3.5.3 Selecting the Optimum Forging Alloy
The material specification on a product drawing occupies a very small part of the total space. However, it is a very important part of the specification—in some cases as important as the dimensioned views.
- On the one hand, the alloy must have the ability to be forged; that is, it must be sufficiently forgeable so that the product can be manufactured. Some alloys are relatively easy to forge and may be used to make components with very intricate features. Grades that are more difficult to forge require distinct design approaches.
- On the other hand, the alloy must be able to achieve the required properties so that the product can meet service requirements.
The effects of differences in forgeability on design are described in Section 4 Characteristics of Forging Alloys. Individual forging firms are in the best position to evaluate these factors.
The forging process, particularly development of grain flow, produces significant effects on material properties. In addition, there is a wide range of available heat treatments, particularly for steel alloys. Arriving at the optimum material, processing and heat treatment from the available matrix requires a balance of product design, forging and materials expertise among the purchaser, forging engineer and material supplier.
The design engineer can usually narrow the choice to one or two of the seven groups of forging alloys. Table 3-1 gives a general overview. Additional information can be found by consulting appropriate areas of Section 4 Characteristics of Forging Alloys.
| Figure 3-7 Start of the trim and pierce operation. |  |
| Figure 3-8 Completion of the trim and pierce operation. |  |
Table 3-1 Overview of Forging Alloys
| Alloy Group | General Characteristics | Typical Applications |
| 1. Steels | Most often selected for forgings | |
| A. Carbon | Wide range of grades and properties Most grades are easily forged |
Nearly all market areas |
| B. Microalloy | Alternatives to quenched and tempered carbon steels. High strength and uniform hardness without heat treatment | Automotive, truck and off-highway |
| C. Alloy | Improved mechanical properties versus carbon steels | When carbon steels do not have the required properties |
| 1. Stainless Steels | High corrosion resistance, more difficult to for than carbon or alloy steels | Where corrosion resistance and high temperature properties are required |
| A.Ferritic | Excellent corrosion resistance, good ductility, can be worked cold or hot. | |
| B. Austenitic | Highly resistance to to acids, good toughness at cryogenic temperatures | |
| C. Martensitic | Can be hardened and tempered, are magnetic | |
| D. Special grades (e.g. PH and duplex alloys) | Combinations of high strength and corrosion resistance | |
| 3. Aluminum | Most easily forged into precise, intricate shapes, low density, generally heat treated, good corrosion resistance | Aerospace, automotive, truck, military components, sporting wear and accessories |
| 4. Copper Base | Excellent corrosion, resistance, excellent forgeability, good dimensional precision, low draft. | Leakproof fittings, plumbing fixtures, gears, bearings, pumps, value bodies, non-sparking applications |
| 5. High Temperature Alloys | Good corrosion and oxidation resistance Good high temperature properties, particularly creep low cycle fatigue |
Gas turbine components |
| 6. Titanium | High strength, low weight, high service temperatures, excellent corrosion resistance | Aerospace, chemical processing, prosthetics |
| 7. Magnesium | Low density, low modulus of elasticity, requires special handling | Where minimum weight is required at relatively low service temperatures |