JP2022032188A - Rolling mill and cold rolling method - Google Patents

Abstract

To improve production efficiency by reducing rolling load, even when rolling a steel strip such as a hard extremely-thin material.SOLUTION: Cluster-type rolling mills 1A and 1B comprise: a pair of upper and lower work rolls 10A and 10B that roll a steel strip; a plurality of intermediate rolls 20A and 20B that support the upper and lower work rolls 10A and 10B respectively; back-up rolls 30A and 30B that support the plurality of intermediate rolls 20A and 20B; intermediate rolls 25 for driving having functions of rotationally driving the upper and lower work rolls 10A and 10B, of the plurality of intermediate rolls 20A and 20B; and a rotationally driving device 40 that rotationally drives the upper and lower intermediate rolls 25 for driving in such a manner that circumferential velocities of the upper and lower work rolls 10A and 10B are different from each other. Diameters Dw of the work rolls 10A and 10B are 20-120 mm, diameters DI of the intermediate rolls 25 for driving are 1.7-4.5×Dw, surface roughness of the work rolls 10A and 10B is 0.05-0.50 μmRa, and surface roughness of the intermediate rolls 25 for driving is 0.10-1.00 μmRa.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steel strip rolling mill and a cold rolling method, and more particularly to a rolling mill and a cold rolling method for rolling a hard and thin steel strip.

Thin steel strips such as special steel, stainless steel, and electromagnetic steel strips have a larger amount of alloy components than conventional steel strips, and the materials to be rolled are becoming harder. Further, since the demand for ultra-thin steel strips including foil materials is increasing, cold rolling technology for efficiently producing hard ultra-thin steel strips is required.

Conventionally, a cluster type rolling mill having a work roll having a small diameter has been used. This is because in a large-diameter work roll, when the steel strip is hard and the plate thickness is thin, the rolling reduction does not proceed even if a large rolling load is applied, that is, the minimum plate thickness that can be rolled cannot be reduced due to the so-called rolling limit. .. The cluster type rolling mill has a structure in which one small diameter roll is supported by two intermediate rolls having a larger roll diameter, and the intermediate rolls are supported by a plurality of roll groups. As a result, the cluster type rolling mill has a form in which a group of rolls supporting the work rolls are arranged in a fan shape.

As such a cluster type rolling mill, Patent Document 1 discloses a 20-stage cluster type rolling mill, and Patent Document 2 discloses a 12-step, 14-step, 16-step, and 20-step cluster type rolling mill. Has been done. As shown in Patent Documents 1 and 2, rolling is performed by a work roll having a small roll diameter, so that the contact length (called contact arc length) between the work roll and the material at the time of rolling becomes small, and the rolling load is reduced. It can be kept low, and the roll flatness, which is the contact deformation of the work roll with the steel strip, can be suppressed. The rolling load can be reduced by the synergistic effect of both.

On the other hand, as a method of reducing the rolling load without reducing the roll diameter, different peripheral speed rolling in which the upper and lower work rolls are rolled at different peripheral speeds is known (see, for example, Patent Documents 3 to 5). Shear strain is positively applied to the steel strip by the different peripheral speed rolling at the roll bite, so that the vertical pressure for causing plastic deformation is reduced and the rolling load is reduced. Rolling at different peripheral speeds disclosed in Patent Documents 3 to 5 directly drives the upper and lower work rolls. When rolling with different peripheral speeds on the upper and lower work rolls, torque is concentrated on the work rolls on the high speed side, and a larger torque is required than in normal cold rolling, which gives the same peripheral speed on the upper and lower sides. be.

Japanese Unexamined Patent Publication No. 4-127901 Japanese Unexamined Patent Publication No. 2011-183450 Japanese Unexamined Patent Publication No. 61-176412 Japanese Unexamined Patent Publication No. 61-242713 Japanese Unexamined Patent Publication No. 2017-127901

In recent years, with the increasing demand for ultra-thin steel strips such as hard foil materials, it is required to roll harder and thinner steel strips. In that case, even in the cluster type rolling mill using the small diameter work roll disclosed in Patent Documents 1 and 2, there is a problem that the flat deformation of the work roll in contact with the thin steel strip becomes large and the rolling load becomes large. be. If the rolling load is large, the rolling reduction rate per pass must be reduced, and as a result, the number of rolling passes increases and the production efficiency decreases. In particular, the thinner the plate, the longer the length of the steel strip per unit weight of the coil, so that the rolling time per pass becomes extremely long, which is a major factor in lowering the production efficiency.

Further, when the work roll is directly driven as in Patent Documents 3 to 5, the spindle that transmits the drive torque to the work roll needs to be smaller than the roll diameter so that the upper and lower spindles do not interfere with each other. .. However, when the spindle diameter becomes small, the shear stress generated on the surface of the spindle becomes excessive and the torsional strength becomes insufficient. Therefore, when rolling at different peripheral speeds using a work roll having a small diameter, there arises a problem that the torque required by the work roll on the high speed side cannot be transmitted from the spindle. As a result, there arises a problem that the production efficiency of cold rolling for steel strips cannot be improved.

The present invention has been made to solve the above problems, and even when rolling a steel strip such as a hard ultrathin material, the rolling load is reduced and the production efficiency is improved. It is an object of the present invention to provide a cluster type rolling mill and a rolling method capable of capable of rolling.

