Feedability of wires during metal active gas welding

Abstract

Feedability of welding wire is controlled by sliding contacts between the contact tube and wire surface. In achieving stable arc discharge, it is very important that feeding speed of the wire does not deviate from the constant speed derived from average welding current. Temperature of the contact tube, current branching, voltage drop, and contact resistance of the sliding contact were measured during welding of Cu coated and non-Cu coated solid wires. For Cu coated solid wire, the sliding contacts can be in either the solid or liquid state, depending on welding current. Conversely, for non-Cu coated solid wire, the sliding contacts are in the liquid state regardless of welding current. Discontinuity of solidification at the sliding contacts causes feeding resistance of the welding wire. The shear strength of a ‘bridge’ solidified at the sliding contact is about 4·5 N, and this force is amplified in the conduit liner by a factor of about 10.