Process stability and weld pool oscillation during short circuiting GMA welding
Book
·
OSTI ID:442977
- Delft Univ. of Technology (Netherlands)
In this paper the results are presented of an investigation dealing with short circuiting GMA welding. Experiments were carried out under different conditions and during these experiments various process parameters were continuously monitored. It was found that the maximum in process stability coincides with the maximum in the short circuit frequency. Outside this maximum either irregular material transfer takes place with a tendency for open arc droplet transfer, or stubbing of the welding wire in the weld pool starts to occur, accompanied by highly irregular melt-off behavior. The results show that process stability is directly related to weld pool oscillation. More specifically, it appears that process stability is maximum (optimum welding conditions) when the short circuit frequency equals the oscillation frequency of the weld pool. Under these conditions the weld pool touches the droplet at every oscillation, which results in regular droplet transfer and high stability of the overall welding process. This was confirmed by high-speed films. In order to determine the influence of the chemical composition of the liquid metal and the shielding gas on the short circuiting behavior, welding experiments were carried out with different base metals and shielding gas mixtures. The results of these experiments show that the chemical composition of the shielding gas and the weld metal has a pronounced effect on the optimal welding conditions. For instance, when austenitic stainless steel AISI 316 is used, the maximum short circuit frequency (being equal to the oscillation frequency) is approximately 6% higher than in the case of unalloyed steel. The results obtained can be explained in terms of the physical properties of the liquid metal, in particular the surface tension.
- OSTI ID:
- 442977
- Report Number(s):
- CONF-950682--; ISBN 0-87170-567-2
- Country of Publication:
- United States
- Language:
- English
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