US2325190A

US2325190A - Metal rolling

Info

Publication number: US2325190A
Application number: US383102A
Authority: US
Inventors: John H Mcelhinney
Original assignee: Wheeling Steel Corp
Current assignee: Wheeling Steel Corp
Priority date: 1939-06-05
Filing date: 1941-03-13
Publication date: 1943-07-27
Anticipated expiration: 1960-07-27

Description

July 1943- J. H. MCELHINNEY ,325,190

METAL ROLLING Original Filed June 5, 1939 6 Sheets-Sheet 1 NEW! i mvmT R: Jenn H-McfLHINHEY BY 4w Armnsy,

July 27, 1943. H, McELHINNEY METAL ROLLING Original Filed June 5, 1939 6 Sheets-Sheet 2 JOHN H. No Euumvz 9562 61,, M 4 ATTDRNEY.

July 27, 1943. J. H. McELHlNNEY 2,325,190

METAL ROLLING Original Filed June 5, 1939 6 Sheets-Sheet 3 J2 J1 o 49 4 INVENTOR. Jorm H-MCELHINNEY {8 Jul ATTORNEY.

BY%%4M Juiy 27,194. J. H. MCELHINNEY METAL ROLLING Original Filed June 5, 1939 6 Sheets-Sheet 4 INVENTOR Jopm H. McELHINNEY fiY fifio' M ATTORNEY.

WWN MWN y 1943. J. H. MOELHINNEY Original' Filed June 5, 1939 6 Sheets I N 0 cELHINNEY m ATTORNEY.

H. MCELHINNEY 2,325,190

METAL ROLLING Original Filed June 5, 1959 6 Sheets-Sheet e INVENTOR: JOHN H- MCELLHINNEX M ATTORNEY Patented July 27, 1943 METAL ROLLING John H. McElhinney, Wheeling, W. Va., assignor to Wheeling Steel Corporation,

Wheeling,

W. Va., a corporation of Delaware Original application June 5, 1939, Serial No. 277,345. Divided and this application March 13, 1941, Serial No. 383,102

6 Claims.

This application is a division of my application Serial No. 277,345, filed June 5, 1939, now Patent No. 2,279,579.

The invention relates to metal rolling and is particularly useful in producing wide, thinmaterial of substantially uniform dimensions and character by continuous cold rolling.

I have observed that in the cold rolling of strip or sheet metal there isa wide variation in surface, contour, thickness, edges, hardness, etc., not only between strip produced on different mills but also between successive strip rolled from the same stock on the same mill and even between different parts of the same strip.

Analysis of the situation indicates that a roller has the following variables to reconcile in trying to cold roll successfully:

Analyses of the metal and segregation of impurities therein; its hardness and ductility, which are particularly affected by the final finishing temperature at which the rolling of the metal was completed on the hot mill and the method of cooling from such temperature; condition of the metal as to flatness, crown, edges, surface, etc; wear of rolls; condition of roll surfaces; swelling or shrinkage of rolls due to change of roll temperature; application of cooling or heating mediums to rolls and Work; applicatlonof lubricant between rolls and work; fluctuation in roll speedsin one stand, and in successive stands; stretch of mill housings; width and gauge of strip and tension thereon.

A roller or mill operator attempts largely by intuition to allow for and reconcile all of the foregoing variables. Correct decision and instant action are of extreme importance because the strip travels at speeds which in some mills exceed 2000 feet per minute. But the fact that one roller may produce 40% more of satisfactory finished product than another from the same run of stock and on the same mill in a given period and that even a skilled roller does not properly reconcile the several varying conditions indicate that the modern practice of cold rolling of strip or sheet is just as much an art as pack rolling.

I havealso observed that frequently inability to judge the net average effect of these several variables results in the work moving either too slowly or too fast with reference to the roll face. For instance in recording the actual working performance of skilled rollers I have found that the relation of strip speed to the roll face speed varied as much as from 5% slower to 15% faster. Both conditions cause excessive and detrimental slippage of the rolls upon the work, which results' in an inferior product, broken metal, roll damage and increased power consumption. Thin steel such as steel cold reduced for tin plate can be buckled to unusable height by a very small amount of heat. It is important therefore, to

keep the friction between the steel and the rolls at a minimum.

