| Author(s) |
Ivan Pigozzo, Daniele D. G. Calista, Kerry Chen, Pooja Saini, Franklin Wang, Samantha Nicole Skiba, Luu Greg Nguyen, Jason Olfert, Patricio Fernando Mendez |
| Abstract Scope |
This work presents an investigation into the production of weld fumes from different GMAW metal transfer modes as a first step in a broader project aimed at understanding the physical mechanisms of weld fume generation. Experiments consisted of depositing ER70S-6 wire onto low carbon steel plate, using five metal transfer modes: short-circuit, Regulated Metal Deposition™ (RMD), globular, spray, and free-flight with pulsed current (FFPC). Fumes were collected using a probe tube positioned in-stream with a full-scale fume exhauster. The mobility diameter (MD) and total concentration of aggregate particles (APs), which were composed of smaller primary particles (PPs), were measured using a Scanning Mobility Particle Sizer (SMPS). AP morphology, including nominal diameter and projected area, was characterized via Scanning Electron Microscopy (SEM). To preserve their inherent structure, these particles were collected directly onto quartz membranes during welding. MD analyses indicated that APs produced from short-circuit, RMD, globular, spray, and FFPC transfer modes had a count mean diameter of 136 nm, 112 nm, 140 nm, 148 nm, 103 nm, respectively. MD analyses also indicated the diameter of APs produced from all transfer modes can require different filtration mechanisms. SMPS measurements also demonstrated that, for all metal transfer modes, the net amount of fumes increased with average current. For the same average current, FFPC produced higher fume concentration than short-circuit, RMD, and globular. The size of PPs and morphology of APs indicated that particles may be produced by different physical mechanisms. Future work includes further investigation in the mobility diameter and aerodynamic diameter of APs produced from GMAW. Applying this fundamental knowledge to the design of engineered safety controls will enable the targeted, controlled reduction of operator exposure risk. |