Patent Publication Number: US-4059003-A

Title: Process for producing heavy-duty high-pressure ferrous metal cup-shaped products having a cylindrical barrel

Description:
This is a continuation-in-part application of my application Ser. No. 519,044, filed Oct. 29, 1974 entitled &#34;Process For Producing Cup-Shaped Ferrous Metal Products Possessing A Cylindrical Barrel&#34; (now abandoned); and it relates to my application Ser. No. 519,043 entitled &#34;Process of Forging Large Seamless Welding Necks&#34; (now abandoned). 
    
    
     The present invention relates to large cup-shaped ferrous heavy-duty, high-pressure metal products having cylindrical barrel portions which are used on or in connection with industrial pressure vessels of various kinds, including nuclear reactors, etc. 
     There is considerable demand for cup-shaped fittings for pressure vessels, including pill boxes, welding necks and the like; all of which, in order to be acceptable, must meet certain requirements of strength, etc., as dictated by the various codes as well: as well as rigid dimensional qualities. 
     As earlier indicated among the advantages which are achieved by the use of the process of the invention is to consistently obtain cup-shaped products of the type described which are possessed of great strength very accurate dimensions, uniform wall-thickness and definitely improved metallurgical properties, due to a very substantial amount of metal-working or kneading of the metal. 
     Another advantage is that the new process permits the forge shop to use a multitude of billets and scrap of widely varying diameter and both with and without rounded corners. This results in tremendously reduced operating costs. 
     A further objective is more uniform extrusion and improved grain orientation than can be obtained by the use of prior art methods of producing heavy-duty, high-pressure cup-shaped ferrous metal products of comparable size and weight. 
    
    
     The foregoing and other objects and advantages will be more readily understood from the following description and the annexed drawings, wherein like references represent like parts, and wherein: 
     FIG. 1 is a sectional elevation of a typical product which is obtained by the practice of the process of the invention. 
     FIG. 2 is a sectional elevational view illustrating certain concentrically disposed basic forging instrumentalities which are employed in the practices of the prior art. 
     FIG. 3 is a view which is similar to that of FIG. 2 but illustrating a very undesirable situation which results from the practice of certain prior art methods represented in FIG. 2, the same being due to misalignments which are completely avoided by the new process. 
     FIGS. 4 and 5 are sectional elevations illustrating the apparatus employed at certain stages of the inventive process, in the latter of which back-extrusion is taking place. 
    
