interstitial-free steels: structure of spot welds
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Interstitial-Free Steels: Structure of Spot Welds. Interstitial-free steel Fe-0.002C wt%. Interstitial-free and unalloyed. Extremely fast transformations. Extremely fast cooling rates. Phase diagram similar to pure iron. Difficult to interpret structure. Interstitial-free steel - PowerPoint PPT PresentationTRANSCRIPT
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Interstitial-Free Steels:Structure of Spot Welds
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Interstitial-free steel
Fe-0.002C wt%
Interstitial-free and unalloyed
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Extremely fast transformations
Extremely fast cooling rates
Phase diagram similar to pure iron
Difficult to interpret structure
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Interstitial-free steel
Fe-0.002C wt%
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0 50 100 150 200
Pressure / kbar
800
400
0
γ
α ε
1200
1600δ
0 50 100 150 200
Pressure / kbar
800
400
0
γ
α ε
1200
1600δ Bundy (1965)
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J. Khan, L. Xu and Y. J. Chao, Science and Technology of Welding and Joining 4 (1999) 201
Completed in a time period
much less than a second
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austenite
ferrite
cementite
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Bhadeshia, Vitek and David, Materials Science and Technology 7 (1991) 50
austenitic stainless ferritic stainless
Physical metallurgy of spot welds in interstitial-free
steels
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Bhadeshia, Vitek and David, Materials Science and Technology 7 (1991) 50
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Diffusion of all atoms during nucleation and growth.Sluggish below about 850 K.
Invariant-plane strain shape deformation with large shear component.No iron or substitutional solute diffusion.Thin plate shape.
Cooperative growth of ferrite & cementite.
No change in bulk composition.
Diffusionless nucleation & growth.
Carbon diffusion during paraequilibrium nucleation. No diffusion during growth.
Carbon diffusion during paraequilibrium nucleation & growth.
ALLOTRIOMORPHIC FERRITE
IDIOMORPHIC FERRITE
MASSIVE FERRITE
PEARLITE
WIDMANSTATTEN FERRITE
..
BAINITE & ACICULAR FERRITE
MARTENSITE
RECONSTRUCTIVE DISPLACIVE
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UPPER BAINITE(High Temperature)
LOWER BAINITE(Low Temperature)
Carbon supersaturated plate
Carbon diffusion into austenite
Carbon diffusion into austenite and carbide precipitation in ferrite
Carbide precipitation from austenite
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Ohmori and Honeycombe
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log{time}
Ms
ferrite
pearlite
bainite
martensite
Ae3
upper bainite
lowerbainite
Widmanstatten ferriteBs
Ws
Widmanstättenferrite
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Hayat, Demir, Acarer, Aslanar, Kovove Materialy 47 (2009) 11
Reproduced with permission
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Bayraktar, Kaplan, Devillers and Chevalier, J. Mat. Proc. Techn. 189 (2007) 114
Reproduced with permission
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Bhadeshia, Metal Science 16 (1982) 159
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12
3 45
6
1. Fe-0.4C2. Fe-0.4C-2Si3. Fe-0.4C-1Ni4. Fe-0.4C-1Mn5. Fe-0.4C-1Mn-1Cr6. Fe-0.4C-2Mn
0 1 2 3 4 5 10 10 10 10 10 10
Time / s
800
700
600
500
400
300
200
Tem
pera
ture
/
C
calculations
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Mukhopadhyay, Bhattacharya and Ray,
J. Mat. Proc. Techn. 209 (2009) 1995
Reproduced with permission
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Mukhopadhyay, Bhattacharya and Ray,
J. Mat. Proc. Techn. 209 (2009) 1995
Reproduced with permission
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Mukhopadhyay, Bhattacharya and Ray,
J. Mat. Proc. Techn. 209 (2009) 1995
Reproduced with permission
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Bhadeshia, Svensson & Gretoft,
Acta Metallurgica
33 (1985) 1271
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