Weld Bead Surface Research Articles

アーク溶接現象に関する界面張力理論(第6章)

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.

アーク溶接現象に関する界面張力理論(第7章)

The author measured various angles on the surface of penetration obtained by rapid hammer blow exerted upon the mother plate in the course of welding in flat position for various welding conditions with five kinds of covered mild steel arc welding electrodes, and discussed on the relation between the contact angle of mother drop covered with various slags and weld bead configurations. Results obtained were as follows.(1) The angle of solidification θs' angle between the extension of bead surface and the solidifying surface of weld bead, is almost a constant value along the total length of the solidifying line except at both ends.(2) Angle of solidification at the mid-point between the end and the center of the solidifying line is almost the same under various currents. 9s, mean value of 0s, seems to be nearly the same as the contact angle θo characteristic to the kind of welding electrode.(3) The order of wetting property of mother drops from various electrodes, which is presumed from the angle of solidification against the solidifying surface in manual welding or in submerged arc welding using slags of the same coated electrode, roughly coincides with what presumed from the shapes of alcoholic water drops of various concentrations placed within the actual surface of penetration coated by paraffin. And the order is the same as the one of JIS code number.(4) The ratio of height to width of bead in various welding electrodes increases according to the JIS code number, except D 4320.(5) The effect of up-and down-hill welding or of welding speed on the shape of penetration and weld bead can explanined by means of the changes of direct and indirect digging action of welding arc.