US1437690A - Tubular forging and process for making the same - Google Patents

Description

J. MCF. SYLVESTER.

TUBULAR FORGING AND PROCESS FOR MAKING THE SAME.

APPLICATlON FILED AUG. 12 I920.

1,437,690, Patented Dec. 5, 1922.

l atented llleci 5, i922.

STATES" ear star oral-ice,

JOHN MGFALL SYLVESTER, OF ROSEMQNT, PENNSYLVANIA, ASSIGNOR TO BETHLEHEM STEEL COMPANY, 0E BETHLEHEM, PENNSYLVANIA, A CORPORATION OF PENNSYL- VANIA.

TU -IBULAR FORGING AND PRQCESS FOR MAKING THE SMEE.

Application filed Augnstm, 1920. Serial No. 402,957.

T 0 all whom it may concern Be it known that l, vEs'rEn, a citizen of the United States, and residing at Rosemont, Lehigh County. State .of Pennsylvania, have invented certain new and useful Improvements in Tubular Forgings and Processes for Making the Same, of which the following is a specification.

My invention relates to an improved process of making tubular steel forgingsof large diameter with relatively thin walls and to the article produced thereby. It has reference particularly to the manufacture of tubular forgings used in making air-flasks for naval torpedoes.

. My invention finds its particular value and utility in the production of large tubular steel torgings with relatively thin walls having an outside diameter of at least 18 inches and a length of not less than six feet. it will be described with special reference to themanui acture of a 21 naval torpedo airflask forging which forgings have an outside diameter of about 22 inches and a length of about 13 feet and walls approximately 23 thick.

in the processes heretofore employed for the manufacture of naval torpedo air-flask iorgings, considerable loss waste of maresults. one of such prior process a cylindrical steel i et is cast and er certain parts are cu to remove elective material produced in casting, got is bored longitudinally of its axis he resultant tubular o is forged v orlzed in sections he er or press. ctions being heated to each for;- operation. The finished for ng is then ii machined to the required dimensions. case of a 21" naval torpedo air lash this process results in the producugh machined weighing lbs. irom an original ingot weigaing ap roximately 22,500 lbs. or a net yield in finished product of only 12% of the original weight or material employed.

4 solar steel ingot is cast and rol In another process a re b led into form of a rectangular plate which, after certain parts are discarded. is sheared into two portions, each of which is then cross-relied into an approximately square plate. roin each of these plates a cir ular blan is cut and such lanlrs are then dished or and drawn JOHN MCFALL Syn must be subjected.

- considerable scale finds its way into the finforging. lln order to cup the circular blanks and draw them into final form, this process requires repeated passage of the blanks through dies and the use of punches of different diameter in the various passes. Approximately eleven passes are necessary, and repeated reheating of the forging is also required. In the case of 21" naval air-flask forgings this process has been found to result in the production of two forgings of 2700 lbs. each roman original ingot of approximately 34,000 lbs, or a net yield oi only about 16%.

In both of the processes above described much loss of material therefore occurs by the fact that portions of the ingot or blank must be bored or cut away causing unavoidable loss of material and further loss is occasioned by the formation. of scale during the repeated beatings to which the forging 7 Such scale must be removed to obtain aperiect product which is difiiculu; to accomplish where numerous reheatings are necessary with "the result that islied product causing the formation of forgings which are defective and lack uniformity. Furthermore, defects such as spurs. cold shuts, laps etc. are common in forgings produced in the hammer or press 8 forging process. while laminations common in forginggs produced the rolling process. And addition to foregoing defects, it is found that necessary in prior processes, reases the percentage of unacceptable precinct on count of overheating or underheating which are apt to occur and in general by working the metal improper teinoeratures.

By the process my invention no cutting" g5 away of the metal is necessary. material usually discarded fro ingot and only a limitd'nv beatings is required. with a forging of a. given duced from a much maller in."

than is possible with former processes referred to. By my process l obtain in the case of a 21 n air-flask forging, a finished to ing approximet iy 2700 lbs. fr weighing 10.500 ibs, which a net yield of approximately as m ingots may be employed to produce forgings of a given weight.