The means for solving the above problems are as follows.
[1] A pair of upper and lower work rolls for rolling steel strips,
A plurality of intermediate rolls supporting each of the upper and lower work rolls,
A backup roll that supports the plurality of intermediate rolls, and a backup roll that supports the plurality of intermediate rolls.
Of the plurality of intermediate rolls, a drive intermediate roll having a function of rotationally driving the upper and lower work rolls, respectively.
A rotary drive device that rotationally drives the upper and lower intermediate rolls for driving so that the peripheral speeds of the upper and lower work rolls are different.
Equipped with
The work roll has a diameter Dw of 20 to 120 mm and has a diameter Dw of 20 to 120 mm.
The diameter DI of the driving intermediate roll is 1.7 to 4.5 × Dw.
The surface roughness of the work roll is 0.05 to 0.50 μmRa.
A cluster type rolling mill having a surface roughness of the driving intermediate roll of 0.10 to 1.00 μmRa.
[2] The plurality of intermediate rolls are in contact with both the work roll and the backup roll, respectively.
The work roll has a diameter Dw of 70 to 120 mm and has a diameter Dw of 70 to 120 mm.
The surface roughness of the work roll is 0.05 to 0.40 μmRa, and the work roll has a surface roughness of 0.05 to 0.40 μmRa.
The cluster type rolling mill according to [1], wherein the surface roughness of the driving intermediate roll is 0.30 to 0.80 μmRa.
[3] The plurality of intermediate rolls include a plurality of first intermediate rolls in contact with the work roll, and a plurality of second intermediate rolls in contact with the first intermediate roll and the backup roll.
The cluster type rolling mill according to [1], wherein the driving intermediate roll is composed of at least one of the plurality of second intermediate rolls.
[4] The diameter Dw of the work roll is 20 to 70 mm, and the work roll has a diameter Dw of 20 to 70 mm.
The surface roughness of the work roll is 0.05 to 0.15 μmRa, and the work roll has a surface roughness of 0.05 to 0.15 μmRa.
The cluster type rolling mill according to [3], wherein the surface roughness of the driving intermediate roll is larger than the surface roughness of the work roll and is 0.15 to 0.25 μmRa.
[5] The rotary drive device rotationally drives the upper and lower intermediate rolls for driving so that the peripheral speed ratio of the work rolls on the high-speed side and the low-speed side is 1.03 to 1.10 [1]. To the cluster type rolling mill according to any one of [4].
[6] A cold rolling method for thin steel strips using the rolling mill according to any one of [1] to [5].
The driving intermediate roll is driven so that the peripheral speed ratio of the work roll between the high speed side and the low speed side is 1.03 to 1.10 with respect to the steel strip having a plate thickness of 0.3 mm or less. Cold rolling method for cold rolling.

According to the cluster type rolling mill of the present invention, the intermediate roll for driving is rotationally driven to perform different peripheral speed rolling with a small diameter work roll, thereby reducing the rolling load by the small diameter work roll and different peripheral speed rolling. By achieving both the effect of suppressing the rolling load and the effect of suppressing the rolling load, the rolling reduction ratio can be increased, so that the production efficiency can be improved.

It is a schematic diagram which shows the preferable embodiment of the cluster type rolling mill of this invention. It is a schematic diagram which shows an example of the rotary drive device in the cluster type rolling mill of FIG. It is a schematic diagram which shows another embodiment of the cluster type rolling mill of this invention. It is a graph which shows the relationship between the peripheral speed ratio and the rolling rate at the time of one-pass rolling of a steel strip having a plate thickness of 0.30 mm. It is a graph which shows the relationship between the peripheral speed ratio and the rolling rate at the time of one-pass rolling of a steel strip having a plate thickness of 0.10 mm. It is a graph which shows the relationship between the peripheral speed ratio and the rolling rate at the time of one-pass rolling of a steel strip having a plate thickness of 0.05 mm.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a preferred embodiment of the cluster type rolling mill of the present invention. The cluster type rolling mill 1A of FIG. 1 is a 12-stage rolling mill, and supports a pair of upper and lower work rolls 10A, a plurality of intermediate rolls 20A that support each of the work rolls 10A, and a plurality of intermediate rolls 20A. It is provided with a backup roll 30A to be rolled. Six roll groups are arranged above and below the steel strip S, and the upper and lower work rolls 10A are each supported by two intermediate rolls 20A, and the two intermediate rolls 20A are supported by three backup rolls 30A. Has been done.

The work roll 10A rotates while in contact with the steel strip S supplied from the coil 2, and applies compressive deformation in the plate thickness direction to the steel strip S to continuously reduce the thickness. The rolled steel strip S is wound on the tension reel 3. The upper and lower pairs of work rolls 10A each have a body length of 600 to 1800 mm and have the same diameter. However, if the difference in roll diameter between the pair of work rolls 10A is about ± 0.5%, they may be regarded as having the same diameter.

Each work roll 10A is preferably made of a cemented carbide having a longitudinal elastic modulus of at least the outer layer 5 mm of the body portion of 450 GPa or more. Since cemented carbide rolls have a higher Young's modulus than ordinary steel rolls, flat deformation, which is elastic deformation, can be reduced and the contact arc length can be shortened, expanding the effect of reducing rolling load and rolling torque. can do. Further, by using a cemented carbide having high hardness and wear resistance for the outer layer of the work roll 10A, it is possible to suppress the occurrence of scratches on the surface. The thickness of the outer layer may be at least 5 mm, and the inside may be made of a steel roll such as cast iron or forged steel, or the entire body may be made of cemented carbide.

