US2025002A - Method of rolling sheet metals - Google Patents

Description

Dec. 17, 1935. y H G, MclLVRlED 2,025,002

METHOD OF' ROLLING SHEET METALS Filed Deo. 29, 1933 5 SheetS-SheetI l I. I y

Dec. 17, 1935. G, MclLVRlED 2,025,002

METHOD OF ROLLING SHEET METALS y Filed bec. 29, 193s s sheets-sheet 2 "1/ i L y lnvno: Hon/neo M-c /L :4e/5p,

Dec. 17, 1935. v H.I G. MclLvRlED Zuozoz METHOD oF ROLLING SHEET METALS Filed Dec. 29,` 1933 3 Sheets-Sheet 3 Patented Dec. 17, 1935 METHOD F ROLLING SHEET METALS Howard G. Mcllvried, Bellevue, Pa., assigner to American Sheet and Tin Plate Company, a corporation of New Jersey Application December 29, 1933, Serial No. 704,564

' s claims. (c1. 2 9-18) This invention relates to a method of cold roll# ing thin, Wide strip metal and has for its object the provision of a novel method of vcold rolling in which the number of passes necessary to getv a desired reduction and commercially flat and uniform gage material is reduced to a minimum.

Prior practice has shown that-in the commercial cold reduction of wide, hot finished strip suchas, for example, .065 hot finished strip cold reduced to .010, it has been the ultimate aim to produce the desired gage of material by cold rolling in as short a time and with as few passes as possible. The rst denite step in this direction was to utilize the conventional two high non-reversing cold mill by reducing the diameter of the rolls as much as possible.

By reducing the size of the rolls, the area. of metal contact was decreased and more reduction per pass was accomplished without increasing the pressure on Athe roll necks and in many cases decreasing the driving load on the power unit. However, as the diameter of the rolls decreased they showed a tendency to be deflected at their centers. I Therefore, in reducing these rolls to a smaller diameter it was necessary to utilize supporting or back up rolls such as, for example, a four high mill. These back up rolls, located above and below the top and bottom work rolls, respectively, prevent the majority of the vertical deilection o1' the small work rolls but do not prevent their horizontal or lateral deflection.

Such a cold reduction mill may commercially be of several types. In the production of wide, 'thin gaged strip in relatively long lengths such a mill might utilize several stands or mills set in line or tandem. Such mills are non-reversing with the workingv rolls being driven. vShould re-rolling be desired it is necessary to convey the material 40 back to the entering side of such mills by crane or similar conveyance.

Rolling on such a tandem mill, with the material being reduced in several stands simultaneously, necessarily'involves very delicate and rapid adjustments of screw pressure, roll contour and speed of the various stands.

Any variation in' gage, physical characteristics or composition of the material being rolledor an adjustment of any one stand for any other reason usually necessitates immediate adjustments to one or more other stands in order to produce flat material of the correct -inal gage. Moreover, tension on the strip on each side of the work rolls has proven in practice to be an essential feature of all types of cold reducing mills and any appreciable adjustments on one stand necessitates corresponding adjustments on one or more other stands v of the tandem arrangement to preserve the proper tension, which adjustments under running con'- 'ditions are extremely diicult to obtain with the 5 promptness required to preserve the essential constant tensional effect on the material being reduced.

The interruption of one four high unit in such a tandem train naturally results in a shut down 10 of all other units. Furthermore, a breaking of the strip in one roll unit often causes other breaks` and surface wrinkling along the strip in other units before they stop rotating, resulting in possible damage to Work `rol1 surfaces requiring roll 1 5 changes. This results in an excessive amount of lost time and consequent loss of production.

- In all probability the major disadvantages in such a train of four high mill lies in the limited amount of product that can be produced in com- 20 parison to the initial investment cost.

This is due to the fact that only the last or finishing stand can workat its maximum desired speed. The other units in line (although of practically the same construction and cost) must be 25 operated more slowly,- their speed being inversely proportional to the gage of the material delivered from their work rolls. y

The operating diiiculties as heretofore discussed, together with the high initial investment 30 cost for a low output, naturally results .in a high cost per ton of metal so cold reduced. Therefore, the next logical and commercial step, in an endeavor to lower production costs per ton, was the four high reversing mill. reversing unit eliminated many of the operating difliculties 1nherent in the tandem train, together with the necessity of slow speeds on the initial reduction.

