(A) study on selection of adequate welding parameters by considering weld bead shape and weld defects and development of seam tracker in horizontal fillet welding

Abstract

The horizontal fillet welding is prevalently used in heavy and ship building industries to fabricate the large scale structures. A deep understanding of the horizontal fillet welding process is restricted, because the phenomena occurring in welding are very complex and highly non-linear characteristics. Furthermore, various kinds of weld defects can be induced due to the improper welding conditions. To achieve a satisfactory weld bead geometry, it is necessary to study the effect of welding conditions on the weld bead geometry. To meet the above necessities, a mathematical model related with the weld bead surface geometry was proposed in conjunction with a two-dimensional heat flow analysis of horizontal fillet welding adopted for computing the melting zone in base metal. The model was based on the minimization of energy which acts on the welded area, and could accurately estimate the surface geometry of weld beads which might include the undercut, overlap or excessive convexity. The results of mathematical modeling was also used as crucial data to predict the relationship between the welding conditions and weld bead shapes. The welding process variables such as the welding current, arc voltage, welding speed, gas flow rate and offset distance influencing the weld bead shape are coupled with each other but not directly connected with the weld bead shape individually. Therefore, the determination of welding process variables for the desired weld bead shape is a very difficult and time consuming work. To get the appropriate welding process variables, mathematical modeling in conjunction with many experiments are necessary to predict the magnitude of weld bead shape. Even though the experimental results are reliable, it has a difficulty in accurately predicting the welding process variables for the desired weld bead shape because of the coupling characteristics. In this study, the $2^{n-1}$ fractional factorial design method was used to investigate the effect of ...