Lubricating oil is supplied to the roll bite (contact interface) between the work roll 10A and the steel strip S. The lubricating oil supplied to the roll bite is also supplied to the contact portion between the work roll 10A and the intermediate roll 20A and the contact portion between the intermediate roll 20A and the backup roll 30A. As the lubricating oil, for example, in addition to neat oil, an emulsion emulsified in water using an emulsifier may be used. The kinematic viscosity of the lubricating oil is not particularly limited, but is preferably 5 to 30 mm ² / s at 40 ° C. When the kinematic viscosity is less than 5 mm ² / s, the oil film thickness introduced into the roll bite becomes thin, the rolling load increases, and surface defects due to seizure are likely to occur. On the other hand, if the viscosity of the lubricating oil exceeds 30 mm ² / s, slip between rolls is likely to occur, and it may not be possible to maintain a different peripheral speed state.

The plurality of intermediate rolls 20A are provided in two each on the upper and lower sides, and the two intermediate rolls 20A have a structure in which one work roll 10A is supported. Since the machining reaction force from the steel strip S is directly applied to the work roll 10A, the work roll 10A tends to bend when the work roll 10A has a small diameter. Therefore, the upper and lower two intermediate rolls 20A each support each work roll 10A. The plurality of intermediate rolls 20A have a diameter larger than that of the work roll 10A and have a higher bending rigidity than the work roll 10A.

Of the plurality of intermediate rolls 20A, one or more of the upper and lower intermediate rolls 20A functions as driving intermediate rolls 25 for rotating the work roll 10A. That is, the work roll 10A is not directly driven to rotate, but the drive intermediate roll 25 is rotationally driven, so that the work roll 10A in contact with the drive intermediate roll 25 is indirectly rotated. In FIG. 1, all four first intermediate rolls 20A function as driving intermediate rolls 25, and two upper and lower intermediate rolls 20A rotate and drive one work roll 10A. In this case, the two driving intermediate rolls 25 are controlled so that the peripheral speeds are the same, and the upper and lower driving intermediate rolls 25 are controlled so as to have different peripheral speeds.

Although the case where all of the four intermediate rolls 20A are the driving intermediate rolls 25 is illustrated, as described above, at least one driving intermediate roll 25 is provided on the upper and lower sides of the intermediate rolls 20A. You just have to. In this case, the other intermediate roll 20A supports the work roll 10A while rotating with the rotation of the work roll 10A.

Three backup rolls 30A are provided on the upper and lower sides, and the three backup rolls 30A have a structure in which two intermediate rolls 20A are supported. Of the plurality of backup rolls 30A, one or more of the upper and lower ones are preferably backup roll bearings having a structure in which a plurality of body portions divided along the roll axis direction are attached to the shaft portion. In particular, it is more preferable that the two upper and lower backup rolls 30A installed on both ends of the steel strip S in the rolling direction are made of backup roll bearings. Then, by providing a mechanism for pushing the shaft portion between the backup roll bearings and a mechanism for eccentricizing the backup roll bearings, the crown in the plate width direction can be adjusted, and the shape control ability can be enhanced.

FIG. 2 is a schematic diagram showing an example of a rotary drive device. The rotation drive device 40 of FIG. 2 rotationally drives the drive intermediate roll 25 so that the upper and lower work rolls 10A are rotated at different peripheral speed ratios. The peripheral speed ratio means the ratio of the peripheral speed of the work roll 10A on the high speed side to the peripheral speed of the work roll 10A on the low speed side. Either the upper or lower work roll 10A may be set to the high speed side or the low speed side.

The rotary drive device 40 rotates and drives the drive intermediate roll 25, and has a drive motor 41, a differential gear (differential gear) 42 connected to the drive motor 41, and one connected to the differential gear 42 and the other. Includes a plurality of spindles 43 connected to the drive intermediate roll 25. The differential gear 42 divides and transmits the rotational driving force transmitted from one drive motor 41 to the upper and lower spindles 43. At this time, the differential gear 42 divides the rotational driving force so as to have different peripheral speeds with respect to the upper and lower spindles 43. As shown in FIG. 1, when two driving intermediate rolls 25 are arranged on the upper and lower sides, two spindles 43 are also provided on the upper and lower sides, and the peripheral speeds of the upper side or the lower side are the same. Is set.

Although the case where the rotational driving force of one drive motor 41 is divided and transmitted to the upper and lower spindles 43 by using the differential gear 42 is illustrated, the drive motors are individually driven for each of the upper and lower intermediate rolls 25 for driving. 41 may be installed. In this case, different peripheral speed control is performed by independently adjusting the peripheral speeds of the upper and lower drive motors 41.

FIG. 3 is a schematic view showing another embodiment of the cluster type rolling mill of the present invention. In the cluster type rolling mill 1B of FIG. 3, the same reference numerals are given to the portions having the same configuration as that of the cluster type compressor of FIG. 1, and the description thereof will be omitted. The cluster type rolling mill 1B of FIG. 3 is a 20-stage rolling mill, and like FIG. 1, a pair of upper and lower work rolls 10B, a plurality of intermediate rolls 20B supporting each of the work rolls 10B, and a plurality of intermediate rolls 20B. It is provided with a plurality of backup rolls 30B that support the intermediate roll 20B. As a 20-stage cluster type rolling mill 1B, a Zendimia type rolling mill is widely known, and 10 roll groups are arranged above and below the steel strip S, respectively.

The work roll 10B of FIG. 3 is often used having a body length of about 400 to 1400 mm, and may be made of, for example, a cemented carbide roll as in FIG. 1. Further, as in FIG. 1, lubricating oil is supplied to the roll bite between the steel strip S and the work roll 10B. In the case of FIG. 3, the lubricating oil is also supplied between the intermediate rolls 20B that are in contact with each other. Further, as for the backup roll 30B, as in FIG. 1, it is preferable that one or more of the upper and lower backup rolls are each composed of backup roll bearings.

