4

TABLE 9.25 (Continued)

Source: Aluminum Association [5].

© When separately forged coupons are used to verify acceptability of forgings in the indicated thicknesses, the properties shown for thicknesses "Up thru 1 inch," including the test coupon elongation, apply.

© As-forged thickness. When forgings are machined prior to heat treatment, the properties will also apply to the machined heat treat thickness, provided the machined thickness is not less than one-half the original (as-forged thickness). © D equals specimen diameter.

© Properties of Hill and HI 12 temper forgings are dependent on the equivalent cold work in the forgings. The properties listed should be attainable in any forging within the prescribed thickness range and may be considerably exceeded in some cases.

© For information only: The Brinell Hardness is usually measured on the surface of a heat-treated forging using a 500 kg load and a 10-mm penetrator ball. © The database and criteria upon which these mechanical property limits are established are outlined elsewhere.

© Material in this temper, 0.750 in. and thicker, when tested in accordance with ASTM G47 in the short transverse direction at a stress level of 75 percent of the specified minimum yield strength, will exhibit no evidence of stress corrosion cracking. Capability of individual lots to resist stress corrosion is determined by testing the previously selected tensile test sample in accordance with the applicable lot acceptance criteria outlined elsewhere. © T74 type tempers, although not previously registered, have appeared in the literature and in some specifications as T736 type tempers. © Material in this temper when tested at any plane in accordance with ASTM G34-72 will exhibit exfoliation less than that shown in Category B, Figure 2 of ASTM G34-72. Also, material, 0.750 in. and thicker, when tested in accordance with ASTM G47 in the short transverse direction at a stress level of 35 ksi, will exhibit no evidence of stress corrosion cracking. Capability of individual lots to resist exfoliation corrosion and stress corrosion cracking is determined by testing the previously selected tensile test sample in accordance with the applicable lot acceptance criteria outlined elsewhere.

© Material in this temper, 0.750 in. and thicker, when tested in accordance with ASTM G47 in the short transverse direction at a stress level of 35 Ksi, will exhibit no evidence of stress corrosion cracking. Capability of individual lots to resist stress corrosion is determined by testing the previously selected tensile test sample in accordance with the applicable lot acceptance criteria outlined elsewhere.

most sharply detailed, highest quantity type, and highest cost. Less intricate forg-ings are used when quantities are small because it is more economical to incur machining costs on each of a few pieces than to incur higher one-time die costs. The most economical forging for a particular application depends on the dimensional tolerances and quantities required.

Blocker-type forgings have large fillet and corner radii and thick webs and ribs so that only one set of dies is needed; generally two squeezes of the dies are applied to the stock. Fillets are about two times the radius of conventional forg-ings, and corner radii about 1.5 times that of conventional forgings. Usually, all surfaces must be machined after forging. Blocker-type forgings may be selected if tolerances are so tight that machining would be required in any event, or if the quantity to be produced is small (typically up to 200 units). Blocker-type forgings can range in size from small to very large.

Finish only forgings also use only one set of dies, like blocker-type forgings, but typically one more squeeze than blocker-type forgings is applied to the part. Because of the additional squeezes, the die experiences more wear than for other forging types, but the part can be forged with tighter tolerances and reduced fillet and corner radii and web thickness. Fillets are about 1.5 times the radius of conventional forgings, and corner radii about the same as that of conventional forgings. The average production quantity for finish only forgings is 500 units.

Conventional forgings are the most common of all die forging types. Conventional forgings require two to four sets of dies; the first set produces a blocker forging that is subsequently forged in finishing dies. Fillet and corner radii and web and rib thicknesses are smaller than for blocker-type or finish-only forgings. Average production quantities are 500 or more.

Precision forgings, as the name implies, are made to closer than standard tolerances and include forgings with smaller fillet and corner radii and thinner webs and ribs.

There are other ways to categorize forgings. Can and tube forgings are cylindrical shapes that are open at one or both ends; these are also called extruded forgings. The walls may have longitudinal ribs or be flanged at one open end. No-draft forg-ings require no slope on vertical walls and are the most difficult to make. Rolled ring forgings are short cylinders circumferentially rolled from a hollow section.

Die forging alloys and their mechanical properties are listed in Table 9.25. Alloys 2014, 2219, 2618, 5083, 6061, 7050, 7075, and 7178 are the most commonly used. The ASTM specification for forgings is B247 Die Forgings, Hand Forgings, and Rolled Ring Forgings.

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