Abstract
Duplex stainless steels (DSSs) are gaining more and more attention in corrosion-resistant applications and also in the transport and automotive industry. The outstanding mechanical and corrosion properties of DSSs highly depends on the austenite-to-ferrite phase balance (A/F). This phase ratio can shift in a large scale during welding. Thus, the heat input and the shielding gas composition should be optimized. Nitrogen addition to argon shielding is frequently used in DSS welding, because it is a potent austenite former. The dissolved nitrogen content in the heat-affected zone and the weld metal (WM) predetermines the A/F. To determine the effect of heat input and nitrogen content in shielding gas, two different heat inputs and six different gas compositions were used in autogenous tungsten inert gas welding. An improved theoretical model was established in order to simulate the WM dissolved nitrogen content, which calculates it with less error than the initial models. The correlation between nitrogen content and arc voltage was also determined. This improved model delivers the basics for shielding gas selection and the subsequent weld design for optimal A/F for industrial applications.
Highlights
Among the growing application of high strength steels [1,2,3,4], duplex stainless steels (DSSs) are gaining increasing attention from the chemical, petrol, and transportation [5,6,7] industries, thanks to their mechanical properties and corrosion resistance [8,9,10,11]
In order to balance this nitrogen loss, nitrogen (N2 )–argon (Ar) mixed shielding gases are used in industrial applications for DSS tungsten inert gas (TIG) welding [23,24,25]
Afterwards, the comparison of our improved theoretical model to the measured total dissolved in nitrogen the weld metal (WM)
Summary
Among the growing application of high strength steels [1,2,3,4], duplex stainless steels (DSSs) are gaining increasing attention from the chemical, petrol, and transportation [5,6,7] industries, thanks to their mechanical properties and corrosion resistance [8,9,10,11]. The N2 dissociates at the arc plasma temperature and the atomic nitrogen can dissolve in the molten pool [26]. During the solidification, this dissolved nitrogen (N) can enhance its γ forming effect on the δ → δ + γ phase transformation. For this diffusion-driven phase transformation, adequate diffusion time is needed, which is expressed
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