In particular, the plurality of intermediate rolls 20B of FIG. 3 includes a plurality of first intermediate rolls 21B that directly support the work roll 10B, and a plurality of second intermediate rolls 22B that support the plurality of first intermediate rolls 21B. Two first intermediate rolls 21B support one work roll 10B and three second intermediate rolls 22B support two first intermediate rolls 21B. Then, the four backup rolls 30B support the three second intermediate rolls 22B. The diameter (roll diameter) of the first intermediate roll 21B is larger than the roll diameter of the work roll 10B, and the diameter of the second intermediate roll 22B is larger than the diameter of the first intermediate roll 21B. This is due to the space limitation for the roll arrangement of the cluster type rolling mill 1B.

Of the plurality of intermediate rolls 20B, the second intermediate roll 22B functions as the driving intermediate roll 25, and the rotation driving device 40 of FIG. 2 is connected to the second intermediate roll 22B. This is because the diameters of the work roll 10B and the first intermediate roll 21B in FIG. 3 are smaller than those of the work roll 10A and the intermediate roll 20A in FIG. This is because the second intermediate roll 22B, which is larger than the 21B, is used as the driving intermediate roll 25 to increase the diameter of the spindle 43 and secure the torque required for controlling the different peripheral speed. Even in the case of FIG. 3, at least one of the three upper and lower second intermediate rolls 22B may function as the driving intermediate roll 25. Then, the rotational driving force of the driving intermediate roll 25 is transmitted to the work roll 10B via the first intermediate roll 21B.

<Diameter of work rolls 10A and 10B>
The work rolls 10A and 10B of the cluster type rolling mills 1A and 1B have a diameter Dw of 20 to 120 mm. When the diameter Dw of the work rolls 10A and 10B exceeds 120 mm, the roll flatness of the work rolls 10A and 10B becomes large, the rolling load increases, and the rolling reduction rate per pass cannot be increased. If the diameters of the work rolls 10A and 10B are less than 20 mm, the deflection deformation of the work rolls 10A and 10B during rolling becomes large, and the deflection deformation cannot be suppressed by the intermediate rolls 20A and 20B, and the shape of the steel strip S becomes unstable. To become. On the other hand, when the diameter Dw of the work rolls 10A and 10B is 20 to 120 mm, the contact arc length between the steel strip S and the work rolls 10A and 10B can be shortened, which is necessary for plastically deforming the steel strip S. Drive torque can be reduced.

The work rolls 10A and 10B can reduce the rolling load if the diameter Dw is 20 to 120 mm regardless of the number of steps, but even if the diameter Dw is in a suitable range according to the number of steps. good. In the case of the 12-stage cluster type rolling mill 1A, it is preferable that the diameter Dw of the upper and lower work rolls 10A is 70 to 120 mm. This is because the effect of suppressing the deflection of the work roll 10A by the intermediate roll 20A is low, and therefore, if the diameter Dw is less than 70 mm, the deflection of the work roll 10A may increase. In the case of the 20-stage cluster type rolling mill 1B, the diameter Dw of the work roll 10B is preferably 20 to 70 mm. This is because the first intermediate roll 21B and the second intermediate roll 22B are arranged as the intermediate roll 20B, so that the effect of suppressing the deflection of the work roll 10B is high, and the rolling load is applied by applying the work roll 10B having a small diameter. This is because it can be greatly reduced.

<Surface roughness of work rolls 10A and 10B>
The surface roughness of the work rolls 10A and 10B is 0.05 to 0.50 μmRa. The surface roughness is the arithmetic mean roughness defined in JIS B 0601-1994, and the measurement direction is a direction parallel to the axes of the work rolls 10A and 10B. This is because when the surface roughness is less than 0.05 μm, slip may occur between the rolls when torque is transmitted from the drive intermediate roll 25 to the work rolls 10A and 10B, and the drive torque cannot be transmitted. When the surface roughness of the work rolls 10A and 10B exceeds 0.50 μm, the coefficient of friction between the steel strip S and the work rolls 10A and 10B increases, and the rolling load and rolling torque increase. Therefore, the work rolls 10A and 10B It offsets the effect of reducing the diameter.

In particular, in the case of the 12-stage cluster type rolling mill 1A shown in FIG. 1, the surface roughness of the work roll 10A is preferably 0.05 to 0.40 μmRa. On the other hand, in the case of the 20-stage cluster type rolling mill 1B shown in FIG. 3, the surface roughness of the work roll 10B is preferably 0.05 to 0.15 μmRa. The larger the diameter of the work rolls 10A and 10B, the more likely it is that slip between rolls will occur, and it is necessary to increase the surface roughness of the work rolls 10A and 10B. The diameter of the work roll 10A of the 12-stage cluster type compressor 1A in FIG. 1 is larger than the diameter of the work roll 10B of the 20-stage cluster type compressor 1B in FIG. Therefore, the upper limit of the surface roughness of the work roll 10B can be made smaller than that of the work roll 10A, and the increase in the coefficient of friction between the steel strip S and the work roll 10B can be suppressed.