    
     It is known that in metal-working in general, and light-weight metal-working in particular, back-extrusion of the metal has been proposed for the manufacture of small rings and short sleeve-like articles for one purpose or another; such as piston rings, bearing races and the like; but to what extent, and with what degree of success, is not known. 
     According to one of the prior art methods of back-extruding to obtain an article having a cylindrical wall, a heated billet is placed in a vertically disposed cylindrical die with a temporarily closed bottom and a round punch moves downwardly on it until the height of the billet is decreased and the metal thereof is forced outwardly into full contact with the adjacent surfaces of the interior of the cylindrical die. A second round punch of smaller diameter than the first is then forced downwardly onto the top of the heated billet, causing the metal thereof to move upwardly between the periphery of the second round punch (of smaller diameter) and the sidewall of the circular forging die. This back-extrusion of the metal of the heated billet is accompanied by a strong tendency on the part of the cylindrical die to move upwardly therewith; and it is therefore essential that the cylindrical forging die be strongly bolted down to the bed of the forging press or machine. 
     During these steps the bottom of the die is constituted by a circular forging knife or shearing ring which closely surrounds a centrally disposed round metallic plate; both the circular forging knife and the central round metallic plate being supported from below and solidly backed by a retractable metallic disc. 
     However, it is believed that such practices are non-analogous to the present invention not only in the matter of industrial environment and vast disparity in sizes, etc. but also due to a very important difference in the manner in which the metal is worked during the back-extrusion itself, and the manner in which the billet or work-piece and the handling instrumentalities therefor are manipulated; all of which will be more fully described hereinafter. 
     In my aforementioned copending patent application Ser. No. 519,043 entitled &#34;Process For Forging Large Seamless Welding Necks&#34;, which is related to the present application, the end products are characteristically of very substantial size and weight, comprising, as illustrative embodiments, a manhole size with long barrels weighing approximately 1083 pounds, and, later on in the Specification a Type H Neck for which the starting solid billet or work-piece weighed 2,044 pounds. Wall thicknesses of 3 inches and more are very frequently the case and quite often run to 8 inches or so. 
     Industrial pill boxes contemplated by the present invention would rarely be under 8 inches in diameter and rarely weigh less than 500 pounds. 
     The present invention involves starting billets and end products of similar size and weight, or smaller or larger, as the circumstances require. 
     Referring more particularly to the drawings, the numeral 1 designates the cylindrical female forging die element having a bore of predetermined length and diameter, and at the bottom of which there is a removable metal disc or round plate 3. 
     The heated work-piece 5 which is placed in the die cavity of the cylindrical female forging die member 1 is a billet of ferrous metal which according to the invention may be square, square with rounded edges, or round; and of lesser diameter than the diameter of the die cavity. 
     Accordingly, it will be appreciated by those skilled in the art that the process may readily utilize many of the scrap pieces which are found in or nearby the forge shop which are not marketable due to dimensional shortcomings or are otherwise not utilizeable except as scrap; thereby tremendously reducing operating costs. 
     Next, there is placed on top of the heated work-piece 5 an annular metal-working and metal-displacing ring 22 having an external diameter which is slightly less than the bore of the cylindrical female die member 1 and within this annular metal-working and metal-displacing ring there is positioned a metal working and metal-displacing disc 11 which is fairly closely fitting, and of the same thickness, which may be 3 inches, for example. 
     Disposed atop both the annular metal-displacing ring 22 and the metal-working and metal-displacing disc 11 is a conventional round forging press follower 23 of a diameter which is less than the diameter of the bore or forging die cavity of the cylindrical female die member 1 but sufficient to adequately cover both the annular metal-working and metal-displacing ring 22 and the metal-working and metal-displacing disc 11. 
     When the vertically movable upper member, or platen, of the forging press is moved downwardly, the follower 23, which is of slightly lesser diameter than the bore of the cylindrical female forging die member 1, exerts downward forging pressure of tremendous magnitude on both the annular metal-working and metal-displacing ring 22 and the metal-working and metal-displacing disc 11; and as they both continue to descend, the metal of the billet or work-piece spreads out and its entire periphery contacts the wall of the die cavity of the cylindrical female forging die member 1. 
     The annular metal-working and metal-displacing ring 22, in its metal-working and metal-displacing capacity besides serving to permit the use of billets of much smaller diameter than would otherwise be the case since its periphery very closely approaches the interior surface of the cylindrical female forging die member 1, serves as an accurate centering guide on its inner wall for the periphery of the metal-working and metal-displacing disc 11. 
     When the metal-working and metal-displacing disc 11 and annular metal-working and metal-displacing ring 22 have been forced downwardly to the point where metal being forged has made full contact with the inner surface of the cylindrical female forging die member 1, the downward movement of the upper and vertically movable platen of the forging press is arrested. 
     This distance is indicated in the drawings at X in FIG. 4. 
     When the immediately aforementioned position has been reached the initial round forging press follower 23 is removed, and replaced by a second round follower 24 of a diameter which is slightly less than the internal diameter of the annular metal-working and metal-displacing ring 22. 
     By this arrangement, the annular metal-working and metal-displacing ring 22 serves as an accurate centering guide for the second round follower 24 of smaller diameter which now rests directly upon the metal-working and metal-displacing disc 11. 
     At this point, the annular metal-working and metal-displacing ring 22 has completely served its metal-working and metal-displacing function. 
     As the second round follower 24 moves downwardly by the action of the forging press, the metal-working and metal-displacing disc 11 presses downwardly on the top of the billet therebelow, now independently of the annular metal-working and metal-displacing disc 11. In this manner the metal of the heated billet is displaced upwardly in the cylindrical female forging die member 1 and between its sidewall and the periphery of the annular metal-working and metal-displacing disc 11 which is concentric therewith. 
     The downward movement of the platen of the forging press and second round follower are discontinued at the point where the metal of the heated work-piece 5 is a minimum distance of approximately 3 inches from the bottom of the die cavity of the cylindrical female forging die member 1, as determined by the position of the metal-working and metal-displacing disc 11 with respect to the underlying removable round disc or bottom closure 3 of the cylindrical female forging die member 1. 
     The reason for providing for an approximate 3-inch or greater thickness of metal below the metal-working and metal-displacing disc at its designated lowermost point of operation in the bottom of the cylindrical female forging die member during the back-extrusion step as described is that as the metal from inside the billet or work-piece is being displaced, it must move to the outside, and reverse its general direction of movement upwardly between the periphery of the metal-working and metal-displacing disc and the adjacent surface of the sidewall of the cylindrical female forging die member and this thickness is believed minimal. 
     Such a thickness (approximately 3 inches or more) of metal below the metal-working and metal-displacing disc 11 will involve the following minimum weight as related to the diameter of the cylindrical barrel of the cup-shaped product: 
     
