1. Carbide Precipitation in Steel Weld Metals

6. Self evident truth, statement which commands general belief, an unverifiable although widely accepted fact

12. CASE 1: Sensitisation
Shimada et al., 2002

14. Sourmail, Too, Bhadeshia, 2003

15. Sourmail, Too, Bhadeshia, 2003

16. CASE 2: elimination of carbides
Carbon supersaturated plate
Carbon diffusion into
Carbon diffusion into
austenite
austenite and carbide
precipitation in ferrite
Carbide precipitation
from austenite
UPPER BAINITE
LOWER BAINITE
(High Temperature)
(Low Temperature)
CASE 2: elimination of carbides

19. Fe-1Mn-C wt % manual metal arc welds
0.2
0.4
0.6
0.8
1.0
Allotriomorphic
Volume fraction
Widmanstatten
Acicular
0.11
0.09
0.07
0.05
0.03
Carbon / wt %

21. wt%

24. CASE 3: carbide strengthening

25. 0.5 µm

26. a
time = t+∆t
time = t

27. b a
time = t+∆t
time = t

29. 2.25Cr1Mo
600 °C
M3C
M2X
M23C6
Time / h
1000 h

30. 3Cr1.5Mo
600 °C
M23C6
Time / h

31. Components of Creep Strength, 2.25Cr1Mo
iron + microstructure
550 °C
solid solution
600 °C
precipitates
Murugananth & Bhadeshia, 2001

32. elements in solution
Murugananth & Bhadeshia, 2001

34. Coarsening diffusion r r flux concentration q a q aq c r aq c r1 2
flux q a q
concentration aq c r 1 aq c r 2
distance

35. Fujita and Bhadeshia, 2002

36. Fujita and Bhadeshia, 2002

37. Fujita and Bhadeshia, 2002

38. Summary Significant advances in theory
Can model diffusion-controlled growth, coarsening
Elimination of cementite
Long-term microstructural stability can be estimated

39. Conclusions