Fixed Heat Source Research Articles

The mother drop in arc welding is always confined within the surface of penetration. The shape of the latter determines the shape of the former, and accordingly the shape of weld bead. In this paper, the author discussed on the inter-relationship among the surface of penetration, mother drop and weld bead, and the following results were obtained.(1) If the surface of penetration, resulting from a very small fixed heat source, is shallow and its angle of penetration Op is less than the angle of contact θ0 of a molten liquid drop of the same metal, the contact line of the drop will slip inward and stand still leaving the bare surface of penetration.(2) A similar bare surface is also conceivable on the surface of penetration in arc welding. If Op is smaller than θ0 at any point along the melting line, the bare surface of the base metal will be wide there, so that it will be liable to induce the direct digging action of the arc, causing uniform penetration along the melting line.(3) The first approximation of the weld bead section is proved to be of a circular arch in the case of very small sectional area, or of the typical liquid drop shape with flat top surface under the gravitional force.(4) Inter-relation between penetration and bead shape was explained, in the case when welding current and speed were fixed so as to keep the sectional area constant, and arc voltage was variable and then the self-regulation mechanism of weld bead configulation in arc welding was made clear.