The strip metal to be cold reduced is fed back 40 and forth between the work rolls which, with the exception of my improved mill, are of extremely small diameter when compared with the work rolls v of the four high tandem mill just described.

Thus, for illustrative and comparative purposes only, the approximate ratio of back up and Work roll diameters of a four high non-reversing mill described above is approximately two or three to one (2 or 3 to l) respectively. contrasted with 50 this mill is the usual four high reversing type mill wherein the ratio of back up andwork'roll diam-I eters is approximately six to one (6 to 1) respectively, the. work rolls usually being under 6 diameter. Ratios for both types of fourhigh cold 55 This single four high 35 reduction lmills just described apply tothe same size of roll width or face.

This four high-reversing mill of the prior art as constructed involves working rolls of extremely small diameter in an effort to reduce the power required to make a predetermined gage reduction.

These Work rolls are of such a'small diameter that they are not mechanically capable of' being directly driven with a large power unit. This necessitated other means for conveying the strip through the work rolls` which in this case are power driven reels adjacent and on either side of this single reversing mill.

These power driven reels alternately act as tension means for pulling the strip between the work rolls. The reels reverse in such a manner as to cause one reel to be the tension or pull reel while at the same time the' other reel is the drag or unwinding reel. When the strip reaches its end on the drag reel, the direction of movement of metal is reversed with the tension reel and the drag reels interchanging in their function. This usually results in an excessive ruining or wrinlrling of the edges of the metal. These conditions def- .initely limit the amount of cold reduction for each pass between the work rolls. Such limited reductions have in practice necessitated 10 tol5 passes through such a mill while reducing relatively soft low carbon, wide hot rolled or nished heavy strip from about 16'USS gage (.065") to about 31 USS gage (.0107"') The above mentioned dime'ulties in cold rediiction of metals are overcome in my method of rolling the' samerelatively wide hot rolled or iinvished sheet metal'V to the same extremely thin gage in less passes than heretofore possible on a single four high reversing, cold mill which fact constitutes one of .the objects of my herein de-` scribed invention.

Another object of my invention is to utilize in combination with a limited number of passes oi strip metal through a four high cold reduction mill, speeds on initial and intermediate passes not heretofore possible.

A still further object is to utilize a single reversing mill unit which by my methods of cold reduction presents minimum investment costs as well as a minimum operating cost and an increased tonnage output oi metal in a given period of time.

These and other objects and advantages of my invention will become apparent in the specica.-

. tions when: considered in conjunction with the illustrative embodiment shown in the accompanying drawings wherein:

Figure l indicates a plan view of a single stand,

reversing cold rolling mill with motors and reels adjacent thereto, while Figure 2 shows a side elevation through A-A of Figure l, andA Figure'3 shows an end view of mill through B-B of Figure l.

In the drawings I have illustrated a conventional four high` reversing cold reduction mill with housings l in which are positioned reducing or work-rolls 3 and top andbottom back up rolls 2. The mill housings are mounted on a bed plate 4 which in turn is supported on suitable foundation 5.

The work rolls 3 are driven by the main mill 5 motor 6, power for which is transmitted from the motor to the rolls by means of gear reduction units 1, hence to a flexible coupling 8 and then through pinions 9, couplings I0 and spindles Il. The top back up roll and top work roll are vertically adjustable by means of motors 3f and screwdown mechanism 3b.

` Adjacent and on either side o! the main mill are reels I5 and I5*L which alternately wind and unwind the metal M. These reels are reversing, being drivenby variable speed motors I2 through gear reducers I3 and couplings Il. Into the reel mounts I6 and I6L are removably mounted reels or drums I5 and I5* onto which the metal M is either coiled or uncoiled, depending 20 on the direction of metal movement.

