Kajiwara, Toshiyuki (Hitachi, JA)
Sonobe, Noriyoshi (Hitachi, JA)
Nishi, Hidetoshi (Hitachi, JA)
Hayashi, Masahiro (Hitachi, JA)

05/368521

06/25/1974

06/11/1973

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Hitachi, Ltd. (Tokyo, JA)

72/241.400

72/245, 72/247

B21B31/18; B21B13/02; B21B13/14; B21B27/02; B21B27/10; B21B31/02; B21B31/20; B21B35/12; B21B35/14; B21B39/08; B21B31/16; B21B13/00; B21B27/06; B21B31/00; B21B35/00; B21B39/02; B21B31/18

72/247,242,243,237

3628362

MILL FOR ROLLING A THIN, FLAT PRODUCT

December 1971

Stone

Mehr, Milton S.

Craig, And Antonelli

This application is a continuation-in-part of application Ser. No. 224,550, filed Feb. 8, 1972, now abandoned.

We claim

1. A rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, a pair of upper and lower backup rolls arranged exteriorly of said work rolls, a pair of upper and lower intermediate rolls respectively interposed between said work rolls and said backup rolls, the diameter of the portions of said intermediate rolls which can contact the work rolls being substantially constant over the length of such portions, means for changing the relative position of the intermediate roll and work roll in the axial direction of the rolls such that one end of said portions of the intermediate rolls be positioned in or adjacent the plane including one widthwise end of the material being rolled thereby to form a non-contacting region on the work roll relative to the intermediate roll, and means for developing a bending moment in one of the work rolls in the same direction as the bending moment developed in the other work roll under the effect of the pressure distribution between the work roll and intermediate roll and the aforesaid relative position, whereby the shape of the rolled material is controlled.

2. A rolling mill according to claim 1, wherein a pair of said upper and lower intermediate rolls are supported by two upper backup rolls and two lower backup rolls respectively and said upper and lower backup rolls are supported by a single metal chock vertically movably mounted in a roll housing.

3. A rolling mill according to claim 1, wherein a pair of said upper and lower intermediate rolls are in contact with one upper and lower backup rolls arranged with their center lines in substantially vertical alignment with the center lines of said intermediate rolls and each intermediate roll is supported by a vertically movable metal chock received in a recess formed in the backup roll supporting metal chock.

4. A rolling mill according to claim 1, wherein a pair of said upper and lower work rolls respectively are supported by metal chocks vertically movably mounted in the inside of left and right projections formed on a roll housing, and hydraulic rams for bending said work rolls are disposed in said projections.

5. A rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, a pair of upper and lower backup rolls arranged exteriorly of said work rolls, a pair of upper and lower intermediate rolls respectively interposed between said work rolls and said backup rolls, the diameter of the portions of said intermediate rolls which can contact the work rolls being substantially constant over the length of such portions, driving shaft for shifting the intermediate roll in the axial direction of the roll such that one end of said portion of the intermediate roll be positioned in or adjacent the plane including one widthwise end of the material being rolled and serving simultaneously as a driving shaft for the work roll, thereby to form a non-contacting region on the work roll relative to the intermediate roll, and means for developing a bending moment in one of the work rolls in the same direction as the bending moment developed in the other work roll under the effect of the pressure distribution between the work roll and intermediate roll and the aforesaid relative position, whereby the shape of the rolled material is controlled.

6. A rolling mill according to claim 5, wherein the driving shafts to drive said work rolls and to cause said intermediate rolls to shift in the axial direction are respectively connected to said intermediate rolls.

7. A rolling mill according to claim 5, wherein the driving shaft to drive said work rolls and to cause said intermediate rolls to shift in the axial direction are extended through roll driving pinion stand speed reduction devices and connected to roll shifting and retaining devices provided rearwardly of said speed reduction devices respectively.

8. A rolling mill according to claim 7, wherein one end of said driving shaft is connected through a universal gear coupling to said intermediate roll and the other end thereof is connected through a universal gear coupling to a spline shaft extending through a pinion gear provided in said pinion stand speed reduction device, and said spline shaft is connected to the roll shifting and retaining device through a coupling having a thrust bearing, and further said pinion gear is connected to a roll driving electric motor.

9. A rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, the diameter of said work rolls being at least 15 percent of the length of the rolling surface thereof, a pair of upper and lower backup rolls arranged exteriorly of said work rolls, a pair of intermediate rolls each arranged on each side of said work rolls between the work roll and backup roll, said intermediate roll having a generally flat surface, means for changing the relative position of the intermediate roll and work roll in the axial direction of the rolls such that one end of the effective portion of said intermediate roll be positioned in or adjacent the plane including one width-wise end of the material being rolled thereby to form a non-contacting region on the work roll relative to the intermediate roll, and means for developing a bending moment in one of the work rolls in the same direction as the bending moment developed in the other work roll under the effect of the pressure distribution between the work roll and intermediate roll and the aforesaid relative position, whereby the shape of the rolled material is controlled.

