Influence of AC frequency, current and stand-off distance on bead profile in AC TIG welding of aluminium

Using Gas Tungsten Arc Welding, or TIG Welding, good quality weld can be obtained. In this process, a shielding Gas is used to avoid atmospheric contamination of the molten weld pool. In the present worl<, bead profile In aluminium worl<piece is observed as welded by AC TIG welding under 100% argon gas shield. Effects of variation of arc frequency, current and stand-off distance on bead profile are investigated. In the experiment, the bead-on-plate welding of 14 treatments is performed on Al 1000 series aluminium plates without a filler wire utilizing Central Composite Design system of Response Surface Methodology (RSI'I). Gas pressure is maintained at 2 l<g/cm" with gas flow rate of 15 litymin, welding speed of 100 mm/min, electrode diameter of 3 mm and wave balance of -25. From this investigation, it is observed that an increase in welding current increases weld penetration. These are caused by the increase in heat input with the increase in weld current and decrease In torch travel speed. An increase in stand-off distance is also observed to cause a decrease in weld penetration. Analysis of variance (ANOVA) is also performed on the observed results. Regression equations are formed relating the response to the factors (independent variables). Linear relationships are found to be quite significant for both
the cases of penetration and weld bead width. Acceptable correlation coefficients (R2) more than 95% are obtained in case of depth of penetration and more than 99% in case of bead width Indicating effectiveness of the results observed.