Abstract Scope |
Gas metal arc welding (GMAW) or gas tungsten arc welding (GTAW)-based wire and arc additive manufacturing (WAAM) includes some intrinsic characteristics, such as coupling interaction between arc-droplet and weld pool, non-linear time variation and strong heat accumulation, resulting in a very unstable deposited process and a poor deposition morphology. The higher deposited accuracy of WAAM is currently desired in many applications. This paper proposes a novel method named double-pulse GTAW-AM with stepped filling wire to independently control the heat input and mass transfer in WAAM process. Its fundamental principle is that the energy of melting the substrate and the wire is separately adjusted by using the double-pulse current waveform cooperated with the stepped filling wire. When the low-frequency pulse current is outputting, the wire is not feed, and the arc energy only melts the substrate, forming a given volumetric molten pool. When the high-frequency pulse current is outputting, the given length of wire is synchronously feed, and the arc energy mostly melts the wire and transfers the droplet to the molten pool. And thus, a whole period of double-pulse current is end, and the interaction of heat-mass transfer is decoupled, achieving a certain deposited molten pool. The next step is repeated by changing the double pulse current parameters under considering the heat accumulation. Based on the above principle, a stepping filling wire assisted DP-TIG system was built, and some verified experiments of DP-TIG AM process was performed. The results show that a stable heat and mass transfer process and a deposited layer morphology with good forming accuracy were obtained, and it is feasible to improve the deposited accuracy of WAAM by adjusting the pulse parameters. This approach may provide a good way to precisely control the deposited accuracy of WAAM. |