US2176412A

US2176412A - Method and apparatus for sizing tubes

Info

Publication number: US2176412A
Application number: US96745A
Authority: US
Inventors: Walter J Assel
Original assignee: Timken Roller Bearing Co
Current assignee: Timken Co
Priority date: 1936-08-19
Filing date: 1936-08-19
Publication date: 1939-10-17
Anticipated expiration: 1956-10-17
Also published as: GB481483A

Description

Oct. 17, 1939. w. .1. ASSEL METHOD AND APPARATUS FOR SIZING TUBES Filed Aug. 19, 1936 2 Sheets-Sheet 1 Oct. 17, 1939. w. J. ASSEL METHOD AND APPARATUS FOR SIZING TUBES Filed Aug. 19, 1936 2 Sheets-Sheet 2 Patented Oct. 17, 1939 UNITED STATES PATENT OFFICE Walter J. Ansel, Canton, Ohio, assignor to The Timken Roller Bearing Company,

Canton,

Ohio, a corporation of Ohio Application August 19, 1936, Serial No. 96,745

18 Claims.

The final operation in seamless tube rolling mills is to size the tube to the final size desired. According to common practice, this sizing is done by passing the tube through two-high grooved roll stands arranged continuously in line with the axes of the rolls of each stand set at an angle of ninety degrees with the adjacent stands. In the case of tubing of a diameter of three inches or larger this sizing is done in a mill consisting m of three to flve stands only. If the finished tubing is to be less than three inches it is reduced in size by passing through from three to twelve oval grooved roll stands which sink or reduce the diameter. The last three stands of mach a 1n mill act as sizing stands, forming the tube to a round shape and bringing it to size. Such grooved roll mills are subject to a number of disadvantages. They require different sets of rolls for every size of tube; the rolls wear rapidly and, when worn, require to be replaced or redressed; the replacement and adjustment of the rolls requires considerable skill and time during which the entire mill is out of commission; and frequently the product bears marks on 5 its surface produced by the parting of the rolls and misalignment and is not as accurate as desirable either in diameter or roundness.

The principal object of the present invention is to devise a method and a mill which will do! 9 the work of the sinking and sizing mill but which will be free from the disadvantages above mentioned. It is a principal object of the invention to devise a mill that will do the work of sinking and sizing in a single pass; another object is to devise a mill whose pass-forming rolls are adjustable for tubes of different sizes. Another object is to devise a mill that will sink and size tubing more accurately as to diameter and roundness than has heretofore been feasible with w sinking and sizing mills; another object is to simplify and facilitate the operation of adapting the mill for tubes of different sizes. The invention consists in the method and in the apparatus and work roll hereinafter described and claimed.

4,5 It also consists in the parts, combinations and arrangements of parts hereinafter described and claimed.

In the accompanying drawings, which form part of this specification and wherein like sym- 60 hole refer to like parts wherever they occur.

Fig. 1 is a diagrammatic view showing the grouping of the work rolls of my mill;

Fig. 2 is a longitudinal sectional view along the line of contact of one roll with the tube being ll sized;

Fig. 3 is an enlarged fragmentary view similar to Fig. 2; and

Figs. 4 to 8 illustrate modified forms of roll and roll arrangements.

The present mill comprises suitable framework and housing for work rolls together with suitable mechanism for adjusting and driving the same. Reference is hereby made to my copending application Serial No. 727,934 filed May 28, 1934 for a full description of framework, housing and adjusting and driving mechanism suitable for use in my present mill.

The present mill comprises a series of work rolls l, preferably three or four, arranged with their axes in planes parallel with and equidistant from the axis of the mill and from each other and inclined respectively at an angle in the neighborhood of from five to ten degrees to a plane passing through the axis of the mill and intersecting the respective roll axis near the middle thereof. The angle thus defined is commonly called the feed angle of the rolls. This feed angle determines the pitch or distance which the tube moves longitudinally during a single rotation thereof; and this distance divided by the number of equidistant rolls constituting the pass is commonly called the advance" of the tube. The rolls are similarly arranged with respect to the axis of the mill, that is, each roll is so disposed that if it were revolved about the axis of the mill to the location of another roll, it would take the same position and arrangement as such other roll.