10. A rolling mill according to claim 9, wherein said means for developing a bending moment in one of the work rolls resorts to the relative positions of the material being rolled, the work roll and the intermediate roll.

11. A rolling mill according to claim 9, wherein said means for developing a bending moment in one of the work rolls consists of means for applying a roll bending force to the end portion of the work roll.

12. A rolling mill according to claim 9, wherein said means for shifting the intermediate roll in the axial direction of the roll serves simultaneously as a driving shaft for the work roll and consists of a drive shaft connected to the respective intermediate rolls.

13. A rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, the diameter of said work rolls being at least 15 percent of the length of the rolling surface thereof, intermediate rolls which are shifted in the axial direction according to the plate width of the material being rolled such that one end of the effective portions thereof be positioned adjacent the plane including one widthwise end of the material, said intermediate rolls being arranged each on each side of the work rolls, a drive shaft for shifting the intermediate roll in the axial direction and serving simultaneously as a driving shaft for the work roll, a pair of upper and lower backup rolls arranged exteriorly of the intermediate rolls for contact with said intermediate rolls, metal chocks respectively disposed vertically movably in left and right peojections provided on a roll housing to support said pair of upper and lower work rolls, hydraulic rams provided on said projections, and roll shifting and holding means provided rearwardly of a roll driving pinion stand speed reducing means, said drive shaft extending through said speed reducing means and connected to said roll shifting and holding means, one end of said drive shaft being connected to said intermediate roll through a universal gear joint with the other end connected to a spline shaft extending through a pinion gear provided in said pinion stand speed reducing means through a universal joint gear, said spline shaft being connected to said roll shifting and holding means through a joint having a thrust bearing, said pinion gear being connected to a roll driving motor, and said hydraulic rams imparting a roll bending action to one of the work rolls in the same direction as the bending moment developed in the other work roll under the effects of the contact pressure distribution between the work roll and intermediate roll, the high rigidity of the work rolls and the aforesaid relative position.

14. A rolling method using a rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, a pair of upper and lower backup rolls arranged exteriorly of said work rolls, and a pair of intermediate rolls each arranged on each side of the work rolls between the work roll and intermediate roll, said method comprising positioning one end of the effective portion of the intermediate roll on that side of the plane including one widthwise end of the material being rolled which is closer to the pass-line and adjusting the position of said end such that a bending moment may be developed in one of the work rolls in substantially the same size and in the same direction as the bending moment developed in the other work roll, during the rolling operation under the effects of the contact pressure distribution between the work roll and intermediate roll and the high rigidity of the work rolls.

15. A rolling method using a rolling mill comprising a pair of upper and lower work rolls of high rigidity to perform rolling of a material by contact therewith, a pair of upper and lower backup rolls arranged exteriorly of said work rolls, and a pair of intermediate rolls each arranged on each side of the work rolls between the work roll and intermediate roll, said method comprising positioning one end of the effective portion of the intermediate roll in or adjacent the plane including one widthwise end of the material being rolled and, when a bending moment is developed in one of the work rolls which is larger than the bending moment developed in the other work rolls under the effect of the contact pressure distribution between the work roll and intermediate roll, the high rigidity of the work rolls and the aforesaid positional relation, applying to said other work roll a bending moment larger than and acting in the opposite direction to the bending moment developed in said one work roll, whereby the directions of the total moments acting on the respective work rolls are made the same and the sizes thereof are substantially equalized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to rolling mills and more particularly to such rolling mills which have a unique roll arrangement and roll structure and are provided with a unique roll driving system.

2. Description of the Prior Art

In recent years, the requirement for accuracy in thickness of rolled products, particularly cold-rolled steel plates, are becoming severer and severer. To meet such requirement, the accuracy in thickness in the longitudinal direction of rolled materials has been increased to an appreciable extent owing to the rapid development of an automatic thickness control method but a method of effectively controlling the thickness in the width-wise direction of rolled materials has not been found as yet. It has of course been known that a work roll bending method has been developed and used in a four-high rolling mill as a measure to control the flatness in the widthwise direction of rolled material, with a considerably good result. However, in the conventional roll bending method the flatness controlling effect or the so-called flatness correcting capacity is limited and is particularly insufficient when the width of materials to be rolled varies largely, and a sufficiently satisfactory result cannot be obtained. This will be described in further detail hereunder.

