Melting Characteristics of C-Type Filler Metal in GTAW

A C-type filler metal was developed to overcome the low deposition rate (DR) of gas tungsten arc welding (GTAW). The present study investigated the maximum DR for a novel C-type filler metal and compared it to conventional circular welding wires during GTAW using an Alloy 625 filler metal. For comparison with conventional circular welding wires, a ø1.2-mm (0.047-in.) welding wire, which is most widely used in practice, and a ø2.4-mm (0.094-in.) welding wire, which has almost the same sectional area as the novel C-type filler metal, were used in this research. An industrial robot was utilized to produce bead-on-plate welds in the flat position. The results revealed that at the same 200-A welding current, the DR of the C-type filler metal was higher than the conventional circular welding wires by 1.17 to 1.4 times according to the sectional area of the circular welding wires. At a high welding current of 500 A, it was impossible for the ø1.2-mm welding wire to deposit quality welds, and the acceptable range of the DR for the ø2.4-mm welding wire was narrow (i.e., 7–8 kg/h [15.4–17.6 lb/h]). However, the acceptable range of the DR for the C-type filler metal was as broad as 5.04–12.1 kg/h (11.1–26.6 lb/h) under the high welding current of 500 A. The maximum DR of the C-type filler metal was 1.51 times that of the ø2.4-mm welding wire. The mechanism of obtaining a high DR using the C-type filler metal was analyzed from the viewpoint of the continuous bridging transfer at the melting edge of the C-type filler metal. The ability of the C-type filler metal to achieve high DRs at high-current regions was superior to the conventional ø1.2- and ø2.4-mm welding wires.