TY - CONF A1 - Steppan, Enrico A1 - Zhang, Lei A1 - Kannengießer, Thomas T1 - Influence of microalloy design on HAZ toughness of S690QL steel N2 - Three high strength Nb-, Ti- and Ti+V- bearing S690QL steels were welded to investigate and compare the effects of microalloy addition on HAZ toughness. Charpy V notch impact tests from three microalloyed welds under different cooling rates have been performed. Fractographic examination shows that several factors including large-sized grain, upper bainite or hard second phase, interact to determine the brittle fracture mode and impaired toughness of Nb bearing weld at high heat input. In contrast to this reduced toughness, Ti bearing welds exhibits satisfied toughness regardless of at a fast or slow cooling rate as a result of limited austenite grain and refined favourable intragranular acicular ferrite structure. Moreover, in the case of such refined structure as matrix, TiN particles are found to be irrelevant to the fracture process and crystallographic misorientation results also confirms that high angle boundaries between fine ferrites plates provide much effective barrier for crack propagation and contribute to improved toughness. T2 - 69th IIW Annual Assembly and International Conference CY - Melbourne, Australia DA - 10.07.2016 KW - Cooling rate KW - High strength steel KW - Microalloy elements KW - HAZ toughness KW - Microstructure PY - 2016 AN - OPUS4-39458 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -