Effect heat input of GTAW process on the microstructure and fracture toughness of weld metal in API ۵LX۹۰ steel

In this study, the effect of GTAW process input heat on the microstructure of fracture toughness of API-۵L X۹۰ micro-alloy steel fittings using ER۱۲۰S-G filler metal in three different inlet temperatures of ۱.۵۰۶, ۱.۶۷۴ and ۱.۸۴۱ kJ Was examined in mm. Optical microscope and SEM electron microscope were used for microstructural studies. Microstructural studies showed that the base metal microstructure consisted of ferrite and granular bainite and it was found that the weld metal included needle ferrite, polygonal ferrite and martensite / austenite (MA) islands. It was found that the amount of needleferrite decreases with increasing inlet temperature. The toughness of base metal and weld metals was determined by Sharpe impact test. The results of Sharpe impact test showed that at ambient temperature, weld metal with high inlet heat has the highest fracture toughness. Be. And at -۲۰ ° C, the base metal had the highest fracture toughness compared to the weld metal; And by increasing the inlet heat, the fracture toughness of the weld metal decreases

Keywords:

API-۵L X۹۰ , GTAW , weld metal , heat input , microstructure , fracture toughness.