1. Microstructure & Property
Reliability of Weld
Microstructure & Property
Calculations
Comfort A. Adams Lecture, 2004

2. Are experiments necessary when designing welding alloys?

3. Fe Ru
6d 2s Os Hs

5. tallest building
in the world
earthquakes

8. Variables C, Mn, Si, Ni, Cr, Mo, V, Co, B, N, O…..
Thermomechanical processing of steel
Welding consumable
Welding parameters
Subsequent heat treatment

10. 100 µm

13. 20 µm
Barrite, 1982

18. Manual Metal Arc Weld
Amps
34 Volts
4 mm/s
200 °C interpass

19. calculations 800 700 600 Temperature / C 500 400 300 2001 3 4
700 5 6
600
Temperature / C
500
1. Fe-0.4C
2. Fe-0.4C-2Si
400
3. Fe-0.4C-1Ni
4. Fe-0.4C-1Mn
5. Fe-0.4C-1Mn-1Cr
300
6. Fe-0.4C-2Mn
200
Time / s

21. Barrite, 1982

24. Barrite, 1982
5 µm

25. 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 %

26. Bhadeshia & Svensson

28. Young & Bhadeshia, 1994

29. Bhadeshia & Svensson

30. critical stress intensity
Charpy
fatigue
tensile
critical stress intensity
corrosion

31. non-linear functions

34. y A B x

37. Cole & Bhadeshia, 1999

39. Cool, 1996

40. Cool, 1996

41. 600 °C
As-welded
700 °C
650 °C
Cool, 1996

44. Weld Shape - Spot Weld Walsh et al. 2002 Power = 1.0 kW Power = 1.4 kW
2 mm
0.15 s
0.15 s
0.15 s
0.65 s
0.65 s
0.165 s
1.15 s
1.15 s
0.18 s
1.65 s
0.195 s
1.65 s
At low powers get conduction mode welding.
At intermediate powers and longer times start getting the formation of a keyhole.
At the highest powers a keyhole is clearly present in all the welds.
Good weld fusion zones with very few pores.
2.15 s
2.15 s
0.21 s
2.65 s
2.65 s
0.225 s

45. Walsh et al. 2002

46. Weld Shape - Stitch Weld at 2.26 kW Laser Output
Laser beam
Fusion Zone
Laser beam
Keyhole
Full penetration welds can be formed at speeds of 40 mm/s with a 2.26 kW laser beam and at 10 mm/s with a 1.4 kW beam.
The weld fusion zones are in generally pore free and without significant defects of any other sort.
Without the use of a shielding gas the welds are more parallel sided but the fusion zones are smaller.
Difference with and without the use of shielding gas will be explained later by the energy transfer model.
Walsh et al. 2002

47. 50mm SPOT WELD STITCH WELD 38.3J/mm; 1 kJ 2.15 s; 325 HV
10 mm/s; 165 HV
Similar values of the energy used to melt the fusion zone (38.3 and 39.4 J/mm).
Spot weld: faster cooling rate, D52X has higher C and Mn content
fewer reconstructive transformations, more displacive transformations
allotriomorphic and Widmanstätten ferrite, bainite and martensite
Stitch welds: slightly slower cooling rate, DC04 contains lower C and Mn content
weld metal transformed at higher temperatures
allotriomorphic and Widmanstätten ferrite only

48. Cooling rate
Composition

51. Are experiments necessary when designing welding alloys?