12 Foot Titanium Bars Heat Treated

Solar Atmospheres Inc, in greater Philadelphia, heat treated three 12 foot long 6Al4V titanium bars in its new VFS model HL 84 vacuum furnace.  The challenge was to keep the 8 1/2″ diameter bars straight while processing with a homogenizing temperature of 1975°F and a solution annealing temperature of 1750°F in one process cycle.  The bars were cooled at 2-bar pressure with helium gas to simulate a water-quenched condition.  The vacuum condition during the heat treating was 10-5 Torr.  The specification called for less than .050″ deviation over the length of the bars.

Not only was the straightness specification met, but also the bars were shipped nick free and were very bright and clean after processing. This condition was imperative to the customer since the bars were forged, rolled and machined to size, to meet military defense requirements.

According to Bob Hill, Vice President of Heat Treating, “The key was a support system for the bars that were continuous and very flat.” Solar was able to accomplish this with 2″ ground flat graphite plates supporting the length of the three bars.  A specific interface layer of ceramic fiber was interposed between the titanium bars and the graphite plate, by Solar engineers, to prevent formation of carbon compounds on the surface of the titanium.