Welding of fully �Austenitic stainless steel using pcgtaw process; Part I: Bead structure
Abu-Aesh M., Taha M., El-Sabbagh A., Dorn L.
SourcetitleJournal of Manufacturing Processes
The Pulsed-Current Gas Tungsten Arc Welding process (PCGTAW) is recently recommended as an approach to eliminate the high susceptibility of austenitic stainless steel sheets to hot cracking. In order to study the hot cracking susceptibility under PCGTAW; an investigation on the weld bead microstructure should be done first. The present work investigates the effects of the PCGTAW process parameters on the shape, size and microstructure of weld beads at three orthogonal reference planes. The main variables of the current pulse form; namely pulse current Ip, current ratio ?i, frequency f and time ratio ?t are considered. These variables are found to influence the fusion zone microstructure affording columnar/equi-axed transition grain structures. A detailed microstructure description is provided for each individual welding condition. Effects of pulse form variables Ip, f, ?t are studied on bead dimensions and shape, as well as on some grain structure measurements; which are originally developed and used in this research; such as grain orientation angle, grain size and columnar structure ratio. The bead shape is found to be substantially affected by both pulse frequency and time ratio. The puddle width is mainly affected by the pulse current, while the bead depth is mainly affected by time ratio. The bead shape is found to be substantially affected by both pulse frequency and time ratio. The puddle width is mainly affected by the pulse current, while the depth is mainly affected by time ratio. Significant influences are noticed for both ?t and f on columnar structure ratio, grain size and grain orientation angle. A band�like columnar dendritic structure is observed axially extending along the bead axis for cases of ?t greater than 50% with frequencies ranging from 0.5 to 10 Hz. � 2018