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Carbide-free Rail Steels

Explore the benefits of carbide-free rail steels in constructing cost-effective, large dimension rail tracks with enhanced wear resistance and rolling contact fatigue. Learn about the origin of strength, hardness, and toughness in these steels and their effective joining methods.

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Carbide-free Rail Steels

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  1. Carbide-free Rail Steels “Building Bridges in Metallurgy”

  2. Cheap • Large dimensions • Rolled into shape • Wear resistance • Rolling contact fatigue • Joining

  3. Origin of strength, hardness, toughness

  4. body-centred cubic (a’) face-centred cubic (g)

  5. displacive transformation

  6. Surface 1 Surface 2 50 µm Srinivasan & Wayman

  7. carbon supersaturated plate carbon partitions into g carbide precipitates from g Design Philosophy

  8. 0.4 C 2 Si 3 Mn wt% 1 µm

  9. Very poor toughness!

  10. 50 µm

  11. Carbide-free alloys wt %

  12. 70 0.4C-3Mn-2Si 0.4C-4Ni -2Si 60 0.2C-3Mn-2Si 50 40 30 20 10 0 -200 -100 0 100 200 Impact Energy Charpy impact / J Temperature / °C Test temperature / °C

  13. 20 µm

  14. Bainite Martensite Pearlite 0 200 400 600 800 1000 1200 kilocycles to Crack Initiation Yates, Jerath

  15. Yates, Jerath

  16. austenite

  17. 0.2C 1.25Si 1.55Mn 0.5Cr 0.15V 0.15Mo wt% 15 mm thick plate, without Mo 550°C for 5 h Chang and Bhadeshia

  18. U.K.

  19. Radcliffe et al.

  20. Kaufman

  21. Devnathan & Clayton

  22. 180 160 140 120 100 80 60 40 20 1000 1500 2000 2500 Further Developments 18 wt% Ni maraging steel Fracture toughness / MPa √m QT Ultimate tensile strength / MPa

  23. Fe-2Si-3Mn-C wt% 800 B S 600 Temperature / K 400 M S 200 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Carbon / wt%

  24. Fe-2Si-3Mn-C wt% 1.E+08 1 year 1 month Time / s 1.E+04 1.E+00 0 0.5 1 1.5 Carbon / wt%

  25. Low transformation temperature Bainitic hardenability Reasonable transformation time Elimination of cementite Austenite grain size control Avoidance of temper embrittlement wt%

  26. g g a a a 200 Å

  27. 650-720 HV 10-30% ductility

  28. Stress / GPa Velocity km s-1 Hammond and Cross, 2004

  29. GRP mild steel “superbainite” vehicle steel GRP Peter Brown (DSTL) Dave Crowther (QinetiQ)

  30. “more serious battlefield threats”

  31. Liou Chun Chang Howard Smith Vijay Jerath (CORUS) Francisca G. Caballero www.msm.cam.ac.uk/phase-trans

  32. French National Railways 0.2C 1.25Si 1.55Mn 0.5Cr 0.15V 0.15Mo wt% UTS > 1100 MPa 320-340 HB elongation > 14% Curve radius 1140 m Cant 124 mm Installed Dec 1998 Traffic Mixed Tonnage 15  106 gt/annum

  33. French National Railways (Howard Smith)

  34. Swiss Railways 0.3C 1.25Si 1.55Mn 0.5Cr 0.15Mo wt% UTS > 1200 MPa 360-390 HB elongation > 13% Curve radius 449 m Cant 120 mm Installed Nov 1999 Traffic Freight Tonnage 30  106 gt/annum

  35. Swiss Railways (Howard Smith)

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