CO₂溶接におけるシールド効果のテレビによる観察

抄録

The shape of the shielding gas stream of CO₂ arc welding was visualized by the television system combined with the Schlieren optical apparatus. Some factors, such as the diameter of welding nozzle, the flow rate of shielding gas and the velocity of wind blow which influenced the core region of shielding gas and also the shielding area on the base metal surface, could be examined by this method. Gas analysis of shielding atmosphere and X-ray inspection of weld metal were also carried out to confirm the results obtained by this method.
The following results were obtained.
(a) In the area where the core region of shielding gas could be observed by the method, an enough CC₂ concentration was measured, which could prevent the porosity of mild steel weld metal.. And the minimum CO₂ concentration for preventing the porosity was found to be about 95 vol%.
(b) An experimental formula, which included shielding distance toward the wind, crosssectional area of nozzle, shielding gas velocity (Vs) and wind velocity (Vw), was obtained. And the critical velocity ratio Vs/Vw, which was the minimum velocity ratio for preventing the porosity under the wind blow, was estimated as 1.62.1. The value was then confirmed by the X-ray inspection on the porosity of weld metal.