Hot Metal Gas Forming
Hot Metal Gas Forming was the title of a NIST sponsored proposal that was originally drafted by Temper. The Hot Metal Gas Forming (HMGF) process was developed as part of a 7.0 million dollar, multi-company collaboration effort, to develop an inexpensive alternative to tubular hydroforming. In this program an automated process setup was developed to demonstrate the rapid cycle and low cost capabilities of the process.
Hot Metal Gas Forming (HMGF) is an outgrowth of superplastic forming (SPF) and hot blow forming (HBF) techniques that the aerospace industry developed to form aluminum and titanium structures. In its most basic sense, a preformed tube is placed into a HMGF forming die. The part is directly heated via induction heating, to a temperature typically in the 90 to 95% of its melting temperature, and is internally pressurized with gas pressure forcing the walls of the tubing to expand to meet the walls of the die cavity. The process was demonstrated in a prototype production forming workcell with process cycle times of 38 seconds for aluminum and 43 seconds for steel, using the same die, with less than a 5 minute change over.
In addition, because of the quenching capabilities demonstrated from the NIST program, aluminum parts can be age hardened to a true T-6 hardness and steel components were actually able to achieve a bainite structure in the as formed condition.
Although the process was highly successful, the design architecture of the light vehicle market changed and became highly sensitive to weight in the 2000's and the process did not find a mass market.
You can read more about the process here on wikipedia.
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