US1970570A - Method and apparatus for tube manufacture - Google Patents

Description

Aug. 21, 1934. c. w. LITTLER El AL METHOD AND APPARATUS FOR TUBE MANUFACTURE Filed Oct. 2, 1931 3 Sheets-Sheet 1 INVENTOR Aug. 21, 1934. c. w. LITTLER ET AL METHOD AND APPARATUS FOR TUBE MANUFACTURE E Sheets-Sheet 2 Filed 001;. 2, 1951 WWW 40 nunnunfiilfinnn INVENTOR (LA ya. LN, FMLF \WPWM BUBDHEI] LWQ'M 5 Sheets-Sheet 3 -||.\||rr wur um m HHHUHM H HMHHN I L A R E L T W L w C METHOD AND APPARATUS FOR TUBE MANUFACTURE Flled 001', 2 1951 BEBE DDDDHEUUUDUDDDUDEDDUDDDDD BUD flmvwum Tatented Aug. 21, 1934 METHOD AND APPARATUS FOR TUBE MANUFACTURE Carl W. Littler and Frederick E. Fieger, Pittsburgh, Pa., assignors to Jones & Laughlin Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application October 2, 1931, Serial No. 566,476

12 Claims.

This invention relates to a method and apparatus for tube manufacture, the term tube being used as a word of general definition and not as limited to that class of tubular articles so designated commercially.

Various processes for the manufacture of seamless tubing have been proposed, but most of these are open to numerous objections. Generally speaking it is necessary to use extreme care in the rolling of the steel intended to be used in seamless tube manufacture because of the very severe stresses to which the metal is subjected in the tube making process. This adds considerably to the manufacturing cost. The push bench process of tube manufacture offers certain advantages, among them the fact that it is possible to employ steel which cannot be used for other processes and yet produce a high grade product. The process also makes possible certain other economies in manufacture. In the push bench process a heated metal billet is pierced in a press to form a bottle which is placed over the nose of a mandrel and pushed through a series of dies, these dies thinning and elongating the bottle over the mandrel to form a tube. The process has proved highly satisfactory, particularly in the smaller sizes, but great care must be taken if it is proposed to materially increase the length of the product. The stiffness of the mandrel decreases as its length is increased, which may result in eccentricity of the formed tubel Furthermore, as the length of the tube is increased it is necessary to greatly enlarge the push bench installation. Another great difficulty arises from the fact that when producing the bottles by the usual piercing operation great care must be taken to insure a proper relationship between the size of the original billet and the size of the bottle. The billets employed are usually squares with rounded corners. A billet of this character is placed in the pot of the piercing press and is of such size as to fit snugly therein. The piercing tool penetrates the billet axially, swelling it out to a cylindrical shape conforming to the pot. The diameter of the piercing tool should be very slightly larger than the diameter of the mandrel, and the ratio of diameter of the piercing tool to the press pot must be such that upon piercing the billet is swelled out to completely fill the pot. However, the cross sectional area of the punch must not be materially in excess of the combined area of the four segmental spaces originally between the billet sides and the inside wall of the pot. The punching operation swells the billet out to fill these segmental spaces, but if the punch area is materially larger than the combined area of such segments, then the metal flows upwardly, producing a bottle which is longer than the original billet. It is found in practice that if this back flow is in an amount greater than that corresponding to a piercing tool area of more than 30 per- 0 cent in excess of the area of the segments there is danger of eccentric punching or of bending of the piercing tool. It follows that there must be provided a large variety of billet sizes to accommodate. the requirements of the trade. This means also that a large variety of sizes of press pots, piercing tools and mandrels must be kept on hand, thus greatly increasing the cost of the plant. According to our invention, the push bench is employed for the formation of relatively short, 0

thick tube blanks which are thereafter rolled, as, for example, in a plug mill, a mandrel bar mill, a pilger mill or a continuous rolling mill, which mill serves to increase the length of the blank,

and are also passed through an expanding mill so as to obtain the desired tube diameter. The push bench is peculiarly well adapted for the manufacture of the short, thick blanks which we propose. These can be formed with a relatively small expenditure of power and with great rapidity. There is little if any danger of eccentricity, the push bench installation may be relatively very small, thus reducing the capital cost, and a single size of tube blank formed on the push bench may be employed for forming a variety of sizes of finished tubes.

