US2118284A

US2118284A - Apparatus for producing sheet material

Info

Publication number: US2118284A
Application number: US7361A
Authority: US
Inventors: Worthington Warren
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-08-07
Filing date: 1935-02-20
Publication date: 1938-05-24
Anticipated expiration: 1955-05-24
Also published as: US2139872A

Description

May 24, 1938; w. WORTHINGTON 4 2,118,284

Flled Aug.. 7, 1933 2 Sheets Sheet 1 y 8- w. WORTHINGTON 4 2,118,284

' APPARATUS FOR PR ODUCING SHEET MATERIAL Original Filed Aug. '7, 1933 2 Sheets-Sheet 2 DRIVE/V Rouf g, I I I v I I r s U mm ZZMMM Patented May 24, 1938 PATENT OFFICE 2,118,284 I APPARATUS FOR PRODUCING SHEET MATERIAL Warren. Worthington, Pittsburgh, Pa.

Original application August 7, 1933, Serial No.

684,001. Divided and this application February 20, 1935, Serial No. 7,361

/ 4 Claims.

This invention relates to apparatus for producing sheet material having new and improved physical characteristics. This is a division of my application for patent Serial No. 684,001 filed on 5 August '7, 1933.

.'By the term sheet material, I mean metal rolled to a thickness comparable to the thickness obtained in present sheet or strip rolling opera-v tions, and independent of the final length or width of the material.

An object of my invention is to produce a new and improved mill and to reduce the cost of production of sheet material.

A still further object is to decrease the cost of the rolling equipment employed in rolling sheet material.

A fundamental object of my invention is to pro- ,duce rolling apparatus wherein both the rolling pressure and the power utilized for cau'sing the material to traverse the roll pass are effectively employed.

For many years it has been generally recognized that the rolling of sheet material may be more effectively accomplishedwith small rolls and for this reason it has long been the practice to employ four-high, and similar mills, such as cluster mills, because they provide structures in v which working rolls of small diameters may be employed without excessive deflection under the 30' forces encountered. I have, however, discovered that in order to most effectively employ the necessary forces, the projected line of contact between the rolls and the material being rolled must' be reduced even further than is possible with existing apparatus. I have also discovered that the projected line of contact can be more effectively reduced by employing opposed working rolls of unequal diameter than with opposed rolls 4 of equal diameter; that is to say, I have found material traversing the pass and apply the rolling pressure to that material, should be of different diameters in order that the most effective reduction of the projected line of contact may be ob tained. In all rolling operations where small rolls are employed, the rollingtorque limits the size of the driving reducing rolls. That is to say, each such reducing roll must be of sumcient size to provide that the opposed rolls which directly contact the diameter, but by employing one driven roll and a smaller undriven roll, which contacts with the material being rolled and is in fact driven by that material. I have also discovered that there is a definite relationship between the projected line of contact and the permissible diameter of this smaller roll. This discovery has led to the furtherdiscovery that in continuous mill operations both reducing rolls and. particularly the smaller and undriven reducing rolls of the various stands may be, and preferably should be, progressively decreased in diameter toward the delivery end of the mill. This follows from the fact that although the percentage of reduction in each of the successive stands of a continuous mill may be maintained the same, the vertical displacement of the material necessarily decreases from stand to stand, and this in turn results in a progressive decrease in the projected line of contact from stand to stand.

It has been recognized that'in any rolling procedure where but one roll is driven, the resulting re-arrangement of the molecules in the material rolled differs, to some extent, from the molecular re-arrangement obtained by employing two driven 5 reducing rolls, but I have discovered that an improved molecular structure and a consequent improvement in the physical properties of sheet material can be obtained by employing an undriven reducing roll which is of materially less diameter than has heretofore been considered practical in any rolling operation.