Each work roll comprises a. cylindrical zone A which is located at or near the middle portion of the roll and is of the maximum diameter of the roll. Along one side (hereinafter referred to as the forward side) of the cylindrical zone is a relatively narrow longitudinally convex zone B whose surface is preferably tangent to or merges into the surface of the cylindrical zone. Alongside of the convex zone is a relatively wide conical zone C which makes an obtuse angle with said zone B and tapers slowly toward the end of the roll and emerges into a narrow endmost zone D that is convex or rounded. In practice, I have had satisfactory results when the side of this conical zone C inclined at the rate of one unit in twelve at an angle of about two and one-half degrees to the axis thereof, which is equivalent to an apical angle of about five degrees. Along the other or back side of said cylindrical zone A is a second conical zone E that tapers more slowly than zone C close to the other end of the roll where it merges into a narrow, rounded or convex zone F. In practice. I have had satisfactory results when the apical angle of this conical zone E was about two and one half degrees, which is equivalent to inclining the side of said zone about one unit in fortyeight with relation to the axis thereof.

By reason of the oblique angle between the zones B and C, the zone B constitutes an inclined shoulder; and this shoulder is an important element in effecting the sizing action as it is located at the gorge of the pass. On account of the nature of the work, this shoulder is quite low. For instance, for sizing small tubing of from one and one-half inches to three inches in outside diameter with rolls of about ten or eleven inches in diameter, I have had very satisfactory results when the difference between the least diameter of the shoulder of zone B and the diameter of the cylindrical zone A is of the order of one-twentieth of an inch, with a longitudinal width of from about three-eighths to liveeighths of an inch. The width of this low shoulder or convex zone is several times its height, say, about ten to twelve times; and as it is the gorge-forming part of the roll, its width and low angle cause considerable frictional resistance to the plastic flow of the metal in a longitudinal direction.

The work rolls are positioned with their shoulders facing the entering side of the mill and with the proximate surfaces of the conical zones E in planes substantially parallel with the axis of the mill. In this position, the proximate surfaces of the zones C converge slightly to the shoulders that form the gorge of the pass; and the work rolls are so adjusted that the circle of the gorge or narrowest portion of the pass will lie in a plane which passes through or close to the large ends of the portions of the roll shoulders in contact with the tube and will be of the diameter required to produce the desired flnished tube.

In the practical operation of the mill hereinbefore described, no mandrel or wall support is used inside of the tube. The tube T to be sized is entered between the rolls endwise at a temperature suitable for rolling, preferably about 1400 to l600 Fahrenheit for steel tubing, and is reduced slightly to the desired outside diameter, which is determined by the adjustment of the pass. The tendency of the tube is to seat itself on the lowermost rolls and the first function of the rolls is to accurately center the tube with respect to all of the rolls. This function is accomplished by sliding the tube endwise along the converging surfaces of the forward portions of the zones C of the lower rolls until the tube comes in contact with the upper roll or rolls. The second function of the rolls is to simultaneously rotate the tube and feed it longitudinally, which i'uncion is accomplished by the rearward portions of zones C which portions are continuations of the centering surfaces of said zones C. The third function of the rolls is to slightly reduce the outside diameter of the tube, which function is performed mainly by the shoulders or zones B, at the rear edges of which the rolls reach their maximum diameter. The principal function of the cylindrical zone A is to nullify the tendency of the shoulders to form helical marks on the tube as well as to feed. This tendency is minimized by the low inclination of the shoulders and is practically overcome by the cylindrical zones A into which the shoulders merge at their greatest diameter and in the plane of the gorge, beyond which the pass 'very gradually increases in diameter throughout the width of the cylindrical zones A, by reason of the skewing of the rolls. Accordingly, the width of the cylindrical zone A is slightly more than the advance of the tube in its helical movement from one roll of the pass to the next roll. This cylindrical zone A also functions to reel the tube and aids in controlling the feed thereof and the plastic flow of the metal. Zone E serves to round up ti: tube which is slightly distorted at zone A, and guides the tube toward the outlet of the mill.

In practical operation, zone C of the rolls will get a frictional grip on tubes requiring a greater reduction to size at a more forward position than is the case with tubes requiring less reduction, due to the taper on zone C. This is an advantage because tubes requiring the greater reduction require greater feed pressures inasmuch as more metal must be displaced on such tubes.

In practical operation, there is nothing inside the tube to resist radial flow of the metal, and the metal displaced in the operation of reducing the outside diameter of the tube goes mainly to increase the wall thickness of the tube with only a slight elongation of the tube. One of the factors contributing to this result is the great frictional resistance to the longitudinal flow of the metal due largely to the long lines of contact with the work rolls and particularly to the longitudinal flow angle being very low, such longitudinal flow angle being the angle between the lines in which a plane through the axis of the pass intersects the surface of the roll shoulder and the adjacent inner surface of the tube.

