GB2157606A - Rolls for rolling mills - Google Patents

Abstract

A roll for a rolling mill comprises a roll core 1 over which a sleeve 6 is fitted. A fluid-tight annular space is defined between the roll core and the sleeve at each end of the roll and at its centre. Each annular space accommodates two independently axially movable annular members 9, 10 and 31, 32, the outer surface of each of which is inclined to the axis of the roll and is opposed to a correspondingly inclined portion of the inner surface of the sleeve 6. Oil passages (not shown) are provided in the roll core and permit oil to be selectively injected into the annular spaces to cause axial movement of the annular members between a position in which they do not firmly engage the opposed surfaces of the roll core and the sleeve and a position in which they do firmly engage the said opposed surfaces and expand the sleeve outwardly thereby varying the profile of the roll. <IMAGE>

Description

SPECIFICATION Rolls for rolling mills The present invention relates to rolls for rolling mills and is concerned with such rolls which can attain precision in the strip thickness in the direction of its width and which can control differing complex profiles of strips.

Figure 1 is a diagrammatic elevation of a conventional four- high rolling mill comprising backup rolls a and work rolls b. Such a four-high rolling mill is disadvantageous in that when a strip d is rolled whose width is shorter than the length of the work rolls b, these rolls b are curved or bent as indicated by the chain dotted lines e with the result that the crown of the rolled strip is increased. In order to prevent the crown from being increased, a method has been employed in which the work rolls have a crown.

Rolling mills have also been used in which the crown of the work rolls is adjustably controlled.

Figure 2, which is a diagrammatic partly sectioned side elevation, shows such a roll in which a sleeve g is fitted over a roll core f and an annular oil chamber h is provided over the centre portion of the roll core f. In use, the oil under high pressure is forced into the oil chamber h so that the sleeve g is expanded and consequently the crown of the roll is adjusted. However, as shown in Figure 3, which is a diagrammatic partly sectioned end elevation of the roll of Figure 2, the sleeve g which is in contact with a mating roll i is bent or deformed at the point of contact and high stresses are developed at portions j adjacent thereto. Therefore such rolls are suitable for use for cold rolling a strip under a low rolling force, but are not suitable for use in a hot strip mill or a plate mill which rolls the strip under a high rolling force.

So-called bending control methods have also been used in which forces are applied in opposite directions to the shafts of the work rolls b. This method is disadvantageous in that bending of the work rolls is prevented at those portions A (Figure 1) where the work rolls b and the backup rolls a contact and thus a satisfactory result cannot be achieved. Using such a method, the desired correct cross sectional profile of the strip cannot be obtained.

In an attempt to solve the above and other related problems, various methods have been proposed. One example is to provide axially offset intermediate rolls c in a six-high rolling mill as illustrated diagrammatically in Figure 4. The above problems have been satisfactorily overcome by this method, but new problems arose. Thus, the total number of rolls is increased and the pressure distribution at the contact surfaces is nonuniform in the axial direction of the rolls. Furthermore the maximum value of the contact pressure is considerably increased so that wear of the rolls is increased which results in an increase in the cost of the maintenance of the rolls. Moreover, the mill housing is of increased height and is more easily lengthened under load. In addition, since the intermediate rolls are offset in the direction of their length, the rolls are rapidly damaged.Six-high rolling mills are constructionally symmetrical about the centre point so that when the strip d deviates laterally from the centre of the rolling mill, the strip tends to adopt a zig-zag mode of movement. Furthermore when a six-high rolling mill is provided with only a pair of bearing boxes, it is difficult to roll a strip with a complex cross sectional profile.

A further proposal is illustrated diagrammatically in Figure 5 in which both ends of the backup rolls are chamfered so that the end portions of the work rolls b and the backup rolls a do not contact one another. In such a rolling mill, a strip with a relatively small width can be satisfactorily rolled, but when a strip with a relatively large width is rolled, the work rolls are not positively supported at their end portions which are in contact with the side edge portions of the strip so that these side edge portions are of increased thickness, resulting in the formation of a negative crown.

In view of the above, the present invention has as its object the provision of a roll for a rolling mill which can substantially overcome the above and other problems so that the correct cross sectional profile of a strip being rolled can be obtained and the rolling efficiency can be improved.

