US3789646A

US3789646A - Planetary mill for producing scallop-free strip

Info

Publication number: US3789646A
Application number: US00295345A
Authority: US
Inventors: T Sendzimir
Original assignee: T Sendzimir Inc
Current assignee: T Sendzimir Inc
Priority date: 1972-10-05
Filing date: 1972-10-05
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05
Also published as: GB1406003A; JPS4991941A; JPS5234265B2

Abstract

This application discloses an improvement in planetary rolling mills, making possible a rolling of flat strip, free from scallop, without the need for a planishing mill to smooth out the scallops which are normally produced by a planetary mill. There is also disclosed how the angle of entry of the work rolls into the slab may be reduced, thus reducing the likelihood of surface defects, or alternatively, making it possible to roll thicker slabs than was possible heretofore on a given size planetary mill. The disclosure teaches that as a particular work roll enters the roll bite, its diametrically opposite work roll engages a cam. The cam has a surface corresponding generally to the circular orbit of the work roll, but is modified so as to deviate from such orbit by a very small amount. An initial deviation may cause the work roll diametrically opposite the rolls which are in engagement with the cam to engage the slab at a more acute angle to the passline, and a final deviation may cause the work rolls which are diametrically opposite rolls in contact with the cam, to follow a path parallel to the passline as they leave the roll bite.

Description

United States Patent- "91 Sendzirnir 1 Feb. 5, 1974 PLANETARY MILL FOR PRODUCING SCALLOP-FREE STRIP [76] Inventor: Tadeusz Sendzimir, PO. Box 1350,

Waterbury, Conn. 06720 22 Filed: Oct. 5, 1972 21 Appl.No.:295,345

[52] US. Cl 72/190, 72/240, 72/241 Primary Examiner-Lowell A. Larson- Attorney, Agent, or Firm-Melville, Strasser, Foster & Hoffman 5 7 ABSTRACT This application discloses an improvement in planetary rolling mills, making possible'a rolling of flat strip, free from scallop, without the need for a planishing mill to smooth out the scallops which are normally produced by a planetary mill. There is also disclosed how the angle of entry of the work rolls into the slab may be reduced, thus reducing the likelihood of surface defects, or alternatively, making it possible to roll thicker slabs than was possible heretofore on a given size planetary mill. The disclosure teaches that as a particular work roll enters the roll bite, its diametrically opposite work roll engages a cam. The cam has a surface corresponding generally to the circular orbit of the work roll, but is modified so as to deviate from such orbit by a very small amount. An initial deviation may cause the work roll diametrically opposite the rolls which are in engagement with the cam to engage the slab at a more acute angle to the passline, and a final deviation may cause the work rolls which are diametrically opposite rolls in contact with the cam, to follow a path parallel to the passline as they leave the roll bite.

8 Claims, 4 Drawing Figures PATENTED FEB 51974 SHEEI 1 or 3 (PR/0k ART) FIG.

PATENTED EB 51974 SHEET 2 OF 3 PATENTEUFEB 519M 3.79.66

SHEEI 3 0F 3 f/G. Z

PLANETARY MILL FOR PRODUCING SCALLOP-FREE STRIP BRIEF SUMMARY OF THE INVENTION FIG. 1 is a longitudinal cross sectional view through The present invention relates to an improvement in 5 a mill according to the present invention.

planetary mills such as are described in U. S. Pat. No. 2,710,550 which makes it possible to produce a scallop-free strip.

In a planetary mill, a heavy backing roll is surrounded by a plurality of work rolls which orbit around the backing roll. The orbit of the work rolls is of course circular. The result of this situation is that the strip produced is made up of short sections, each of which has been rolled by one pair of the procession of work rolls. These short sections, because of the circular orbit of the work rolls, show up noticeably as small corrugations or scallops. In order to produce a saleable strip, it has been necessary to follow the conventional planetary mill with a so-called planishing mill. While the planishing mill has been successful in smoothing out the scallops produced by the planetary mill, there are nevertheless drawbacks to such an arrangement. The stripin passing from the planetary mill to the planishing mill cools at such a rate that it has to be substantially overheated in the furnace, which results in increased scale losses and degradation of the surface. It should be remembered that hot rolling must be completed on such materials as low carbon sheets for deep drawing, at temperatures above the AC3 recrystallization point (about 830 0.

I According to the present invention, the above mentioned difficulties are overcome by causing the work rolls of the planetary mill to deviate very slightly from their circular orbit during the last portion of their contact with the workpiece, so that during this last portion of their contact with the workpiece their path is parallel to the passline. In this way, the planetary mill will produce a finished strip and it is possible to eliminate the conventional planishing mill. Furthermore, since the temperature of the workpiece increases by as much as 50 to 100 C. in the roll bite,.the initial overheating of the slab can be eliminated with the consequent reduction in scale losses and improvement of the surface.

