-rolls a steel sheet S that is a material to be rolled. The first stand 21 has a pair of upper and lower work rolls 210 including an upper work roll 211 and a lower work roll 212. The steel sheet S is rolled in a state of being pulled by the entrance tension T _EN and the exit tension T _EX .

Mill 20 according to this embodiment, the roll diameter r ₁ of the upper work roll 211 in that it has a role diameter difference in the roll diameter r ₂ of the lower work rolls 212, the first embodiment described above This rolling mill 10 is different. Here, by offsetting the pair of upper and lower work rolls 210, the steel plate S is wound around the upper and lower work rolls 210 on the roll bite exit side, so that a slight L warp may occur depending on the material and shape of the steel plate S. is there. However, even in such a case, as in the present embodiment, by providing a roll diameter difference between the upper work roll 211 and the lower work roll 212, the L warpage due to the offset of the upper and lower work rolls 210 is caused. Since the L warp (reverse warp) in the opposite direction can be generated, the L warp is corrected by being offset by the L warp caused by the offset and the reverse warp. Therefore, when temper rolling is performed using a rolling mill having the same roll diameter of the upper and lower work rolls like the rolling mill 10 according to the first exemplary embodiment, depending on the material and shape of the steel plate S, the L Even when the warp occurs, the tempering rolling is performed using the rolling mill 20 according to the present embodiment, whereby the occurrence of the L warp can be more effectively suppressed.

To obtain such L warp suppressing effect, the roll diameter difference Δr _{= (r} 2 -r ₁₎ of the radius _{r 2} of a radius _{r 1} and the lower work roll 212 of the upper work roll 211, the lower work roll 212 The roll diameter r ₂ is preferably 0.2 times or less.

Further, which of the upper work roll 211 and the lower work roll 212 is to be made larger may be determined according to the direction of the L warp (convex upward or convex) due to the offset of the upper and lower work rolls 210. In the present embodiment, since a downward convex L-warp can occur due to the offset of the upper and lower work rolls 210, the diameter of the lower work roll 212 is set so that the upward convex L-warp can be generated. It is larger than the diameter of the work roll 211.

<Third Embodiment>
As shown in FIG. 7, the rolling mill 30 according to the third embodiment includes two stands (a first stand 31 and a second stand 32) so that so-called DR (Double Role) rolling can be performed. It is a rolling mill for temper rolling a steel sheet S which is a rolled material. The first stand 31 has a pair of upper and lower work rolls 310 composed of an upper work roll 311 and a lower work roll 312, and the second stand 32 has a pair of upper work rolls 321 and a lower work roll 322. It has upper and lower work rolls 320. The steel sheet S is rolled in a state of being pulled by the entrance tension T _EN and the exit tension T _EX .

The rolling mill 30 according to the present embodiment is for correcting the L warp generated in the steel plate S at the first stand 31 on the rear side in the rolling direction of the first stand 31 in which the pair of upper and lower work rolls 310 is offset. The rolling mill 10 according to the first embodiment described above is different in that the second stand 32 is provided. In the rolling mill 30, a roll diameter difference may be provided between the upper work roll 311 and the lower work roll 312 installed on the first stand 31 as in the second embodiment. As a result, the L warp correction effect can be maximized.

The second stand 32 is provided to correct the L warp generated on the steel plate S at the first stand 31, and by the temper rolling by the first stand 31, the vertical buckling and the cross buckling are performed. The occurrence of the above is suppressed or prevented. Therefore, the pair of upper and lower work rolls 320 provided on the second stand 32 need not be offset.

In order to enhance the L warp straightening effect in the second stand 32, it is preferable to roll the steel plate S at an elongation rate of more than 0 to 0.3% in the second stand 32. By rolling the steel sheet S at an elongation in this range, it is possible to have both an excellent effect of suppressing shape defects such as crossback rings and an excellent effect of suppressing L warpage.

According to the above-described first to third embodiments, buckling of vertical back rings, cross back rings and the like and shape defects such as L warp are suppressed or prevented with almost no new facility improvement costs. It becomes possible to manufacture thin steel sheets.

In the above embodiment, the present invention has been described by using the example in which the vertical buckling and the cross buckling occur in the material to be rolled, but the present invention is also applied to the case where a shape defect such as an ear wave occurs. can do.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. It is obvious to those skilled in the art that various changes or modifications can be conceived within the scope of the idea described in the claims, and naturally, they also belong to the technical scope of the present invention. Understood.

(Example 1)
A steel plate having a plate thickness of 0.2 mm was temper-rolled using the rolling mill 10 shown in FIG. As the rolling conditions, the rolling load is 10 kN/mm, the roll diameter of the upper work roll 111 and the lower work roll 112 is 480 mm, the tension on the rolling mill entrance side is 100 MPa, and the tension on the rolling mill exit side is fixed at 150 MPa. The offset amount between the roll 111 and the lower work roll 112 was changed. Under the above conditions, the maximum height (μm) of the crossback ring generated on the steel sheet after temper rolling was measured and plotted for each offset amount. The result is shown in FIG. The vertical axis in FIG. 8 is the maximum height (μm) of the crossback ring, and the horizontal axis is the dimensionless offset amount (value obtained by dividing the offset amount between the upper work roll 111 and the lower work roll 112 by the plate thickness). Is.
In addition, except for the offset amount, the condition shown in FIG. 8 is also performed under the condition that the offset amount is increased from the condition shown in FIG. 8 and is set to 60 mm (0.125 times the diameter of the work roll). The maximum height and appearance were evaluated.
As for the appearance, it was visually evaluated whether the difference in glossiness between the front and back surfaces when used as a steel sheet for a container was a problem (○: almost no difference in glossiness was observed Δ: there was a difference in glossiness However, it can be used as a steel sheet for containers. x: There is too much difference in glossiness, and it is difficult to use as a steel sheet for containers).
The results are shown in Table 1.

