Thermoelectric power measurements on duplex stainless steel weldments

Abstract

In our research bead-on-plate autogenous TIG welds were prepared on 2 mm thick UNS S32205 (EN 1.4462) duplex stainless steel sheets using different shielding gases: argon, and argon+nitrogen shielding with +2 vol. % N2, +5 vol. % N2 and +10 vol. % N2 nitrogen content beside argon. The welds were reheated in argon atmosphere up to 1250 °C peak temperature, using Gleeble® 1500 thermomechanical simulator. Both in the as-welded and reheated state the austenite fraction, total nitrogen content and thermoelectric power (TEP) values were measured. Correlation was found between the austenite content in the weld metal, the total nitrogen content in the wed metal and the TEP value as a function of the used shielding gases and the subsequent reheating thermal cycle. We also attempted to differentiate between the total dissolved nitrogen and interstitial atomic nitrogen. This work is a part of an extended project in order to understand the sometimes controversial effects of nitrogen on duplex stainless steel welding.