Case Study: Clutch Hub for 4-Wheel Drive Transfer Case

Process: Conventional Press & Sinter (PM)

Density: 7.0 g/cm³

Material: FL-4405-150HT Prealloyed Steel

Weight: 850 g

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End Use and Function

Used as a hub in the clutch of a transfer case of a four-wheel-drive car, powder metallurgy was selected over forging due to the ability of PM to combine complex part shapes, high dimensional accuracy reducing machining, low material waste, and competitive cost.  

Fabrication

The 850 g part is compacted using tooling with two upper and three lower punches. The part is made using FL-4405-150HT Prealloyed steel and has a 7.0 g/cm³ minimum density in any section of the component after sintering at 1,120 °C. The inner diameter of the part is turned as well as the flange, and lateral holes are drilled. The parts are case hardened, tempered, and shot blasted. The tolerance on the cylindrical inner diameter is 0.030 mm, the flange inner diameter 0.022 mm, the perpendicularity of the spline vs. the flange face is 0.1 mm maximum, and the parallelism of the opposed outer flange vs. the inner flange face is 0.1 mm. 100% of the parts are checked for cracks using magnetic particle inspection.

Results

The customer qualified the parts by applying four bench tests—a static strength test, a pulse fatigue test, a dynamic fatigue test, and a balancing rotary test. The PM process was selected rather than a machined forging due to its ability to combine complex part shape, high accuracy of some characteristics without machining, low material waste, and a competitive cost. A 25% reduction in material waste was achieved compared with machining the part from a forging.