Effect of Heat Input on Microstructural and Mechanical Properties of AISI ۳۰۴ Welded Joint Via MIG Welding

In this experimental work, AISI ۳۰۴ was welded via metal inert gas (MIG) welding process with Argon (Ar) as shielding gas. In the present study, AISI ۳۰۴ was subjected to different heat input using a standard ۳۰۸L electrode. Weld quality i.e. ultimate tensile strength, toughness, microhardness, and microstructure of AISI ۳۰۴ were examined. Microstructures of welded joints were studied using scanning electron microscopy (SEM), linked to the SEM was used to determine the chemical composition of phases formed at the joint interface and from the result, it was revealed that at low heat input ultimate tensile strength is higher than those at medium and low heat input. From the result, it was also observed that grain coarsening extent in the HAZ increases with an increase in the heat input. It was also found that the fractures of toughness samples were brittle in nature which shows the low ductility and brittle fracture. Weld zone microstructure exhibited skeletal δ-ferrite in austenite matrix with various ferrite contents. Microhardness of weld bead was found to decrease with increases in the heat input. It was also observed that at medium heat input there was an improvement in tensile strength, elongation, and hardness due to finer grain structure and smaller inter-dendritic spacing.

Keywords:

AISI ۳۰۴ , fracture mode , heat input , microhardness , Microstructure , MIG Welding , SEM