Powder-metal parts earn top honors

In the Metal Powder Industries Federation's annual Powder Metallurgy Design Excellence competition, an end cover for a dipole cryomagnet used in the Large Hadron Collider (LHC) took top honors in the Other category for atypical PM components. The winning parts in this competition represent advances in conventional press and sinter PM processing, metal injection molding (MIM), and hot-isostatic pressing (HIP).

The superconducting dipole cryomagnets in the LHC operate at cryogenic temperatures (–456°F). The complex geometry of the end covers made HIP and PM an attractive near-net-shape technique for fabrication, says Stefano Sgobba, section leader in the Mechanical and Materials Engineering group of CERN, the European Organization for Nuclear Research, in Switzerland, which is building the LHC. "Closed or open-die forging would require significantly more machining. Welded covers would need extensive inspections and stress relieving. And casting would have poorer mechanical properties."

The end covers are made from 316LN stainless-steel powder and HIPed to full density by Bodycote HIP-Surahammar in Sweden. Along with FEA and CAD, "Bodycote used CNC sheet-metal cutting and robotic welding and part manipulation to glean production rates 50 times greater than typically possible with fully dense HIPed near-net shapes," says Stephen Mashl, director of engineering and technology at Bodycote. The 253-lb near-net shape parts go to Metso Materials Technology Oy, Finland for finishing. The machined 153-lb parts have complex features and tight mechanical tolerances. The outside of the curved surface has eight or 10 projections, and covers differ slightly depending on which side the dipole magnet is located. At cryogenic temperature the PM HIPed covers meet or exceed tensile properties and ductility of 316LN wrought stainless steel, while maintaining exceptionally high impact toughness compared to other PM HIPed products of the same grade.

Stackpole Automotive Gear Div., Mississauga, Ont., Canada, and its customer Magna Powertrain, New Process Gear Div., East Syracuse, N.Y., took the Automotive – Transmission Grand prize for their six-level steel clutch hub for four-wheel-drive transfer cases in light trucks and SUVs. It helps distribute torque to the vehicle's front wheels on the fly. High-temperature sintering gave the hub a minimum density of 7 gm/cm³, an apparent hardness of 35 HR_C, and tensile and yield strengths of 165 and 150 kpsi, respectively. The complex castellated geometry required innovative tooling to precisely control lengths, diameters, densities, weight, and run-out, as well as an even density distribution. The clutch replaces a manual synchronizer for full-time active control of torque.

FMS Corp., Minneapolis, and its customer Team Industries, Bagley, Minn., shared the Grand Prize for Lawn & Garden/Off-Highway. Their sixpiece assembly is a forwardreverse actuator used in golfcart transmissions. The PM parts are made to a typical density of 6.9 gm/cm³. Most parts required a heat-treated hardness of 35 HR_C and tensile, minimum yield, and fatigue strengths of 120, 110, and 43 kpsi, respectively. The netshape parts also needed secondary zinc plating and vacuum oil impregnation. PM reportedly cut part costs in half over competing processes.

Metal Powder Products-Anaheim, Calif., won the Hardware/Appliances Grand Prize for a 316L stainlesssteel cap cover used in a fireprotection locking system. The cover features large outside tabs precisely oriented to an internal depressed wave form that lets it mesh with two other PM parts. Cap cover density is 6.5 gm/cm³ and the cover has a 20-kpsi yield strength and a 55-HR_B hardness. Its as-sintered elongation exceeds 20%. To ensure parts withstand abuse from vandals, three external lugs on test parts get hit with a 10-lb sledgehammer and are torqued to over 500 lb. And the main body must resist drilling. PM shaved off more than 80% of total costs compared to conventional machining.

The Hand Tools/Recreation Grand Prize went to Megamet Solid Metals Inc., Earth City, Mo., for its MIM trigger guard for muzzle-loading hunting rifles. Modern Muzzleloading Inc., Knight Rifles, Decatur, Ala., designed the guard to support the trigger group and hammer in its "quick-detachable trigger" for the 50-caliber rifle. The 3.1-oz steel part has a density of 7.4 gm/cm³ and as-sintered tensile and yield strengths of 94.25 and 58 kpsi, respectively. The part is held to critical dimensions of ±0.005 in. Secondary operations include: reaming three holes, tapping two screw holes, and deburring.

Flomet LLC, DeLand, Fla., and its customer Ormco Sybron Dental Specialties, Orange, Calif., earned the Grand Prize for Medical/Dental. The three netshape MIM parts — bracket, slide, and removable drop-in hook — are used in the Damon 3MX self-ligation orthodontic tooth positioner. A bracket and slide go on each tooth, with the hook an option for about 5% of the teeth.

The complexity of the part dictated the use of MIM, says FloMet's Vice President of Operations Ted Tomlin. "Machining would have been cost prohibitive even if it could have been done, which is doubtful." The exact ratio of volumes between part numbers was not known and could change over time, says Tomlin, so it was necessary to design the molds using a modular approach. "This allowed us to produce various combinations of parts to meet the customer demand. Additional lower volume modules have been added to meet market demand." The small, intricate parts are made from 17-4 PH stainless-steel powder to a density of 7.5 gm/cm³ and feature tensile and yield strengths of 172 and 158 kpsi, respectively. The customer tumble polishes and brazes them before assembly.

Lovejoy Sintered Solutions LLC, Downers Grove, Ill., and its customer PetrotecIndia/Portugal, in India, took the Industrial Motors/Controls & Hydraulics Grand Prize for a complicated five-level rotor. The rotor is part of an assembly in hydraulic pumps that draws petroleum fuel from an in-ground tank to the above-ground nozzle. The part has nine legs, each 50-mm-long and 10-mm-wide, creating a 5:1 aspect ratio. The legs are pressed to a density of 7.1 gm/cm³. Rotors are made from MPIF F-0005-25 PM material and feature a 56 HR_B hardness and tensile and yield strengths of 33 and 27 kpsi, respectively. PM provided a 30% cost savings over machined castings.

Other powdermetals parts that glean an Award of distinction will be featured in the July 12 issue of MACHINE DESIGN or click here to see more winners.

MAKE CONTACT
Metal Powder Industries Federation, (609) 452-7700, www.mpif.org