Effect of Welding Variables on Toughness of Mild Steel Saw Joints Under Ambient Conditions

Under dynamic load conditions, toughness becomes the most important mechanical property. Some of the main factors which control weld metal toughness include flux basicity, wire chemistry, post weld heat treatment and welding heat input. The present research describes the experimental work carried out on 12 mm thick mild steel plates butt welded (with double V-groove) using submerged arc welding process. The main objective of the study is to establish correlations (using method of least squares) between the input welding variables (viz. welding current, arc voltage, welding speed) and the output variable i.e. the impact strength of the joints at ambient temperatures. The outcome of this study is beneficial in predicting the range of toughness values (Charpy-V notch) of the welded joints prior to actual welding, thus saving experimental resources as well as time and thus enhancing the productivity of the welding process. The study reveals that increased heat input rates result in low Charpy-V impact values (owing to presence of pro-eutectoid ferrite and upper bainite) whereas low heat input rates tend to increase the impact values (due to the interlocking acicular ferrite structure).