<Diameter of intermediate roll 25 for driving>
The diameter of the driving intermediate roll 25 is 1.7 to 4.5 × Dw with respect to the diameter Dw of the work roll. When the diameter DI of the driving intermediate roll 25 is smaller than 1.7 × Dw, the diameter of the spindle 43 must also be reduced. If torque is concentrated on the drive intermediate roll 25 on the high speed side when rolling at different peripheral speeds, the strength of the spindle 43 is insufficient, and the risk of equipment damage increases. On the other hand, when the diameter DI of the driving intermediate roll 25 exceeds 4.5 × Dw, the degree of freedom in arranging the equipment for arranging the roll group in a fan shape as the cluster type rolling mills 1A and 1B decreases, and the lubricating oil Space for installing supply pipes, etc. is restricted.

<Surface roughness of the driving intermediate roll 25>
The surface roughness of the driving intermediate roll 25 is 0.10 to 1.00 μmRa. When the surface roughness of the driving intermediate roll 25 is smaller than 0.10 μmRa, the surface roughness on the contact surface between the rolls becomes small, and slip between rolls is likely to occur. On the other hand, when the surface roughness of the driving intermediate roll 25 exceeds 1.0 μmRa, a flaw is generated on the surface of the work roll 10A or the first intermediate roll 21B in contact with the driving intermediate roll 25, and the surface roughness is transferred to the steel strip S. This may cause surface defects in the steel strip S. Therefore, the surface roughness of the driving intermediate roll 25 is formed to be 0.10 to 1.00 μmRa.

In particular, in the case of the 12-stage cluster type rolling mill 1A shown in FIG. 1, the surface roughness of the driving intermediate roll 25 is preferably in the range of 0.30 to 0.80 μmRa. On the other hand, in the case of the 20-stage cluster type rolling mill 1B shown in FIG. 3, the surface roughness of the driving intermediate roll 25 is preferably 0.15 to 0.25 μmRa. If the diameter is small, slipping between rolls can be prevented even if the surface roughness of the driving intermediate roll 25 is reduced. Therefore, as the number of stages is increased and the diameter is reduced, the surface roughness can be reduced, and the occurrence of surface defects generated between the rolls can be suppressed.

Further, in the cluster type rolling mill 1A of FIG. 1, it is desirable that the surface roughness of the driving intermediate roll 25 is larger than the surface roughness of the work roll 10A. This is because in the case of FIG. 1, the surface roughness on the work roll 10A side is reduced as much as possible to reduce the rolling load, and the surface roughness on the driving intermediate roll 25 side is increased to prevent slip between rolls. be. Further, in the case of FIG. 3, the rotational driving force of the driving intermediate roll 25 is transmitted to the work roll 10B via the first intermediate roll 21B. Therefore, from the viewpoint of reducing the rolling load and slipping between rolls, it is preferable that the surface roughness of the first intermediate roll 21B is larger than the surface roughness of the work roll 10B. Further, the driving intermediate roll 25 may be any as long as it does not cause inter-roll slip with the first intermediate roll 21B, but it is preferably larger than the surface roughness of the work roll 10A.

In the case of the cluster type rolling mill 1B of FIG. 3, the surface roughness of the first intermediate roll 21B is larger than the surface roughness of the work roll 10B and smaller than that of the driving intermediate roll 25. Regarding the surface roughness, if the surface roughness is smaller than that of the work roll 10B, slip between rolls is likely to occur, and if the surface roughness is larger than that of the driving intermediate roll 25, surface damage is likely to occur between rolls. be.

The surface finish of the work rolls 10A and 10B and the driving intermediate roll 25 described above may be any processing method as long as the desired surface roughness described above can be obtained. For example, the surface of the roll can be finished by roll polishing by machining, shot blasting, electric discharge machining, electron beam machining, laser machining, or the like. Of these, when performing roll polishing using a grinder, the count of the grindstone used is changed to finish the surface roughness to a desired value.

Further, it is preferable that polishing streaks extending in the circumferential direction (perpendicular to the roll axis direction) are formed on the surfaces of the work rolls 10A and 10B and the intermediate rolls 20A and 20B. The polishing streaks are polishing lines in which microscopic irregularities are formed in rows in the roll width direction by polishing. In cold rolling, when torque is transmitted from the driving intermediate roll 25 to the work rolls 10A and 10B by rolling contact, lubricating oil is introduced between the rolls to form a fluid film. Then, slip between rolls is likely to occur when the rolling speed is accelerated or decelerated. For this reason, it is preferable to provide polishing streaks in the circumferential direction on the surfaces of both rolls that rotate in contact with each other so that the lubricating oil can be removed from between the rolls.

<Peripheral speed ratio of upper and lower work rolls 10A and 10B>
The rotation drive device 40 controls the peripheral speed by the upper and lower driving intermediate rolls 25 so that the peripheral speed ratio of the upper and lower work rolls 10A and 10B is 1.03 to 1.10. If the peripheral speed ratio is less than 1.03, the effect of reducing the rolling load by different peripheral speed rolling cannot be sufficiently obtained. On the other hand, when the peripheral speed ratio exceeds 1.10, the torque applied to the driving intermediate roll 25 for rotationally driving the work roll on the high speed side increases, and the possibility of slip between rolls increases.

<Cold rolling method>
A preferred embodiment of the cold rolling method of the present invention will be described with reference to FIGS. 1 to 3. When cold rolling is performed, the cluster type rolling mills 1A and 1B of FIGS. 1 to 3 function as reverse rolling mills for rolling by reciprocating the steel strip S in the rolling direction, for example. In addition, a plurality of cluster type rolling mills 1A and 1B are installed along the rolling direction, and each cluster type rolling mill 1A and 1B may function as a tandem compressor in which rolling is sequentially performed. Cold rolling is performed. The rolling reduction rate per pass can be set in the range of about 5 to 60%. As the reduction rate per pass is larger, the number of passes from the base metal thickness to the product thickness can be reduced, so that the production efficiency can be improved. However, the larger the deformation resistance of the material and the thinner the plate thickness, the larger the rolling reduction rate per pass cannot be obtained. To determine.

