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

7. Surface Surface 2
50 µm
Srinivasan & Wayman

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

16. 0.4 C
2 Si
3 Mn
wt%
1 µm

17. Very poor toughness!

18. 50 µm

20. Carbide-free alloys
wt %

22. Impact Energy Charpy impact / J Temperature / °C Test temperature / °C10 20 30 40 50 60 70
0.4C-3Mn-2Si
0.4C-4Ni -2Si
0.2C-3Mn-2Si
Charpy impact / J
200
100
-100
-200
Temperature / °C
Test temperature / °C

23. 20 µm

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

26. Yates, Jerath

28. austenite

29. 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

30. U.K.

31. Radcliffe et al.

32. Kaufman

33. Devnathan & Clayton

34. Further Developments Fracture toughness / MPa √m 18 wt% Ni20 40 60 80
100
120
140
160
180
18 wt% Ni
maraging steel
Fracture toughness / MPa √m QT
2500
2000
1500
1000
Ultimate tensile strength / MPa

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

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

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

39. g g a a a
200 Å

40. HV
10-30% ductility

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

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

44. “more serious battlefield threats”

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

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

48. French National Railways
(Howard Smith)

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

50. Swiss Railways
(Howard Smith)

51. 15 mm thick plate, without Mo
air-cooled after hot rolling
Chang and Bhadeshia

52. 15 mm thick plate, without Mo
quenched after hot rolling
Chang and Bhadeshia

53. 20 µm

54. ballistic mass efficiency
consider unit area of armour

55. a g a g g
50 nm

56. Chatterjee & Bhadeshia, 2004