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Presentation on Powder Methods

Presentation on Powder Methods. VIJAY 2008AMD2925. I ntroduction. M anufacturing process in which fine powder of materials are- Blended or mixed , Compacted (pressed) in to required shape, size and surface finish S intered (heated)

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Presentation on Powder Methods

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  1. Presentation on Powder Methods VIJAY 2008AMD2925

  2. Introduction • Manufacturing process in which fine powder of materials are- • Blended or mixed, • Compacted (pressed) in to required shape, size and surface finish • Sintered (heated) • Controlled atmosphere to bond the contacting surfaces of particles and to achieve required properties like strength, density etc. • High quality, complex parts to close tolerances in an economical manner (eliminating additional machining or finishing operations ). • Controlled degree of density, porosity, strength and other properties of material, with minimum waste

  3. Applications Table1:- Application of powder methods [1] Tungsten lamp filaments, oil-less bearings, automotive transmission gears, electrical contacts, nuclear power fuel elements, aircraft brake pads, jet engine components, printed circuit boards, explosives, welding electrodes, rocket fuels, etc [2]

  4. Production of a component • Production of powder • Preparation of powder including blending and mixing • Compacting • Sintering • Post sintering treatment [3]

  5. Production of Powder 1. Mechanical method (milling) • Ball mills and roller mills • Ferrous and non ferrous materials • Brittle Fig 1:- Ball mill Image courtesy: - Ref. [4]

  6. Production of Powder 2. Electrolytic Deposition • Spongy or powdery state of metal • Suitable conditions; composition and strength of the electrolyte, temperature, current density, etc • Copper, chromium and manganese powders • Pure powder Image courtesy: - Ref. [2] Fig 2:- Electrolytic deposition

  7. Production of Powder 3. Reduction of ores • Iron powder 4. Atomisation • Liquid metals – Orifice- Jet stream of gas, water, or steam –Broken into fine particles • To control particle size distribution- • Parameters; design and configurations of the jets, pressure and volume of the atomising fluid, thickness of the stream of metal, etc • Production of iron, tool steels, alloy steels, copper, brass, bronze and the low-melting-point metals, such as aluminium, tin, lead, zinc, cadmium powders. [2]

  8. Fig 3:- Vertical gas atomization unit Image courtesy: - Ref. [5]

  9. Preparation of powder • Blending and Mixing To obtain desired properties and characteristics we have to mix • Powder of different materials -different grades and sizes- different composition • Lubricants and binders. • Alloying elements Fig 4:- Powder contents Image Courtesy: - Ref. [2]

  10. Fig 5:- Compaction sequence • Cycle start • Charge die with powder • Compaction begin • (4) Compaction completed • (5) Ejection of part • (6) Recharging die • Image Courtesy: - Ref.[2] • Compacting • Loose powder of material is compressed and densified –Green compact- At room temp. • Mechanical, hydraulic and pneumatic presses.

  11. Sintering • Green compact is heated in a controlled atmosphere • Below the melting point but high enough to permit solid state diffusion • Held for sufficient time to permit bonding of the particles • Sintering temperature range for iron-based alloys is 1100-1150°C and the time varies between 10 and 60 minutes, depending on the application [6] Fig 6:- Sintering process Image Courtesy: - Ref. [7]

  12. Post sintering treatments • Machining • De-burring • Joining • Heat treatment • Double Pressing • Oil Impregnation

  13. Advantages of the powder methods • Complex shapes can be produced. • Close dimensional accuracy with elimination or reduction in machining. • High production rate due to automation. • Wide range of properties like density, porosity and particle size can be obtained. • No waste during fabrication. • Highly skilled labour is not required.[8]

  14. Disadvantages and limitations • Pure metal powders are very expensive. • Size of part produced is limited. • Alloy powders are not easily obtained. • Strength properties are lower than product manufactured by convention way. • Increased tendency to oxidation due t pores. • Poor plastic properties like impact strength, elongation etc. • High pressure and severe abrasion involved in process increase the die cost. [8]

  15. References:- • Manufacturing Engineering and Technology by SeroprKalpakjian and Steven R. Schmid , Chapter 17, Table 17.1 Page 461 • http://www.turktoz.gazi.edu.tr • Manufacturing Engineering Processes by Leo Alting, Chapter 9, Page 281-299 • http://www.ktf-split.hr/glossary/image/ball_mill.gif • http://www.xstreamscience.org/H_Glaze/assets/Powder%20Atomizer.gif • http://www.substech.com • http://www.azom.com/details.asp?ArticleID=132 • Elements of Workshop Technology by S.K. and A.K. HajraChoudhury, Chapter 12, Page 431-440.

  16. Thank You…….

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