It is an important advantage of my invention that the tubes sized thereby are more truly circular and closer to size and freer from longitudinal surface marks than the product of the ordinary sinking and sizing mill, Besides, my operation requires much less apparatus. It is a special advantage of my apparatus that it is adjustable and that the same rolls can be used for tubes of different sizes and are not seriously affected by wear that would be ruinous to the rolls of the common sinking and sizing mill. Heretofore, the reduction of the diameter of tubing has usually been accompanied with varying elongation and an unequal heavying-up of the wall thickness, resulting in out-of-round holes in the tubing. It is a considerable merit of my invention that it enables the diameter of the tubing to be decreased and the wall thickness to be uniformly increased. While I have described my process as applied to the sizing of hot steel tubing, it is applicable also to tubing of other metals, such for instance, as copper or brass tubing which requires little or no heating.

Fig. 4 shows a modified design of roll positioned with reference to the pass line and with the arrow indicating the direction of movement of the work. This roll is of general conical shape with an enclosed apical angle of about 20, that is, the element of the imaginary cone makes an angle of about 10 with the axis thereof. About midway of the roll is a longitudinally convex zone, alongside of which on the front or entering side is a conical surface radially beyond the general imaginary cone and meeting said imaginary cone at the front end of the roll, making an angle of about 5 therewith. Alongside of said convex zone on the rear side thereof is a conical zone that makes an angle of about 2% with the imaginary general cone. The convex zone merges into the rear conical zone and makes a very 7 wide angle with the forward conical zone and thus forms a very low rib.

In the modification illustrated in Pig. 5, the roll is of maximum diameter about midway between its ends where there is a convex zone of large radius and from this convex zone the surface of the roll tapers in both directions, the taper on the forward or entering side being about two inches per foot on the diameter and the taper on the rear side being about one inch per foot on the diameter; that is, the forward zone inclines toward the axis of the roll at an angle of about 5; and the surface of the rear conical zone tapers toward the axis at an angle of about 2%. The working position of the roll with reference to the pass line is shown in Fig. 5 and the direction of movement is indicated by the arrow therein.

My process of sizing is not dependent on the specific type of tube mill hereinbefore described but may be carried out with mills of other types known in the art. Thus, all of the roll axes may lie in planes parallel with the pass; or one roll axis may diverge from the pass in the direction of feed and the coacting roll axis, or axes, converge toward the pass in the direction of feed; or all roll axes may diverge from the pass in the direction of feed. The important consideration is that the pass shall converge in the direction of feed so slowly that the frictional resistance to longitudinal flow of the metal is greater than the resistance to flow thereof in a radial direction when there is no interior support for the metal.

Figs. 6 and 7 illustrate diagrammatically a tube mill of the Stiefel or disk-roll type adapted and arranged for carrying out my process, the coacting disk rolls overlapping in Fig. 6 and being opposite each other in Fig. 7. In both cases, however, the pass forming portions of the disk rolls converge in the direction of feed at such a low angle that the frictional resistance to longitudinal flow of the metal is greater than the resistance of the unsupported wall of the tube to fiow of the metal radially inwardly. As indicated in Figs. 6 and '7, I prefer to have the pass-forming surfaces incline at an angle in the neighborhood of five degrees to the pass line and to have the reeling surfaces diverge from the pass line at an angle in the neighborhood of two and one-half degrees; but these angles admit of variation.

It is not necessary that all of the rolls should be of the same kind. For instance, as illustrated in Fig. 8, one of the rolls may be of the disk type and its mate may be of barrel or conical shape; but in all cases, the longitudinal flow angle should be small enough to bring about a frictional resistance to longitudinal flow that is greater than the resistance to radial flow of the unsupported wall.

The process of sizing hereinbefore described is especially applicable to the production of tubing within close limits of tolerance and is not dependent upon any particular method or apparatus for converting the work piece into the tube to be sized. In practice, the hot work piece is converted by any suitable mill into a rough or unfinished tube whose diameter approximates but is somewhat larger than the diameter of the finished tube. Then, while the tube is still hot, it is cross-rolled without interior support between rolls or pass-forming members so arranged that the frictional resistance to the longitudinal flow of the metal is greater than the resistance therepracticable to size without changing the setting;

and, of course, it is a greater advantage that the same rolls may be set to produce finished tubes of diflei'ent diameters.

