Table 1.
Parameters for low metal and high metal resistance spot-welding.
| Low metal (LM) | High metal (HM) | |
|---|---|---|
| Weld process | Resistance spot welding | Resistance spot welding |
| Fabrication metal | Low alloy carbon steel strip (24 gauge; 1/40″ thick; 1″ width) | Low alloy carbon steel strip (24 gauge; 1/40″ thick; 1″ width) |
| Weld current | 7.5–9.0 kA | 10.5 kA |
| Weld time | 140 ms | 140 ms |
| Post-weld hold time | 50 ms | 50 ms |
| Lag-time between weld | 5 s | 20 s |
| Spot-weld distance | 3/4″ apart | 3/4″ apart |
| Bonding adhesive | Terokal® 2300 | Terokal® 2300 |
By varying weld current and lag-time between weld, aerosols with different characteristics were generated. Aerosols generated at a weld current of 7.5–9.0 kA or 10.5 kA produced good quality spot welds. At a weld current of 7.5–9.0 kA, there was no sparking or expulsion of molten metal, which produced aerosols with low metal content (LM). At a weld current of 10.5 kA, sparking and expulsion of molten metal was observed, which produced aerosols with higher metal content (high metal, HM).
To achieve a chamber aerosol concentration of 25 mg/m3, the average lag-time between welds was 5 s when operating in the no spark mode (weld current of 7.5–9.0 kA), whereas an average lag-time of 20 s was needed to generate the same chamber concentration of 25 mg/m3 when operating at the spark mode (weld current of 10.5 kA).