A Research on the Characteristics of GTAW Shielded Flow ……(Ⅱ) -on the relation between the form of shielded flow and the nitrogen content in the metal of welding seam

In this paper, the law of change of nitrogen content in the metal of welding seam under different forms of shielded flow is studied by means of Laser shadowgraph flow field showing equipment and the gas pulse-chromatography. The concept of critical flow volume Q_cr is proposed that the flow have perfect shielded effect when Q≥Q_cr. The effect of welding standards and the torch structure are also studied systematically.