1、i5 i The Aluminum Associatiun $30.00 Aluminum Forging Design Manual o The IncofccrJlea Aluminum Association ABOUT THE COVER Top left: aluminum auto forgings and the 1995 Lincoln Continental (photo courtesy of Ford Motor Company); left: aircraft forgings and the Boeing 737-400 Jet Airplane (photo cou
2、rtesy of Boeing Company). Published by The Forgings it was also among the earliest fabricating techniques applied to aluminum. But the greatest advances of aluminum forging technology occurred with the development of modem aircraft. The demands of aeronautics for lightweight, high-strength component
3、s with complex configurations led to the rapid growth and great sophistication of the alu- minum-forging art. This, in turn, resulted in greater use of aluminum forgings in a remarkably wide num- ber of applications-in fields far removed from the aircraft industry. The scope of the aluminum industry
4、s research and development activities in metallurgy and forging technology is substantial-it reflects more than a half- century of forging experience and vastly expanded production facilities. This book is intended as a general guide to the solution of design and production problems. The Aluminum As
5、sociation is, of course, aware that no book can provide special or specific answers to all forging problems. As performance requirements vary widely, the design and details used for a specific prod- uct can only be determined through consultation with a forging specialist. And, while forging special
6、ists can and should be consulted at any stage of component design or development, ideally this assistance can be of greatest benefit during the conceptual or early plan- ning stages. Tolerance data shown herein were developed pri- marily by historical empirical evolution. Today, statis- tical proces
7、s control techniques are being utilized to help forging producers better understand the true capa- bilities of their processes. At the same time, customers are demanding higher and higher ratios of tolerance to capability (Cpk). The result of these two actions should be the development of realistic
8、tolerance under- standing that better satisfies the producers capability and the users requirements. With this in minci, the authors would anticipate changes to some of the infor- mation contained in this document in the near future. Die Forging Design Hand Forgings and forgings are sometimes called
9、 open die forgings-as the name suggests, the metal is not confined laterally when being forged to ired shape. The forger manipulates the stock between repeated squeezes of the hydraulic press, or ring roller or blows of the hammer in progressively shaping the forging to the desired form. Hand forg-
10、ings are not discussed in this manual. ses on the more common forg- ing type, die forgings-sometimes also called closed die forgings. These forgings receive their accurate and uniform shape from a hammering or pressing of the forging stock into counterpart cavi- ties or impressions machined into a s
11、et of dies. ings includes Hammers-typically hammers rely on repeated blows in the die cavity to shape the part. The metal progres- sively adapts to its desired configuration with each blow. Hydraulic Presses-rely on forces generated by one or more hydraulic rams forcing the dies together. These pres
12、ses move metal by a slower squeezing action rather than by a sharp blow. Mechanical Presses-denve their force from the ener- gy stored in a rotating flywheel, Coupled through a clutch this energy is imparted to the dies each time the press is activated. Like hydraulic presses, usually a com- plete f
13、orging operation is completed with each stroke. The primary equipment used to make die forg- Figure 1. This rib is 100 in. long and weighs 350 Ibs. in alloy 7075. Figure 2. Aircraft landing gear beam 184 in. long and weighs 2280 Ibs. in alloy 7050. 3 Figures 3a, 3b, and 3c. These three forgings are
14、typical medium to large aircraft frame parts in alloy 7075 and vary in weight and size. Upsetters-are basically double acting mechanical presses in a horizontal plane. The force from the fly- wheel is directed, through a clutch, to the workpiece gripped between dies and deformed by a punch that exer
15、ts force on the end of the workpiece. Forging design, forging tolerances, quantities required, and alloy selected must all be considered in determining the best and most economical equipment to use in making a specific part. Die Forging Types Die forgings are broadly classed as blocker-type, fin- is
16、h only, conventional and precision. Other classifica- tion may be encountered such as close tolerance, low draft and near net shape forgings. These latter types are designed with the customer and forging supplier working together. A forging encompassing all three categories, close tolerance, low, dr
17、aft and near net shape, is shown in Figure 9. A comparison of closed die forging types and theoretical example of a forging processed through different types of forging is included in the appendix, Tables A and B. Other, more special die forgings are those of can or tube-type, impacts and no-drafts.