Furthermore, it has been found that tubular forgings produced according to my invention possess few if any of the defects due to the presence of scale and that they are uniformly free from defects such as spurs. cold shuts, laps and 'laminations. And in addition to being free from such defects, these forgings, as will later appear, possess qualities much superior to those produced by former processes.

in the drawings accompanying this specification and forming a part thereof, 1 have illustrated in a diagrammatic way the opera tions involved in producing a torpedo airflask forging according to my improved process.

Referring to the drawings in detail:

Figure 1 illustrates an ingot of metal from which the forging is to bemade;

Figure 2 shows the ingot with the upper portion of the same cut away to eliminate defective material;

Figure 3 illustrates diagrammatically the operation of upsetting the ingot;

Figure l villustrates in a more or less diagrammatic way the operation of partially piercing the ingot igure 5 is a diagrammatic View showing a step in the operations of drawing the ingot after it has been subjected to the operations previously referred to; and

Figure 6 is a view similar to Figure 5 illustrating a further step in the drawing operation.

In the practice of my invention as applied to the production of a naval torpedo airfiask forging, I first cast a steel ingot from metal having approximately the following chemical composition:

0 Mn. P. s. Ni. 0:. Si.

25 to 55 .15 to .so% 415% 04% 1.0 m 3.0 .60 m 2.0 20

In producing air-flask forgings of the kind mentioned, it is necessary to cast an ingot approximately 30" in diameter and weighing approximately 10,500 pounds, and I prefer to use for that urpose an iron mold. 'Heretofore, cylin rical ingots of more than 20" in diameter have never been cast in an: iron mold and it has been thought impracticable or impossible to cast ingots of that size in such a mold. However, I have found that this can be done by pouring the metal at a slow rate and by em ployin molds having extremely thick walls at the% ottom, tapering to thinner walls at the top and by using a stool having a deep concave portion. Cylindrical in ots so cast are particularly adapted fort e subsequent operationsof my process. The term :nasaeeo cylindrical as used herein is intended to include ingots having a slight taper as well as those of true cylindrical form.

In practicing my invention ingots may be used in which the exterior surface is provided with flutes or corrugations but forgin s made from such ingots are not as satisfactory as those made from cylindrical ingots. lhis is due to the fact that in the upsetting and piercing operations hereinafter described difiiculty is experienced in filling out the die. The metal at the root of the corrugationsis thus worked less than other portionswhich results in lack of uniformity in the metal of the forging. ingots cast in sand or in sand-lined molds also may be em loyed but such ingots are apt to "be contaminated by the presence of sand cylindrical ingot B as shown in Figure 2 of.

the drawing.

After the discard is cut therefrom the ingot B is reheated to a temperature from 900 C. to 1200 C. and it is then placed in a die illustrated at C in Figure 3 which'is somewhat larger in diameter than the diameter of the ingot as will appear from the dotted lines in said figure, such dotted linesrepresenting the size of the ingot before further treatment. The inner wall of the die. while approximately cylindrical in shape tapers slightly, thegreater diameter being at the top. While in the die C the ingot is compressed or upset by means. of a flat punch D which is operated from any suitable source of power such as a hydraulic press. The diameter of the punch 1) is slightly less than the top diameter of the die. understood that after the upsetting operation is completed the ingot is enlarged radially so that it assumes the shape of the die C as shown by the solid lines in said Figure 3. This upsetting operation refines and compresses and densifies the metal to a considerable extent and improvesits structure so that in the subsequent operations of drawing the metal, the development ofdefects on the surface of the forging is largely prevented. While the ingot is still confined in the die C and preferably without being reheated, it is partially pierced by a piercing punch E as diagrammatically illustrated in Figure 4 of the drawing, this punch being slightly It will be 4 aasaeeo tapered. lhe punch E is also operated by a hydraulic press or from any other suitable source of power. The ingot is pierced to such a depth as to leave a bottom disc F in the ingot of sufiicient thickness to withstand the pressure exerted thereon by the drawing punch during the drawing operations hereinafter described;

' The operation of piercing the ingot causes the metal to flow in a direction generally opposite to the direction of travel of the punch as shown at G in Figure l, and in addition to partially piercing the ingot, this operationi'urther works the inner and outer surfaces of the pierced ingot and also ma terially compresses, works and refines the crystalline structure of the metal throughout the ingot.