To illustrate more specically my invention, as well as to compare its operation with prior cold rolling mills, IA will utilize, for example, a heavy 16 (USS) gage (.065") hot rolled. and pickled 25 strip or sheet metal which will be reduced to approximately-3l (USS) gage (0107"). 'I'hishot rolled and pickled strip is rst wound tightly onto a removable reel I5. The removable reel I5 with its tight coiled hot strip .is `then mounted, onto 30 the reel mount I6 and the strip M is then fed into the cold reduction mill by passing over strip guide I1 and guide plates I8, thence between the work rolls 3 and over corresponding strip guides on. the other side of the min and nneuy wound onto reel |51, this last mentionedlreel now acting as a tension reel whereas the rst mentioned reel on which the hot rolled stripis now mounted being for the moment the drag reel. i

The work rolls 3 for illustrative purposes will 40 be assumed to have a diameter of approximately about 16" in contrast to the diameters of their respective backing up rolls which have a diameter of approximately about 48". These work and back up roll' diameters are for a mill roll having 45 a face or length approximately about 42".. Thus it will be noted that I prefer to use a ratio of approximately 3 to 1 between the baci: up'and work rolls, respectively, las contrasted with the ratio of 2 or 3 to 1 on tandem non-reversing cold 50 rolling-mills and a ratio of 6 to 1 on a. reversing single stand lcold rolling mill having-rolls not` driven, both types of which have been previously described.

This 3 te 1 ratio ultimately aids in giving me e. 55 more quickly produced product at less production cost by virtue of the fact that the work rolls are driven andof a size to vprevent horizontal deflection together with back up rolls of such a large diameter as to allow screw pressures suillciently great to accomplish heretofore impossible reductions per .pass without their excessive vertical deilection.

To further aid in obtaining my maximum reduction of metal in a limited number of passes either one or both of 4thework rolls preferably carry a slight convexity which for the size of roll to be utilized in this foregoing example `might be as much as '.0015" to .0025" crown at the center, or an average increase of diameter 70 of about .0045" at center over' the diametervof same roll at both ends.

I ilnd that this convexity of either one or both of the work rolls together with other mechanical improvements herein disclosed, aids 7 active pass conditions which permit in my single stand more `or Aless the equivalent of what is otherwise accomplished by two or more fourhigh mills arranged in tandem.

'I'hus for example, this slight convexity of work rolls is lost during the active pass, it being taken up by the spring of the rolls. Such a condition permits each active pass to produce a Isubstantially flat sheet yet leaving sufficient material to finish to a given gage without excessivel edge r'uille or center buckle. These mechanical conditions will lvary with the starting gage and analysis of the material and during rolling operations the shape and temperature of the metal contacting rolls and screw pressures utilized. All of these conditions are coordinated to produce maximum reduction in a minimum number of passes through the mill to secure the yrequired uniform gage. Y

The motor- 6 which drives the work rolls 3 while in the process of reducing Astrip is capable and does develop power which is greater than the combined and utilized power of both of the real motors I 2. Thus, forthe size of the mill just described, I prefer to use a mill motor which develops approximately 1200 horse-power as contrasted with reel motors which develop approximately 250 horse-power. It will be obvious to one skilled in the art that with larger'mills rolling wider sheets and hence using wider rolls,

with the speed of the drag and tension reels, a

very decided cold reduction of the metal takes place. In the first or initial pass of the metal to be reduced, I am able to obtain gage reductions and speed of metal not heretofore possible on any type of cold rolling mill.

Thus, for illustrative purposes, I may in this first pass cold reduce at a linear speed of about 500feet per minute, relatively soft, low carbon hot finished sheet or strip having a width of approximately 32", from heavy 16 (USS) gage (.065")v to approximately about .032 or heavy 22 (USS) gage which is a metal reduction of approximatelyfifty-one percent (51%).

The mill and the reels are then reversed in 4their direction of rotation,the mill adjusted for further reduction and the partially reduced strip or sheet metal is simultaneously cold reduced and re-'wound onto reel I 5. This second cold reduction is at a speed and a gage reduction not heretofore possible as an intermediate pass on any type of cold reduction mill.

Thus,'for further illustrative purposes, I may in this second pass cold reduce, ata linear speed of about 800 feet per minute, the above mentionedstrip from heavy 22 (USS) gage (.032") to approximately about 27 (USS) gage (.0l7") which is a metal reduction of approximately forty-seven percent (47%).

Uponthe reversal of the mill and reel motors and adjustment 'of the mill, the sheet metal or strip is again passed through the cold mill in 1 a speed comparable with the finishing speeds obtainable on other cold reduction mill units.

However, I am able to obtain on my mill a gage reduction which has never to my best knowledge and belief been possible at this point on any single stand reversing cold reduction mill and at a speed not known by me to be possible 5 on the finishing pass of a tandem mill.

