The 7018 electrode is one of the most widely used stick welding (SMAW) electrodes, valued for its strong, ductile welds and versatility with mild steel and low-alloy steel. The current required to run a 7018 electrode depends primarily on its diameter, but other factors like joint design, base metal thickness, and welding position also play a role. Below is a detailed breakdown of the typical current ranges, along with key considerations for setting the right current.
Core Factor: Electrode Diameter
The diameter of the 7018 electrode is the most critical determinant of current. Larger diameters require more current to melt properly, while smaller diameters need less to avoid overheating and burning through the base metal. Here are the standard current ranges for common 7018 diameters:
| Electrode Diameter (inches) | Electrode Diameter (millimeters) | Typical Current Range (Amperes) |
|---|---|---|
| 1/8" | 3.2 mm | 70 – 140 A |
| 5/32" | 4.0 mm | 110 – 210 A |
| 3/16" | 4.8 mm | 160 – 275 A |
| 1/4" | 6.4 mm | 250 – 350 A |
These ranges are general guidelines. For example:
A 1/8" (3.2 mm) 7018 electrode works well for thin to medium-gauge steel (1/8" to 3/8" thick) at 90–120 A for most joints.
A 3/16" (4.8 mm) electrode, used for thicker metal (3/8" to 1/2"+), typically performs best at 180–240 A.
Other Factors Affecting Current Settings
While diameter is primary, adjust current based on these variables to ensure proper arc stability, penetration, and weld bead shape:
1. Base Metal Thickness
Thin base metal (e.g., 1/8" thick): Use the lower end of the electrode's current range to avoid burning through. For a 1/8" 7018 on 1/8" steel, 70–100 A is safer.
Thick base metal (e.g., 1/2"+): Use the upper end of the range to achieve sufficient penetration. A 3/16" 7018 on thick steel may need 220–275 A.
2. Welding Position
The 7018 is classified as an "all-position" electrode, but current may need adjustment for vertical, horizontal, or overhead welding (compared to flat/horizontal fillet welds):
Flat/horizontal: Can use the full current range for the diameter, as gravity helps control the weld pool.
Vertical/overhead: Reduce current by 10–15% to prevent the molten weld pool from sagging or dripping. For a 5/32" 7018 in vertical position, 100–180 A (instead of 110–210 A) is better.
3. Arc Characteristics
The 7018 electrode has a low-hydrogen flux coating, which requires a stable, slightly forceful arc to burn off flux properly and avoid porosity. Signs that current is incorrect include:
Too low current: The arc sputters, penetration is shallow, and the flux may not melt evenly (leaving slag that's hard to remove).
Too high current: The arc is erratic, the weld pool is too large (causing burn-through or excessive spatter), and the flux coating may "blow out" (exposing the weld to contaminants).
4. Polarity
While not a "current" factor, 7018 electrodes require direct current reverse polarity (DCRP) (also called DC electrode positive, DC+). Using DC straight polarity (DCSP) or AC can reduce arc stability, even if current is correct-so ensure your machine is set to DCRP.
Summary
The current needed to run a 7018 electrode is primarily determined by its diameter, with typical ranges as follows:
- 1/8" (3.2 mm): 70–140 A
- 5/32" (4.0 mm): 110–210 A
- 3/16" (4.8 mm): 160–275 A
- 1/4" (6.4 mm): 250–350 A
Adjust based on base metal thickness (thicker = higher current), position (vertical/overhead = lower current), and arc stability. Always start in the middle of the range, test on scrap metal, and tweak until the arc is smooth, penetration is adequate, and the weld bead is uniform.