According to the present invention a roll for use in a rolling mill comprises a rolling core and a sleeve fitted over the roll core, one or more annular spaces being defined between the roll core and the sleeve, the or each annular space accommodating one or more axially movable annular members, at least one of the opposed surfaces of each annular member and the roll core and the sleeve being axially tapered, whereby each annular member is movable between a position in which it does not firmly engage the opposed surfaces of the roll core and the sleeve and a position in which it does firmly engage the said opposed surfaces and expands the sleeve outwardly.

The roll preferably includes means for axially moving the or each annular member and in the preferred embodiment the or each annular space constitutes a substantially fluid-tight chamber and the roll core is provided with passageways through which pressurised fluid may be introduced to cause the or each annular member to move between the two said positions.

An annular space accommodating a movable annular member may be situated adjacent one or both ends of the roll core and the sleeve and/or at the longitudinal centre of the roll core and the sleeve.The or each annular space may contain only one movable annular member but it may contain two or even more independently movable annular members.

It is not of critical importance which surface of each opposed pair of surfaces is tapered provided that the taper is such that axial movement of the or each annular member results in the distance between the outer surface of the annular member and the inner surface of the sleeve varying. In the preferred embodiment the opposed surfaces of the or each annular member and the roll core extend substantially parallel to the axis of the roll and the opposed surfaces of the or each annular member and the sleeve are both tapered in the same sense, preferably at the same angle. The opposed surfaces of the or each annular member and the sleeve and/or the roll core are conveniently provided with means for supplying lubricant between the said surfaces, e.g. a groove for conducting oil between the said surfaces.

The present invention also embraces a rolling mill in which at least one of the work or backup rolls and/or the intermediate rolls if these are present comprises a roll of the type defined above.

Further objects, features and details of the present invention will be apparent from the following description of certain specific embodiments thereof which is given by way of example with reference to Figures 6 to 13 of the accompanying diagrammatic drawings, in which: Figure 6 is a side view, partly in section, of a roll in accordance with the present invention; Figure 7 is a detailed side view of an end portion of the roll of Figure 6; Figure 8 is a detailed side view of the centre portion of the roll of Figure 6; Figure 9 is a view similar to Figure 8 of another embodiment of the present invention; Figures 70A to lOD are views showing the variations in the roll profile; Figure ii is a sectional side view of the centre portion ofa further embodiment of the present invention; and Figures 12 and 13 are side views of rolling mills incorporating rolls in accordance with the present invention.

Referring first to Figures 6 to 8, reference numeral 1 designates a roll core; 2, a bearing box supporting the roll; 3, a bearing; 4, a bearing retainer; and 5, an oil seal fitted into the bearing retainer 4 A sleeve 6 constituting a roll barrel is fitted over the roll core 1 and is spaced apart from the outer surface of the roll core 1 by a suitable distance.

Two spaced spacer rings 7 are interposed between the sleeve 6 and the roll core 1 at positions in which they are spaced from both the ends and the centre of the roll.

As best seen in Figure 7, the inner surfaces of the end portions 6a of the sleeve 6 are tapered, that is to say inclined to the axis of the roll, as indicated by reference numeral 8 and a pair of tapered rings 9 and 10 are disposed in each annular space defined between the tapered surfaces 8 and the outer surface of the roll core 1 such that the tapered rings 9 and 10 are movable in the axial direction of the roll. The outer surfaces of the tapered rings 9 and 10 are so tapered that they mate with the associated tapered surface 8 of the sleeve end portion 6a.The outer surfaces of the tapered rings 9 and 10 are formed with an annular groove which receives a piston ring 11.The inner surfaces of the tapered rings 9 and 10 are formed with a groove which receives an O-ring 12.

A part of the sleeve end portion 6a extends outwardly beyond each tapered surface 8 and is stepped so that its diameter is greater than that of the tapered surface 8 and screw threads 13 are formed in the inner surface of the stepped portion.

A seal ring 14 fits agairst the step and and O-ring 15 is disposed between the vertical surface of the seal ring 14 and the step while another O-ring 15 is disposed between the inner surface of the seal ring 14 and the outer surface of the roll core 1. The seal ring 14 is securely held in position by means of a ring nut 16 threadably engaged with the screw threads 13.

The space in which the tapered rings 9 and 10 are accommodated is oil-tight. A first oil chamber 17 is defined between the outer end of the adjacent spacer ring 7 and the inner end of the tapered ring 9, a second oil chamber 18 is defined between the tapered rings 9 and 10 and a third oil chamber 19 is defined between the tapered ring 10 and the seal ring 14. Oil pasages 20, 21 and 22 are formed in the roll core 1 and communicate with the first, second and third oil chambers 17, 18 and 19, respectively, and with an oil source (not shown).