Thus, for example, I may cold reduce in this third pass at a linear speed of about 800 feet per minute the vgage of the metal being cold re'- duced from 27 (USS) gage (.0l7") to about 10 3l gage (USS) (.0107) or lower, giving a gage reduction oi? about 37 percent. V v

While I have shown and illustrated a method of cold reducing to gages which are most desirableI such as the reduction of heavy hot strip 15 to tin plate gages further reductions are possible beyond that described by one or more additional passes.

Therefore, to one skilled in the art of cold reducing sheet or strip metal it can be seen that 20 by my method 'I am able to produce in three or four passes, preferably the former, as above described, a total metal reduction' possible only by ten to fifteen passes in other single stand reversing cold mills. It is further noted that I 25 y am able to produce by my method speeds on initial and intermediate passes greater than the same passes on tandem cold reducing mills. Speed as mentioned herein is the rate of travel of the strip metal through the cold reducing mill 30 expressed in linear feet of travel per minute.

It is also noted that by my extreme reductions per pass together with high speeds on all passes that I am able to produce in a given period of time tonnages of sheet metal not heretofore possible on any other type of cold reducing mill and hence at a production cost notA here--y tofore possible.

Thus, for example, I am able to produce as o high as 45 tons in lone consecutive eight hour turn Dor shift, of tin plate stock' in 31 (USS) gage, approximately 30 inches widel as cold reduced from heavy hot rolled and pickled 16 (USS) gage. 45

While I have shown and described present preferred embodiments it is understood that various changes and modifications may be vmade within the scope of the invention and of the following claims.

1. A method of working a thin and relatively wide metal strip which includes moving the same through a single-stand cold-rolling mill at alinear speed of at least 400 feet per minute, reducing the 55 cross-sectional larea of the metal strip at least 35 per cent on its first pass therethrough, and further reducing'its cross-sectional area at least an additional 35 per cent while confining the same to not more than three passes after the first pass. 00

2. A method of working a thin and relatively wide metal strip which includes moving the same f through a single-stand cold-rolling mill at a linear speed of at least 400 feet per minute, reducing the cross-sectional area of the metal strip 05 approximately 50 per cent on its first pass there through, and further reducing its cross-sectional area at least an additional 35 per cent while conflning the same to not more than three passes after the first pass. 70 ,3. A method of working a thin and relatively wide metal strip which includes moving the same through a single-stand cold-rolling mill at a linear speed of at least 400 feet per minute, reducing the cross-sectional area of the metal strip y' approximately 50 per cent on its flrst pass therethrough, and further reducing its cross-sectional Varea at least an additional 30 per cent on each succeedingy pass.

4. A method of working a thin and relatively wide metal strip which includes moving the same through asingle-stand cold-rolling mill at a linear speed of at least 400 feet per minute, reducing the cross-sectional area of the metal strip approximately 50 per cent on its rst pass, further reducing its cross-sectional area approximately 45 per cent in a succeeding pass through the mill, and finally reducing the cross-sectional arealof the metal strip an approximate additional 35 per cent,fwhereby the total reduction in the cross-sectional area of the metal strip in the singie-stand cold-rolling mill is approximately 82 per cent while confined to only three passes therethrough.

. 5. The method of working a thin and relatively wide metal strip which includes moving the same through a single-stand cold-rolling mill, reducing the cross-sectional area of the metal strip approximately 35 per cent on its rst pass therethrough, and further reducing its cross-sectional area at leastv35 per cent in a single succeeding passwhile moving the strip at a speed of approximately 800 feet per minute.

6. A method of Working a thin and relatively vg5 wide metal stripin a single-stand cold-rolling mill employing a pair of metal-working rolls of which at least one is slightly convex and a pair of substantially cylindrical backing-up rolls which includes the steps of disposing the metal strip between the metal-working rolls, tightening the mill screws until the convexty of the slightly convex metal-working roll is taken up by the spring inherent in all ofv said rolls, whereby the mill provides a substantially flat activemetal pass under high screw pressure, moving the metal strip through said mill at a linear speed of at least 400 feet per minute, reducing the cross-sec tional area of the metal strip at least 35 per cent on itsv first pass therethrough and further reducing its cross-sectional area at least an additional per cent While conningthe same to not more than three passes after the first pass.

HOWARD G. MCILVRIED.

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