A Study on Bead Shape in Submerged Arc Horizontal Fillet Welding

Abstract

It is often observed that the shape of horizontal fillet weld bead is influenced by welding variables and flux.
From the viewpoint of the interfacial tension phenomena, this study was done to investigate the relation among the shape of horizontal fillet weld bead, welding variables and flux composition.
Firstly, a theoretical consideration on the formation of horizontal fillet weld bead was made on the assumption that the shape of weld bead would be determined by the balance of interfacial tensions between slag, molten metal and solid metal, gravity of liquid metal and so forth.
Secondly, the effect of interfacial tension between slag and metal on the bead shape was examined experimentally.
The interfacial tension was measured by a new method proposed in this paper.
That is, flux and wire were melted by TIG arc in a copper crucible cooled with water. The interfacial tension was calculated from the shape of a frozen steel drop.
The following results were obtained:
(1) The shapes of horizontal fillet weld bead are classified into three types in submerged arc welding.
(2) The main factor which determines the bead shape of submerged arc horizontal fillet weldindg is the interfacial tension between slag and metal.
(3) In order to get a good shaped horizontal fillet bead, it is necessary to use a flux which exhibits as large values as possible of interfacial tension and specific gravity.
But, according to theoretical consideration, more than 9.5 mm of leg length could not be attained for the horizontal fillet bead welded in one pass.
(4) It was confirmed that the interfacial tension between molten slag and molten metal was able to be measured by the shape of a frozen steel drop.
(5) With the above-mentioned method, the interfacial tension between weld slag and wled metal was measured.
The values of the interfacial tesion were 1250 dyne/cm for the maximum case and 750 dyne/cm for the minimum case, respectively.