A further object of my invention is, therefore, to provide a strip mill which is particularly a'dapted to produce stripmaterial having a molecular formation different from sheet material here'tofore produced and having physical characteristics which correspond to its molecular characteristics. These and other objects are attained by means of the apparatus herein defined and illustrated in 40 the accompanying drawings. In the drawings, Figure 1' is a more or less diagrammatic sectional M, view. of a mill or roll stand embodying my invention;

Fig. 2 is a diagram illustrating the relationship of the forces encountered and their effect on the material rolled; and

Fig. 3 is a diagrammatic view corresponding to the view of Fig. 2, except that it is predicated on forces illustrated in Fig. 2,

The mill diagrammatically disclosed in Fig. 1 employs two backing rolls it of relatively large diameter such as are usually employed in fourhigh A relatively large reducing roll ll the horizontal and vertical components of. the

adapted to be driven in the usual manner is backed by the lower backing roll IS. A relatively small undriven or idler work roll 2| having its axis laterally offset with relation to the plane defined by the axes of the two backing rolls and the driven roll IT with driven roll I? form the roll pass. With this arrangement it is possible to prevent lateral displacement 'of the small undriven work roll, but at the same time employ rolls of small diameter for accomplishing this purpose.

As shown in Fig. 1, the small undriven Work roll 2! is backed by an idler roll 220. which is in turn backed, and therefore reinforced by the upper backing roll l6. It should be noted that the axis of the roll 22a; lies within the vertical plane defined by the axes of the two rolls Hi. This arrangement transmits the major portion of the vertical force encountered by the undriven roll direct to the upper backing roll through the roll 22a. That is to say, the vertical component of the rolling forces transmitted to the undriven work roll 2| is almostwholly taken care of by the upper backing roll l6, consequently a backing roll 23a of small diameter may be employed which, like the backing rolls I6, is suitably journaled in bearings carried by the housings of the mill. A small idler roll 2% is preferably employed between the undriven work roll 2l'- and the lateral backing roll 23a, but primarily for the purpose of making it possible to employ a backing roll 23a. of adequate diameter without interfering with the delivery of material to and from the pass.

In Fig. 1 I have also diagrammatically illustrated coilers 2626' and the position of the strip or sheet material 25 with relation to these coilers and the pass. It will be understood that the mill illustrated in Fig. 1 is a reversing mill and that consequently each coiler is alternately employed as a receiving and delivering coiler. It will also be understood that independently of the direc-- tion of rolling the arrangement of the rolls is such that the lateral displacing forces imparted to the undriven work roll 28 are adequately taken care of by the rolls l6, 22a, 22b and 23a.

' Such lateral displacing forces as are transmitted to the work roll H are taken care of by the roll necks and the journals of that roll.

In the operation of a stand such as illustrated in Fig. 1, the vertical deforming force is applied to the material by adjusting the screw-downs so.

and I have also illustrated by force diagrams the forces encountered. In Fig. 2, R is any radius of the driven roll II; R is a radius extending to the so-called neutral point within the pass; L represents the magnitude and direction of the distorting force applied through the roll H; M represents the magnitude and the direction of the tangential force acting at the periphery of the roll on the material 25 as it passes the neutral point; and P represents the magnitude and the 7 direction of the resultant of these two forces. The force diagram associated with the roll 21' in Figure 2 may be termed a diagram of the reactive force 1. ifistructure of the material.

closes the forces which are in effect transmitted to the roll 2| through the material acted upon. As there illustrated, r is any radius of the undriven roll and r a radius extending to the socalled neutral point; L' represents the magnitude and the direction of the vertical distorting force occasioned by roll 2| and it isapparent that this force is equal and opposite to the force represented by L. T represents the direction and magnitude of the tangential force transmitted by the periphery of the roll 2 I to the material 25 at the neutral point within the pass, and S represents the direction and magnitude of the resultant of the two forces T and L.