Cold rolling is performed on a steel strip S having a plate thickness of 0.3 mm or less. In the rolling of an ultrathin material having a plate thickness of 0.3 mm or less, it is a condition that the flat deformation of the work rolls 10A and 10B becomes large and the rolling load increases when the hard material is to be rolled. Under such conditions, the advantageous characteristics of the present embodiment can be exhibited. In particular, it is preferably applied to a steel strip having a plate thickness of 0.1 mm or less, and more preferably 0.07 mm or less. Further, the so-called foil material, which is a plate thickness of 0.01 to 0.02 mm, may be rolled.

As the steel strip S, an ultrathin steel strip including special steel such as high carbon steel, stainless steel, foil material such as electromagnetic steel strip, and the like is targeted. However, the present invention is not limited to this, and can be applied to materials other than steel materials such as aluminum alloys, titanium alloys, and copper alloys.

According to the above embodiment, the diameters of the work rolls 10A and 10B are 20 to 120 mm, the diameter of the driving intermediate roll 25 is 1.7 to 4.5 × Dw, and the upper and lower work rolls 10A are used. The peripheral speed ratio of the upper and lower driving intermediate rolls 25 is controlled so that the peripheral speeds of 10B are different. As a result, it is possible to realize different peripheral speed rolling with small diameter work rolls 10A and 10B, the effect of reducing the rolling load by reducing the roll flatness of the work rolls 10A and 10B, and the addition of shear deformation in different peripheral speed rolling. Both of the effects of reducing the rolling load can be obtained. As a result, the effect of further reducing the rolling load and the effect of reducing the rolling torque are realized as compared with the conventional case.

In particular, in different peripheral speed rolling, the torque acting on the high-speed side roll is larger among the upper and lower work rolls 10A and 10B, and the larger torque is applied to the high-speed side work rolls 10A and 10B as compared with the upper and lower work rolls 10A and 10B. You will concentrate. Therefore, when the work rolls 10A and 10B have a small diameter, the spindle 43 also has a small diameter, resulting in insufficient torque. Therefore, by rotationally driving the drive intermediate roll 25 having a diameter larger than that of the work rolls 10A and 10B, the torque required for different peripheral speed rolling is secured. On the other hand, when the driving intermediate roll 25 rotationally drives the work rolls 10A and 10B, it is necessary to transmit the rotational driving force from the driving intermediate roll 25 to the work rolls 10A and 10B, and it is necessary to suppress the occurrence of slip between rolls. be. Therefore, the surface roughness of the work rolls 10A and 10B is set to 0.05 to 0.50 μmRa, and the surface roughness of the driving intermediate roll 25 is set to 0.10 to 1.0 μmRa. As a result, it is possible to realize different peripheral speed rolling while using the work rolls 10A and 10B having a small diameter, and by reducing the rolling load, it is possible to roll a hard thin steel strip.

An example in which cold rolling of a hard ultrathin material is carried out using the 20-stage cluster type rolling mill 1B of FIG. 3 will be described. The diameter Dw of the upper and lower work rolls 10B was 60 mm, the surface roughness of the work roll 10B was 0.1 μmRa, the diameter of the driving intermediate roll 25 was 170 mm (= 2.83 × Dw), and the diameter of the backup roll 30B was 300 mm. .. The surface roughness of the driving intermediate roll 25 was 0.2 μmRa, and the polishing was finished in the circumferential direction so that the polishing streaks were formed in the circumferential direction.

The vertical peripheral speed ratios of the driving intermediate roll 25 were set to 1.00, 1.03, 1.05 and 1.10. At this time, since there was almost no difference in diameter between the upper and lower work rolls 10B, it is considered that the peripheral speed ratio of the upper and lower work rolls 10B is the same as the upper and lower peripheral speed ratios of the driving intermediate roll 25, and in this embodiment, it is assumed. A certain rolling condition was realized.

The tension on the entry side (upstream side of the work roll 10B with respect to the traveling direction of the steel strip S) in the cluster type rolling mill 1B is 294 MPa, and the tension on the exit side (downstream of the work roll 10B with respect to the traveling direction of the steel strip S). The tension on the side) was set to 441 MPa and kept constant. The rolling speed was 100 m / min, and lubricating oil having a kinematic viscosity of 14 mm ² / s was supplied from the loading / unloading side of the rolling mill at 500 l / min to perform reverse rolling.

Under such conditions, a rolling experiment was conducted using a special steel thin plate having a plate thickness of 0.3 mm and a plate width of 910 mm as the steel strip S. The deformation resistance k of the steel strip S identified by the rolling tensile test was a hard material having l = 1046 MPa, m = 0.005, and n = 0.116 based on the deformation resistance formula shown in the formula (1). .. However, ε is a considerable strain.

k = l × (ε + m) ⁿ ... (1)

First, the effect was verified by rolling the steel strip S having a plate thickness of 0.3 mm in one pass. In the experiment, the peripheral speed ratio of the work roll 10B was 1.00 (same peripheral speed), 1.03, 1.05, 1.10 while the rolling load per unit width was controlled to be constant at 3.6 kN / mm. The rolling reduction was measured. FIG. 4 is a graph showing the relationship between the peripheral speed ratio and the rolling reduction ratio when a steel strip S having a plate thickness of 0.3 mm is rolled in one pass. As shown in FIG. 4, for the same rolling load, when the peripheral speed ratio is larger than the same peripheral speed ratio, the reduction rate per pass is also large, and when the peripheral speed ratio is 1.05, the reduction rate is. It was 1.2 times that of the conventional example.

