Abstract: Applying the longitudinal magnetic field to the process of streaming transfer MAG welding with 98%Ar+2%O2 and 80%Ar+20%CO2 shielded gases, the influence of the longitudinal magnetic field on arc shape and motion character is researched by means of a high speed camera. It is revealed that the essential effect of the outer longitudinal magnetic field on MAG welding arc is arc constriction. Through analyzing the force of the liquid metal on the end of liquid metal jet, the drop transfer mechanics under the effect of the longitudinal magnetic field is proposed. The result shows that the application of the longitudinal magnetic field can change arc shape from pyramidal and static to spiral and rotational with high speed. With the increment of exciting current, the angular velocity of arc is accelerated and arc length is shortened and electric-field intensity is raised. Also the application of the longitudinal magnetic field can decrease the welding current and increase the transfer frequency of molten drop and the melting coefficient of wire. The stability of MAG welding process is affected by the outer longitudinal magnetic field and the physics nature of shield gas.

Key words: Arc shape, Drop transfer, Longitudinal magnetic field