PSI - Issue 14

Vijay Sai et al. / Procedia Structural Integrity 14 (2019) 491–498

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Ch. Vijay Sai/ Structural Integrity Procedia 00 (2018) 000–000

Fig. 2. Temperature profile in Dissimilar, P91, and SS304 plate weld joints.

Fig. 3. Temperature profile in Dissimilar, P91, SS304 circumferential weld joints.

The dimensions of fusion zone are 2.49mm, 1.9 mm and 3.27mm, in dissimilar weld, P91 and SS304 plate butt weld joints respectively and 4mm, 3.62mm, and 4.22mm in circumferential butt weld joints. In the dissimilar welds, fusion zone is observed to be larger in SS304, than in P91. Owing to low thermal diffusivity, highest temperatures are observed in the SS 304 joints. Heat input was applied equally to all the joints except SS304 circumferential joint where the heat input was reduced by 5 J/mm to limit the fusion zone size and peak temperature. Minimization of fusion zone is necessary to limit dilution and reduce uncertainty of the material properties in the weld region. Taking into account the fusion zone dimensions of both the base materials, Scheffler’s diagram predicts a zone of Austenite and Martensite (A+M) as seen in Fig.4 from simulation showing a graded presence of martensite, across the fusion zone. Temperature contours in dissimilar joints are observed to be asymmetric. Fig.5b and Fig.6b show the temporal variation of temperature in the dissimilar joint, and Fig.5a and Fig.6a show the spatial variation of peak temperature across the weld zone in all the joints. Variation in temperature is not seen in immediate vicinity of weld, but only after the molten zone. In the dissimilar weld, only beyond the tempered zone (20 mm), temperature rises faster in P91. The time to attain peak temperatures within this zone is nearly similar on both base metals in the dissimilar joint, as inferred from Fig.5b. The higher thermal diffusivity of P91 means it cools faster near the weld zone and heats faster away from it. Thus peak temperature within 20 mm from the centre is higher in SS304

Fig. 4. Martensite fractions in dissimilar weld joint.