Forgings are stronger. Casting cannot obtain the strengthening effects of hot and cold working. Forging surpasses casting in predictable strength properties – producing superior strength that is assured, part to part. Forging refines defects from cast ingots or continuous cast bars. A casting has neither grain flow nor directional strength and the process cannot prevent the formation of certain metallurgical defects. Pre-working forge stock produces a grain flow oriented in directions requiring maximum strength. Dendritic structures, alloy segregation, and like imperfections are refined in forging.
Forgings are more reliable, and less costly. Casting defects occur in a variety of forms. Because hot working refines grain patterns and imparts high strength, ductility, and resistance properties, forged products are more reliable. And they are manufactured without the added costs for tighter process controls and inspection that are required for casting. Forgings offer a better response to heat treatment. Castings require close control of melting and cooling processes because alloy segregation may occur. This results in a non-uniform heat treatment response that can affect the straightness of finished parts.
Forgings respond more predictably to heat treatment and offer better dimensional stability. Forgings’ flexible, cost-effective production adapts to demand. Some castings, such as special performance castings, require expensive materials and process controls, and longer lead times. Open-die and ring rolling are examples of forging processes that adapt to various production run lengths and enable shortened lead times.