In general, in order to obtain rolled products which are satisfactory in shape, particularly in thickness in the widthwise direction, the following two factors are most important:

1. TO MINIMIZE THE INFLUENCE OF THE BENDING MOMENTS OCCURING IN THE WORK ROLLS UNDER ROLLING LOAD;

2. TO INCREASE THE FLATNESS CORRECTING CAPACITY BY ROLL BENDING.

The phenomenon in which the work rolls are bent under rolling pressure is attributable to the fact that the opposite end portions of the working rolls which are not in contact with the material being rolled are subjected to the bending moments caused by the contact load with backup rolls, and such a phenomenon naturally causes a remarkable thickness unevenness of the rolled plate near the boundary between the portions of the work rolls which are in engagement with the material and the portions of the same which are not in engagement with the material, or at the opposite edge portions of the rolled plate. The thickness unevenness becomes particularly greater as the width of the rolled plate becomes narrower relative to the length of the work rolls because the bending moments becomes larger and the deflection of the work rolls becomes greater.

On the other hand, the effect of the roll bending method is largely influenced by the diameter of the work rolls. For instance, when the diameter of the work rolls is small, the roll bending action is restricted by the backup rolls and its effect appears only at the end portions of the rolls. Furthermore, since the roll bending force is subjected to a limitation by the strength or roll necks and the service live of bearings, the adjustment of the roll bending effect is possible only within a limited range and it is practically difficult to change the roll crown as desired. After all, the initial crown of the rolls must be changed at each time the width of the rolled plate changes as being practiced at the present time. If such measure is not taken, it would be impossible to prevent the thickness unevenness in the widthwise direction of the rolled plate, and this will result in a substantial degradation of the product quality.

However, in actual rolling mills it is usual that the width of the rolled materials frequently changes and, if the rolls are exchanged at each time the width changes, the working efficiency would be reduced greatly. In addition, a large number of rolls having different initial crowns must be provided, which increases the number of spare rolls and increases the operational cost, with the result that the production cost becomes high.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a rolling mill in which, in transmitting the rolling load to work rolls, the influence of the bending moments occurring in the work rolls on the flatness in the widthwise direction of the rolled material is minimized, thereby to improve the flatness of the rolled material.

The second object of the invention is to provide a rolling mill in which the values of the bending moments acting on work rolls are made small, thereby to minimize the bending of the work rolls and improve the flatness of the rolled material.

The third object of the invention is to provide a rolling mill in which, even when the width of the rolled material is required to be changed frequently, the shape of each rolled material can be controlled without changing rolls, so that the working efficiency of the rolling mill is enhanced.

The fourth object of the invention is to provide a rolling mill having work rolls of high rigidity, in which the flatness of the rolled material can be improved without making the end portions of the work rolls or intermediate rolls complicated in shape.

Namely, the present invention is applied to rolling mills of the type having work rolls of high rigidity, e.g. work rolls whose diameter is substantially larger than 18 percent of the length of the rolling surface (the effective length of the roll surface which can substantially be used for rolling), and backup rolls respectively disposed exteriorly of the work rolls. The rolling mill according to the invention is characterized in that intermediate rolls are interposed respectively between work rolls and backup rolls, said intermediate rolls being of such type that the diameter of the portions which can be brought into contact with the work rolls is substantially constant over the length of such portions and there is provided means for shifting each intermediate roll relative to the associated work roll in the axial direction of the roll so that one end of said portions of said intermediate roll may be positioned in a vertical plane including one widthwise end of a material being rolled or adjacent to said plane, whereby a bending moment is developed in one of the work rolls which acts in the same direction as the direction of the bending moment developed in the cooperating work roll, due to the pressure distribution between the work roll and intermediate roll, the high rigidity of the work roll and the relative position of the work roll and the relative position of the work roll and intermediate roll.

For developing the bending moment in the cooperating work roll, the relative position of the work roll and the material being rolled may be adjusted based on the rolling load distribution between said work roll and said material, or means for applying a roll bending force to the end portion of the work roll may be used.

The fifth object of the present invention is to provide a novel and effective rolling mill in which the relation between the plate width change and the deformation of work rolls and the relation between the roll bending effect and the length of backup rolls are combined in an ingenious manner, whereby the above-described problems have been solved. Practically, the rolling mill comprises a pair of upper and lower work rolls supported by metal chocks respectively being vertically movable and providing for a roll bending action, a pair of upper and lower intermediate rolls respectively arranged above and below said work rolls for contact therewith and being shiftable in the axial direction according to the width of a material to be rolled and backup rolls arranged above and below said intermediate rolls for contact therewith, said intermediate rolls being adjustably axially shifted to control the flatness of the rolled material in cooperation with the roll bending action.

