Carbidefree Rail Steels Building Bridges in Metallurgy Cheap
Carbide-free Rail Steels “Building Bridges in Metallurgy”
• Cheap • Large dimensions • Rolled into shape • Wear resistance • Rolling contact fatigue • Joining
Origin of strength, hardness, toughness
body-centred cubic (a’) face-centred cubic (g)
displacive transformation
Surface 1 50 µm Surface 2 Srinivasan & Wayman
carbon partitions into carbon supersaturated plate g carbide precipitates from g Design Philosophy
0. 4 C 2 Si 3 Mn wt% 1 µm
Very poor toughness!
50 µm
Carbide-free alloys wt %
Impact Energy 70 Charpy impact / J 60 0. 4 C-3 Mn-2 Si 0. 4 C-4 Ni -2 Si 0. 2 C-3 Mn-2 Si 50 40 30 20 10 0 -200 -100 0 100 Test temperature // °C Temperature °C 200
20 µm
Bainite Martensite Pearlite 0 200 400 600 800 1000 1200 kilocycles to Crack Initiation Yates, Jerath
Yates, Jerath
austenite
0. 2 C 1. 25 Si 1. 55 Mn 0. 5 Cr 0. 15 V 0. 15 Mo wt% 15 mm thick plate, without Mo 550°C for 5 h Chang and Bhadeshia
U. K.
Radcliffe et al.
Kaufman
Devnathan & Clayton
Further Developments 180 Fracture toughness / MPa √m 160 140 18 wt% Ni maraging steel 120 100 80 60 40 20 1000 QT 1500 2000 Ultimate tensile strength / MPa 2500
Fe-2 Si-3 Mn-C wt% Temperature / K 800 BS 600 400 MS 200 0 0 0. 2 0. 4 0. 6 0. 8 1 Carbon / wt% 1. 2 1. 4
Fe-2 Si-3 Mn-C wt% 1. E+08 1 year Time / s 1 month 1. E+04 1. E+00 0 0. 5 Carbon / wt% 1 1. 5
Low transformation temperature Bainitic hardenability Reasonable transformation time Elimination of cementite Austenite grain size control Avoidance of temper embrittlement wt%
g g a a a 200 Å
650 -720 HV 10 -30% ductility
Stress / GPa Velocity km s-1 Hammond and Cross, 2004
GRP mild steel “superbainite” vehicle steel GRP Peter Brown (DSTL) Dave Crowther (Qineti. Q)
“more serious battlefield threats”
Liou Chun Chang Howard Smith Vijay Jerath (CORUS) Francisca G. Caballero www. msm. cam. ac. uk/phase-trans
French National Railways 0. 2 C 1. 25 Si 1. 55 Mn 0. 5 Cr 0. 15 V 0. 15 Mo wt% UTS > 1100 MPa 320 -340 HB elongation > 14% Curve radius Cant Installed Traffic Tonnage 1140 m 124 mm Dec 1998 Mixed 15 106 gt/annum
French National Railways (Howard Smith)
Swiss Railways 0. 3 C 1. 25 Si 1. 55 Mn 0. 5 Cr 0. 15 Mo wt% UTS > 1200 MPa 360 -390 HB elongation > 13% Curve radius Cant Installed Traffic Tonnage 449 m 120 mm Nov 1999 Freight 30 106 gt/annum
Swiss Railways (Howard Smith)
15 mm thick plate, without Mo air-cooled after hot rolling Chang and Bhadeshia
15 mm thick plate, without Mo quenched after hot rolling Chang and Bhadeshia
20 µm
ballistic mass efficiency consider unit area of armour
a g g a g 50 nm
Chatterjee & Bhadeshia, 2004
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