The tapered ring 9 is formed with spiral grooves 23 and 24 on its inner and outer surfaces respectively. The spiral groove 23 communicates with the second oil chamber 18 while the second spiral groove 24 communicates with the first oil chamber 17. The tapered ring 10 is also formed with similar grooves 25 and 26, of which the first spiral groove 25 communicates with the third oil chamber 19 while the second spiral groove 26 communicates with the second oil chamber 18.

In the upper half of Figure 7 the tapered rings 9 and 10 are shown as being in engagement with the tapered surface 8 of the sleeve end portion 6a, that is to say, the rings 9 and 10 are securely engaged between the end portion 6a of the sleeve 6 and the roll core 1. However, in the lower half of Figure 7 the tapered rings 9 and 10 are shown as being loosely fitted between the sleeve end portion 6a and the roll core 1, that is to say, the rings 9 and 10 are slightly spaced from the tapered surface 8.

An oil chamber 27, whose cross section converges from both ends towards the centre, is defined between the two spacer rings 7, as best seen in Figure 8, and communicates with a central oil passage 28 and left and right oil passages 29 and 30. A pair of tapered rings 31 and 32, which are tapered inwardly, are accommodated in the oil chamber 27.They are moved toward each other when oil is forced through the side oil passages 29 and 30 into the oil chamber 27 and are moved away from each other when oil is forced into the oil chamber 27 through the central oil passage 28.The inner surfaces of the centre portion 6b of the sleeve 6 which define the oil chamber 27 are tapered as indicated at reference numeral 33. The angle of taper of the tapered surfaces 33 is equal to that of the tapered rings 31 and 32 and is so selected that when the tapered rings 31 and 32 are spaced apart from each other in the oil chamber 27 by the maximum distance, there are small gaps between the tapered surfaces 33 and the tapered rings 31 and 32.

Similarly to the tapered rings 9 and 10, the ta pered rings 31 and 32 are formed with spiral grooves.

When oil under pressure is forced into the first oil chamber 17, the tapered rings 9 and 10 are caused to move towards the adjacent bearing box 2 so that they are a loose fit between the roll core 1 and the sleeve 6, as shown in the lower half of Figure 7, but when oil under pressure is forced only into the second oil chamber 18, the tapered ring 9 is caused to move inwardly and engages the roll core 1 and the sleeve 6. If oil under pressure is then forced into the third oil chamber 19, the tapered ring 10 is caused to move inwardly and become wedged between the roll core 1 and the sleeve 6, as shown in the upper half of Figure 7.

Thus in response to the pressure of the oil selectively forced into the first, second and third oil chambers 17, 18 and 19, the tapered rings 9 and 10 are forced to move axially outwardly or inwardly.

The pressurised oil flows along the spiral grooves 23, 24, 25 and 26 so that the cooperating surfaces of the tapered rings 9 and 10, the roll core 1 and the sleeve end portion 6a are lubricated and the axial movement is facilitated. As a result the sleeve end portions are expandable outwards by a desired distance.

When rolls of the type described above are incorporated into a rolling mill and when the tapered rings 9 and 10 are positioned so that they are a loose fit between the roll core 1 and the sleeve 6, the rolling force exerted on the sleeve end portion 6a is not transmitted to the end portion of the roll core 1. As a result, when both the tapered rings 9 and 10 are a loose fit, the effective length of the roll over which the rolling force is transmitted is tO.

When only the tapered ring 9 is wedged between the roll core 1 and the sleeve 6, the rolling force is transmitted through the tapered ring 9 so that the effective roll length becomes t,. When both the tapered rings 9 and 10 are wedged between the roll core 1 and the sleeve 6, the effective roll length becomes t2' When the pressure of the working oil is increased so that the tapered rings 9 and 10 are firmly wedged between the roll core 1 and the sleeve 6, the sleeve end portion 6a is expanded as indicated by the chain dotted outline in Figure 7.

As a consequence, the cross sectional profile of the roll is varied so that the cross section of the strip being rolled may be more accurately controlled. In the construction shown, the axially inward movement of the tapered rings 9 and 10 causes the sleeve end portion 6a to expand and become larger in diameter that the other portions of the sleeve. Alternatively, the arrangement may be such that axially inward movement of the tapered rings 9 and 10 causes the sleeve end portion 6a to expand and become equal in diameter to the other portions of the sleeve. In such a case, when the rings 9 and 10 are moved axially outwardly, i.e. towards the associated bearing box 2, the sleeve end portion 6a is contracted to become smaller in diameter than the other portions of the sleeve, with the rings 9 and 10 just contacting or slightly spaced from the tapered surface 8.Needless to say, the choice of which arrangement to adopt is dependent on the use to which the roll is to be put.

