The microstructures were computed first for the temperature field, Figure 4-10, obtained from ref. .
The steady state temperature field was computed on a mesh with about 12,000 elements. The welding speed was 1.5 mm/s. Weld pool size and shape were measured from an experimental weld. The maximum length was 35 mm, the maximum width 22 mm, and the maximum depth 11 mm. The gross power input in this weld would be approximately 1.5 kJ/mm. The test plate size was 150 x 40 x 19 mm and the composition is given in Table 4-1.
Figure 4-10: Temperature field in a weld computed by a steady state thermal analysis . The microstructures in Figures 4-11,-12 and -14 were computed for this field.
Table 4-1: Chemical composition of the low alloy steel analyzed
С Si Mn P S Al Nb N
0. 12 0.16 0.91 0.002 0.005 0.04 0.021 0.011
The second modeling was performed on a temperature field, Figure 4-15 taken from the transient thermal analysis . A double weld pool phenomenon in this weld was described by Harlow . Special treatment of the boundary conditions, as presented in ref. , was used. The speed for this weld was also 1.5 mm/s. The test plate size was 250 x 160 x 19 mm. The composition was the same as the first test case.
Before welding, the initial microstructures for both welds were 20% pearlite and 80% ferrite. The initial grain size of austenite was assumed to be 10 /um.