Manufacturing: Metal Forming

Sheetmetal Forming - Superplastic Forming

The superplastic forming (SPF) operation is based on the fact that some alloys can be slowly stretched well beyond their normal limitations at elevated temperatures. The higher temperatures mean the flow stress of the sheet material is much lower than at normal temps. This characteristic allows very deep forming methods to be used that would normally rupture parts. Superplastic alloys can be stretched at higher temperatures by several times of their initial length without breaking. Superplastic forming can produce complex shapes with stiffening rims and other structural features as well.

The process begins by placing the sheet to be formed in an appropriate SPF die, which can have a simple to complex geometry, representative of the final part to be produced. The sheet and tooling are heated and then a gas pressure is applied, which plastically deforms the sheet into the shape of the die cavity.

Process Advantages --

• Reduced weight for high fuel efficiency
• Improved structural performance
• Increased metal formability and part complexity
• Near net shape forming of complex shapes reduces part count
• Cost/weight savings
• Low-cost tooling
• Low environmental impacts - non-lead die lubes, low noise

Materials used -

1. Titanium alloys
2. Aluminum alloys
3. Bismuth-tin alloys
4. Zinc-aluminum alloys
5. Stainless steel
6. Aluminum-lithium alloys