Predicting the Microstructure and Properties of Steel Welds

MULTIPASS ARC WELD L.-E. SVENSSON

100 µm

20 µm Barrite, 1982

Manual Metal Arc Weld 180 Amps 34 Volts 4 mm/s 200 °C interpass Manual Metal Arc Weld 180 Amps 34 Volts 4 mm/s 200 °C interpass

Fe-0.4C 2. Fe-0.4C-2Si 3. Fe-0.4C-1Ni 4. Fe-0.4C-1Mn 5. Fe-0.4C-1Mn-1Cr 6. Fe-0.4C-2Mn Time / s Temperature / C calculations

Barrite, 1982

5 µm Barrite, 1982

Carbon / wt % Volume fraction Allotriomorphic Widmanstatten Acicular Fe-1Mn-C wt % manual metal arc welds

Bhadeshia & Svensson

Charpy toughness Murugananth & Bhadeshia

7Ni 2Mn

7Ni 0.5Mn

7Ni 2Mn

7Ni 0.5Mn

Weld Shape - Stitch Weld at 2.26 kW Laser Output Laser beam K eyhole L aser beam F usion Z one

 m w

Optically: mainly  -ferrite some w-ferrite <5% martensite TEM:  -ferrite much w-ferrite 155, 157 and 170 HV Mean Hardness: 161 HV Grain size 100 ±20  m 46%  -ferrite 21% w-ferrite 30% acicular ferrite & bainite 3% martensite 168 HV Grain size 103  m Measured Calculated

Charpy fatigue corrosion tensile critical stress intensity

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

Empirical Equations  y = a + b (%C) +c (%Mn) + d (%Ni)....  y = a + b (%C) +c (%Mn) + d (%Ni)

 y = a + b (%C) +c (%Mn) + d(%C x %Mn)  y = a + b (%C) +c (%Mn) + d(%C x %Mn)

 y = a + b (%C) +c (%Mn) + d(%C x %Mn)  y = sin (%C) + tanh (%Mn)  y = a + b (%C) +c (%Mn) + d(%C x %Mn)  y = sin (%C) + tanh (%Mn)

Hyperbolic Tangents

non-linear functions

Predict what the next two numbers are likely to be: 2, 4, 6, 8, …….

Brun, Robson, Narayan, MacKay & Bhadeshia

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

Cole & Bhadeshia

Cool, 1996

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

Siemens Mitsui Babcock Nippon Steel ABB

Thank you.