Silicon-Rich Bainitic Steel Welds www.msm.cam.ac.uk/phase-trans M. Lord L.-E. Svensson

Previous work Inspiration from steels Novel weld microstructure Two weld design models Experimental results Difficulties

G. M. Evans, Metal Construction, 1986 Mn 0.60-1.82 Si 0.20-0.95 wt%

100 µm

Allotriomorphic ferrite Widmanstätten ferrite Acicular ferrite Microstructures: Allotriomorphic ferrite Widmanstätten ferrite Acicular ferrite Recrystallise easily

Carbon supersaturated plate diffusion Cementite precipitation UPPER BAINITE LOWER BAINITE

g g a a a 20 nm

50 µm

T-zero curves

kilocycles to Crack Initiation Pearlite Martensite Bainite 1200 1000 800 600 400 200 kilocycles to Crack Initiation Yates, Jerath

Yates, Jerath

Design criteria for welds T0 curve at high carbon Sufficient hardenability

MULTIPASS ARC WELD L.-E. SVENSSON

20 µm Barrite, 1982

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

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 0 1 2 3 4 5 10 10 10 10 10 10 Time / s

Bhadeshia & Svensson, 1989

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 %

wt%

equilibrium Si Fe

paraequilibrium Si Fe

Weld microstructures, with good properties, containing mixtures of austenite and bainitic-ferrite can be created. Data and theory for silicon in steel needs improvement

Best wishes for the next 30 years