Namely, in the present invention there are provided, as means for reducing the bending of work rolls under rolling pressure, a pair of upper and lower intermediate rolls which are axially shifted such that one end of each roll is placed in line with one end of the material being rolled, whereby one end of each work roll has the same rolling effect as obtainable when one end of each backup roll is in alignment with one edge of the rolled plate, and thus the bending moments as mentioned above are decreased. However, with such means only, the effect on the other end of each work roll is insufficient because the opposite ends of a pair of the upper and lower intermediate rolls cannot always be located in registration with the opposite edges of of the material being rolled in response to the change of width of said material. In the present invention, however, this problem can be solved by the combination of said means and roll bending means. Namely, in the rolling mill according to the invention, one end of each work roll is not bound by the backup roll and, therefore, the bending force is extremely amplified. The bending of the work roll becomes larger as the plate width becomes narrower, and the roll bending effect also becomes larger, so that the thickness unevenness in the widthwise direction can be effectively positively eliminated. Thus, an extremely remarkable functional advantage is brought about by the above-mentioned combination.

The sixth object of the invention is to provide a rolling mill of the character described above, which is provided with a novel roll driving system to drive said work rolls and cause axial shifting of the intermediate rolls.

Namely, in the rolling mill described previously there must be provided means for shifting the intermediate rolls in the axial direction and retaining them at the desired positions, in addition to the driving shafts to drive the work rolls. Therefore, the rolling mill tends to become large in size and complicated in construction. Further, the space around the main body of the rolling mill becomes extremely narrow, making the maintenance and inspection difficult.

In order to solve such problems, the present invention provides a rolling mill of the character described above, which is so constructed that driving of the work rolls and axial shifting of the intermediate rolls are effected by the same driving shafts. By so constructing, the construction of the entire rolling mill can be remarkably simplified and the facility cost can be substantially decreased.

The seventh object of the invention is to provide a rolling mill of the character described above, in which the thrust loads acting on the axially shiftable intermediate rolls are received rationally and effectively. Practically, the rolling mill is characterized in that the driving shafts to drive the work roll and cause axial shifting of the intermediate rolls are extended through a roll driving pinion stand speed reduction device and connected to a roll shifting and retaining device. By so doing, the roll shifting and retaining device need not be disposed in the narrow space around the main body of the rolling mill and can be disposed rearwardly of the pinion stand speed reduction device where the maintenance and inspection are easy. Moreover, the thrusts acting on the intermediate rolls can be received by the roll shifting and retaining device, without the necessity for providing any additional means.

The rolling mills according to the present invention each is a sort of multistage rolling mill comprising eight or six rolls, but is substantially free of the following defects of the conventional multistage rolling mills.

Namely, in the conventional multistage rolling mills the space around the upper and lower work rolls has been so narrow that accessories necessary for carrying out a smooth rolling operation, e.g. plate pressing means required on the entrance and exit sides of the roll stand for guiding the material being rolled, cobble guards necessary for protecting rolls against damage at the breakage of rolled material and cooling means for cooling the work rolls, cannot be effectively provided therein. Further, the narrow space around the upper and lower work rolls has inevitably impaired the workability and safety in maintenance and inspection. In the rolling mills of the present invention, such problems are substantially solved owing to the novel roll arrangement which provides a sufficiently wide space around the work rolls.

The eighth object of the invention is to provide a rolling method in which is used a rolling mill of the type having work rolls of high rigidity and in which the shape of the rolled material can be controlled without changing the rolls even when the required plate width of the rolled material varies.

The ninth object of the invention is to provide a novel and simple rolling method.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a front elevational view of an embodiment of the rolling mill according to the present invention;

FIG. 2 is a view looking in the direction of the arrows II--II of FIG. 1;

FIG. 3 is a view of another embodiment of the invention looking in the direction of the arrows III--III of FIG. 4;

FIG. 4 is a sectional side view of the rolling mill shown in FIG. 3;

FIG. 5 is a sectional view of one form of the universal gear coupling used in the rolling mill of the invention;

FIG. 6 is a top plan view of one form of the roll shifting and retaining device used in the rolling mill of the invention;

FIG. 7 is a schematic illustration showing the arrangement of accessories of the rolling mill of the invention;

FIG. 8 is a graphic diagram showing the thickness distribution of a rolled material rolled by a conventional four-high rolling mill; and

FIG. 9 is a graphic diagram similar to FIG. 8 but showing the thickness distribution of a rolled material rolled by the rolling mill of the invention.