The present invention also contemplates a modification in the path of the workroll at its entry into the roll bite whereby the angle of entry is reduced or made more acute with respect to the pass line. If there are slivers present in the slab, such defects tend to open up during rolling on ordinary planetary mills and produce surface defects and rupture. However, with a more gradual entry into the roll bite, these dangers are greatly reduced and slivers, if they are present, are more likely to pass through the roll bite without defects opening up. Alternatively, it makes it possible for a given mill to roll a thicker slab than would otherwise be possible without exceeding the permissible angle of entry of the rolls into the roll bite. It should be carefully noted that these modifications of the roll path at the entry into, and exit from the roll bite, are in fact, and need be, very small. In no case are they bigger than the natural elastic deflection of the backing roll of the planetary assembly rotating in its two chocks ahd having no supplementary backing means as hereinafter described.

FIG. 2 is an elevational view with parts in section looking along the passline of the structure shown in FIG. 1.

FIG. 3 is a cross sectional view on a greatly enlarged scale and broken through the middle to conserve space showing at the bottom the path of a work roll and show-- ing at the top the path of a roll diametrically opposite the particular work roll and in engagement with a cam.

FIG. 4 shows guide means according to the prior art, in a somewhat diagrammatic manner.

DETAILED DESCRIPTION By referring to FIGS. 1 and 2 it will be observed that the backing rolls 5 and 5 would be subject to deflection by the roll separating forces and would thus produce a strip which was thicker than the roll gap had been set for, had they not been, in turn, bodied by rigid beams. According to the invention, instead of backing beams there are provided the beam backed

cams

8 and 8. From their locations, it will be observed that the

cams

8 and 8 respectively are diametrically opposite the roll bite of the mill so that pairs of diametrically opposed work rolls are disposed with one in the roll bite and the other bearing against the cam. The extent of the cams 8 and 8' around the work rolls is generally equivalent to the distance from when a work roll enters the roll bite to the point where it leaves the finished strip.

If the profile of the cams 8 and 8' are exactly circular so as to be in the orbit of the work rolls when the mill is not loaded, i.e., when there is no roll separating force, roll deflection may be virtually eliminated be cause the beam and housing structure disclosed herein is many times more rigid than the backing and work rolls.

However, applicant utilizes the above noted arrangement for controlling backing roll deflection by means of the

cams

8 and 8 to achieve major improvements in the design and operation of a planetary mill and in the quality of the finished product. Referring to FIG. 3,

' a work roll is shown at 6a as it first engages the slab at the beginning of the roll bite. Its diametrically opposite work roll 6a is at the same time in contact with the cam 8. At 6b the work roll is shown as it leaves contact with the finished strip 1' while its diametrically opposite work roll 6b is also in contact with the cam 8. It is these two positions at the entrance into and at the exit from the roll bite where useful and important corrections are made by the means provided by the present invention. 'These improvements are distinct and apart from each other. At the entrance of the work roll 6a into the roll bite, the objective is to reduce the angle at which the orbit of the work roll 6a intersects the surface of the workpiece 1. For hot steel, an entrance angle of 16 is approximately the maximum which is permissible. Various defects result from too large an entrance angle and there-is a tendency of slivers forming on the surface of the-workpiece if the angle of incidence is greater than 169.

On the other hand, the part of the path of the work roll 6b where it makes its last contact with the strip 1' should be flat, i.e., parallel to the passline in order to produce flat strip, so that the circular orbit of the work roll at 6b should be straightened out.

Both the above noted objectives are accomplished by the same means. Suitably shaped inflexible supports are provided for the work rolls which are diametrically opposed to the work rolls which are in the roll bite and according to the present invention these inflexible supports are in the form of beam-backed cams.

It must be observed that while the cam 8 will reduce or prevent deflection of the backing roll 5 under the influence of roll separating forces, the cam can also be utilized to force the work roll 6 which is diametrically opposite the work roll in contact with the cam, and the backing roll 5 out of its non-loaded state in a direction to oppose the roll separating force and thereby roughly double the effect of the correction. It should be noted that deflection of the backing roll 5 either by roll separating forces or by the effects of the cam causes stresses in the backing roll and excessive stresses will cause fatigue in the backing roll. Therefore the deviation produced by the cam must be less than an amount which would cause a deflection sufficient to produce fatigue in the backing roll.

The entrance correction, i.e., the correction which causes the work roll entering the roll bite at 6a in FIG. 3 to enter at a more acute angle to the passline, is produced by providing a projection 80 in the cam 8. It will be clear that as the work roll 6a moving clockwise in FIG.3 engages the projection 80, it will produce a downward deflection of the backing roll 5 which in turn will cause the work roll 6a entering the roll bite down so that it enters the roll bite at a more acute angle x rather than the angle at which it would enter without such correction which is indicated at y. By the time the work roll 60 has reached a position where the surface of the slab l is intersected by the unloaded orbit c of the work rolls and where therefore the roll separating force has attained its full value, the profile of the cam 8 is hollowed out slightly in the opposite direction as indicated at 811. The result of this sequence of corrections at 8c and 8d as can be seen clearly from FIG. 3, is that the angle of incidence is lowered from y to .r.