18、 These special types are illustrated but their design cri- teria are not discussed in this manual. Blocker-Type Forgings A blocker-type forging is generously designed, with large fillet and comer radii and with thick webs and ribs, so that it can be produced in a set of finish dies only. Producing s
19、uch a forging may typically require a unit pressure of 1 O to 15 tons per square inch of pro- jected plan area, depending on the alloy and the com- plexity of the design. Greater pressures are required to make a more inticate forging. The projected plan area of the forging is used to arrive at the e
20、stimated total tonnage required. A blocker-type forging generally requires machining on all surfaces. Economics may dictate such a design if quantity requirements are limited or if the finished part tolerances necessitate compIete machining. A blocker-type forging is an end product and should not be
21、 confused with a blocker forging, which is a preliminary shape requiring a subsequent finishing die operation to attain its final shape. Figs. 1,2,3a, 3b and 3c illustrate typical blocker-type forg- ings varying from small to very large. Finish Only Forgings Finish only forgings require more than on
22、e pass through the press; depending on the complexity of the forging, successive passes are required to reduce the starting stock to the necessary configuration. If the quantity of forgings is low or prototype forgings are intended, finish only forgings can be designed. This type of forging utilizes
23、 one set of dies with the design being a cross between a blocker type and conventional design. The major difference, over a blocker type, being a decrease in the web thickness, reduced fillet and corner radii and also a reduction in some tolerances. the cycle of a conventional die; due to the proces
24、sing of the forging between heats, this causes a high degree of die wear and also high die stress. Conventional Forgings Most common of all die forging types, a conventional forging is more intricate in configuration than a blocker-type forging, having proportionately lighter sections, sharper detai
25、ls and tighter tolerances, and thus is more difficult to forge. The design differences between these two types of forging are illustrated graphically in Figs. 4 and 5. A conventional forging may require 100% or less machining depending on application and/or size. A typical unit pressure of 15 to 25
26、tons per square inch of plan area is required, and usually a blocking operation is required prior to the finishing operation. Typical forgings of the conven- tional type are shown in Figs. 6,7,8 and 9. blocker-type forging has a lower die cost but will be heavier, requiring more extensive machining;
27、 a con- ventional forging has a higher die cost but will be lighter, requiring much less machining. Only a cost comparison by the customer with the forging supplier The finish only type of die may see 3 to 4 times The designer must evaluate the cost difference-a Blocker-type Forging-Requires only on
28、e die operation and a trimming and piercing operation to remove surplus metal. Conventional Forging-Requires two die operations and a trimming and piercing operation to remove surplus metal. Figure 4. Blocker-type forgings save on die and prod- uction costs although machining may be increased somewh
29、at. I I I I Y I Generous Fillets Parting Line Blocker-Type Forging Conventional-Type Forging Figure 5. These two connecting rods illustrate the usual differences between blocker-type and conventional forging designs. 5 Figure 6. Note the sharper and greater amount of detail in these conventional-typ
30、e forgings. A set of blocking or preliminary shaping dies and a set of finishing dies are necessary. This forging in 7050 alloy, weighs 400 Ibs. and is 105 in. long. Figure 7. Automotive parts showing characteristic sharp detail, close tolerance and intricate configuration of the conventional forgin
31、g process used to make these parts. . .11.1._._._._I_- I -l._.r” . I” -l-l-l-.l.” .I_” .I” -l_l_ll_._ll -. 6 Figure 8. Conventional-type forging in 7050 alloy produced this aircraft spar bulkhead that is 105 in. long and weighs 535 Ibs. (Hard hat in lower right shows scale.) can determine which type
32、 of forging will give lowest total cost. A chronological sequence of metal forming for a conventional forging is in the appendix, Table C. Precision Forgings A precision forging denotes closer-than-normal toler- ances. It may also involve a more intricate forging design than a conventional type and
33、may include smaller fillet radii, corner radii, draft angles and thin- ner webs and ribs. The higher cost of a precision forging, including increased cost of dies, must be justified by the reduced machining required for its end use. This type of forging may typically require pressures of 15 to 50 to