FIGS. 10a, 10b and 10c are schematic views respectively showing the rolling mill according to the present invention in operation, wherein the intermediate rolls are axially shifted to control the flatness of the rolled material in co-operation with the roll bending action.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described with reference to the drawings. Referring to FIGS. 1 and 2, a pair of vertically arranged work rolls 2, 3 which directly rolls a material 1 to be rolled are supported by metal chocks 4, 4' and 5, 5' mounted in roll housings 6, 6'. The metal chocks are vertically movably arranged in the inside of left and right projections 7, 8 of the roll housings 6, 6' respectively. In the projections 7, 8 are also disposed hydraulic rams 9, 10 for bending the work rolls. Therefore, while the rolling mill is a multiple stage rolling mill, bending of the work rolls is easily achieved as in a conventional four-high rolling mill. A pair of intermediate rolls 11, 12 which are brought into contact with the upper and lower work rolls 2, 3 are arranged with their center lines substantially vertically aligned with the upper and lower work rolls 2, 3 are arranged with their center lines substantially vertically aligned with the center lines of said work rolls. These intermediate rolls 11, 12 are supported by two upper and lower backup rolls 25, 26 and 27, 28 respectively. Further, each of the intermediate rolls 11, 12 has at least one end thereof progressively reduced in diameter in a conical or other suitable shape. In the embodiment shown, the right hand end 13 of the intermediate roll 11 is tapered into a conical shape and the opposite end 14 of the intermediate roll 12 is tapered into a conical shape. The ends of the intermediate rolls may be formed in a cylindrical shape. The intermediate rolls 11, 12 respectively have extensions 15, 16 at one ends thereof for causing an axial movement of said rolls and joints 17, 18 are connected to said extensions 15, 16, through which the intermediate rolls are connected to suitable driving sources (not shown) consisting of hydraulic devices or electric motors. Each of the joints 17, 18 is composed of a bearing 19, a bearing box 20, a universal coupling piece 21, a metal 22, an end of a spindle 23 and a pin 24. The backup rolls 25, 26 are supported by metal chocks 29, 29' mounted in the roll housing 6, 6', and the backup rolls 27, 28 are supported by similar metal chocks 30, 30', all through a roll neck bearing 31. These metal chocks respectively have recesses 32, 33 at the central portions thereof for receiving the intermediate rolls 11, 12. In FIGS. 1 and 2, reference numerals 34, 35 designate backup roll balancing hydraulic rams; 36, 36' depression screws connected with the metal chocks 29, 29' for depressing the rolls; 37 backup roll driving couplings and 38 spindles.

Here, the tapered ends 13, 14 are substantially in the region out of contact with the work rolls 2, 3 and backup rolls 25, 26, 27, 28. Therefore, the end portions which can contact the work rolls 2, 3 do not include the tapered ends 13, 14. Namely, the tapered ends do not perform special functions in the rolling operation. Therefore, the end portions of the intermediate rolls refer to the portions adjacent the ends of the effective surfaces of the rolls substantially participating in the rolling operation, and the ends of the intermediate rolls refer to the terminal ends of the effective rolling surfaces and not the terminal ends of the tapered ends. In the production of the intermediate rolls, however, it is permissible to form the tapered ends and incorporate such intermediate rolls in the rolling mill. The end portions of the intermediate rolls which can contact the work rolls 2, 3 may substantially be the same in diameter as the central portions thereof, it being unnecessary to use a complicated tapered end portion as in U.S. Pat. No. 2,776,586 to Sendzimir.

The work rolls 2, 3 used in the present invention is characterized by high rigidity. Namely, the present invention is applied to rolling mills of the type wherein work rolls, because of their high rigidity, are each supported by one intermediate roll. The present invention has no significance when applied to rolling mills of the type using work rolls of low rigidity which are each supported by two intermediate rolls to prevent horizontal deflection thereof. Describing the work rolls used in the present invention in further detail, the diameter of the work rolls is substantially larger than 18 percent and at least 15 percent and usually 25 percent of the length of the rolling surfaces thereof, and is 250 mm for 18 percent and 350 mm for 25 percent. The diameter to surface length ratio of the work rolls in Sendzimir is smaller than 6.15 percent and the diameter of the work rolls is smaller than 86 mm.

