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Engine materials for camshaft and crankshaft

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State of art and fundamentals of materials engineering for two important engine components.

Published in: Automotive

Engine materials for camshaft and crankshaft

  1. 1. Material and technology for Automotive engine: brief overview o The camshaft o The crankshaft Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  2. 2. The camshaftMaterials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  3. 3. The camshaft - 1 The valve operating mechanism transforms rotation of the crankshaft into reciprocating motion in the valves. The valves protrude into the combustion chamber and are pushed back by the reactive force of the valve spring. Ωcamshaft= Ωcrankshaft/2- Ωcamshaft high: contact pressure is reduced by the inertia of the valve lifter (oil isproviding hydrodynamic lubrication);- Ωcamshaft low: contact pressure is highest and lubrication most challenging. Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  4. 4. The camshaft - 2 Machining, dimension accuracy, clearance, rou Wear of sliding portion ghness Friction condition 1. Rugged surface due to wear 1. Lubrication 2. Contact 2. Adhesive wear Lubricating oil 3. Foreign object 3. Fatigue wear condition 4. Corrosive wearFlaking (scagliatura)Pitting (corrosione per vaiolatura) • It is very important to choose an appropriate combination of materials. • The torque from the crankshaft drives the camshaft: it must have high torsional rigidity. Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  5. 5. The camshaft - 3Chill hardening cannot be used where the gap between the cam lobes is narrow becauseof the difficulty in using the chiller, so forged camshafts are used.Tough martensite is more resistant to pitting than the chill microstructure. Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  6. 6. The camshaft - 4• Finishing – boring and grinding• ASSEMBLING • E.g.: Hydroforming Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  7. 7. The crankshaftMaterials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  8. 8. The crankshaft - 1 The crankshaft converts reciprocative motion to rotational motion.Two types:• the monolithic type• the assembled type Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  9. 9. The crankshaft - 2 Note: Included lead or MnS Carbon steel particles significantly function as a chip breaker and a solid Alloyed steel lubricant and increase machinability. Micro Alloyed steelTypical materials • less expensive• nodular cast iron: for high- volume, low-load production. • lower rigidity: abnormal vibrations (resonance) • increases in rigidity of more than 10% • reduces noise levels and harshness• forged steel: for fuel-efficient • makes possible a careful design engines requiring a high power-to- displacement ratio. • more expensive Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  10. 10. The crankshaft - 3 • Static: combustion pressure, inertial forces of the piston and con- rod, bearing load and drive torque.STRESS onCrankshaft • Dynamic: The vibration causes dynamic stress. If it occurs at the resonating frequency, the deformation Fatigue fracture of a carbon steel will be very high and will instantly S50C crankshaft rupture the crankshaft. HIGH STATIC AND DYNAMIC RIGIDITY: - increasing the crankpin diameter (increasing weight) - using forged steel - Surface-hardening methods Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  11. 11. Fatigue behaviour: principles and survey Principi (macro) σa Wöhler [1860] Ampiezza tensione applicata Vita finita * Legge di Basquin: σa = σf’ (2Nf)b * Tipici Curva tipica acciai per acciai σL Leghe di alluminio Vita infinita 104 105 106 107 Cicli alla rottura, NfDipende da:•Tipo di materiale • Concentrazione di • Contenuto di inclusioni e tensioni impurezze • Trattamento termico • Tensione media e superficiale tipo di sollecitazione Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  12. 12. The crankshaft - 4HOT FORGING PROCESS (for a four-stroke crankshaft) • The coarse structure is broke down and is replaced, as recrystallisation proceeds, by one which is of relatively fine grain • Impuritires are redistribuited in a fibrous form • Introduction of compressive residual stresses Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  13. 13. The crankshaft - 5 SURFACE HARDENING (carburizing, nitring, carbonitring and nitrocarburizing):• CARBURIZING O: origins S: a few beachmarks B: arrest lines R: ratchet marks Pitting observed at a crankpin surface Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  14. 14. The crankshaft - 6 SURFACE HARDENING (carburizing, nitring, carbonitring and nitrocarburizing):• CARBURIZING Compressive residual stress generated by carburizing Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  15. 15. The crankshaft - 7Modern carburizing technology: Acetylene Vacuum Carburizing- AvaC Steel Fe Acetilene Siti di adsorbimento Cr C H2 Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  16. 16. The crankshaft - 7 Avac - Adsorbimento (T>Taustenitizzazione) SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  17. 17. The crankshaft - 7 Avac - Decomposizione in radicali SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  18. 18. The crankshaft - 7 Avac - Inizio cementazione (T>Taustenitizzazione) SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  19. 19. The crankshaft - 7 Avac - Inizio cementazione (T>Taustenitizzazione) SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  20. 20. The crankshaft - 7 Avac - Inizio cementazione (T>Taustenitizzazione) SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  21. 21. The crankshaft - 7 Diffusione nell‘acciaio (T>Taustenitizzazione) SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  22. 22. The crankshaft - 7 Saturazione SteelFe Acetilene Siti di adsorbimentoCr C H2Mn Materials and technology for automotive engine A. Manicone Catania, 06/07/2012, A.Manicone
  23. 23. The crankshaft - 7 SURFACE HARDENING (carburizing, nitring, carbonitring and nitrocarburizing):• NITRING: NH3 decomposes at the steel surface to catalytically generate elemental nitrogen, which diffuses into the material. The nitrogen expands the iron lattice and also forms hard compounds (the nitrides Fe4N and Fe3N) with iron atoms. Nitridable steel reaches the necessary hardness by forming stable nitrides (Al, Cr, V…)• NITROCARBURIZING, CARBONITRURING • higher hardness surface, • but lower toughness• INDUCTION HARDENING Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  24. 24. The crankshaft - 8 RECENT TRENDS: Micro alloyed steel, via plasma ion nitringPrecipitation hardening is the main method for increasing strength at thecooling stage after hot forging.Micro-alloyed steel contains a small amount of V, which dissolves in thematrix during hot forging above 1,200 °C. During air cooling, the dissolved Vcombines with carbon and nitrogen to precipitate as vanadium carbide andnitride at around 900 °C. the vanadium carbide and nitride will be more finely dispersed. Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  25. 25. The crankshaft - 9Manufacturing process • Trade-off: machinability-fatigue resistance • Surface roughness For low and medium loaded bearings: Ra = 15 microinch max. Rz = 60 microinch max. For highly loaded bearings: Ra = 10 microinch max. Rz = 30 microinch max. Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  26. 26. The crankshaft - 10Conclusions: Methods to strengthen crankshafts Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone
  27. 27. Material and technology for Automotive engine: brief overview Thanks for attention Materials and technology for automotive engine Catania, 06/07/2012, A.Manicone

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