M processes notes_15


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M processes notes_15

  1. 1. Powder Metal Processing Manufacturing Processes
  2. 2. OutlineIntroductionPowder ManufacturingPowder Metallurgy ProcessSinteringOther Powder Metal ProcessesPowder Metal ProductsPowder Metallurgy Design
  3. 3. Powder Metallurgy
  4. 4. Powder Metallurgy Metal Powder Metal Product
  5. 5. Examples of Powder Metal ProductsGearsCamsCranksBearingsRoller bearing cagesHousingsLight bulb filamentsSprinkler mechanisms
  6. 6. Powder Metal MaterialsElemental A pure metal, most commonly iron, aluminum or copperPrealloyed An alloy of the required composition, most commonly copper alloys, stainless steel or high-speed steel
  7. 7. Powder ManufacturingConversion of molten metal to powderAtomization
  8. 8. Powder ManufacturingOther 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. 9. Particle Shape
  10. 10. Particle SizeThe process of separating particles by size is called classification
  11. 11. Particle SizeMicrograph of screened powder particles, showingthat particles may be longer than the mesh is wide
  12. 12. Particle SizeMixing 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. 13. Powder Metallurgy Process
  14. 14. Blending and MixingBlending Combining powders of the same material but possibly different particle sizesMixing Combining powders of different materials
  15. 15. CompactionHigh pressure is applied to squeeze the powder into the desired shape
  16. 16. Example of a Powder Press
  17. 17. SinteringHeats the powder below the melting point to allow solid-state diffusion and bond the particles together
  18. 18. SinteringDiagram of particles in sintering, showing the possible movements of atoms
  19. 19. Sintering
  20. 20. Sintering
  21. 21. Sintering Production Lines
  22. 22. Examples of Sintering Production Lines
  23. 23. SinteringStrength of sintered structures as related to density,showing that the strength is higher when the density is higher (less residual porosity)
  24. 24. Other Powder Metal ProcessesCold Isostatic PressingHot Isostatic PressingInjection MoldingPowder RollingPowder ExtrusionPlasma Spraying
  25. 25. Isostatic PressingUses pressurized fluid to compress the powder equally in all directionsCold Isostatic Pressing Compaction performed at room temperatureHot Isostatic Pressing Performed at high temperatures and pressures
  26. 26. Example of an Isostatic Press
  27. 27. Injection MoldingThe powder is mixed with a binder and molded, and the binder is removed before sintering
  28. 28. Powder RollingPowder is compressed in a rolling mill to form a strip
  29. 29. Powder ExtrusionThe powder can be extruded within a container or after being formed into billets
  30. 30. Plasma SprayingUses a plasma arc to propel molten droplets at a surface at a high velocity, forming a high-density structure
  31. 31. Plasma Spraying
  32. 32. Powder Metal Products1. Porous or permeable products2. Products of complex shapes3. Products made of materials that are difficult to machine or have high melting points4. Products which require the combined properties of multiple materials5. Products in which powder metallurgy produces superior properties
  33. 33. Powder Metallurgy Design1. The shape must permit removal from the die2. The shape should not have thin walls or sharp corners3. The shape should permit the construction of strong tooling4. The shape of the part should be within the thickness range for which the powder can be properly compacted5. The part should have as few changes in section thickness as possible
  34. 34. Powder Metallurgy Design6. Parts can be designed to take advantage of the capabilities of the powder metallurgy process7. The design should be consistent with available equipment8. Consideration should be given for product tolerances9. Design should consider the dimensional changes that occur after pressing, such as shrinkage during sintering
  35. 35. Powder Metallurgy Design
  36. 36. Powder Metallurgy Design
  37. 37. Powder Metallurgy Advantages1. Elimination/reduction of machining2. High production rates3. Complex shapes can be produced4. Wide composition variations are possible5. Wide property variations are possible6. Scrap is eliminated or reduced
  38. 38. Powder Metallurgy Disadvantages1. Inferior strength properties2. Relatively high die cost3. High material cost
  39. 39. SummaryPowder metallurgy can create parts that would otherwise be difficult to form, including those with complex shapes or porositySintering bonds particles together by allowing atoms to move, forming necks and grain boundaries between the particles