US1664580A - Rolling metal strips - Google Patents

Description

A ril 3, 1928.

'- J. B. TYTUS ROLLING METAL STRIP Filed June 11 1926 06 k ix IN VEN TOR.

,1 TTORNEYS Patiented Apr. 3, 1928.

UNITED STATES PATENT OFFICE.

JOHN B. TYTUS, OF MIDDLETOWN, OHIO, ASSIGNOR TO THE AMERICAN ROLLIYG m1. COMPANY, OF MIDDLE-TOWN, OHIO, A CORPORATION OF OHIO.

ROLLING METAL STRIPS.

Application filed June ll,

, my process it is readily possible to do so.

The strip mill is formed of a series of stands of rolls, into which a relatively short thick piece is fed and without cutting into short lengths, during the passing of the piece through the several stands is re.- duced in thickness and consequently elongated into a very long strip. In many strip mills the strip as it becomes longer is looped through guides before passing from one stand of rolls to another, so as to take up the excessive length and compensate between diflerent speeds required to clear the piece from the several stands due to its increase in length In other mills the piece is engaged by a series of stands of only, two high rolls arranged in a row, with the piece passing from one stand to the next, and each stand running enough faster than the previous one to prevent undue accumulation of the piece.

Since a single thickness of material is passed through the rolls in strip rolling, the

rolls must be held quite closely together in the finishing stands and furthermore a thin piece of metal will not flow sufficiently to take form in the pass of a stand-of rolls. Instead of taking form, the result of gripping the thin piece more at one point than another is to reduce the thickness of the more tightly gripped portion more than that of the less tightly gripped. Since the piece is quite thin, a very slight increase in amount of reduction will result in a quite 1926. Serial no. 115,885. i

portions will, buckle up. Sometimes the piece will be pushed into the necks of the rolls, and it is impossible to operate a. mill on strips where such conditions are present,

So long as the piece of metal being reduced is quite narrow, the rolls do not tend to grip the piece sounevenly, for the reason that the mass of the rolls, and the point of application of strain thereon, does not result in deforming the pass between the rolls of a stand.

When the piece has its width very greatl in excess of. the thickness, however, the e feet of attempts to roll it, is to spring the rolls of the mill, and thus to roll the piece more atsome points than others, resu ting in the accumulation of error heretofore referred to, which takes place as a result of uneven gripping.

Thus, in no strip mill of the past of which I have any knowledge, has it been possible to reduce pieces of any substantial width, and the production of strips over 20 inches in width is a rarity, whereas by my process there is but little more limitation in width,

than there is in the sheet rolling process.

The problem is to produce a strip by ma.-

nipulation in a continuous process in such a way as to avoid the accumulation of error in the reduction of the metal and allow for words, those factors which control the shape 5 between the rolls, when the piece is between them, are as follows 1. The composition and shape of the piece.

52. The temperature of the piece.

3. The composition and shape of the rolls.

4. The amount of pressure applied to the journals ornecks of the rolls.

5. The temperature ofthe rolls. By the term active pass I mean the pass in the condition it is in during actual operation.

It requires a control of all of the above factors, in order to accomplish my invention, which essentially speaking is as follows:- The various stands of rolls should be designed to form an active pass in each stand as applied successively to the piece or strip, such that in each stand the active pass is less convex than in the preceding stands. In other words, the active pass in each stand must be one that reduces the central portions of the piece more than it does the edge portions.

When the piece is .thin, it should be quite hot in order to provide for some slight flow of metal transversely of the piece, thus avoiding small inaccuracies following from the roll grinding operation, and from. the use of the rolls. Naturally the degree of thickness of the piece, and the nature of the material composing it will efiect the amount that it forces the rolls apart in the active pass.

-Also naturally the original shape of the rolls when cold, and the nature of the metal of which they are formed is one of the controlling factors in the way the rolls will react to the passage of a piece therethrough, and obviously, also the amount of screw applied to the journals or necks of the rolls, and tending to force them together, will be a controlling factor. The rolls should be ground with a convexity which the roll grinder can readily arrange, knowing the requirements.

The temperature of the rolls has a decided efiect upon their shape, and the hottest portions of the rolls will increase in dimension more than the cooler parts. Given a normalcondition of sufficient lubrication at the necks, and a hot piece passing through the rolls, the center will become the hottest as it is here that the rcatest heat is applied and here that the ra iation is less than the absorption.

A mill for the purpose of accomplishing the invention must be equipped with means for control of the factors noted.

Thus it should be'equipped with means for temperature control on the piece, and on the rolls. Furnaces for the piece to pass through, and means for applying. gas and cooling medium to the rolls are used for this purpose.

Naturally the control is one involving the entire mechanism, since a progressive nature of active pass is called for. In the very thick sections of piece this is not so important, since such a piece more readily conforms to the shape of the rolls themselves.