Referring next to Figure 8, when the oil passages 29 and 30 are closed so that the oil under pressure is forced inly into the oil passage 28, the centre portion 6b of the sleeve, i.e. the surface profile of the sleeve or roll, is expanded as indicated by the chain dotted line. Thus the roll is formed with a crown. Under these conditions, rolling can be accomplished with a light rolling force as in the case of conventional rolls.

When oil under pressure is forced through the oil passages 29 and 30, the tapered rings 31 and 32 are moved towards each other. As a result, the tapered surfaces of the tapered rings 31 and 32 engage with the tapered surfaces 33 of the sleeve centre portion 6b, i.e. the tapered rings 31 and 32 become wedged between the roll core 1 and the sleeve 6. As a consequence, the surface profile of the roll is expanded to form a crown as indicated by the chain dotted line. The roll crown thus formed is substantially similar to that formed when oil under pressure is forced into the oil chamber 27 through the oil passage 28, but it should be noted that since the tapered rings 31 and 32 are wedged between the roll core 1 and the sleeve centre portion 6b the roll behaves in a manner substantially similar to that of a solid roll.As a consequence, the roll can be used for high pressure rolling which has not been possible with conventional rolls.

When used as a solid roll, the expansion of the sleeve centre portion 6b can be suitably controlled by adjusting the positions of the rings 31 and 32.

Another method of expanding the sleeve centre portion 6b is to supply oil under pressure through the centre oil passage 28 into the chamber 27 and then to cause the tapered rings 31 and 32 to move towards each other. Alternatively, first the tapered rings 31 and 32 are caused to move toward each other and then oil under pressure is forced through the oil passages 28, 29 and 30.

When rolling, the positions of the tapered rings 9, 10, 31 and 32 are suitably adjusted depending upon the width and shape of a strip to be rolled, and the rolling precision is thereby improved. It is possible to use the roll of the present invention with the work roll bending method referred to above so that the cross section of the strip being rolled can be controlled with a very high degree of accuracy.

In the embodiment shown in Figure 9, the taper angle of the tapered surfaces 33 on the sleeve centre portion 6b is slightly greater than that of the tapered rings 31 and 32. In this case, the surface of the sleeve centre portion 6b can be gradually expanded, i.e. the roll surface profile can be gradually increased, as shown in Figures 10A and 10D.

In the further embodiment of the present invention shown in Figure 11, only a single tapered ring is used to change the profile of the sleeve centre portion 6b. In this embodiment, the central oil passage 28 is not needed. In a similar manner, at the end portions of the sleeve only a single tapered ring 9 and 10 may be used.

In the above embodiments, the oil-tight spaces which are defined between the roll core end portions and the sleeve end portions and in which the tapered rings are received are defined with the aid of spacer rings 7. Alternatively, the function of the spacer rings may be fulfilled by stepped portions of the roll core andlor the sleeve and the latter may be directly fitted over the roll core.

In the above embodiments the tapered surfaces of the movable rings are flat, but it is to be understood that the tapered surfaces of the movable rings may be slightly convex and the inner surface of the sleeve may be complementarily tapered. It will also be understood that rings with no taper may be used.

The inner surfaces of the sleeve end portions and the sleeve centre portion have been described as being tapered but it will be understood that these surfaces may be flat while the outer surface of the roll core may be tapered. Alternatively, both the inner surfaces of the sleeve and the outer surface of the roll core may be tapered.

Figure 12 shows a rolling mill incorporating work rolls 34 which are rolls in accordance with the present invention and backup rolls 35.

When a strip 36 with a relatively small width is rolled, both the rings 9 and 10 are positioned so that they are a loose fit, that is to say, they are not wedged between the roll core and the sleeve. As a result, the rolling force is not transmitted at the end portions of the roll. Under these conditions, the effective length of the work rolls 34 is 0.

When a strip of medium width is to be rolled, only the tapered rings 9 are wedged between the roll core and the sleeve 6. In this case, the effective length of the work rolls 34 is t,. When a strip with a greater width is to be rolled, both the tapered rings 9 and 10 are wedged between the roll core 1 and the sleeve 6. In this case the effective length of the work rolls 34 is t2.

