PSI - Issue 17

Jan Kec et al. / Procedia Structural Integrity 17 (2019) 230–237 Jan Kec / Structural Integrity Procedia 00 (2019) 000 – 000

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DBTT values are caused a greater number of pearlitic bands per unit area, higher elongation of MnS inclusions and, last but not at least, by higher elongation of ferritic grains in T-L orientation.

Fig. 5. Charpy impact transition curves: (a) variation of absorved energy with temperature; (b) variation of percent shear fracture with temperature.

Analogically to BM specimens, Charpy impact transition curves for weld centre line, fusion zone, fusion zone + 2 mm and fusion zone + 4 mm were obtained (Fig. 6). In comparison with the base material, a marked decrease of absorbed energy is observed. It results from the heterogeneity of microstructure both from the view of the size of structural constituents and from the view of phase distribution. The rate of shear fracture could not be investigated, because the fracture surface did not show typically detached regions as in case of BM; nevertheless, a detailed SEM analysis revealed some differences in the fracture micromorphology. In fracture surfaces of specimens tested at higher temperatures (40 °C and 20 °C) the dimple morphology prevailed, but at 0 °C and lower temperatures, cleavage facets began to occur. The areal rate of cleavage facets increased with the decreasing temperature up to -60 °C when only cleavage facets were observed on the fracture surface.

Fig. 6. Charpy impact transition curves for (a) weld metal, fusion zone and (b) HAZ.