What I claim is:

1. A tube sizing mill comprising a series of rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis to form a slowly converging pass, each roll being of greatest diameter near the middle thereof and decreasing slowly toward both ends thereof, the rate of decrease being most rapid in a narrow gorge-forming zone next forward of the zone of maximuni diameter whereby a low inclined shoulder is formed thereon whose width is several times its height and whose surface merges into the zone of greatest diameter.

2. A tube sizing mill comprising a series of rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis, each work roll comprising a cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a longitudinally convex zone alongside of the forward edge of said cylindrical zone and with its surface merging into the surface of said cylindrical zone, a conical zone alongside of said convex zone and tapering slowly toward one end of the roll, and a second conical zone alongside of said cylindrical zone and tapering more slowly toward the other end of the roll.

3. A tube sizing mill comprising a series of pass-forming rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis, each roll being of greatest diameter near the middle thereof and decreasing to both ends thereof, the rate of decrease being most rapid in a narrow zone next forward of the zone of maximum diameter whereby a low inclined shoulder is formed thereon whose surface merges at the gorge of the pass into the zone of'greatest diameter and whose width is somewhat greater than the advance of the work piece.

4. A tube sizing mill comprising a series of pass-forming rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis, each roll being of geratest diameter near the middle thereof and decreasing to both ends thereof, the rate of decrease being most rapid in a narrow zone next forward of the zone of maximum diameter and of a width of several times its height whereby a low inclined shoulder is formed thereon whose surface merges at the gorge of the pass into the zone of greatest diameter and whose width is somewhat greater than the advance of the work piece.

5. A tube sizing mill comprising a series of pass-forming rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis, each work roll comprising a cylindrical zone of the maximum diameter of the roll whose i'll proximate elements are nearly parallel with the axis of the pass located at the middle portion of the roll and of a width somewhat greater than the longitudinal advance of the work between successive rolls, a longitudinally convex zone alongside of and merging with the forward edge of said cylindrical zone and of a width of about ten times its height and located atthe gorge of tire pass, a conical zone alongside of said convex zone and tapering toward one end of the roll with an apical angle of about five degrees, and a second conical zone alongside of said cylindrical zone and tapering toward the other end of the roll with an apical angle of about two and onehalf degrees.

6. A tube sizing mill comprising a series of pass-forming rolls similarly arranged equidistantly from the axis of the pass with their own axes askew with relation to the planes of said axis. each work roll comprising a cylindrical zone 01' the maximum diameter of the roll located at the middle portion of the roll and of a width somewhat greater than the longitudinal advance of the work between successive rolls, a longitudinally convex zone alongside of and merging with the forward edge of said cylindrical zone and located at the gorge of the pass, the width of said convex zone being several times its height, a conical zone alongside of said convex zone and tapering toward one end of the roll with an apical angle of about five degrees, and a second conical zone alongside of said cylindrical zone and tapering toward the other end of the roll with an apical angle of about two and one half degrees.

7. A work roll for a tube sizing mill oi the kind described comprising a narrow cylindrical zone of the maximum diameter of the roll and located at the middle portion 01' the roll, a narrow longitudinally convex zone alongside of and merging tangentially with said cylindrical zone, and forming a shoulder whose width is about ten to twelve times its height, a relatively wide conical zone alongside of said convex zone and tapering slowly toward one end of the roll, and a second conical zone alongside of said cylindrical zone and tapering more slowly toward the other end of the roll.

8. A work roll for a tube sizing mill oi the kind described comprising a narrow cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a narrow longitudinally convex zone alongside of and merging tangentially with said cylindrical zone, a conical zone alongside of said convex zone and tapering slowly toward one end of the roll, and a second conical zone alongside of said cylindrical zone and tapering more slowly toward the other end of the roll.

9. A work roll for a tube sizing mill of the kind described comprising a narrow cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a narrow longitudinally convex zone next to each side of said cylindrical zone and merging tangentially therewith, a conical zone alongside of said convex zone and tapering slowly toward one end of the roll. and a second conical zone alongside of the other convex zone and tapering more slowly toward the other end of the roll.