Thus, depending upon the width of the strip to be rolled, the tapered rings 9 and 10 are loosened or wedged in the manner described above. But even when a strip with a relatively small width is to be rolled, the work rolls may have thermal crowns under some rolling conditions so that sometimes it is preferable that the work rolls are bent under the rolling force. In this case, the tapered rings 9 and 10 are wedged between the roll core 1 and the sleeve 6 so that the curved profile of the work rolls 34 is transferred to the strip 36 being rolled. Depending upon the rolling conditions, the tapered rings 9 and 10 are loosened or wedged so that the effective length of the work rolls is varied and the crown of the strip being rolled is controlled.

Depending upon whether or note the tapered rings 9 and 10 are wedged between the roll core 1 and the sleeve 6, the bending conditions of the work rolls may be varied over a wide range. Therefore in order to make a fine adjustment of the bending of the work rolls, the work roll bending procedure may be employed.

Sometime it is required to reduce the crown of a strip being rolled. In this case, the tapered rings 9 and 10 are loosened. As a result, the work rolls 34 are bent in the opposite direction so that the crown of the strip being rolled may be reduced too much, i.e. a negative crown is developed. In this case, the work roll bending force is decreased so as to provide an optimum crown.

Whilst a four-high rolling mill with work rolls according to the present invention has been described, it will be understood that the rolls of the present invention can be used as backup rolls as shown in Figure 13. In the latter case, the effective roll length may be t2, t3 or t'4.

Needless to say, various strips with different widths can be rolled by varying the width of the tapered rings of the upper and lower work rolls and backup rolls and by varying the combinations of the loosened and wedged tapered rings. The number of the tapered rings may be one or more than three.

Furthermore, rolls in accordance with the present invention may be incorporated, as intermediate rolls, in a six high rolling mill.

The effects, features and advantages of the present invention can be summarized as follows: the effective lengths of the work and/or backup andlor intermediate rolls of a rolling mill can be varied (the rolling force can be varied) so that the bending of the work rolls can be controlled. The crown of a strip being rolled can be optimally controlled so that the yield can be improved, the cross sectional accuracy can be improved and an energy saving can be attained. Strips with different widths can be rolled without having to exchange the work rolls so the output of the rolling mill can be substantially improved. The rolling forces are symmetrical about the centre of the rolling mill so that zig-zag movement of the strip being rolled can be prevented. The rolls of the present invention can be used as solid crown rolls so that rolling can be performed with various rolling forces regardless of the width of the strip being rolled, the cross sectional control can be optimally effected by the work roll bending method.

Claims (9)

1. A roll for use in a rolling mill comprising a roll core and sleeve fitted over the roll core, one or more annular spaces being defined between the roll core and the sleeve, the or each annular space accommodating one or more axially movable annular members, at least one of the opposed surfaces of each annular member and the roll core and the sleeve being axially tapered, whereby each annular member is movable between a position in which it does not firmly engage the opposed surfaces of the roll core and the sleeve and a position in which it does firmly engage the said opposed surfaces and expands the sleeve outwardly.

2. A roll as claimed in Claim 1 in which the or each annular space constitutes a substantially fluid-tight chamber and the roll core is provided with passageways through which a pressurised fluid may be introduced to cause the or each annular member to move between the two said positions.

3. A roll as claimed in Claim 1 or Claim 2 including an annular space accommodating one or more movable annular members adjacent one or both ends of the roll core and the sleeve.

4. A roll as claimed in any of Claims 1 to 3 including an annular space accommodating one or more movable annular members situated substantially at the longitudinal centre of the roll core and the sleeve.

5. A roll as claimed in any one of the preceding claims in which the or each annular space contains two independently movable annular members.

6. A roll as claimed in any of the preceding claims in which the opposed surfaces of the or each annular member and the roll core extend substantially parallel to the axis of the roll and the opposed surfaces of the or each annular member and the sleeve are both tapered in the same sense.

7. A roll as claimed in any one of the preceding claims in the opposed surfaces of the or each annular member and the sleeve and/or the roll core are provided with means for supplying lubricant between the said surfaces.

8. A roll for a rolling mill substantially as specifically herein described with reference to Figures 6, 7 and 8 of the accompanying drawings, optionally modified as described herein with reference to Figure 9 or Figure 11.

9. A rolling mill in which at least one of work, backup and intermediate rolls comprises a roll as claimed in any one of the preceding claims.