In the drawings, I have so considered the forces acting on the material 25 that. the neutral points on the upper and lower surfaces of the material are opposite each other. This, however, may or may not be an absolutely accurate representation of the conditions, but it gives a fair approximation of the action of the opposed forces on the material rolled and the force diagrams substantially disclose the relative directions and magnitude of the forces acting on both the material being rolled and on the undriven working roll. I

Figure 3 shows the magnitude and direction of the vertical and horizontal components of the resultants P and Sof Figure 2'. In both Figures 2 and 3, the resultant force P is equal in magnitude and acts in the same direction. This is also true of the resultant S. The vertical and horizontal components N and Q of the resultant P, necessarily differ in magnitude from the forces L and M, but they disclose both the direction and magnitude of the deforming and the propelling forces transmitted to the material 25 by the roll II. The components 0. and :c of the resultant S necessarily differ in magnitude from the forces L and T as illustrated in Fig. 2, but they represent the direction and magnitude of the vertical force and the retarding force transmitted to the material rolled by the roll 2 i From the foregoing it is apparent that the" these forces, acting as a couple, not only have a deforming effect on the material itself, but they also have a very particular effect on the molecular The components Q and x, operating in opposed and offset relation, not only tend to advance the molecules or crystals on the driven roll side of the material 25 ahead of the molecules or crystals on the undriven roll side, but the relationship of these two forces is such that 'they also tend to impart a rotative movement to each of the various crystals, with the result that the crystals are not only displaced longitudinally of the piece and with reference to each other, but each crystal is turned about a point within itself during the deforming operation.

-I have discovered that this longitudinal translation' of the molecules with relation to each other should bear some relation to the percentage of reduction, or better, to the amount of vertical distortion to which the piece is subjected and that the relationship of the opposed forces acting on the material should be such that the longitudinal displacement of the molecules on the driven roll be so proportioned that this longitudinal translation of molecules should somewhat exceed 4% of the vertical distortion. Under such conditions, the piece 25, after having passed the desired number of passes, will not only be reduced to the is turned about an internal axis, that the characteristics of the sheet material are materially improved.

The direct eifect of this new molecular structure is that the material being rolled does not increase in hardness in proportion to the rolling strains to which it is subjected and consequently, in cold rolling operations, the material may be subjected to greater reductions per pass and a greater number of passes than is possible in ordinary rolling operations without the necessity of intermediate annealing.

These beneficial results are the direct result of employing working or reducing rolls of small diameter, one of which is an undriven roll of a diameter substantially lessthan that of the driven roll. I have discovered that there is a relationship between the diameters of. the driven and undriven working rolls and the draft of the pass which must be adhered to in order to obtain the best results. In designing the rolls, I take into consideration the percentage of reduction to be accomplished in the pass, and I necessarily consider the torsional strength of the driven working roll under the conditions of draft encountered. This fixes the minimum diameter of the driven work roll. The diameter of the undriven work roll must then be such that the projected line of contact will at least equal the draft divided by the coeflicient of friction between the material rolled and the surface of the driven roll, or in round numbers equal to about ten times the draft where cold rolling operations are contemplated, and this relationship of the two reducing rolls should be more or less closely maintained for the best results. From the foregoing it is apparent that I employ small reducing rolls of unequal diameter, and that I drive the roll of larger diameter, while maintaining the undriven roll as small as possible, and while maintaining the proper relationship between the rolls and the projected line of contact. It is also apparent that my improved sheet rolling procedure consists in subjecting the material being rolled to opposed deforming forces so applied that the forces act onthe material as a couple, and not only decrease the thickness, but produce a new molecular structure by in eifect longitudinally displacing one portion of the material with relation to another portion and to such an extent that each molecule or crystal is rotated about an axis within itself.

I not only contemplate successive applications of such forces to the material rolled in a succession of stands, such as in a continuous mill, or in a tandem arrangement of stands, but I also contemplate a modification of the procedure above outlined wherein the material after traversing one or more such passes is subjected to a cross rolling operation under conditions above defined, so that the molecular structure is further modified by longitudinally advancing the molecules or crystals on one side of the material with relation to those on the other side, and in causing each such molecule to roll or turn about an internal axis substantially at right angles to the axis of its former rotation. It will also be apparent that the direction of rolling may be varied after each pass or after any desired number of passes so that after one or more cross rolling passes the material may again be rolled in the original direction of rolling or even in a reverse direction and may then again be subjected to one or more cross rolling passes.

