A New Approach to Lowering Exposure to Manganese During Welding

In recent years, some involved in the welding industry have become increasingly concerned about the potential for exposure of workers to fumes containing manganese and manganese oxides during welding. While the OSHA permissible exposure limit (PEL) for manganese remains unchanged since 1992 (ceiling limit of 5 mg/m3), the American Conference of Governmental Industrial Hygienists (ACGIH) reduced the threshold limit value (TLV) for manganese from 1.0 mg/m3 to 0.2 mg/m3 in 1995. In 2009, the ACGIH issued a Notice of Intended Change (NIC) for manganese that would reduce the allowable exposure to 0.02 mg/m3, a ten-fold reduction. In February of 2013, the NIC was adopted. Although no action from OSHA appears to be imminent, some US states and Canadian provinces have adopted the new guideline. Even with effective local exhaust ventilation systems, these new limits are extremely difficult to meet in most manufacturing facilities.

All mild- and low-alloy steel welding electrodes currently on the market contain some level of manganese for deoxidation and strengthening. In flux-cored electrodes, that manganese is typically in the form of manganese or manganese alloy powder, manganese oxide powder, and the manganese that is present in the carbon-steel sheath of the electrode. Hobart has recently developed a new, innovative line of very low-manganese flux- and metal-cored welding electrodes. These electrodes contain little or no manganese in the core—in many cases, the only source of manganese in the electrodes is the manganese that is present in the sheath material. As a result, the amount of manganese in the fume is dramatically reduced as compared to a standard flux- or metal- cored electrode, or even a solid wire.

The new electrodes were developed at various strength levels and cover a range of AWS classifications. They include electrodes formulated for both CO2 and mixed gas (Ar/CO2) shielding. They exhibit excellent mechanical properties and operability.