Because of the construction described above, when the intermediate rolls 11, 12 are arranged with their tapered ends 13, 14 located at the opposite sides of the material 1 to be rolled, the work rolls 2, 3 are deformed by the moments caused by the contact load with the backup rolls and thus excessive rolling pressures otherwise applied to the material 1 by the opposite ends of the work rolls can be greatly prevented. By changing the relative position of the work rolls 2, 3 and intermediate rolls 11, 12 in the manner described, the ends of the intermediate rolls are positioned on that side of a vertical plane including one widthwise end of the material 1 being rolled which is closer to the pass-line and adjacent said plane, or alternatively it is possible to position the ends of the intermediate rolls 11, 12 in said plane or on that side of said plane remote from the pass-line and adjacent said plane. By so doing, a so-called non-contact region of each work roll is formed in which said work roll does not contact the effective end portion of the associated intermediate roll, as may be seen in the drawings. Such change in the relative position can be achieved in accordance with the desired plate width of the rolled material without replacing the work rolls 2, 3 or intermediate rolls 11, 12. In addition, a remarkable roll bending effect of the hydraulic rams 9, 10 can be obtained since one ends of the work rolls 2, 3 are not bound by the backup rolls. In the event when the material 1 changes in width, a satisfactory rolling result can be obtained merely by shifting the intermediate rolls 11, 12 in the axial direction by the driving sources, not shown, through the joints 17, 18 so that the tapered ends 13, 14 of said rolls will be located at the opposite sides of the material 1. Thus, an unevenness in thickness in the widthwise direction of the rolled material can always be avoided and a high quality product can always be obtained by the effect of preventing deformation of the work rolls under the rolling pressure and expanded roll bending effect, even if the width of the material varies.

Now, the effect of the present invention will be described in detail.

FIGS. 10a, 10b and 10c are for explaining the effect of the present invention. FIG. 10a shows the arrangement in which one end of each of the upper and lower intermediate rolls 11, 12 is positioned on that side of the vertical plane including one widthwise end of the material 1 being rolled which is closer to the pass-line 150 and adjacent said line (the tapered ends 13, 14 are not shown as they have no relation with the effect of the present invention). FIG. 10b shows the case wherein the rolling is carried out by applying roll bending forces 151, 151' between the end portions of the work rolls 2, 3, i.e., between the work roll chocks 4, 4' and 5, 5', in the state of FIG. 10a, and FIG. 10c shows the case wherein the rolling is carried out with one end of each of the intermediate rolls 11, 12 positioned on the opposite side of the pass-line with respect to the vertical plane including one widthwise end of the material 1 being rolled and adjacent said line (including the case where said one end is positioned in said plane) and with roll bending forces applied to the end portions of the work rolls 2, 3 as described above.

Since the same phenomenon occurs on both the left and right sides of the rolling mill, the right half portion only will be described, and the explanation on the right half portion is applicable similarly to the left half portion.

In FIG. 10a, the relative positions of the work rolls 2, 3 and intermediate rolls 11, 12 are different between the upper and lower sides as shown and a contact pressure distribution F ₁ exists in the lower work roll 3 which results from the contact between the end portion of said work roll 3 and the intermediate roll 12 and which does not exist in the upper work roll 2. As a result, a counterclockwise bending moment M ₁ is developed in the lower work roll 3, and a counterclockwise bending moment M ₂ is developed in the upper work roll 2 due to the rolling pressure distribution F ₂ between the work roll 2 and the material 1 being rolled because the end of the intermediate roll 11 is located on that side of the vertical plane including widthwise end of the material 1 which is closer to the pass-line. The bending moments acting on the work rolls 2, 3 are substantially M ₁ and M ₂ . The feature of the arrangement of FIG. 10a lies in that the bending moment M ₂ is developed in the work roll 2 which acts in the same direction as the bending moment M ₁ developed in the other work roll 3. The fact that the bending moments M ₁ , M ₂ are developed in the two opposite work rolls 2, 3 in the same direction means nothing but that the influence of the bending moments on the flatness of the rolled material 1 can be minimized. Namely, the influence of the bending moments can be completely eliminated when │ M ₁ │ = │ M ₂ │. In other words, the flatness of the rolled material can be controlled with high accuracy, simply by changing the relative position of the intermediate roll and work roll by shifting the intermediate roll 11, without requiring any other means. It will be understood from the foregoing that the bending moment M ₂ can be developed in one of the work rolls which is acting in the same direction as the bending moment M ₁ develoepd in the opposite work roll, by the effects of the contact pressure distribution F ₁ between the work roll and intermediate roll, the contact pressure distribution F ₂ between the work roll and the material being rolled, the high rigidity of the work rolls which provides such contact pressure distributions and the aforesaid relative positions.

