ABSTRACT
Duplex stainless steel (DSS) are materials with high mechanical strength and corrosion resistance in aggressive environments, the main requirements in chemical and petrochemical industry. These properties are assigned to its microstructural composition, which is around 50% ferrite and 50% austenite, based on balanced alloying elements and solubilization temperature. Generally, welding DSS applications involve thermal cycles, causing microstructure transformations. Therefore, welding processes must be properly controlled in order to reduce the occurrence of severe microstructural changes, as intermetallic phases, harmful to mechanical properties and corrosion resistance. The aim of this paper is to analyze a Heat Affected Zone (HAZ) on two DSS UNS 31803 welded joints resultant from GMAW process. The first one was welded according to standard ISO 13847, with inter-pass temperature up to 150ºC (joint A). The second one was welded through simultaneous passes, without cooling time, and inter-pass temperature range of 250ºC-300ºC (joint B), measured with contact thermometer. HAZ and intermetallic phases were larger in joint B than in joint A. Phase counting ferrite/austenite (δ/γ) was carried out in the HAZ, and detected similar percentage for both welded conditions, comparing these results with base metal composition, there is a 10% reduction in austenite phase.
Keywords:
Duplex stainless steel; Pulsed GMAW process; Inter-pass temperature, Phase counting