Since an entry angle of about 16 is permissible, it is obvious that another way of benefiting by applicants improvement is to increase the thickness of the slab 1 with the same mill and still maintain the entrance angle of 16. In this way a smaller planetary mill can take the same slab which would normally require a much larger mill and of course this results in a great reduction in capital investment.

FIG. 3 also shows the configuration of the cam 8 which converts the paths of the work rolls from circular to straight during the final portion of the roll bite whereby to obtain a scallop-free strip. Thus, the portion of the cam 8 which is opposite the final portion of the roll bite is profiled to provide a protrustion 6e followed by a depression 6f and followed by a furtherprotrusion 6g approximately symmetrical to the protrusion 6e. The total effect of these profile changes 6e, 6f, and 6g is to produce deflections of the backing roll 5 through the roll 6b and thereby to alter the path of the roll 6b as it is leaving the finished strip. The roll 6b is caused to follow a straight path from the point R (where it has been deflected by the protrusion 62) to the point Q (where it is deflected by the protrusion6d).

It will be understood that the specific profiles described above are in the nature of general rules and that the final shaping of the cam profile for a particular mill and for particular steels will take some experimentation since each mill may behave slightly differently from another mill. Furthermore, roll flattening, unavoidable play in bearings, housing and beam deflections, small as they may be, strip thickness, and the like, have to be taken into consideration in order to produce a truly smooth and even-gauged strip.

It is possible in some mills where the work rolls 6 are very small that two rolls may be in the roll bite simultaneously. In such a case their diameters must be such that the distance between them is considerably shorter than the length of the roll bite, so that opposite rolls will not enter the corrected profile sections of the cam 8 simultaneously thereby interfering with one another.

Referring now back to FIGS. 1 and 2, the slab l is first reduced and fed forward by a pair of feed rolls 2 and 2 and thence through a pair of guide rolls 3 and 3' and a further set of guide rolls 4 and 4 and finally through the roll bite of the planetary assemblies 5 and 5' so as to emerge in the form of the strip 1,

The planetary assemblies 5 and 5' consist of backing rolls surrounded by work rolls 6 and 6. The backing rolls run in bearings which are located in

chocks

25 and 25 which chocks are slidably mounted against the wall of the housing 10 and adjustable by screwdown means such as the pressure means 27 (FIG. 1). The work rolls 6 and 6 are rotatably mounted in bearings located in cages 26 and 26' which are coaxial with the backing rolls and they are synchronized by means which are not shown. The rigid beams 9 and 9' are connected to or preferably made integral with the

housing columns

10 and 10 to further reduce elastic deflection of the

beams

9 and 9. The

cams

8 and 8 are installed in the

beams

9 and 9 with

wedges

11 and 11 interposed between the respective beams and cams. By means of these wedges, the position of the cams in relation to the passline may be adjusted by means such as the screws 28 and 28'.

It must be borne in mind that the portion of the slab 1 which is between the bite of the rolls 2 and 2' and the planetary assemblies 5 and 5 is subject to strong and fluctuating upsetting forces produced by horizontal components of roll pressure by the planetary rolls and opposed by the feed rolls through frictional contact with the slab 1 in their roll bite. Since slabs are never perfectly straight or correct in dimensions, guides have heretofore been provided which were parallel to but clear of the top and bottom faces of the slab. In FIG. 4

such guides

23 and 23 are shown diagrammatically to guide the end of the slab l and the butting leading end of the next slab. Sheared ends of slabs are never square and tend to slide off each other under the butting pressure if there were no guide to prevent it. However sliding contact with the slab produces scratches which are not removed by subsequent rolling. Consequently, the gap between the stationary guides on existing mills must be wide enough to permit small deviations of the slab at the entry into the planetary roll bite to avoid scratching. Such deviations cannot be tolerated on mills, according to the present invention because the benefits of the corrections of the roll paths would be substantially diminished.