I have discovered that all of the variables referred to above effect the relative speeds of the rolls and of the work, and that if these relative speeds are brought into proper relationship the conditions of mechanism and of the work that are within the mill operators control will be those which are necessary for turning out a satisfactory product. For the purpose of giving the operator instantaneous indications of this speed of travel relationship, which in effect tells him whether he has sufficiently reconciled the variable conditions which lie within his control, I prefer to employ indicating or recording means at one or more of the roll stands which indicate the speed of one of the working roll faces and of the work adjacent to or at such roll'stand or stands. Such means indicate to the operator what such speeds are and permit him to bring the speed of travel of work and of roll faces into proper relationshipby such adjustments of tension, of roll pressure and of roll revolutions, etc., as may be necessary to compensate substantially for the continuously changing variables encountered. With the information obtained from such means applied to a tandem mill, the roller can change or regulate the speeds of the rolls so as to maintain the desired speed relationship at each stand.

Proper correlation of these factors result in the control of the quality and quantity of the output. A further advantage of my invention is that the differential between the strip speeds at succes sive stands shows the percentage of reduction in metal thickness at individual stands.

It is an object of my invention to provide apparatus for measuring the relative speeds of the roll surfaces and of the work at a given cold rolling station or stand so that the rolling mill can be quickly adjusted to maintain a predetermined relationship between these speeds.

Another object is to provide apparatus for measuring these relative speeds and for providing simultaneously thereby a measurement of the percentage of reduction in thickness of the work at a given cold rolling stand.

Other objects and advantages in addition to those referred to above will be described and will become apparent from the following description of certain apparatus illustrated in the drawings and embodying measuring means in accordance with my invention. 1

Figures 1 and 1A together illustrate diagrammatically a five stand tandem continuous cold rolling mill in side elevation showing the rolls in section and single line wiring connections, each single line representing a cable carrying two wires.

Figures 2 and 2A illustrate a diagrammatic plan view of this rolling mill with single line wiring connections.

Figur 3 illustrates diagrammatically in elevation apparatus for measuring the relative speeds of the work roll surfaces and of the emerging strip being rolled at a given stand.

Figure 4 is a schematic wiring diagram for the measuring apparatus in Figure 3.

Figure 5 is a vertical sectional diagrammatic view of one form of apparatus for measuring percentage reduction in the work at a given rolling stand.

Figure 6 is a schematic wiring diagram of the measuring apparatus in Figure 5.

Figure '7 is a vertical sectional view illustrating a modification of apparatus for measuring percentage reduction of the work at a given rolling stand.

Figure 8 is a schematic wiring diagram for the apparatus in Figure 7.

Figure 9 is an alternative schematic wiring diagram for the apparatus in Figure 7.

The invention is illustrated and will be described as applied to a five stand tandem cold rolling mill in which the work rolls at the different stands are individually driven. The metal strip to be rolled may be supplied to the mill from any suitable source (not shown) such as an unwind stand or coil box. This strip is indicated in Figures 1, 1A, 3, 5 and 7 by the dot and dash lines l0, and in each case the strip is moved .in the direction of the arrows from right to left of the figures.

Referring more particularly to Figures 1, 1A, 2 and 2A, the strip is first pass'ed between the work roll H of the first stand or rolling station and thereafter proceeds successively between the pairs of work rolls l2, I3, I4 and I5 of the other four rolling stands and is then coiled for further treatment or out directly into sheets as desired. The work rolls may be provided with the usual backing rolls l6 and one or both of the work rolls at each stand may be driven by individual motors IT, or from other suitable sources of power through the gearing l8 and shafting I9, or by other suitable connections between the sources of power and the work rolls.

