Abstract: A welding apparatus spot welds an upper sheet and a lower sheet together. A substantially semi-circular hole or notch is formed at an edge of the upper sheet at the desired location of spot welding. When the semi-circular hole or notch is formed, the process does not wrinkle or deform the upper sheet. A clamping cup of the welding apparatus surrounds the semi-circular hole or notch and contacts the upper surface of the upper sheet. A plasma arc torch heats the sheets, allowing entrapped vapors in a coating on the lower sheet to vent freely to the atmosphere. Filler wire is added and melted to fill the semi-circular hole or notch and to secure the overlapping sheets together.

Abstract: A welding apparatus welds two or more overlapping members having a tenacious surface oxide layer. The apparatus includes a plasma arc torch operable to form a weld pool in a work piece and a weld pool disturbing device operable, in use, to disturb a weld pool formed by the plasma arc torch. The weld pool disturbing device includes a disturbing member which is movable into the weld pool. The apparatus may include a support member adapted to support the weld pool.