10. A work roll for a tube sizing mill of the kind described comprising a cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a second narrow zone alongside of and continuous with said cylindrical zone and gradually decreasing in diameter away from said cylindrical zone and constituting a low shoulder whose smallest diameter is about one twentieth of an inch less than its largest diameter. a conical zone alongside of said second zone and tapering slowly toward one end of the roll, and a second conical zone alongside of said cylindrical zone and tapering more slowly toward the other end of the roll.

ii. A work roll for a tube sizing mill of the kind described comprisinga cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a second zone immediately alongside of and continuous with said cylindrical zone and of even diameter therewith when they meet and gradually decreasing in diameter away from said cylindrical zone and constituting a low shoulder whose width is several times its height, a conical zone alongside of said second zone and tapering slowly toward one end of the roll, and a second conical zone alongside of said cylindrical zone and tapering more slowly toward the other end of the roll, said second zone being slightly wider than the ad vance of the work piece.

12. A work roll for a tube sizing mill or the kind described comprising a cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a relatively narrow longitudinally convex zone alongside of and merging tangentially into said cylindrical zone, a conical zone alongside of and making an oblique angle with said convex zone and tapering slowly toward one end of the roll, and a second conical zone alongside of and merging with said cylindrical zone and tapering more slowly toward the other end of the roll.

13. A work roll for a tube sizing mill or the kind described comprising a cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a relatively narrow low longitudinally convex zone alongside of and merging into said cylindrical zone and of a width of about ten to twelve times its height, the diameter of the small end of said convex zone being about one-twentieth of an inch less than the diameter of the large end thereof, a conical zone alongside of and making an oblique angle with said convex zone and with its sides tapering at the rate of about one in twelve toward one end of the roll, and a second conical zone alongside oi and merging with said cylindrical zone and with its sides tapering at the rate of about one in twenty-four toward the other end 01' the roll.

14. A work roll for a tube sizing mill of the kind described comprising a cylindrical zone of the maximum diameter 0! the roll and located at the middle portion of the roll, a longitudinally convex zone next to each side of said cylindrical zone and of equal diameter therewith where they meet, a conical zone alongside of the forward convex zone and tapering slowly toward one end of the roll, and a second conical zone alongside of the other convex zone and tapering more slowly toward the other end of the roll, the forward convex zone being narrow relatively to the forward conical zone but somewhat wider than the advance of the work piece.

15. A work roll for a tube sizing mill 0! the kind described comprising a narrow cylindrical zone of the maximum diameter of the roll and located at the middle portion of the roll, a narrow longitudinally convex zone next to each side of said cylindrical zone and merging tangentially therewith, a conical zone alongside oi the forward convex zone and tapering with an apical angle 1 of about ten degrees toward one end of the roll, and a second conical zone alongside of the other convex zone and tapering with an apical angle of about five degrees toward the other end of the roll.

16. The method of sizing tubing which comprises cross-rolling hot tubing, without interior support, between three or more skewed rolls in three immediately consecutive pass stages in the first of which the work piece is rotated and fed forwardly without appreciable convergence of its wall, in the second of which the wall of the work piece is converged only slightly, and in the third of which the work piece is reeled without further convergence of its wall, the middle pass stage being narrow relatively to the other stages but somewhat wider than the advance of the work piece and merging into the third stage parallel with the axis of the work piece.

17. The method of sizing tubing which comprises cross-rolling hot tubing, without interior support, between three or more skewed rolls in three immediately consecutive pass stages, in the first of which the work piece is rotated and fed forwardly with a frictional grip without appreciable convergence of its well, in the second of which the wall of the work piece is converged only slightly, and in the third 01' which the work piece is reeled without further convergence of its wall, the middle pass stage being narrow relatively to the other pass stages and merging into the third stage without any angle' between them.

18. The method of sizing tubing which comprises cross-rolling hot tubing, without interior support, between three or more skewed rolls in three immediately consecutive pass stages, in the first of which the work piece is rotated and fed forwardly with a frictional grip without appreciable convergence of its wall, in the second of which the wall of the work piece is converged only slightly altogether and at a decreasing rate, and in the third of which the work piece is reeled without further convergence of its wall, the middle pass stage being narrow relatively to the other pass stages and merging into the third stage without any angle between them.

W. J. ASSEL.

CERTIFICATE OF CORRECTION Patent No. 2,176,1 12.

October 17, 1959.

WALTER J. ASSEL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1;, first column, line t l cleim'f, before "second" insert relatively wide; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 12th day of December, A. D. 1959.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.