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Powder Metal Processing

Powder Metal Processing. Manufacturing Processes. Outline. Introduction Powder Manufacturing Powder Metallurgy Process Sintering Other Powder Metal Processes Powder Metal Products Powder Metallurgy Design. Powder Metallurgy. Powder Metallurgy. Metal Powder Metal Product.

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Powder Metal Processing

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  1. Powder Metal Processing Manufacturing Processes

  2. Outline • Introduction • Powder Manufacturing • Powder Metallurgy Process • Sintering • Other Powder Metal Processes • Powder Metal Products • Powder Metallurgy Design

  3. Powder Metallurgy

  4. Powder Metallurgy Metal Powder Metal Product

  5. Examples of Powder Metal Products Gears Cams Cranks Bearings Roller bearing cages Housings Light bulb filaments Sprinkler mechanisms

  6. Powder Metal Materials Elemental A pure metal, most commonly iron, aluminum or copper Prealloyed An alloy of the required composition, most commonly copper alloys, stainless steel or high-speed steel

  7. Powder Manufacturing Conversion of molten metal to powder Atomization

  8. Powder Manufacturing Other methods of producing powder: • Chemical reduction of particulate compounds • Electrolytic deposition • Pulverization or grinding of brittle materials • Thermal decomposition • Precipitation from solutions • Condensation of metal vapors

  9. Particle Shape

  10. Particle Size The process of separating particles by size is called classification

  11. Particle Size Micrograph of screened powder particles, showing that particles may be longer than the mesh is wide

  12. Particle Size Mixing particles of different sizes allows decreased porosity and a higher packing ratio void smaller, more numerous voids voids filled by smaller particles, small voids remain

  13. Powder Metallurgy Process

  14. Blending and Mixing Blending Combining powders of the same material but possibly different particle sizes Mixing Combining powders of different materials

  15. Compaction High pressure is applied to squeeze the powder into the desired shape

  16. Example of a Powder Press

  17. Sintering Heats the powder below the melting point to allow solid-state diffusion and bond the particles together

  18. Sintering Diagram of particles in sintering, showing the possible movements of atoms

  19. Sintering

  20. Sintering

  21. Sintering Production Lines

  22. Examples of Sintering Production Lines

  23. Sintering Strength of sintered structures as related to density, showing that the strength is higher when the density is higher (less residual porosity)

  24. Other Powder Metal Processes Cold Isostatic Pressing Hot Isostatic Pressing Injection Molding Powder Rolling Powder Extrusion Plasma Spraying

  25. Isostatic Pressing Uses pressurized fluid to compress the powder equally in all directions Cold Isostatic Pressing Compaction performed at room temperature Hot Isostatic Pressing Performed at high temperatures and pressures

  26. Example of an Isostatic Press

  27. Injection Molding The powder is mixed with a binder and molded, and the binder is removed before sintering

  28. Powder Rolling Powder is compressed in a rolling mill to form a strip

  29. Powder Extrusion The powder can be extruded within a container or after being formed into billets

  30. Plasma Spraying Uses a plasma arc to propel molten droplets at a surface at a high velocity, forming a high-density structure

  31. Plasma Spraying

  32. Powder Metal Products • Porous or permeable products • Products of complex shapes • Products made of materials that are difficult to machine or have high melting points • Products which require the combined properties of multiple materials • Products in which powder metallurgy produces superior properties

  33. Powder Metallurgy Design • The shape must permit removal from the die • The shape should not have thin walls or sharp corners • The shape should permit the construction of strong tooling • The shape of the part should be within the thickness range for which the powder can be properly compacted • The part should have as few changes in section thickness as possible

  34. Powder Metallurgy Design • Parts can be designed to take advantage of the capabilities of the powder metallurgy process • The design should be consistent with available equipment • Consideration should be given for product tolerances • Design should consider the dimensional changes that occur after pressing, such as shrinkage during sintering

  35. Powder Metallurgy Design

  36. Powder Metallurgy Design

  37. Powder Metallurgy Advantages • Elimination/reduction of machining • High production rates • Complex shapes can be produced • Wide composition variations are possible • Wide property variations are possible • Scrap is eliminated or reduced

  38. Powder Metallurgy Disadvantages • Inferior strength properties • Relatively high die cost • High material cost

  39. Summary Powder metallurgy can create parts that would otherwise be difficult to form, including those with complex shapes or porosity Sintering bonds particles together by allowing atoms to move, forming necks and grain boundaries between the particles

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