         ______________________________________                                    
                Weight of Metal Below the                                 
                Metal-working and                                         
Diameter of Cylindrical                                                   
                Metal-Displacing Disc at                                  
Barrel          Three-Inch Thickness                                      
______________________________________                                    
14 inches       122 lbs.                                                  
16 inches       182 lbs.                                                  
18 inches       204 lbs.                                                  
20 inches       254 lbs.                                                  
24 inches       369 lbs.                                                  
______________________________________                                    
 
    
     and, of course, is reflected in the weight of the metal displacement disc 11 which should, in any event be at least 11/2 inches in thickness and preferably considerably more. 
     Because of the necessity of regulating the process of the invention in order to provide the minimum 3-inch metal displacement described, and to utilize a metal-working and metal-displacing disc of comparable size and weight, it is only applicable to the manufacture of heavy-duty, high-pressure resistant ferrous metal cup-shaped industrial articles of very substantial size and weight, such as are used for Pill Boxes in connection with heat exchange apparatus, the end product of which may weigh anywhere between at least several hundred pounds and several thousand pounds. 
     The product shown in FIG. 1, with the metal-working and metal-displacing disc 11 still in place, possesses a circular interior cavity A of desired diameter; with corresponding regulated side-wall of uniform wall-thickness B. The height of the product plus the thickness of the metal-working and metal-displacing disc 11 is indicated at D and the thickness of the bottom of the product minus the thickness of the metal displacement disc 11 is indicated at C. 
     From the foregoing, it will be perceived that the annular metal-working and metal-displacing ring 22 is very essential to the practice of the process of the invention serving as it does to not only permit the processing or metal-working of billets having much lesser diameter than otherwise be the case, but also to 
     1. accurately center the position of the metal-working and metal-displacing disc 11 on the top of the billet 
     2. together with the metal-working and metal-displacing disc, in compressing the billet until it makes full contact with the sidewall of the cylindrical female forging die member and 
     3. accurately center and second round follower 24 (of smaller diameter). 
     As long known to those who are skilled in the art of back extrusion, with the use of a cylindrical female forging die member 1 there is inescapably bound to be a tendency on the part of said die member to move upwardly with respect to the work-piece; and there are numerous well-known ways of eliminating this problem, such, for example, as the use of a stationary circular integrally-formed ledge on the bottom of the wall of the cylindrical female forging die member which protrudes slightly into the mold cavity, and various hold-down means on the exterior of the cylindrical female forging die member such as bolt and nut arrangements and the like. The present invention is not limited in any way to a particular back-extrusion hold-down means; and accordingly none is described herein nor illustrated in the drawings. 
     The term &#34;metal-displacing&#34; is used herein in conformity with its well-recognized meaning in the metal-working arts as indicating compression of the metal such as will change the cross-sectional area thereof.