As the metal strip Ill emerges from between each pair of work rolls it passes under an idler roll and over a second idler or tension roll 2|. Idler rolls 20 are not necessary but assist in maintaining a constant and uniform contact between the metal strip and the idler rolls 2!. Rolls 2! may be journaled in brackets 22 which are pivotally secured to the framework of the mill as at 23. A spring 24, or group of springs or other suitable force, may be employed to press the rolls 2| firmly against the metal strip m.

I prefer to measure the various speeds to be determined by, means of electrical tachometers comprising essentially small generators supplying current to suitable meters. rolls at each stand may be connected by chains and sprockets or other suitable driving means 25 One of the work to the

small generators

2B, 21, 28, 29 and 30, respectively. Each of the

generators

26, 21, 28, 29 and 30 is connected electrically to the respective potentiometers 3|, 32, 33, 34-, 35, which in turn are connected electrically to various meters. A bank of meters 37 located in a group at any convenient place near th rolling mill may be employed for indicating directly and instantaneously the relative speeds of the work roll surfaces and of the material emerging from the work rolls at each rolling station or stand. For this purpose, the potentiometers ill, 32, 33, 34 and are each connected to one of the instruments in the bank 31. The

lines

38, 39, 40, 4| and 42 indicate cables each carrying two wires connecting the potentiometers to the respective instruments. The lines connecting the generators with their respective potentiometers likewise indicate cables, each carrying two wires.

The instruments in the bank 31 may also be connected to the

generators

43, 44, 45, 46, and 41 by the

cables

48, 49, 50, 56 and 52, each of which carries two wires for this purpose. The

'

tachometer generators

43, 44, 45, 46 and 41 are ters 54, 55, 56 and 51 preferably supported on the brackets 22 and are suitably connected to and driven by the idler rolls 2i through chains and sprockets 53. Thus each instrument in the bank of meters 31 may be equipped with two separate indicating pointers 31a and 31b, or other means for indicating, and/or recording if desired, the relative speeds of the work roll faces and the work emerging from each rolling station or stand.

In addition, extra meters for indicating these relative speeds may be provided at each stand where they are needed. When the bank of meters 31 is located near the last rolling station of the mill, it is only necessary to provide the meat the first four rolling stands. These four meters may be connected to 'the potentiometers 3|, 32, 33 and 34 by pairs of stations of the rolling mill, a bank wires in the

cables

58, 59, 60 and BI. These meters may also be connected to the

generators

43, 44, 45 and 46 by wires carried in the

cables

62, 63, 64 and 65.

The foregoing measuring and indicating apparatus is all that is needed to operate the mill uring apparatus also to provide a direct indica-' tion of the percentage of reduction in the work in a simple manner at each of the last four stands or rolling stations of the mill. If desired, the percentage reduction can be measured at the first stand in a similar manner by providing a generator driven by a roll in contact with the work before it enters the first pair of work rolls. This is generally unnecessary, however, since the work at this point is moving sufliciently slowly to enable the operator' to easily determine or estimate the percentage of reduction at the first stand by the usual methods.

In order to provide an instantaneous measurement of percentage reduction on the last four reduction meters 66 may be provided adjacent the bank of relative speed indicating meters 37 or at any other convenient location. In the rolling of metal under tension, the metal is precluded from spreading sideways to any great extent and consequently the elongation of the metal strip during rolling at a given stand is a direct function of the percentage of reduction in thickness effected by the work rolls at this stand. Similarly, the difierential between the of percentage I speeds of the strip entering and leaving the work rolls is also a direct function of the percentage of reduction in thickness at such a stand. The

I bank of meters 66 thus indicate the percentages of reduction at the different stands directly by measuring the differential in speeds of the strip immediately before and after each stand. For this purpose, the meters 66 are connected to different pairs of the

generator

44, 45, 46 and 41. For example, the meters 66 on one side are con nected to the

generators

44, 45, 46 and 41 through the wires in the

cables

49, 5i and 52 by means of the wires in

cables

61, 68, 69 and 10. The other sides of these meters 66 may be connected to the

generators

43, 44, 45 and 46, respectively, by means of the wires in the cables I l, l2, l3 and i4.

