Predicting the Microstructure and Properties of Steel Welds

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Predicting the Microstructure and Properties of
Steel Welds
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MULTIPASS ARC WELD
L.-E. SVENSSON
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L.-E. SVENSSON
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20 µm
Barrite, 1982
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Manual Metal Arc Weld 180 Amps 34 Volts 4
mm/s 200 C interpass
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calculations
800
2
1
3
4
700
5
6
600
500
1. Fe-0.4C
Temperature / C
2. Fe-0.4C-2Si
3. Fe-0.4C-1Ni
400
4. Fe-0.4C-1Mn
5. Fe-0.4C-1Mn-1Cr
300
6. Fe-0.4C-2Mn
200
0 1 2 3
4 5
10 10 10 10 10
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Time / s
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Barrite, 1982
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Barrite, 1982
5 µm
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Fe-1Mn-C wt manual metal arc welds
Allotriomorphic
Volume fraction
Widmanstatten
Acicular
Carbon / wt
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Bhadeshia Svensson
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Bhadeshia Svensson
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Charpy toughness

• Murugananth Bhadeshia

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7Ni 2Mn
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7Ni 0.5Mn
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7Ni 2Mn
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7Ni 0.5Mn
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Weld Shape - Stitch Weld at 2.26 kW Laser Output
Laser beam
Fusion Zone
Laser beam
Keyhole
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Measured Calculated
Optically mainly a-ferrite
some w-ferrite lt5
martensite TEM a-ferrite
much w-ferrite
46 a-ferrite 21 w-ferrite 30 acicular ferrite
bainite 3 martensite
155, 157 and 170 HV Mean Hardness 161 HV
168 HV
Grain size 100 20 mm
Grain size 103 mm
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Charpy
fatigue
tensile
critical stress intensity
corrosion
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Variables

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

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Empirical Equations
?y a b (C) c (Mn) d (Ni)
....
1223
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?y a b (C) c (Mn) ?y a b (C) c
(Mn) d(C x Mn)
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?y a b (C) c (Mn) ?y a b (C) c
(Mn) d(C x Mn) ?y sin (C)
tanh (Mn)
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Hyperbolic Tangents
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non-linear functions
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Predict what the next two numbers are likely to
be 2, 4, 6, 8, .
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Brun, Robson, Narayan, MacKay Bhadeshia
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Components of Creep Strength, 2.25Cr1Mo
iron microstructure
550 C
solid solution
600 C
precipitates
Murugananth Bhadeshia
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Cole Bhadeshia
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Cool, 1996
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Cool, 1996
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600 C
As-welded
700 C
650 C
Cool, 1996
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Siemens Mitsui Babcock Nippon Steel ABB
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Thank you.