PSI - Issue 5

Lars Sieber et al. / Procedia Structural Integrity 5 (2017) 1011–1018 Sieber et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 4. Details of the grain texture in the heat affected zone of an old steel; (a) base material; (b) heat affected zone; (c) fusion line

The unkilled steel includes oxides, mainly close to the plate-thickness center. Its sulphide morphology is typical for this level of deoxidisation, mainly type I according to Sims et al., see Figure 4a. Due to the absence of chain-like distributions of the sulphides, lamellar cracks are not facilitated by them. However, in the direction of rolling several prominent lines are visible which probably originate from voids created during casting and insufficient pressure during rolling. As they appear only in line with the sheet plane, their influence will probably not be visible in tensile testing but could increase lamellar crack risk. Hardness indentation measurements were carried out across the welds in various distances to the surface. Figure 5 shows such a line exemplary for sample AV.1.2. As can be seen, the thermal cycle during welding in combination with the chemical composition of both base metals and filler material created a generally rising hardness level across both HAZs and weld.

Fig. 5. Micro-section of sample AV1.2 with hardness test results