In the accompanying drawings illustrating a present preferred embodiment of our invention,

Figure 1 is a plan view of a portion of the tube making plant;

Figure 2 is a continuation of the plant shown in Figure 1; and

Figure 3 is, in turn, a continuation of the apparatus shown in Figure 2.

Referring first to Figure 1 there is shown a continuous heating furnace 2 through which square billets B are fed by a pusher 3. As the billets approach the discharge end of the furnace they are engaged by tongs through doors 4 and separated from one another so as to insure uniform heating. The heated billets are discharged at 5 to transfer cars 6 which carry them to the press 7. They are there pierced to form bottles and transferred by a radial arm 8 to the push bench which is indicated generally by the reference character 9. The push bench comprises a ring bed 10, a rack bed 11, a rack 12, a drive 13 for the rack, and a mandrel bar 14 carried by the rack 12. The drive 13 is actuated to move the rack back and forth.

A mandrel 15 is engaged by the mandrel bar 14 110 and the nose of the mandrel is inserted in the heated bottle which is indicated at C. The rack is driven from right to left as viewed in Figure 1, thus forcing the bottle through a series of dies 16 on the ring bed 10. The dies thin and elongate the bottle over the mandrel to form a tube blank D.

As shown in Figures 1 and 2 the mandrel withthe tube blank thereon is fed by conveyor rolls 17 to a cross rolling mill 18 which serves to loosen the tube on the mandrel. This is more fully set forth in Peters Patent No. 1,720,345. In certain cases it may be possible to entirely eliminate the cross rolling mill because the short, thick tube blanks which we preferably employ may be more readily stripped from the mandrel than thinner and longer tubes. At any rate the mandrel with the tube thereon eventually reaches the position indicated at 19 in Figure 2 and is fed across skids 20 to bring it into alinement with a mandrel stripping device 21. After the mandrel has been removed from the tube it is carried by rollers 22 back to a kick-off 23 (Figure 1) from which it can be returned over skids 24 to the push bench, or it may be diverted from the rolls 22 by a kick-off 26 and skids 27 to conveyor rolls 28 which carry the mandrel to a mandrel warming furnace 29.

Referring again to Figure 2, the tube blank is fed across skids 30 to conveyor rolls 31 and thence past a saw 32 which, cuts off the ends of the blank, forming an open-ended blank 33 which is fed by conveyor rolls 34 to a heating furnace 35 (Figure 3) After being heated in the furnace 35 the blank 33 is fed across skids 36 into alinement with a plug mill 37 wherein its wall thickness is reduced and the blank is materially elongated. In case there is sufiicient heat in the blank 33 it may be by-passed around the furnace 35 by means of a kick-off 38 which lifts it off the conveyor rolls 34 onto skids 39, which skids transfer the blank to conveyor rolls 40 leading to the skids 36.

After the tube has been plug rolled (Figure 3) it is discharged by a kick-off 41 to skids 42 which take it to conveyor rolls 43. These rolls feed the tube to a heating furnace 44 and, after heating, it is discharged onto conveyor rolls 45 which feed it to an expanding mill 46. The expanding mill increases the diameter of the blankto the desired final diameter and it is discharged from the expander 46 onto skids 47 and thence onto conveyor rolls 48 which carry it to a reeler 49 for the final rolling operation. The rolled tube is discharged onto skids 50 (Figure 2) and passes thence to conveyor rolls 51 leading to a sizing mill 52, from which the tube passes to a cooling bed 53.

If desired the furnace 44 may be by-passed by utilizing a kick-01f 54 which lifts the tube off the conveyor rolls 43 and onto skids 55 leading to the conveyor rolls 45.

Referring to Figure 2, it will be noted that there are provided a kick-off 56 and skids 57 between the conveyor rolls 40 and the conveyor rolls 43, and further that there is a kick-oil 58 and skids 59 between the conveyor rolls 43 and the conveyor rolls 51. Also, as shown in Figure 3, a kickoff 60 and skids 61 lie between the conveyor rolls 45 and the conveyor rolls 48. This permits of by-passing the tube, should occasion arise, around any of the reducing units.

