Open AccessEffects of TIG Reheating on Duplex Stainless Steel Weld Microstructure
Author(s) -
Balázs Varbai,
Ferenc Tolnai,
Kornél Májlinger
Publication year - 2019
Publication title -
international journal of engineering and management sciences
Language(s) - English
Resource type - Journals
ISSN - 2498-700X
DOI - 10.21791/ijems.2019.1.37.
Subject(s) - materials science , metallurgy , microstructure , gas tungsten arc welding , shielding gas , welding , austenite , ferrite (magnet) , inert gas , arc welding , corrosion , heat affected zone , composite material
Duplex stainless steels (DSS) gaining their excellent mechanical properties and corrosion resistance due to their austenitic-ferritic microstructure, ideally in the same amount. However, to keep this ideal phase ratio during arc welding is very difficult. Generally, the arc welding processes will result in more ferritic microstructure in the weld metal and in the heat affected zone, due to the rapid cooling. The ferritic microstructure can cause chromiumnitride precipitation, because the nitrogen solubility in ferrite phase is very low below 700 °C. These chromiumnitride precipitations can cause loss of corrosion resistance and mechanical properties. However, during subsequent reheating, the chromium-nitrides can dissolve and act as a secondary austenite nucleation site in the ferritic microstructure. In our research we welded DSS specimen autogenously, with tungsten inert gas welding using pure argon and 94 % argon + 6 % nitrogen as shielding gasses. In the first case the sub-sequent solid-state reheating caused 20 % increase in the austenite fraction of the weld metal but with the use of mixed shielding gas only 5 % increase.