But the development of an error in application of the progressive convexity rule will normally require the re-adjustment of more than one stand, and a shifting of the mill from rolling one: gauge to rolling another will require a general resetting of all .rolls, and /a test piece or so to be run.

My process involves the deliberate deformation of the piece from a true rectangular cross section, and'a gradual bringing own of the difference from pass to pass until in the last pass the difference is not great rolling sheet metal in single thicknesses and great'length of using of the progressive convexity reduction, roll control of my patent together with the use of the small diameter roll to give radical drafts particularly as the piece becomes thinner. The advantageous action of the rolling mill having the small diameter rolls, backed up by rolls of greater diameter is well known, but the necessity of the use of progressive convexity reduction plus the radical draft, as a sine qua non .of making long single thickness sheets, (after the fashion of strips) is a very valuable contribution to the art and is What I wish to cover herein.

In order to describe a specific mechanism I submit in the drawings several diagrammatic views showing a mill suitable for use with my process.

In the drawing:-

' Figure 1 is a plan view of a suitable strip 7 mill, operating as a continuous mill.

' Figures 2, 3 and 4 are diagrams illustrating a progressive smaller active pass, in which the convexities have been greatly exaggerated.

Figures 5, 6 and? are diagrams showing three high, four high and two high rolls, all designed for giving but a single pass to a piece.

Referring to Figure 1, I shown nine stands of rolls as 1, 2, 3, 4, 5, 6. 7,8 and 9. I show direct current motors 10 for driving each stand, and gear reductionboxes 11, in which the gears on the roll shafts are arranged to be larger than in present strip mills, and will preferably be smaller at the finishing end,

than at the starting end of the series ofstands.

The mill shown is a continuous mill, and I have indicated a plant for providing direct current to the several motors. This enables me to adjust the motor for each stand as to speed, and then to control the Whole'series of motors by a single element to adjust the speeds of all motors at once- Each stand must carry the piece through it faster than the previous one, the speed difference bein greater between stands at the starting en in normal practice.

In order to start the rolling operation with a thick piece having a uniform temperature throughout, I provide afurnace 12, with a shears 13, at the delivery end thereof, so that the piece will lie within the furnace .vvhile rolls.

the sections are being-cut therefrom, or a. hot, sheared piece'at a standard temperature may be provided otherwise.

- I have shown chutes 13 between the several stands of rolls, through which the piece is v to be passed. These chutes may be furnaces, and I will provide for heating the chutes at a number of points, or replace them with roller bed furnaces, in order to keep up the heat in the piece in the finishing stands of I have indicated but one such furnace at 14, and have indicated a flying shears at 15, to sever a piece it a defect should be found to be building up therein.

In the finishing stands I will preferably employ a small middle roll and two large rolls, as indicated at 16, 16 and 17 in Figure 5. Alternatively I may employ four high stands, with two small middle rolls 18, and two outside larger rolls 19. The purpose of these is to give a greater amount of reduction in a single pass, in'proportion to the spring of the rolls therein.

I have not indicated water and gas pipes to the several stands, but will provide them, and will normally apply water to the stands, and make the housings very rigid to avoid springing thereof in the finishing stands at least, and preferably in all of the stands.

In Figures 2, 3 and 4. I have shown typical rolls A and B with a piece of metal 0 between them. The space between the rolls, which is the same as that of the piece, is the active pass. Thus the piece C illustrates the active pass in three successive stands, in which the convexity is reduced in each stand.

By reduction of convexity I mean that the amount of reduction of the central crown of the piece shall be more in each stand than the reduction of the edges thereof. The

proportionate convexity between the edges and the middle of the piece will remain sub stantially the same in all active passes. The amount of convexity is, of course very small, and observable only with a micrometer gauge, except at the very start of the continuous reduction process.

The finishing stands in which it is o greatest importance that my process be followed, are the last four 01' five stands of rolls.

It will be understood that my invention. is not limited to type of mill, but merely to the strip rolling process which is well known, and the nature of work done on the piece in the several successive passes given thereto in successive stands of rolls. Furthermore it is not limited to the useof hot metal in the process may not be employed.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, 1s:

A strip rolling process which consists in passing a piece of metal through a series of stands of rolls arranged as a continuous mill so as to produce long, single thickness strips of great width, which consists in forming a piece of convex "cross section, and in giving an active pass to the strip, in the finishing stands at least, which reduces the center of the piece in each stand more than the edges, said active pass in said finishing. stands at least applied so as to engage a restricted portion of the metal with a minimum of flexibility, such as is applied when small diameter rolls engage the piece, and the small diameter rolls are backed up by large diameter JOHN B. TYTUS.

' rolls.

and the attendant furnaces andshears of the illustrative diagram may or

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