In FIG. 10b, it will be understood that, when the roll bending forces are applied to the opposing work rolls, the sizes of forces exerted to said rolls are the same but the resulting bending moments are in the relation of │ M ₃ │ < │ M ₄ │ and acting in the opposite directions to each other. Therefore, when │ M ₁ │ > │ M ₂ ,│ the influence of the bending moments on the flatness of the rolled material can be minimized by arranging the rolls such that │ M ₁ + M ₃ │ = │ M ₂ + M ₄ │. Namely, the feature of the arrangement of FIG. 10b lies in that M ₄ is applied to one work roll in the same direction as M ₁ developed in the other work roll.

In FIG. 10c, a bending moment M ₁ ' is developed in the work roll 3 due to F ₃ similar to the preceding case and a bending moment M ₂ ' smaller than M ₁ ' is developed in the other work roll 2 due to F ₄ . Further, by the application of the roll bending force 153 in the same manner as in FIG. 10b, bending moments M ₃ ' and M ₄ ' are respectively developed acting in the opposite directions to each other, which are in the relation of │ M ₃ ' │<│ M ₄ ' │ due to the relative position of the rolls. Thus, it is possible to make │ M ₁ ' + M ₃ ' │ = │ M ₂ ' + M ₄ ' │ and to minimize the influence of the bending moments on the flatness of the rolled material.

Further, in FIGS. 10b and 10c, the bending of the work roll 3 can be minimized by applying the roll bending forces 151, 153. Namely, │ M ₁ + M ₃ │<│ M ₁ │ (because M ₁ and M ₃ have reverse symbols). As for the work roll 2, │ M ₂ + M ₄ │<│ M ₁ │ (because │ M ₁ + M ₃ │ ≉ │ M ₂ + M ₄ │ as described above. Therefore, the bending of the work roll can be made smaller when the roll bending force is additionally applied than when merely the bending moment is developed in the work roll by adjusting the relative position of the intermediate roll and work roll. It will be obvious that, while two backup rolls are arranged on each side of the work rolls in FIG. 2, only one backup roll may be arranged on each side.

Another embodiment of the present invention will be described with reference to FIGS. 3 through 6. A pair of upper and lower work rolls 46, 47 are rotatably supported at their opposite ends by metal chocks 52, 53 mounted in a roll housing 41. The metal chocks 52, 53 respectively are vertically movably arranged in the inside of left and right projections 54, 55 of the roll housing 41. In the projections 54, 55 are also disposed hydraulic rams 56, 57 for bending the upper and lower work rolls and a backup roll balancing hydraulic ram 63.

A pair of upper and lower intermediate rolls 44, 45 respectively in contact with the work rolls 46, 47 are arranged with their center lines substantially vertically aligned with the center lines of said upper and lower work rolls, and are supported at their opposite ends by metal chocks 50, 51. The intermediate rolls 44, 45 are progressively reduced in diameter at one ends opposite to each other, into a conical or other suitable shape. In the embodiment shown, the right hand end 64 of the intermediate roll 44 is tapered in a conical shape and the opposite end 65 of the intermediate roll 45 is tapered in a conical shape. Above and below the intermediate rolls 44, 45 are provided a pair of upper and lower backup rolls 42, 43 with their center lines thereof in substantially vertical alignment with the center lines of the former and with the opposite ends thereof supported by metal chocks 48, 49 mounted in the roll housing 41. Roll position adjusting screws 62 are connected to the upper side of the metal chock 48, and hydraulic rams 61 and cylinders 60 are provided below the metal chock 49 to perform a roll depressing operation. The intermediate roll supporting metal chocks 50, 51 are respectively received in recesses 58, 59 in the backup roll supporting metal chocks 48, 49 to provide for movement of the intermediate rolls 44, 45 in the vertical and axial directions.

On the other hand, driving shafts 70, 71 to drive the work rolls 46, 47 and cause an axial movement of the intermediate rolls 44, 45 are connected to one ends of said intermediate rolls 44, 45 through universal gear couplings 72, 73 respectively. The driving shafts 70, 71 in turn are connected through universal gear couplings 74, 75 to spline shafts 77, 78 extending through a pinion stand speed reduction device 76. The spline shafts 77, 78 are respectively connected to roll shifting and retaining devices 87, 88 through couplings 81, 82 each having a thrust bearing 79, said roll shifting and retaining devices 87, 88 respectively comprising reciprocating shafts 83, 84 and hydraulic cylinders 85, 86. Each of the universal gear couplings 72-75, as illustrated in FIG. 5, is of the construction in which an inner sleeve 90 shrink-fitted over the driving shaft 70 and an outer sleeve 90 fixed to the intermediate roll 44 by a pin 94 are rotatably connected together by means of gears 91, 93 and further said inner and outer sleeves 90, 92 are coupled together by means of a coupler 95 having a spherical head 96, a pressing plate 97 and a nut 98. The thrust bearing 79 rotatably supports the spline shafts 77, 78 and also receives thrusts acting on the intermediate rolls 44, 45.