Next, after rolling the steel strip S having a plate thickness of 0.3 mm to 0.1 mm, the effect of rolling the steel strip S having a plate thickness of 0.1 mm in one pass was verified. For the steel strip S hardened by work hardening, the reduction ratio is measured by changing the peripheral speed ratios to 1.00 (same peripheral speed ratio), 1.03, 1.05, and 1.10 in the same manner as above. did. The rolling load at that time was controlled to be constant at 2.2 kN / mm. FIG. 5 is a graph showing the relationship between the peripheral speed ratio and the rolling reduction ratio when a steel strip having a plate thickness of 0.1 mm is rolled in one pass. As shown in FIG. 5, when the peripheral speed ratio is 1.03 or more with respect to the same peripheral speed ratio, the reduction rate per pass increases, and the reduction rate at the peripheral speed ratio of 1.05 is 1. . Doubled.

Further, after rolling the 0.1 mm steel strip to a plate thickness of 0.05 mm, the effect of rolling the steel strip S having a plate thickness of 0.05 mm in one pass was verified. The rolling load at that time was 3.4 kN / mm. FIG. 6 is a graph showing the relationship between the peripheral speed ratio and the rolling reduction ratio when a steel strip having a plate thickness of 0.05 mm is rolled in one pass. As shown in FIG. 6, the larger the peripheral speed ratio, the higher the reduction rate, and at the peripheral speed ratio of 1.05, the reduction rate was 1.2 times.

In this way, by cold rolling the thin steel strip S using the 20-stage cluster type rolling mill 1B shown in FIG. 3, the rolling reduction rate is increased under the same rolling load as compared with the conventional (same peripheral speed ratio). As described above, it is possible to improve the production efficiency.

Using the 12-stage cluster type rolling mill 1A in FIG. 1 and the 20-stage cluster type rolling mill 1B in FIG. 3, the diameters of the work rolls 10A and 10B and the driving intermediate roll 25, the work rolls 10A and 10B and the driving intermediate are used. Tables 1 and 2 show the cases where the surface roughness of the roll 25 is changed. In Tables 1 and 2, a rolling load corresponding to the plate thickness of the steel strip S on the entry side is set, and the rolling reduction ratio for that condition is obtained. In addition, Tables 1 and 2 describe the problems that occurred during rolling. The rolling conditions are the same as those in the first embodiment, including the rolling oil used. In Tables 1 and 2, the diameters of the work rolls 10A and 10B are expressed as Dw, the diameter of the driving intermediate roll 25 is expressed as DI, and the conditions that do not satisfy the present invention are underlined. ..

Comparative Example Nos. In Tables 1 and 2. When the peripheral speed ratio is less than 1.03 as in 1, 4, and 7, the reduction rate is lower than when the peripheral speed ratio is 1.03 to 1.10 (see FIGS. 4 to 6). On the other hand, the invention examples No. 1 and Table 2 are shown. When the peripheral speed ratio is 1.03 to 1.10 as in 2, 3, 5, 6, 8, 9, 17 to 25, the rolling load can be reduced without slip between rolls. Was done.

Comparative Example No. in Table 1 When the diameter Dw of the work roll 10A is larger than 120 mm as in No. 10, even when different peripheral speed rolling is performed, the rolling reduction rate decreases with respect to the steel strip having the same entry side plate thickness, and the production efficiency decreases. Invited. In addition, Comparative Example No. in Table 2 When the diameter of the work roll 10B is smaller than 20 mm as in No. 10, the plate shape of the steel strip S becomes unstable even if rolling is started under the condition that a predetermined rolling load is applied, and the desired rolling reduction ratio is obtained. Could not be identified. On the other hand, the invention examples No. 1 and Table 2 are shown. When the diameters of the work rolls 10A and 10B are 20 to 120 mm as in 2, 3, 5, 6, 8, 9, 17 to 25, the rolling load can be reduced without slipping between rolls. Was made.

Tables 1 and 2 No. Under the condition that the diameter DI of the driving intermediate roll 25 is less than 1.7 × Dw as in No. 11, when rolling is started with a predetermined rolling load applied, the limiting torque of the driving intermediate roll 25 is exceeded. Rolling was stopped. In addition, No. 1 and Table 2 No. Under the condition that the diameter DI of the driving intermediate roll 25 is larger than 4.5 × Dw (DI = 4.55 × Dw) as in 12, the intermediate rolls 20A and 20B and the backup rolls 30A and 30B are arranged in a fan shape. Rolling could not be carried out because it was found that there was a space limitation for this. On the other hand, the invention examples No. 1 and Table 2 are shown. 17, No. When the diameter DI of the driving intermediate roll 25 is 1.7 to 4.5 × Dw as in No. 18, different peripheral speed rolling can be performed without exceeding the limit torque, and the rolling load reduction effect can be obtained. I was able to.

Tables 1 and 2 No. When the surface roughness of the work rolls 10A and 10B is less than 0.05 μmRa as in No. 13, the torque to be transmitted from the drive intermediate roll 25 to the work rolls 10A and 10B is insufficient due to the occurrence of inter-roll slip. Therefore, stable different peripheral speed rolling could not be realized. In addition, No. 1 and Table 2 No. When the surface roughness of the work roll is larger than 0.50 μmRa as in No. 14, the rolling reduction rate is lowered even when the different peripheral speed rolling is performed, which causes the production efficiency to be lowered. On the other hand, the invention examples No. 1 and Table 2 are shown. When the surface roughness of the work rolls 10A and 10B was 0.05 to 0.50 μmRa as in 19 and 20, the occurrence of slip between rolls was suppressed, and the effect of reducing the rolling load could be obtained.

