Optimization of the Weld Bead Volume of Tungsten Inert Gas Mild Steel Using Response Surface Methodology

Abstract

Welding defects unfavorably influence the desired properties of
welded joints. The bead volume is key determining factor affecting
the quality of welded joints. This study was carried out with the aim
of optimizing and predicting the bead volume of low carbon steel
using Response Surface Methodology (RSM). Thirty (30) sets of
experiments were done, adopting the central composite
experimental design. The tungsten inert gas welding equipment was
used to produce the welded joints. Argon gas was supplied to the
welding process to shield the weld from atmospheric interference.
10 mm thickness of mild steel plates was cut to size, measuring
60mm in length and 40mm in width. This study has shown that the
current has very strong influence on the bead volume. The models
developed possess a variance inflation factor of 1 and P- values <
0.05, indicating that the models are significant. The models also
possessed a high goodness of fit with R2
(Coefficient of
determination) values of 91%. Adequate precision measures the
signal to noise ratio. A ratio greater than 4 is regarded as desirable
and the value obtained in this research was 15.5331. The model
produced numerically obtained optimal solution of current of
143.095 Amp, voltage of 15.538 volts, weld speed of 2.19688
mm/min and showed that a gas flow rate of 12.2133 L/min produces
a bead volume of 432.39 mm3
. This solution was selected by design
expert as the optimal solution with a desirability value of 98.8%.