34、ns per square inch of plan area. Can and Tube Forgings Can- and tube-type forgings are shapes which are open at one or both ends. They are sometimes called extrud- Figure 9. Numerous and large-sized punchouts made it possible to forge thin walls in this aircraft nose-wheel truss. This unit is made o
35、f 2014 alloy has an overall length of 104 in. and weighs 133 Ibs. 7 Figures 10a and lob. On this can-type forging, the head end (at top) was rough-machined prior to heat-treating to obtain optimum mechanical properties. The slots were machined to facilitate the final machining operations. This part
36、is made of 2014-T6 alloy, weighs 199 Ibs. and is 30.5 in. long. ed forgings; the term is appropriate, as the dies may be designed to extrude the tubular walls of the forgings. They are usually produced on forging press equip- ment. The side walls may include longitudinal ribs and may be flanged at o
37、ne open end. The interior or exteri- or surfaces of the bottom wall may be configured with details normally possible in conventional forgings. Figs. 10a and lob, 55,56,57 and 58 show forgings of this type. No-Draft Forgings As suggested by the name, these are draftless forgings. Normally, a no-draft
38、 forging is the most difficult of all forgings to make because of the typically close design proportions and tolerances. They differ from precision or conventional types of forgings in the draftless fea- ture and the relatively high vertical wall height-to- width ratio, which require specialized die
39、-making and forging facilities. No-draft forgings require the least Figure 11. The ?Undesirable? parting line requires a more expensive die and the metal will not flow as easily into the deep pockets as it will with the ?Preferred? forging orientation. 8 amount of machining of any forging type, whic
40、h may offset generally higher forging and die costs. Basic Design Features discussion of forging design cannot practical- ly cover in detail all the considerations that arise from the infinite variations in size, shape and function of different specific parts. However, certain fundamentals apply in
41、all cases and it is essential, for good forging design, that they be known and adhered to. the following pages as they relate to the usual prob- lems that confront the designer. The examples cited will, for the most part, refer to relatively simple shapes. The principles involved become all the more
42、 significant with increasing complexity of design. These fundamentals are graphically presented in Parting Line The planes of separation between the upper and lower parts of a closed die set are called the parting line. It is established usually, but not always, through the maxi- mum periphery of th
43、e forged part. It may be straight or irregular. It must be designated on all forging draw- ings. Its position can measurably affect the initial cost and ultimate wear of dies, the ease of forging, the grain flow, related mechanical properties, and the machining requirements for the finished part. Th
44、e dia- grams in Figs. l l through 19 show various methods of positioning the parting line. Maximum Periphery-It is preferable to place the parting line around the largest periphery of the forg- ing. It is easier to force metal laterally in a spreading action than it is to fill deep, narrow die impre
45、ssions, as indicated in Fig. 1 1. Flat-Sided Forgings-These present an opportunity to reduce die costs, since the only machining is in the Plane surface formed by flat upper die / Contour of forging formed by impression in bottom die Figure 12. A flat surface at the parting line reduces die costs, s
46、implifies the trimming operation and die mismatch is eliminated. Direction of trimmer punch stroke A Parting Line Figure 13. A raggedly trimmed edge on the forging may result if the flash on the parting line is inclined more than 75 degrees. lower block, the upper being a completely flat surface (Fi
47、g. 12). This simplifies production by eliminating the possibility of mismatch between the upper and lower impressions. While a top die is always essential, in flat-sided designs the forge shop can use a stock or “standard” flat-top die to mate with the impression die. Obviously, there can be no inte
48、grally forged part iden- tification characters appearing on the flat surface when a standard flat-top die is used. Inclination of the Parting Line-Forgings in which the parting line is inclined to the forging plane may present difficulties in trimming if the inclination is too great. As pointed out
49、in Fig. 13, it is generally good practice to limit the inclination to no more than 75 degrees out of parallel with the forging plane, thereby avoiding raggedly trimmed edges. Parting Line Effect on Grain Flow Location of the parting line has a critical bearing on grain flow and the directional properties of the forged piece. In the forging process, excess metal flows out of the cavity into the gutter as the dies are forced togeth- er. In this flow toward the parting line, objectionable flow patterns may be created if the flow path is not smooth, as illustrated in F