Tables 1 and 2 No. When the surface roughness of the driving intermediate roll 25 is smaller than the surface roughness of the work rolls 10A and 10B and is less than 0.10 μmRa as in 15, transmission is transmitted from the driving intermediate roll 25 to the work rolls 10A and 10B. The power to be torque became insufficient due to the occurrence of slip between rolls, and stable different peripheral speed rolling could not be realized.

In addition, No. 1 and Table 2 No. When the surface roughness of the driving intermediate roll 25 is larger than 1.00 μmRa as in 16, the surface of the work roll 10A or the first intermediate roll 21B that comes into contact when torque is transmitted from the driving intermediate roll 25. Rolling was stopped because a surface scratch was generated on the steel strip S due to the scratch on the steel strip S. On the other hand, the invention examples No. 1 and Table 2 are shown. When the surface roughness of the driving intermediate roll 25 is 0.10 to 1.00 μmRa as in 21 and 22, the occurrence of slip between rolls can be suppressed and the rolling load can be reduced.

The embodiment of the present invention is not limited to the above embodiment, and various modifications can be made. For example, FIGS. 1 and 2 exemplify the 12-stage or 20-stage cluster type rolling mills 1A and 1B, but the present invention is not limited thereto, and a known 14-stage or 16-stage cluster type rolling mill is used. May be used.

Further, as a cold rolling method, a case where a steel strip S having a plate thickness of 0.3 mm or less is cold rolled is mentioned, but the cluster type rolling mills 1A and 1B of FIGS. 1 and 2 have a thickness of 0.3 mm. It can also be applied to rolling of a steel strip S having a thicker plate thickness. Further, in the above embodiment, the case of so-called same-diameter different peripheral speed control in which the upper and lower work rolls 10A and 10B have the same diameter but different rotation speeds is illustrated, but the upper and lower peripheral speed ratios of the steel strip S are illustrated. However, different diameters and different peripheral speeds may be controlled in which the rotational angular velocities are the same but the upper and lower diameters are different. Further, in FIG. 3, a case where the second intermediate roll 22B functions as the driving intermediate roll 25 is illustrated, but if the required torque can be transmitted, the first intermediate roll 21B is used as the driving intermediate roll 25. It may work.

1A, 1B Cluster type rolling mill 2 Coil 3 Tension reel 10A, 10B Work roll 20A, 20B Intermediate roll 21B First intermediate roll 22B Second intermediate roll 25 Driving intermediate roll 30A, 30B Backup roll 40 Rotation drive device 41 Drive motor 42 Differential gear 43 Spindle DI Drive intermediate roll diameter Dw Work roll diameter S Steel strip

Claims (6)

A pair of upper and lower work rolls for rolling steel strips,
A plurality of intermediate rolls supporting each of the upper and lower work rolls,
A backup roll that supports the plurality of intermediate rolls, and a backup roll that supports the plurality of intermediate rolls.
Of the plurality of intermediate rolls, a drive intermediate roll having a function of rotationally driving the upper and lower work rolls, respectively.
A rotary drive device that rotationally drives the upper and lower intermediate rolls for driving so that the peripheral speeds of the upper and lower work rolls are different.
Equipped with
The work roll has a diameter Dw of 20 to 120 mm and has a diameter Dw of 20 to 120 mm.
The diameter DI of the driving intermediate roll is 1.7 to 4.5 × Dw.
The surface roughness of the work roll is 0.05 to 0.50 μmRa.
A cluster type rolling mill having a surface roughness of the driving intermediate roll of 0.10 to 1.00 μmRa. The plurality of intermediate rolls are in contact with both the work roll and the backup roll, respectively.
The work roll has a diameter Dw of 70 to 120 mm and has a diameter Dw of 70 to 120 mm.
The surface roughness of the work roll is 0.05 to 0.40 μmRa, and the work roll has a surface roughness of 0.05 to 0.40 μmRa.
The cluster type rolling mill according to claim 1, wherein the surface roughness of the driving intermediate roll is 0.30 to 0.80 μmRa. The plurality of intermediate rolls include a plurality of first intermediate rolls in contact with the work roll, and a plurality of second intermediate rolls in contact with the first intermediate roll and the backup roll.
The cluster type rolling mill according to claim 1, wherein the driving intermediate roll includes at least one of the plurality of second intermediate rolls. The work roll has a diameter Dw of 20 to 70 mm and has a diameter Dw of 20 to 70 mm.
The surface roughness of the work roll is 0.05 to 0.15 μmRa, and the work roll has a surface roughness of 0.05 to 0.15 μmRa.
The cluster type rolling mill according to claim 3, wherein the surface roughness of the driving intermediate roll is 0.15 to 0.25 μmRa. The rotary drive device according to claims 1 to 4 rotationally drives the upper and lower intermediate rolls for driving so that the peripheral speed ratio of the work rolls on the high speed side and the low speed side is 1.03 to 1.10. The cluster type rolling mill according to any one item. A method for cold rolling a thin steel strip using the cluster type rolling mill according to any one of claims 1 to 5.
The driving intermediate roll is driven so that the peripheral speed ratio of the work roll between the high speed side and the low speed side is 1.03 to 1.10 with respect to the steel strip having a plate thickness of 0.3 mm or less. Cold rolling method for cold rolling.

Images