Investigation the Effect of Welding Heat Input on Microstructure and Mechanical Properties of AISI310 Stainless Steel and API5LX60 Low Alloy Steel Dissimilar Joint

In this research, the microstructure and mechanical properties of AISI310 austenitic stainless steel/API5LX60 low alloy steel dissimilar joints welded in three different heat inputs, were studied. Gas tungsten arc welding (GTAW) Process and ER2209 filler metal was used for preparing the joints. After welding, the microstructure of different regions of each joint, including base metal, weld metal, heat affected zone (HAZ) and the interface were investigated using optical microscope. Studying fracture surface of the weldments prepared in different heat inputs was performed using scanning electron microscope (SEM). Mechanical properties of the joints were evaluated using impact and micro-hardness tests. Microstructural studies showed that using ER2209 filler metal has led to a ferritic-austenitic microstructure at the weld metal. It was found by increasing the heat input, no significant microstructural change occured at the heat affected zone of AISI310 steel, but the change in microstructure at the heat affected zone of API5LX60 steel was clearly visible. The results of impact tests showed a considerable increase in fracture energy of the weld metal by increasing the heat input. In addition increase in the heat input, has not a noticeable effect on the weld metal hardness, and change in hardness of the weld metal due to increasing the heat input was quite low and negligible.