Hazard of ultraviolet radiation emitted in gas metal arc welding of mild steel.

Objectives: Ultraviolet radiation (UVR) emitted during arc welding frequently causes keratoconjunctivitis and erythema in the workplace. The degree of hazard from UVR exposure depends on the welding method and conditions. Therefore, it is important to identify the UVR levels present under various conditions.

Methods: We experimentally evaluated the UVR levels emitted in gas metal arc welding (GMAW) of mild steel. We used both a pulsed welding current and a non-pulsed welding current. The shielding gases were 80% Ar + 20% CO and 100% CO. The effective irradiance defined in the American Conference of Governmental Industrial Hygienists guidelines was used to quantify the UVR hazard.

Results: The effective irradiance measured in this study was in the range of 0.51-12.9 mW/cm at a distance of 500 mm from the arc. The maximum allowable exposure times at these levels are only 0.23-5.9 s/day.

Conclusions: The following conclusions were made regarding the degree of hazard from UVR exposure during the GMAW of mild steel: (1) It is more hazardous at higher welding currents than at lower welding currents. (2) At higher welding currents, it is more hazardous when 80% Ar + 20% CO is used as a shielding gas than when 100% CO is used. (3) It is more hazardous for pulsed welding currents than for non-pulsed welding currents. (4) It appears to be very hazardous when metal transfer is the spray type. This study demonstrates that unprotected exposure to UVR emitted by the GMAW of mild steel is quite hazardous.