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Microstructure & Property
Reliability of Weld Microstructure & Property Calculations Comfort A. Adams Lecture, 2004
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Are experiments necessary when designing welding alloys?
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Fe Ru 6d 2s Os Hs
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tallest building in the world earthquakes
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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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100 µm
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20 µm Barrite, 1982
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Manual Metal Arc Weld Amps 34 Volts 4 mm/s 200 °C interpass
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calculations 800 700 600 Temperature / C 500 400 300 200
1 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
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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
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 %
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Bhadeshia & Svensson
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Young & Bhadeshia, 1994
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Bhadeshia & Svensson
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critical stress intensity
Charpy fatigue tensile critical stress intensity corrosion
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non-linear functions
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y A B x
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Cole & Bhadeshia, 1999
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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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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
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Walsh et al. 2002
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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
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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
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Cooling rate Composition
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Are experiments necessary when designing welding alloys?
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