Applicant obtains the necessary accuracy of slab position with respect to the passline and particularly at the entry into the planetary roll bite by providing contacting but non-sliding guides. In FIG. 1 there are shown guide rolls 4 and 4 which are fulcrumed on a common pin 14 which is mounted in the column 10. The position of the rolls 4 and 4' is controlled by means of

rods

15 and 15 which are positioned by worm driven nuts 16 and 16' at their far end and engaging levers l7 and 17 which carry the chocks for the rolls 4 and 4. In this way, the adjustment path of the rolls 4 and 4 is nearly parallel with the path of the planetary rolls so that the rolls 4 and 4' can be placed very close to the roll bite entry. FIG. 1 also shows a pair of guide rolls 3 and 3' contacting the slab l ahead of the rolls 4 and 4'. While these rolls could be used to stabilize the slab jointly in the same way as the roll 4 and 4, it is preferable to cause them to deflect the slab l slightly so that the thrust to which the slab is subjected will press it against one of the rolls 3 as shown. Once the slab is so deflected, it will continue to press against the roll 3' and the roll 3 may then be withdrawn to the position indicated at 3 and shown in broken lines. This makes it possible to reduce the heat loss by the slab. The light flexing of the slab also insures a better correction of slab that may not have been straight originally.

With accurate guiding thus assured, and buckling prevented, the distance between the two roll bites is no longer critical. In other words, the feed rolls do not have to be situated as close as possible to the planetary rolls. FIG. 1 shows such a mill with the width of the column 10 added to the minimum distance obtainable. This arrangement provides enough space for the installation of additional rapid heating means to restore a part of the heat loss suffered by the slab on its path from the furnace to the planetary roll bite. This is a very important advantage since the heat loss usually amounts to between 100 and 250 F. and imposes the need to overheat the slab in the furnace. This means a longer furnace together with fuel and scale losses. The rapid heating means may be any of the well known means such as induced eddy currents, direct impinging, high temperature burners and the like. The heating means shown in FIG. 1 (only between the feed rolls 2 and 2 and the guide rolls 3 and 3' so as not unnecessarily to complicate the figure) are high temperature resistors of refractory metals surrounded by quartz tubes 18 and provided with water cooled reflector shields 19 which are preferably made of a reflecting metal such as stainless steel. These protect the slab 1 against radiation losses and also protect the mill parts against heat damage. It may be also mentioned that for reasons of drawing clarity, butting guides have been omitted in FIG. 1.

It will be clearthat numerous modifications may be made without departing from the spirit of the invention. No limitations other than those specifically set forth in the claims are intended and no such limitations should be implied.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

-l. A planetary mill for rolling flat articles, comprising a mill housing, at least one backing roll mounted in said housing, and having a number of planetary work rolls orbiting around it, and a cam arranged to contact the major part of the face of the work roll which is diametrically opposite the work roll which is actually in the roll bite, said cam being mounted in a rigid beam secured to said mil] housing, said cam having a surface generally following the circular orbit of the work rolls, but modified gradually out of said orbit by a radial distance less than the deflection which would cause fatigue stresses in said backing roll.

2. A mill according to claim 1 wherein said cam is modified in its last portion, which corresponds to the last portion of the roll bite of the diametrically opposite work roll, to cause said last named work roll during said last portion of the roll bite, to follow a straight line parallel to the passline.

3. A mill according to claim I, wherein said cam is modified in its initial portion, which corresponds to the first contact of the diametrically opposite work roll with the workpiece, and up to the point where the roll separating force has reached its full value, to cause said last named work roll to follow a path at a more acute angle to the passline than it would follow without said modification. I

4. A mill according to claim 1, wherein two work rolls are in the roll bite simultaneously during at least a part of the cycle, and wherein said cam is modified for two diametrically opposite work rolls in succession, and wherein the distance between succeeding work rolls is substantially less than the length of the roll bite, to avoid interference of the two profile modifications of the cam surface.

5. A mill according to claim 1, wherein non-slidable slab guiding means are provided, said means contacting at least a part of the face of the slab, said guiding means being disposed close to the roll bite entry to insure the exact position of the slab with respect to the passline.

6. A mill according to claim 5, wherein said guiding means comprise small diameter rolls.

7. A mill according to claim 6, wherein additional opposed guide rolls are disposed ahead of said small diameter rolls, at least one of said additional guide rolls being positioned to deflect the slab slightly into a curve, whereby to produce a pressure component forcing one face of said slab against the opposite guide roll.

8. A mill according to claim 7, wherein the distance between said additional opposed guide rolls is less than the length in which the slab would buckle.

Claims

1. A planetary mill for rolling flat articles, comprising a mill housing, at least one backing roll mounted in said housing, and having a number of planetary work rolls orbiting around it, and a cam arranged to contact the major part of the face of the work roll which is diametrically opposite the work roll which is actually in the roll bite, said cam being mounted in a rigid beam secured to said mill housing, said cam having a surface generally following the circular orbit of the work rolls, but modified gradually out of said orbit by a radial distance less than the deflection which would cause fatigue stresses in said backing roll.

3. A mill according to claim 1, wherein said cam is modified in its initial portion, which corresponds to the first contact of the diaMetrically opposite work roll with the workpiece, and up to the point where the roll separating force has reached its full value, to cause said last named work roll to follow a path at a more acute angle to the passline than it would follow without said modification.