Comparative Studies on Tensile and Impact Properties of 20 mm Thick AISI SS 304 SMA (Shielded Metal Arc) And GMA (Gas Metal Arc) Butt Welded Joints

Fabrication challenges including joining of larger thicknesses of the order of 20 mm and above poses a great challenge as many problems are encountered during the welding. In view of the above facts welding of thick plates of AISI SS 304 grade it was decided to undertake the present work with different welding processes viz. SMAW & GMAW to study the problems and challenges faced during welding and to study various mechanical properties of 20 mm thick plates.

The main objective of this work was to investigate how SMAW and GMAW affect the microstructure of the weld metal and the HAZ under different welding conditions and consequently, how the mechanical properties viz. transverse tensile strength, ductility and impact toughness of the weld joints were affected. Butt welded joints were made using double V-groove design and welding was accomplished with SMAW (Shielded metal arc welding process) using 9 weld passes and GMAW (gas metal arc welding) using 8 weld passes. The fabricated joints were subjected to radiographic testing so as to make a fair assessment about the quality of the joints. The welded specimens were then subjected to transverse tensile testing and Charpy V-notch impact testing. Tensile results obtained from this study show that the average UTS value is 655.81MPa for base metal, 666.81MPa for the GMAW combination and 565.36MPa for SMAW combination. This shows that the welding of AISI 304 SS is beneficial with GMAW. The impact result show that the average impact value of base material is 163.3J. For SMAW it is 187J and similarly it shows that impact value of 176J for GMAW weld joints. The microstructural studies show that in GMAW continuous dendritic structure is formed in GMAW but in SMAW continuous dendritic structure is disturbed. This work in the present form has helped in establishing a correlation between the microstructure and the mechanical properties and proves to be useful as a welding procedure database for the fabrication industry using thick sections of AISI 304 SS grades.