Effect of Oxygen on Stabilization of Arc in 9% Ni-Steel GMA Welding
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Unstable phenomena of welding arc in DCRP GMA welding of 9%Ni-Steel with a similarly composed nickel alloy filler metal in commercially pure argon gas shielding are observed with a high speed cine-camera. Two types of unstable phenomena appear in the arc during welding. One is the fluctuation of the arc column associated with the erratic behavior of the arc roots on a plate surface under the higher arc voltage condition and the other is the alternation between spray transfer mode and short-circuiting arc dip transfer mode under the lower arc voltage condition. These unstable phenomena can be stabilized by the adding of O_2 or CO_2 gas to argon gas shroud or by the use of pre-oxidized surface as the cathode plate, which narrow the "cathode area" and smear the cathode spots diffusively over this area. Minimun O_2 or CO_2 gas content in argon shielding gas necessary for stabilizing the arc is 0.3〜0.5% or 0.7〜1.0% respectively. These minimun values are significantly low and make it possible to suppress the oxygen content in the weld metal to the one below 100ppm.
- Transactions of JWRI
Transactions of JWRI 7(1), 93-100, 1978