PSI - Issue 68

Sakari Pallaspuro et al. / Procedia Structural Integrity 68 (2025) 802–808 Pallaspuro S. et al./ Structural Integrity Procedia 00 (2025) 000–000

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Fig. 2. Master Curve plots for the base materials and the weld seam: a) martensitic-austenitic base material DQ&P, b) essentially martensitic direct-quenched base material DQ, c) electron-beam welded seam WS, d) post-weld heat-treated weld seam WS PWHT. The dashed curves indicate 95 % and 5 % probability limits. At -40 °C, all the tested materials have K Jc between ~100 MPa√m and ~150 MPa√m with more scatter than statistically significant differences between the materials. Base material of the DQ&P achieves T 0 of -41 °C, 11 °C lower than essentially martensitic DQ, but both have practically the same level K Jc at -40 °C (Table 1). Despite less than half of the residual austenite content and coarser grain size, the as-welded EB WS has T 0 of -37 °C, statistically the same as that of DQ&P. PWHT lowers provisional T 0Q (provisional due to too few samples tested) for the EB WS + PWHT and the HAZ variants. This is in with the earlier reported changes in T 28J levels reported by Pallaspuro et al. (2022). This can be partly explained with lower RA content that can undergo strain-induced martensite transformation. Another reason for this can be detrimental decomposition of retained austenite to high-C secondary martensite and cementite clusters. Overall, the here tested steels and welds from a clearly robust alloy demonstrate great potential for high-toughness welded AHSS components and structures. The good toughness levels in the as-welded condition motivate omission of additional PWHT treatments. For applying these procedures into industrial practices will still benefit of further analysis of the present residual stresses and optimisation of the electron-beam welding parameters.