The roll shifting and retaining devices 87, 88 cause axial movement of the intermediate rolls 44, 45 and also retain said intermediate rolls in predetermined positions by receiving the thrusts acting on said rolls. The roll shifting and retaining devices may be of the type utilizing a screw and a link mechanism as shown in FIG. 6. Namely, the device shown in FIG. 6 reciprocates the spline shaft 77 through a link 101 which makes a pivotal movement about a frame 100 connected to the pinion stand speed reduction device 76, and a universal coupling 102. The other end of the link 101 is connected with a nut 104 through a lever 103. The nut 104 is reciprocably mounted on a screw 106 rotatably mounted on a frame 105. The screw 106 is rotated from an electric motor 107 through pulleys 108, 109 and a belt 110. On the other hand, a transmission shaft 115 connected to a roll driving electric motor not shown is connected through a coupling 116 to a pinion 117 which is provided in the pinion stand speed reduction device 76. The pinion 117 meshes with an upper pinion gear 118 which is meshing with a lower pinion gear 119. Both of the pinion gears 118, 119 are rotatably supported by a frame 122 through bearings 120, 121 respectively. Further, the pinion gears 118, 119 respectively are formed with axial bores through which the spline shafts 77, 78 extend and splines 123, 124 are formed in said axial bores to provide for reciprocal motion of the spline shafts 77, 78 and to rotate the same.

Such being the construction, when the roll driving electric motor not shown is set in motion, all of the intermediate rolls 44, 45, the work rolls 46, 47 in contact with said intermediate rolls 44, 45 and the backup rolls 42, 43 can be rotated concurrently through the transmission shaft 115, the pinion stand speed reduction device 76, the spline shafts 77, 78 and the driving shafts 70, 71. Further, by adjustably shifting the intermediate rolls 44, 45 in the axial direction by the roll shifting and retaining devices 87, 88 through the spline shafts 77, 78, the driving shafts 70, 71, etc., so as to locate the tapered ends 64, 65 of said rolls at the opposite edge portions of the material to be rolled, the work rolls 46, 47 are deformed by the moments caused by the contact load with the backup rolls 42, 43 and thereby excessively large rolling pressure otherwise applied to the material by the opposite ends of said work rolls can be prevented. Furthermore, since one end portions of the work rolls 46, 47 are not bound by the backup rolls 42, 43, a remarkable roll bending effect by the roll bending hydraulic rams 56, 57 can be obtained.

Furthermore, in the rolling mills of the invention described above a sufficiently wide space can be secured around the work rolls without making the diameter of the rolls particularly large. Therefore, it is possible to provide upper and lower plate pressing devices 130, 131, cobble guards 132, 133 and cooling devices 134, 135 sufficiently close to the work rolls as exemplified in FIG. 7.

FIGS. 8 and 9 illustrate the thickness distributions of rolled materials having different widths which were rolled by the same work rolls. FIG. 8 shows the results of rolling by a conventional four-high rolling mill and FIG. 9 shows the results of rolling by the rolling mill according to the invention. The work rolls used had a diameter of 250 mm and a length of 1,420 mm. The rolling operation was carried out on three types of material respectively having a width of 760 mm, 920 mm and 1,220 mm, under three different roll bending forces of 0, 10 Ts and 20 Ts. The symbols A1, A2, A3 .... depicted in the figures indicate the run numbers. ------------------------------------------------------------ ---------------

Run No. Roll bending force (Ts) Plate width (mm) ____________________________________________________________ ______________ A1 0 760 A2 10 Do. A3 20 Do. B1 0 920 B2 10 Do. B3 20 Do. C1 0 1220 C2 10 Do. C3 20 Do. ____________________________________________________________ ______________

As may be apparent from FIG. 8, in the conventional four-high rolling mill, the roll bending force is insufficient when the plate width is small and is excessively large when the plate width is large, and, even if the best conditions of A3, B3 and C1 are selected, the deformation of the work rolls cannot be compensated at all by the roll bending force, with the result that a considerably large thickness unevenness occurs.

On the contrary, as shown in FIG. 9, in the rolling mill of the invention, the roll bending effect is outstandingly amplified and the deformation of the work rolls is essentially compensated over the width range of the material from a small width to a large width. Namely, it will be obviously understood that by selecting the optimum conditions of A3, B3 and C1, the thickness unevenness of the rolled plate can be remarkably improved as compared with the conventional four-high rolling mill, for any width of the material.