Fundamental Researches on Bead Formation in Overlaying and Fillet Welding Processes (Report 3)

Theoretical Analysis of Welding Conditions in Overlaying Process

Abstract

In this paper, welding conditions in overlaying process are discussed on the basis of heat conduction theory and surface tensional analysis of bead surface profile which was described in the previous papers.
In setting up welding parameters such as arc current and travelling speed, the following two conditions are of great importance. The first condition is concerned with the quantity of deposit metal corresponding to the required reinforcement and the second one is concerned with the heat input, ensuring the required melting width.
As for penetration shape, shallow one is required in this process. Hence, an important problem to be considered is associated with a property of distributed heat source. So, the property of typical distributed heat source is clarified, i.e., dimensions of penetration by the disk heat source and the line heat source of finite length are made clear and compared with those by the point heat source. Such a calculated heat input condition is correlated to the another necessary condition derived from the surface tensional analysis, where the wire meling rate is taken to be a reasonable value. Consequently, theoretical welding condition is obtained for each of heat source models.
As a result of these estimations, the available bead-width is limited in the overlaying by the point heat source model or the disk heat source model, where overlap bead is inevitable under the condition of wide bead. Accordingly, it may be concluded that one dimensional distributed heat source, such as submerged arc with strip electrode and high frequently weaving arc, is necessary for the overlaying process of wide bead.