Investigating the microstructure and uniform corrosion of P۴۶۰NHsteel welded using TIG welding process

P۴۶۰NH micro-alloy steel is used in applications such as boilers and pressure vessels.Different welding processes and fillers can be used to weld this steel. In this study,manual arc welding process (SMAW) with E۸۰۱۸-G electrode and tungsten arc weldingprocess with argon shielding gas (TIG) with ER۸۰S-G welding wire were used and toobtain optimal welding parameters, according to ASME standards. IX, welding wasperformed. Then, by sampling from the welding section, the corrosion behavior of theaffected areas of heat, welding pollen and base metal was investigated separately usingTafel polarization test in ۳.۵% NaCl solution. Evaluation of corrosion behavior ofdifferent regions also showed that in tungsten arc welding with argon shielding gas withER۸۰S-G welding wire, the weld metal has the highest corrosion potential (-۰.۶۸۹ volts)and the lowest corrosion current density (۵.۴× ۱۰-۵ amps per square centimeter). And thebase metal with corrosion potential (-۰.۶۹۳ V) has the highest corrosion current density(۱.۲ × ۱۰-۵ amps per square centimeter) compared to the weld metal and the area affectedby heat. This is despite the fact that the microstructure ofthe base metal is ferrite-pearliteand it can be found in the weld metal area and the heat-affected area of those types, suchas acicular ferrite, polyhedral ferrite, grain boundary ferrite (GBF) and Wiedmannstattenferrite (WF). observed According to the obtained results of the corrosion potential, theweld metal and the base metal are in a nobler position compared to the heat-affected area,and the corrosion current density has increased from the base metal to the weld metal,respectively, and has reduced the polarization resistance to So that the weld metal has thehighest corrosion current density and the lowest polarization resistance. These changeshave also been achieved with the increase of needle ferrite, which can be justified by theincrease of needle ferrite in the weld metal area and the heat-affected area compared tothe base metal, the increase in the corrosion current density.

Keywords:

P۴۶۰NH Steel , ER۸۰S-G Electrode , Corrosion Potential , Corrosion Current Density , Hardness , Tafel Polarization Test.