The operation of piercing the ingot produces what will hereinafter be termed a cupped blank, this blank in the case of air-flask forgings having an internal diameter or" approximately 16 and a cylindrical wall approximately 6 thick.

lhe cupped blank is now removed from the die slightly reheated, preferably to a temperature from 900 to 1200 C. and is placed on a punch H of a draw bench diagrammatically illustrated in Figure 5 of the drawing. The cradle of the draw bench has three or four circular dies I centered on the path of the axis of the punch H, each successwe die being of smaller diameter than i the preceding one. In the case of air-flask Gill forgings, the stroke of the punch should be approximately 35 feet. The cupped blank is passed through all the dies of the series, each die in turn reducing the overall diameter of the blank. .The blank is again slightly reheated and given a pass through a second set of circular dies of smaller diameter than those of the first set and after .being again reheated, it is passed through a third set of dies smaller in diameter than those of the second set. Each successive die in the second and third sets is also preferably smaller than the preceding die.

A single draw punch H may be used for the three sets 0 dies, this punch being slightly tapered to facilitate stripping and the diameter and taper thereof being substantially the same as the taper and diameterof the piercing punch E heretofore described. The draw punch is preferably provided with means tor stripping the blank from the punch and the. blank is stripped after each drawing operation. After the third pass through the drawing dies, the bottom disc F is discarded and the resulting tube is'rough machined to the required dimensions, giving as heretofore noted, a rough machined 21 naval torpedo air-flask forging weighing approximatel 2700 lbs. from an ingot weighing. 10,500 1 s. or a net yield of approximately 26%.

rI-r y During the foregoing drawing operations the cylindrical wall or" the blank, in the case of torpedo air-fiask torgings, is-re-- to the art. These operations result in working the metal so that the same is compressed and refined and densified throughout resulting in a forging having a uniform grain and a compact, V homogeneous structure throughout, and which. is practically free from the defects found in. iorgings produced by rior processes. My process therefore resu ts in a superior product and at the same time requires less metal to produce a forging of a given weight.

flask 'forgings are exceedingly rigid and heretofore great difiiculty has been experienced by manufacturers in producingforgings of sufficient strength and uniformity] of structure to meet such requirements, A very high percentage of such forgings have heretofore been rejected by the Government because of their failure to meet the standard required. With my process such diliiculty is practically obviated. The forgings made by this process possess properties which fully meet the Government requirements and practically one hundred per cent of the forgings thus made are found to be acceptable.

While the invention has been described with special reference to the production of naval torpedo air-flask forgings. it is obviously applicable for the production of large size tubular forgings for any purpose and it is not therefore intended to limit the inlhe requirements for naval-torpedo airinc vention to forgings adapted for use as airfiasks for torpedoes.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is: p

1. A process of making torpedo air flask forgings which consists of the following operations substantially, as described, upsetting a cylindrical ingot in a confining die, partially piercing said ingot to form a cupped blank,drawing said blank through a series of dies, thereby reducing its overall diameter, all of said operations being performed while the metal is in a heated condition.

2. A process of making naval torpedo air flask forgingsconsisting in confining a solid cylindrical ingot of, steel in a die closely surrounding the same, forcing a plunger into ice said die to partially pierce the ingot and form acupped blank and drawing said blank through order dies to elongate the same.

3. A torpedo air flask forging made by casting a cylindrical ingot, partially piercing the same to form a blank and drawlng the blank through a series of dies to reduce its overall diameter.

4. A torpedo air flask forging made by upsetting a cylindrical ingot in a. confining die, partially piercing the ingot to form a got to form a cupped blank and drawing the blank through a series of dies to reduce its overall diameter.

In testimony whereof I afiix my signature.

JOHN llIoFALL SYLVESTER.

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