The relation between welding conditions and the bead formation results are experimentally clarified and a method of the automatic setting of the suitable welding conditions by digital computer are discussed, on the horizontal narrow gap welding. The main results obtained are as follows: 1) The formula by which weld bead height is given as the function of two parameters, that is, welding speed and current, was derived and its propriety was verified experimentally. 2) The experimentally obtained

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... eld beads were divided into three classes on the basis of their configuration. They are evaluated by their flatness factor, smoothness factor and symmetry factor. The domain in which the bead situation is satisfactory was established in the three dimensional space of groove width, welding speed and welding current. 3) The method to set the suitable welding condition automatically by computer on considering the conclusions of (1) and (2) was proposed. The constant bead height and the satisfactory bead configuration will be obtained by adjusting welding speed and welding current according as the change of the root gap in this method.