The apparatus diagrammatically illustrated in Fig. 1 contemplates back and forth rolling, in

which the direction of rolling is reversed after each pass. The strip material entering the mill is received from the coiler 26 and on leaving the mill is delivered to the coiler 26'. Upon thereversal of the mill, the coiler- 26' becomes the delivering coiler, whereas the coiler 26 becomes the receiving coiler. It is, of course, apparent that the usual mechanism may be employed for driving the collers and that they be operated in accordance with usual procedure and that in some cases it may be desirable to interpose a roller or similar table between each coiler and the mill.

' Sufiicient tension is preferably imposed on the material 25 by the coilers to maintain ithorizontal while entering and leaving the pass.

'Where cross rolling is resorted to, I of course, contemplate the necessary cutting of the material in order that it may be rolled in a direction at right angles to its previous direction of rollmg.

In accordance with my invention, the material rolled is not only reduced in gauge by each pass, but it is also subjected to a longitudinal deformation. This longitudinal deformation not only involves the extrusion normally resulting from subjecting metal to the action of a reducing roll pass, but also consists of a relative offsetting of the molecules or crystals under such -conditions that each crystal is rotated through an appreciable are about an internal axis. As previously pointed out, this molecular displacement and rearrangement produces a new molecular pattern.

In accomplishing this I contemplate a relation between the diameter of the driven roll and the undriven work roll on the order of more than two to one, that the diameter of the undriven work roll may be 1 or less, in the case of extremely thin material, and that the diameter of the co-operating driven rollmay be 16" or more. It will be understood that this general relationship in size of driven and undriven work rolls X is reproduced in all-' of the mill stands except,

as heretofore stated, I contemplate a successive per hearing, all of which reduces the power-re-- quired to accomplish the rolling operation and thus results in a reduction in the cost of rolling. The smaller and lighter rolls employed are not only in themselves cheaper, but the bearings, bearing housing and all parts of the stand structure are proportionately reduced in size and in this way the cost of rolling equipment is reduced.

' One important feature of my invention in connection with cost of equipment and cost of upkeep is that by employing but one driven working roll, I eliminate the necessity for employing pinions.

It will be apparent that the use of my imreduction in the diameter of the undriven work proved mill is not limited to cold rolling operations, but that it may also be employed in hot rolling operations and that various modifications of the structural details herein shown and described may be made without departing from the spirit and scope of my invention as defined by the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a mill structure for rolling sheet material, a pass forming pair of reducing rolls one of which is of relatively small diameter and the other of which is of materially larger diameter, means for driving the larger of such rolls, the axis of the smaller roll being laterally displaced with relation to that of the larger and being driven solely by the material traversing the pass, and a plurality of idler rolls so arranged that the larger work roll is reinforced by at least one such idler roll and the smaller undriven work roll is reinforced by at least two such idler rolls and is located within the crotch formed thereby.

2. In a mill for rolling sheet material, a roll assembly comprising a pair of pass forming work rolls of difierent diameter with the roll of smallor diameter being driven entirely by the material traversing the roll pass and having its axis laterally displaced with relation to that of the other roll, means for driving the roll of larger diameter and a plurality of backing rolls for the roll of smaller diameter so arranged that such roll is located within a crotch formed by two adjacentbacking rolls.

3. In a mill for rolling sheet material, a roll assembly including two work rolls located in pass forming relationship and of unequal diameter, the smaller of said rolls being driven solely by the material traversing the pass and having its axis offset laterally with relation to that of the larger roll, means for drivingthe larger roll and a plurality of idler rolls so located that the driven work roll is reinforced by at least one such roll and the undriven work roll is reinforced by at least three such idler rolls and is located within the crotch formed by adjacent idler rolls.

4. In a mill for rolling sheet material, a roll assembly including two work rolls of unequal diameter located in pass forming relationship, the smaller of said rolls being driven solely by the materialtraversing the pass and having its y axis offset laterally with relation to that of the larger roll, means for driving the larger roll, at least one idler roll for reinforcing the larger work roll and idler rolls of difierent diameters for reinforcing the smaller work roll. I

' WARREN WOR'I'HING'IONQ