Abstract
The butt welding of 0.3 mm thick very thin Al sheets by the ordinary inverter controlled TIG welder at ultra high speed(12, 000 mm/min)have been debeloped by means of the improvements of the nozzle. The welding procedures are as follows;
(1)Fine 2%Th-W electrodes of 1.0 or 1.6 mm diameter were employed. The polarity is DCEN. No filler metal rod was used.
(2) The Al sheets were clamped between two 30 mm thick Cu plates except some part of the sheets, thus avoiding the heat flow to the preceeding parts which cause the deflection of the sheets.
(3) As the welding speed becomes higher and higher, the arc is dragged backward more and more. At last the arc goes out of the atmosphere of the protective Ar gas. To prevent this phenomenon, the size of the cross section of the nozzle was expanded, as the shape of a ellipse of which the long axis lies on the welding line.
(4) On the other hand, some sheets of wire cloths were inserted vertically to the gas flow as the "damper"in the gas flow hole of the nozzle, to chenge the type of gas flow from the turbulent to the laminar one.
(5) However the empty gap without the wire cloth is set in the surrounding narrow area around the electrode. Thas the strong gas blow from this gap squeezes and focuses the arc stably on the welding spot.
(6) By the nozzle with the combination of the shape of its cross section and the variety of the wire cloths, the butt welding of 0.3 mm thick Al sheets at 12, 000 mm/min speed became possible and that of 18, 000mm/min became hopeful.
