| 摘要 |
<p>Ternary gas mixt. providing protection during the arc-welding or -resurfacing of alloy steels, where the gas contains by vol. 2.5-3.5% CO2, 0.8-1.2% H2, remainder argon. The pref. gas mixt. (A) is 96% Ar, 3% CO2, 1% H2. The gas is pref. used to protect a consumable alloy steel electrode wire and the molten weld pool formed by the arc, esp. where the transfer of the molten wire is made by:- (1) sprayed drops, known as the "Spray-Arc" (RTM) method; (2) repeated short circuits between the wire and the bath using short arces and the process "Short Arc" (RTM); or (3) controlled pulses by the process known as "Arc-Pulse" (RTM). When welding by method (2), the workieces are pref. 0.5-1.5mm thick. The gas may also be used in welding or resurfacing austenitic steels, which may contain a small amt. of ferrite, e.g. Ni-Cr steels. The presence of CO2 permits the transfer of metal in a finely divided state, thus avoiding projections, and the H2 exerts a pickling action so correct wetting is obtd. without porosity; the gas also prevents an increase in the % C in the weld deposit and the expensive gas He is not used in the mixt.</p> |