As shown in FIG. 8, when the dimensionless offset amount (that is, the ratio of the offset amount to the plate thickness) is 20 times or more, the maximum height of the crossback ring is remarkably low, and the effect of suppressing the crossback ring is remarkable. It can be seen that it is. Further, when the dimensionless offset amount is 30 times or more, the effect of suppressing crossback ring can be further ensured.

(Example 2)
Using a rolling mill 20 shown in FIG. 6, a steel plate having a plate thickness of 0.2 mm was temper-rolled. As the rolling conditions, a dimensionless offset amount (offset amount of the upper and lower work rolls 210/plate thickness), a rolling load of 10 kN/mm, a roll diameter r ₂ of the lower work roll 212 of 480 mm, and a tension on the inlet side of the rolling mill are set. It is dimensionless by fixing the tension on the delivery side of the rolling mill to 100 MPa and the tension on the delivery side of the rolling mill to 150 MPa, and adding the upper work roll 211 radius r ₁ to the roll diameter difference Δr=(r ₂ −r ₁ ) of 4.8 mm, 9.6 mm,... The roll diameter ratio (α=Δr/r ₁ ) was changed. Under the above conditions, the L warp curvature (1·mm ⁻¹ ) generated in the steel sheet after temper rolling was measured and plotted against each dimensionless roll diameter ratio. The result is shown in FIG. The vertical axis of FIG. 9 is the L warp curvature (1·mm ⁻¹ ) and the horizontal axis is the dimensionless roll diameter ratio.

As shown in FIG. 9, since the warp curvature can be reduced in the range where the dimensionless roll diameter ratio is 0.15 or more, the L warp can be effectively suppressed in this range. It is presumed to be a thing.

(Example 3)
Using a rolling mill 30 shown in FIG. 7, a 0.2 mm thick steel plate was temper-rolled. The rolling conditions include a dimensionless offset amount (offset amount of the upper and lower work rolls 310/plate thickness) of 43, a rolling load of 10 kN/mm, an upper work roll 311 and a lower work roll 312 of the first stand 31, and a second stand. All the roll diameters of the upper work roll 321 and the lower work roll 322 of 32 are fixed to 480 mm, the tension at the rolling mill entrance side is fixed at 100 MPa, and the tension at the rolling mill exit side is fixed at 150 MPa, and the elongation percentage of rolling at the second stand 32 ( %) was changed. Under the above conditions, the maximum height (μm) of the crossback ring and the L warp curvature (1·mm ⁻¹ ) generated in the steel sheet after temper rolling were measured and plotted for each elongation. The result is shown in FIG. The vertical axis in FIG. 10 represents the maximum height (μm) of the crossback ring and the L warp curvature (1·mm ⁻¹ ) and the horizontal axis represents the elongation rate (%).

As shown in FIG. 10, the maximum height of the crossback ring is almost zero and the L-curvature curvature is also small in the range where the elongation rate is more than 0 to 0.3%. From this result, it is speculated that as a result of performing temper rolling on the second stand 32 while preventing crossback ring from occurring on the second stand 32, the slight L warpage that occurred on the first stand 31 was eliminated. To be done.

INDUSTRIAL APPLICABILITY The present invention is useful, for example, in a rolling mill used for temper rolling of thin plates such as steel plates for containers (for example, tinplate) used for beverage cans and the like.

10, 20, 30 Rolling machine 11, 21, 31 First stand 32 Second stand 110, 210, 310 (1 pair) upper and lower work rolls 320 (1 pair) upper and lower work rolls 111, 211, 311 Upper work roll 321 Upper work roll 112, 212, 312 Lower work roll 322 Lower work roll S Steel plate

Claims (5)

A rolling mill for temper-rolling a material to be rolled, comprising a first stand having a pair of upper and lower work rolls having an upper work roll and a lower work roll having the same roll diameter ,
The pair of upper and lower work rolls are offset forward and backward with respect to the plate passing direction,
The offset amount in the sheet passing direction of the pair of upper and lower work rolls is 20 times or more the plate thickness of the material to be rolled, and less than 0.1 times the average value of the diameters of the upper work roll and the lower work roll. der is,
The rolling machine , wherein the pair of upper and lower work rolls temper-rolls the material to be rolled only once in the first stand . A rolling mill for temper rolling a material to be rolled, comprising a first stand having a pair of upper and lower work rolls each having an upper work roll and a lower work roll having different roll diameters,
The pair of upper and lower work rolls are offset forward and backward with respect to the plate passing direction,
The offset amount in the sheet passing direction of the pair of upper and lower work rolls is 20 times or more the plate thickness of the material to be rolled, and less than 0.1 times the average value of the diameters of the upper work roll and the lower work roll. And
The difference in roll diameter between the upper work roll and the lower work roll is 0.2 times or less the diameter of the lower work roll,
The rolling machine, wherein the pair of upper and lower work rolls temper-rolls the material to be rolled only once in the first stand. The rolling mill according to claim 2, wherein the diameter of the lower work roll is larger than the diameter of the upper work roll. The rolling mill according to claim 1, further comprising a second stand having a pair of upper and lower work rolls on the exit side of the first stand. The rolling mill according to claim 4, wherein the second stand rolls the material to be rolled at an elongation rate of more than 0 to 0.3%.

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