| Abstract |
In the present work, gas tungsten arc welding (GTAW) technique was carried out to join different steel grades under different heat inputs. The study involves GTAW of low carbon steel (LCS) to AISI 304 and AISI 204Cu stainless steels (SS) as well as similar joining of AISI 204Cu SS and dissimilar joining of the AISI 204Cu to AISI 304 SS. Filler metals ER309MoL and ER308L were employed to join the LCS with AISI 304 and AISI 204Cu SS, and the joining of AISI 204Cu SS with AISI 204Cu and AISI 304 SS, respectively. The microstructural analysis, hardness records, tensile strength, and elongation% of the welded joints were studied by using optical microscopy, Vickers hardness technique, and universal testing machine.
The results revealed that a duplex structure consisting of austenite matrix and delta ferrite was promoted in the fusion zone (FZ) of the welded joints at low and high heat inputs. The width of the FZ increased with the increase of the heat input due to the formation of a molten pool with a size higher than that formed at the low heat input condition. The welding of the LCS to 304 SS and 204Cu SS under high heat input exhibited a FZ with hardness values higher than the joints welded at low heat input. However, the FZ of the welded 204Cu SS to 304 SS and 204Cu SS at high heat input exhibited hardness values lower than the joints welded at low heat input.
The tensile strength of the welded LCS to 304 SS and 204Cu SS increased with the increase of the heat input, while during tensile testing, the fracture of the welded joints happened at the LCS side. On the other hand, the tensile strength of the welded 204Cu SS to 304 SS and 204Cu SS decreased with the increase of the heat input, while during tensile testing, the fracture of the welded joints happened at the weld zone. The strengths of the welded joints were lower than the strengths of the base metals 204Cu SS and 304 SS. The fracture surfaces of the welded joints were studied by scanning electron microscopy. The joints welded at low and high heat inputs exhibited dimples features, which are typical characteristic features of the ductile fracture. |
