TY - CONF A1 - Czeskleba, Denis A1 - Nietzke, Jonathan A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Investigation of the Stress Relief Cracking mechanism through the simulation of uniaxial stress conditions in the coarse grain HAZ of CrMoV-steel SAW joints N2 - Creep-resistant steels such as the 13CrMoV9-10 used in pressure vessel construction, with wall thicknesses of 250 mm and above, are most commonly submerged arc welded (SAW). The characteristic high heat input during the SAW-process introduces very high, localized residual stresses, which can lead to stress relief cracking (SRC) if the mandatory post weld heat treatment (PWHT) of the welding joint is performed improperly. Current PWHT parameters, such as heating rate and holding time at a specific holding temperature are mostly based on both empirically experience and conventional free shrinking welding experiments to characterize the SRC-susceptibility of the weld. These cannot adequately depict the higher residual stresses caused by the structurally induced stiffness of the surrounding construction and its constraint on the thermal shrinkage of the weld. Nor do they consider the resulting metallurgic effects such as the growth of precipitates during the PWHT and the resulting differences in hardness of the grain boundaries or the premature aging via a dissimilar precipitation behavior. The effect of the heating rate of the PWHT on the SRC susceptibility has to date not been adequately studied either. This study discusses the development of a repeatable, precise and time efficient methodology to study the effects of different stress levels and heating rates on the SRC susceptibility of the coarse grain heat affected zone (CGHAZ). For that purpose, samples were thermically treated to simulate a CGHAZ and subsequently exposed to representative levels of stress during PWHTs with defined parameters. The recorded stress and heating rate dependent strains were mathematically analyzed via curve tracing/ calculus to identify interdependent effects. This procedure facilitates the measurement of material characteristics such as carbide growth on grain boundaries at the µm-scale via an integrated value over the entire sample volume. The first and second derivate show a slight, precipitate dependent, increase in hardness of the sample, depending on the heating rate and applied stress. Additionally, the formation and growth of special carbides is well known to have a volumetric effect, which together with the material characterization and this new methodology is believed to generate an improved assessment of the SRC susceptibility of SAW microstructures of creep-resistant CrMoV steels. The main advantage of the suggested methodology is the material independence. It thus provides, a comparative value between welds under ideal conditions in the lab and real-world scenarios by including an idealized, simulated component rigidity. T2 - IIW 2022 CY - Tokyo, Japan DA - 16.07.2022 KW - Repair-welding KW - High-strength steels KW - Transient stresses KW - Residual stresses PY - 2022 AN - OPUS4-55441 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -