February 2022 Volume 4

MATERIALS

Forging Aluminum & Titanium – FAQ By Richard Polenick

How is forging aluminum (Al) and titanium (Ti) metals different from forging steels? At a basic level three elements of the forging process differ when handling Al or Ti: • Billet temperature • Die temperature • Die lubrication What Are the Details for Forging Aluminum? Aluminum alloys are classified via four-digit industry standard groups that designate chemical composition, e.g. 2618, 6061, 7075. Forging temperatures vary by the alloy group. Aluminum forges at lower temperatures than steels in the range of 600-900 degrees Fahrenheit. However, the hot working temperature ranges for individual alloys are much tighter with some alloys requiring a high to low limit of less than 100 degrees Fahrenheit. Flow stress or the forging force applied to deform a given alloy varies greatly with temperature making control of billet heating critical.

affects the properties of the forging. There are industry references for understanding die temperatures vs. alloy type. Various heating methods are used to maintain proper die temps dependent upon the forge process. Lubrication for forging aluminum is the third critical aspect. Die lubes must overcome friction to enable metal flow, resist the temperatures and pressures of the process, and not foul the surfaces of the forging or the die. These specialized lubricants vary by the type of forging process and their composition may be proprietary to the lube supplier or the forge user. Generally, they are graphite based with special additives and may be mixed in solution with oils or water. Application methods can be very automated and controlled or simply hand applied.

Aluminum forgings | Photo: CSF Forge

So How is Forging TitaniumDifferent from Aluminum?

Aluminum aerospace forging | Photo: CSF Forge Die steels for closed-die forging of aluminum are the same as those used for steels. The hardness levels specified for tooling may be lower due to the lower forces required. But there is always the trade-off of lower hardness that increases the opportunity for wear of the die impression. Optimum die hardness may require monitoring to achieve a good balance of properties. Of greater importance is die temperature. Aluminum forging requires dies to be heated and maintained to specific temperature ranges that enable process consistency. These temperatures are dependent on the type of forge equipment used. Hammers can employ lower die temps while mechanical and screw presses are in the middle ranges. Hydraulic presses that are slow in applying forces require higher die temps close to the temperature of the incoming aluminum stock. This is due to the extended contact time with the stock and how that contact

Titanium forging | Photo: CSF Forge

FIA MAGAZINE | FEBRUARY 2022 34