Provision may also be made for additional meters such as meters l5, l6 and ii indicating percentage of reduction and located at the second, third and fourth stands of the mill, alongside of the relative speed meters 55, Eli and 5?. Meters l5, l6 and it are connected by wires in the cables l8, l0 and 80 to the generators and 45, and also by wires in the cables 8!], $2 and 33 to the generators it, it? and #6, respectively.

These relative speed and reduction meters and the electrical connections thereof preferably comprise complete circuits which are not grounded, each line indicating wiring connections in Figures 1, 1A, 2 and 2A representing a cable carrying two wires. This is desirable to avoid leakage oi currents and to provide thus a more accurate measurement. However, each meter and each generator may be suitably grounded to the machine, in which case the lines of these figures wouldindicate single wires. In a grounded systern, fewer wiring connections would be needed but it would be difflcult to maintain the instruments in a calibrated condition to provide accurate measurements.

Figures 3 and 4 illustrate in more detail the connection of a relative speed or slippage indi cating meter for indicating the relative speeds of a work roll face and the emerging work at any given rolling station, together with the electrical connections therefor. It will be seen that the indicating device 635 is connected by two wires in cable iii to the generator 87 mounted in one of the supporting brackets 22, while the other generator 38 driven by one of the work rolls at the rolling stand is connected by wires in the cable 89 to a potentiometer 90 or other variable resistance and thence by wires in the cable 9! to the other side of the instrument 85. In effeet, the instrument 85 comprises a pair of independent volt meters calibrated to indicate the speeds to be measured directly on the same scale. These two meters are preferably mounted in the same housing for purposes of convenience and the rolling mill operator after determining the optimum conditions has only to adjust the mill to maintain a certain predetermined variation between the speeds indicated by the two pointers. The potentiometer 90 or other variable resistance is useful in calibrating the system by varying the voltage balance in that portion of the circuit to compensate for wear on the rolls, changing of a work roll and other variable factors that might otherwise cause an inaccurate reading of the speed of the work roll face during difl'erent operations of the mill.

Figures 5.and 6 indicate one manner of connecting a percentage reduction meter -92 to indicate directly the percentage reduction. One

side of the instrument is connected by wires in the cable 93 to the generator 94 in advance of a given rolling station and the other side of the meter is connected by wires in the cable 95 to the generator 96 driven by the work emerging from this rolling station. In this instance, the pointer of the meter is moved in one direction or the other a greater or lesser amount, depending upon the voltage balance between the wires carried by the two

cables

93 and 95. Since the work will always be traveling at a greater speed as it emerges from the rolling stand, generator 96 will be driven at a faster rate and will generate more "voltage than the generator 94. Fixed resistances may be interposed in either side of the circuit to calibrate the instrument. Thus, percentage reduction will be indicated on the meter, since the needle of the meter will always be defiected in one direction.

Another way of measuring percentage of reduction at a given stand with apparatus employed in accordance with my invention is illustrated in Figures 7, 8 and 9. In this modification, the percentage of reduction may be indicated directly on the instrument 91 which may be connected on one side directly to the generato 98 through wires in the cable 939, and on the other side to the potentiometer or other variable resistance 500 through the wires in the cable Mi. The potentiometer in turn may be connected by wires in the cable N12 to the generator l0? driven by one of the work rolls. The voltage differential between these two generators will likewise be a function of the percentage of reduction in work thickness after due allowance is made for slippage taking place between the work roll faces and the work. The potentiometer tilt? is useful in adjusting the meter to compensate for variations in the work roll due to wear and the like. If desired, the circuit illustrated in Fig. 8 may be employed with another variable resistance lllda used to adjust the sensitivity of the meter or in other words to vary the extent of needle deflection under -diiierent working conditions. Resistance 904 may be used for calibration if desired.

While the arrangement in Figs. 5 and 6 is preferred for measuring percentage reduction, the device of Figs. '7, 8 and 9 has the advantage of making it possible to measure instantaneously the percentage of reduction at the first stand of a rolling mill without providing a generator driven by the work before. it enters the first stand. The arrangements shown in Figs. '7, 8 and 9 may be used as alternate methods of measuring the differences between speed of the strip and roll surface.

