Abstract
SAF 2507® is a super duplex stainless steel (SDSS), widely used in highly corrosive environments where high strength is required, for example in offshore and chemical industries. It is known that SDSS below room temperature exhibits a ductile-to-brittle transition in fracture behaviour. The present study is aimed at understanding this behaviour in SDSS weldments using instrumented impact toughness testing. Testing was performed between the room temperature and liquid nitrogen temperature (−196 °C) on the base metal, tungsten inert gas welding (TIG) and submerged arc welding (SAW) material. Results showed that there is a significant difference in the ductile-to-brittle transition temperature (DBTT) between the base metal and the weld metal. In base metal, DBTT was observed to be about −75 °C, −105 °C in TIG weld metal and −55 °C in SAW weld metal. This shows that the DBTT is lowered for the TIG weld metal than compared to the base metal and SAW weld metal due to finer distribution of austenite in the microstructure. The possible reasons for the change in fracture behaviour are discussed.
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