E7018 Welding Parameters
Strict Control of Welding Parameters
Current Type and Polarity
E7018 electrodes must use DC reverse polarity (workpiece connected to negative, electrode to positive). AC power or DC straight polarity is strictly prohibited:
DC reverse polarity ensures stable arcs, sufficient penetration, and reduces spatter and porosity. Incorrect polarity causes erratic arcs, poor fusion, or premature coating detachment.
Matching Current Range
Excessive or insufficient current affects welding quality; it must be strictly controlled based on electrode diameter (reference ranges below):
| Electrode Diameter (mm) | Welding Current (A) | Notes |
|---|---|---|
| 2.5 | 60~90 | Thin plates or root passes |
| 3.2 | 90~130 | Filling passes for medium-thick plates |
| 4.0 | 140~180 | Filling or capping for thick plates |
| 5.0 | 180~230 | Multi-pass welding for thick plates |
Excessive current: Coating melts faster than the core, causing poor protection and porosity; it also overheats the weld, leading to coarse grains and reduced toughness.
Insufficient current: Unstable arcs, insufficient penetration, incomplete fusion, slag inclusion, and poor slag removal.
Arc Voltage and Length
A short arc (arc length ≈ 1/2~2/3 of electrode diameter) is required. Short arcs reduce air intrusion into the molten pool, enhance protection, and lower porosity risk. A long arc allows N₂ and O₂ from the air to enter the pool, causing weld embrittlement or porosity.
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