As set forth above, there is some one preferable percent of slippage for a given reduction of any particular type of metal, but for rolling the soft steels of commerce, I have found that exceptionally satisfactory results are obtained if the speed of the strip issuing from the working rolls is maintained at approximately from 2 to 10% faster than the surface speed of such rolls, the best conditions I have observed being when the strip speed is about" 5% faster than the surface speed of the rolls from which the strip has just issued. It is to be understood that this particular speed relationship has been found very satisfactory for cold rolling 0.05 to 0.20% carbon steel on the five stand tandem mill described above, said steel having an initial Rockwell hardness of 50 to '70 on the B scale, an initial thickness of 0.62" to .109" gauge and a finished gauge of .007" to .037" produced by successive reductions on the five stands as follows:

The low minimum reduction for No. 1 stand is occasioned by using a very light pass at this stand when rolling steel to heavier finished gauges.

With other rolling conditions, the foregoing speed relation between issuing work and work roll surface may be varied to obtain the optimum results. Having once established the best speed relationship for a given set of operating conditions, a less skilled worker can, by adjustments of the mill settings, such as roll speed, roll pressure and tension on the strip maintain such relation with assurance that he is producing a high grade and satisfactory product.

This invention is not limited to the rolling of steel or to the use of tandem mills although it is particularly adapted to these conidtions. In general, it facilitates rolling operations where rolling is carried out with the work under tension and the work'rolls are driven. The invention has been described as carried out by the measuring of the relation between the speeds of rolled work and the work roll surfaces, but the same principle may also, of course, be utilized by measuring the relation between the speeds of work r011 surfaces and work entering such rolls.

While electrical speed measuring devices have been illustrated and described, it is to be understood that the work and work roll surface speeds may be measured by other means. Recording devices may also be employed.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and arranged in tandem to roll 2. In: a'tandem rolling mill having driven work rolls, a plurality of pairs of work rolls a continuous strip under tension, means for measuring the relationship of the different speeds of the material being rolled to the surface speeds of adjacent work rolls, means for indicating the speeds measured, and means actuated by said measuring means for indicating percentages of reduction in the material effected by the work rolls.

3. In a tandem mill for cold rolling a continuous strip under tension, a plurality of pairs of driven work rolls, means for measuring the speeds of the strip between said pairs of rolls, means for measuring the speeds of the work roll faces, means for indicating said speeds to provide an instantaneous indication of slippage by comparison therebetween, and means connected to said strip speed measuring means for computing and indicating directly percentages of reduction in the strip at different work rolls.

4. In a tandem mill for cold rolling a continuous strip under tension, a plurality of pairs of driven work rolls, means for measuring the speeds of the strip between said pairs of rolls,

' means for measuring the speeds of the work described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

I claim: a

1. Apparatus for rolling strip material comprising working rolls, means for passing strip material therebetween under tension, means for measuring and indicating the relationship of strip speed to the speed of the surfaces of said work rolls to provide an indication of slippage of the strip, and means for computing from such measurement the percentage of reduction in the thickness of the strip.

roll faces, means for indicating said speeds to provide an instantaneous indication of slippage at the work rolls by comparison therebetween, and means actuated by said measuring means for indicating percentage of reduction in strip thickness at individual stands of said mill.

5. In a tandem mill for rolling strip metal under tension by driven work rolls, electrical tachometers for measuring surface speed of a I work roll at each stand, electrical tachometers for measuring speeds of the strip issuing from the Work rolls at each stand, means for indicating said work roll and strip speeds to provide by comparison an indication of slippage, and means connected to pairs of said second mentioned tachometers for indicating percentages of reduction in strip thickness at individual stands.

6. In a tandem mill for rolling strip metal by driven work rolls, electrical tachometers for measuring surface speed of a work roll at each stand, electrical tachometers for measuring speeds of the strip issuing from the work rolls at each stand, means for indicating said work JOHN H. MCELHINNEY.