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P/M: Basics

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  • 1. Powdered Metallurgy : The Basics
  • 2. Basics of P/M
    • Highly developed method of manufacturing precision metal parts
    • Made by mixing elemental or alloy powders then compacting the mixture in a die. The resulting shape is sintered in an atmosphere controlled furnace to convert mechanical bonds into metallurgical bonds.
    • Basically a ”chip-less” process, P/M uses roughly 97% of the starting material in the finished part.
  • 3. Advantages of P/M
    • Versatile in numerous industries
    • Eliminates or minimizes machining
    • Minimizes scrap
    • Maintains close dimensional tolerances
    • Permits a wide variety of alloy systems
    • Facilitates manufacture of complex shapes which would be impractical with other processes
    • Provides excellent part to part repeatability
    • Cost Effective
    • Energy and environmentally efficient
  • 4. Basic P/M Steps
    • Raw Material
    • Mixing
    • Forming
    • Sintering
    • Optional Operations
    • Finished Products
  • 5. Mixing
    • Elemental, partially alloyed or pre-alloyed metal powders are first blended with lubricants to produce a homogeneous mixture.
  • 6. Compaction
    • A controlled amount of a mixed powder is gravity fed into a precision die and then compacted. Compaction occurs at room temperature, at a pressure range of 25-50 tons per sq. in.
    • Compacting the loose powder produces a “green compact” which, with conventional pressing techniques, has the size and shape of the finished part when ejected from the press. Green compacts have sufficient strength for in-process handling.
    • Typical compaction techniques use rigid dies, set into mechanical or hydraulic presses.
  • 7. Conventional Mechanical Press
  • 8. Compaction Tooling
  • 9. Compaction Cycle
    • Cycle Start
    • Charge die w/powder
    • Compaction begins
    • Compaction complete
    • Ejection of compact
    • Recharging of die
  • 10.  
  • 11.  
  • 12.  
  • 13.  
  • 14. Sintering
    • Typically, the “green compact” is placed on a mesh belt which then moves slowly through a controlled atmosphere furnace. The parts are heated below the melting point of the base metal, held at the sintering temperature, then cooled. Basically a solid state process, sintering transforms compacted mechanical bonds between powder particles into metallurgical bonds.
    • Typical sintering temperatures for ferrous based metals range from 2050- 2100 degrees F.
    • Standard cycle times range from 2-3 hours.
  • 15. Conventional Furnace Profile
  • 16. Optional Operations
  • 17. Optional Operations
  • 18. Powdered Metallurgy: Design Considerations
  • 19. Material Selection
  • 20. Design Considerations
    • Dimensional accuracy depends upon:
      • Control of powder composition
      • Size of dimension
      • Control of powder fed to the tools with each stroke
      • Control of press and tooling variables
      • Control of sintering variables
  • 21. MPIF Reference Tolerance Guide
    • Typical tolerances for ferrous P/M components up to 2.00 inches in dimension
    • Tolerances, inch/inch
    ±.001 ±.0015 Parallel of Ends ±.001 ±.002 Flatness on Ends .004 .006 Concentricity ±.001 ±.002 Outside Diameter ±.001 ±.002 Inside Diameter ±.003 ±.005 Length Possible Practical Characteristic
  • 22. Design Details
    • Fillets and Radii
      • Tooling with such fillets are more economical, longer lasting
      • Parts made with generous fillets are more economical
      • Parts made with fillets have greater structural integrity
  • 23. Design Details
    • Holes in the pressing direction can be round, D-Shaped, keyways or splines
    • Wall thickness is all important; walls thinner than .060 inches are avoided.
    • Flatness depends on part thickness and surface area.
    • Thin parts tend to distort more than thick parts
    • Chamfers rather than radii are necessary on part edges
  • 24. Questions:

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