Age-hardening an Aluminum Underwater Buoy Frame

TrimMaster is a full-service contract manufacturer that has been in business in Reading, PA since 1938. Their roots starting in the manufacture of thread trimming equipment for the sewn product industry, and they have branched out to serve a variety of industries. TrimMaster’s core strengths are waterjet cutting, using 5-axis equipment, CNC machining, turning, fabrication, inspection including CMM and assembly. Other on site processes includes painting, polishing and part assemblies in quantities large or small for customers.
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Metlab recently assisted TrimMaster in fabricating an aluminum frame for an underwater buoy that would meet customer specifications. Mike Allard, Sales Manager, explains “We were faced with the prospect of welding the aluminum assembly to put it together, and knew that there would be reduced strength at the weld joint. By changing the welding wire we used, we could take advantage of Metlab’s heat treating process, especially their large furnaces to accommodate these parts, to raise the strength of all weldment components to a T-6 condition, giving us the strength that we needed for the application.”

Metlab’s President, Mark Podob elaborates on the project specifics; “Before the parts were formed and welded by TrimMaster, a 6061 aluminum plate was picked up from the customer and annealed to Condition T-0. Condition T-0 is annealed or dead soft. Heat treating the sheet allowed it be formed into the components comprising the weldments. When welding aluminum the localized heating at the weld joint results in a softer heat affected zone. In order to make the parts functional they need to be re-heat treated. The two large pieces that were provided to us after assembly, were re-hardened in Metlab’s large 15’ diameter by 12’ deep pit furnace. Parts measured approximately 48″ in diameter by 48″ tall. ”

Podob provides insights in to the treatment process, “The process consisted of solution treating the parts at 985°F, holding at this temperature for 1 hour, then quenching into heated water. The solution treatment portion of the cycle, floor-to-floor is about 8 hours. After solution treating, parts are artificially aged at 350°F for 8 hours, and air cooled. Age hardening, including heating, holding at temperature and cooling is about a 24 hour process. Critical to the heat treatment process is fixturing which ensures that the parts will not move, flex or distort during thermal processing. In this case, parts were braced with additional supports to keep movement to a minimum.”

Aluminum frame of underwater buoy- Before heat treating

Aluminum frame of underwater buoy    Before heat treating

Aluminum frame After heat treating

Aluminum frame
After heat treating

Metlab’s process enabled TrimMaster to produce a frame with a hardness of 60 HRB, ready for service in an underwater buoy exploring the ocean floor. Podob summarizes, “We have worked with TrimMaster on several other projects including heat treating, induction and flame hardening and black oxide finishing of various components.”

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