As an example ofour process, assume that it is desired to produce a 16 inch diameter tube 50 feet long and with a tube wall of .250 inch. There might be formed 'onthe push bench a tube blank 10.93 inches outside diameter by 26 feet 3 inches long with a wall ofu840 inch. The

plug mill will elongate this blank to 54 feet (final length with provision for end trimming), reduce the outside diameter to 9.72 inches and reduce the wall thickness to .420 inch. This' blank will in turn be expanded to final size in the expanding mill. It isthus possible to form 50 foot tubes from blanks made on a push bench nominally suited for the manufacture of tubes having a finished length of 25 feet or less. The cost of an installation according to our invention' is materially less than the cost of a push bench installation for the production of 50 foot tubes, and the difficulties attendant upon the use of extremely long mandrels as would be necminimum. If billets are employed, it is not eco nomical to utilize a tube process which requires a wide'variety of billet sizes. The billet length, of course, can be readily adjusted, but it is highly desirable that the cross sectional dimensions remain the same. In such case the outside diameter and wall thickness of the tube blank as it leaves the push bench remain the same, although the length will be varied by changing the length of the original billet.

As an example, a tube blank from the push bench having the outside diameter and wall thickness above noted, but with a length of 21 feet, may be passed through the plug mill and formed into a tube having an outside diameter of 9.55 inches and a wall thickness of .340 inch, which tube, when fed through the expander, will give a finished tube 12% inches outside diameter by .250 inch wall thickness; or the push bench blank may be made 30 feet 9 inches long and formed into a tube in the plug mill of 9.87 inches outside diameter by .50 inch wall and then expanded into a 12% inch diameter tube by .375 inch wall; or the push bench tube blank may be made 18 feet 0 inches long, formed in the plug mill to a tube 9.45 inches outside diameter by a .29 inch wall and then expanded to a tube 10% inches outside diameter by .250 inch wall. In each of the above examples the tube length as it leaves the plug mill will be approximately 54 feet long so as to give a finished length of 50 feet.

We have referred herein to the use of a metal billet. It will be understood, however, that if desired an ingot or other metal body might be employed.

While we have illustrated and described a present preferred embodiment of the invention, it will be understood that the invention is not thus limited but may be otherwise embodied or practiced within the scope of the following claims.

We claim:

1. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thereby to form a tube blank, and thereafter further elongating and expanding the blank.

2. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thereconsisting in forming a bottle from a metal body,

placing the same on a mandrel and pushing it through dies to thin and elongate it, thereby to form a tube blank, passing the blank between rolls to further thin and elongate it, and thereafter expanding the blank.

4. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thereby to form a tube blank, acting on the blank to simultaneously thin the wall and elongate the blank, and thereafter acting on the blank to simultaneously thin the wall and enlarge the tube diameter.

5. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thus forming a tube blank, removing the ends of the blank, and thereafter elongating and expanding the blank. 7

6. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thereby to form a tube blank, thereafter further elongating and expanding the blank, and reheating the metal body subsequent to its passage through the dies.

'7. In the method of making tubes, the steps consisting in forming a bottle from a metal body, placing the same on a mandrel and pushing it through dies to thin and elongate it, thus forming a tube blank which is relatively short and thick-walled, removing such blank from the mandrel, and thereafter thinning the wall, elongating the blank and expanding the diameter thereof.

8. In the method of making tubes, the steps consisting in forming bottles from metal bodies, placing the same on mandrels and pushing them through dies to thin and elongate the bottles, thus forming a series of tube blanks of substantially the same size, and thereafter elongating the blanks and expanding the same to form tubes of different sizes.

- 9. Apparatus for the manufacture of tubes comprising a push bench, a mill having tube engaging rolls adapted to elongate a tube blank formed on the push bench, an expanding mill for enlarging the diameter of the tube, and tube conveying means between the push bench and said mills.

10. Apparatus for the manufacture of tubes comprising a push bench, a mill having tube engaging rolls adapted to elongate a tube blank formed on the push bench, an expanding mill for enlarging the diameter of the tube, tube conveying means between the push bench and said mills, and heating means interposed between the push bench and a mill.

11. Apparatus for the manufacture of tubes comprising a push bench, a mill having tube engaging rolls' adapted to elongate a tube blank formed on the push bench, an expanding mill for enlarging the diameter of the tube, tube conveying means between the push bench and said mills, and a furnace interposed in at least one of the conveying means.

12. Apparatus for the manufacture of tubes comprising a push bench, a plug mill adapted to elongate a tube formed on the push bench, an

CARL W. LITTLER. FREDERICK E. FIEGER.

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