E7018 is the most widely specified structural welding electrode in the world. Its low-hydrogen iron powder coating produces smooth, strong, crack-resistant welds that meet AWS D1.1 structural requirements right out of the oven. The “70” means 70,000 PSI minimum tensile strength. The “18” means it’s an all-position, low-hydrogen, iron powder electrode that runs on AC or DCEP. If you only stock one stick rod in your shop, 7018 is it.
The catch: 7018 demands proper storage. The low-hydrogen flux coating absorbs atmospheric moisture, and wet 7018 causes hydrogen cracking. This is the most common welding defect you can’t see during the weld itself. It shows up hours or days later as cracks in the heat-affected zone under load. A rod oven isn’t optional with 7018; it’s a requirement for any work that matters.
AWS Classification Breakdown
E7018 is classified under AWS A5.1 (carbon steel covered electrodes). The designation encodes four pieces of information:
- E = Electrode
- 70 = 70,000 PSI (480 MPa) minimum tensile strength
- 1 = All-position capability (flat, horizontal, vertical up/down, overhead)
- 8 = Low-hydrogen potassium iron powder coating, AC/DCEP
The “8” coating designation is the critical one. It identifies the flux as low-hydrogen type with iron powder additions. The iron powder increases deposition efficiency (the percentage of electrode weight that becomes weld metal) to about 110-120%, meaning you deposit more metal per rod than non-iron-powder electrodes. That iron powder also stabilizes the arc on AC by providing a conductive path through the flux.
Mechanical Properties
| Property | AWS A5.1 Minimum | Typical Value |
|---|---|---|
| Tensile Strength | 70,000 PSI (480 MPa) | 78,000 - 88,000 PSI |
| Yield Strength | 58,000 PSI (400 MPa) | 62,000 - 72,000 PSI |
| Elongation (2") | 22% min | 26 - 32% |
| CVN Impact (-20F) | 20 ft-lbs | 60 - 100 ft-lbs |
| Hydrogen Level (H16) | 16 mL/100g max | 4 - 8 mL/100g (typical) |
The hydrogen level is the spec that separates 7018 from non-low-hydrogen rods like 6013 and 7024. At under 16 mL of diffusible hydrogen per 100g of deposited weld metal (and typically under 8 mL for premium brands), 7018 dramatically reduces the risk of hydrogen-assisted cracking. Some manufacturers offer H8 or H4 designations, meaning they certify even lower hydrogen levels.
Amperage Chart by Diameter
| Rod Diameter | Amperage Range (DCEP) | Amperage Range (AC) | Best Position |
|---|---|---|---|
| 3/32" (2.4 mm) | 70 - 110A | 75 - 110A | All positions, root passes |
| 1/8" (3.2 mm) | 100 - 150A | 110 - 150A | All positions, general work |
| 5/32" (4.0 mm) | 130 - 200A | 140 - 200A | Flat, horizontal, vertical up |
| 3/16" (4.8 mm) | 175 - 250A | 185 - 250A | Flat and horizontal fill |
| 7/32" (5.6 mm) | 225 - 310A | 235 - 310A | Flat and horizontal |
| 1/4" (6.4 mm) | 275 - 375A | 290 - 375A | Flat only |
Start in the middle of the range and fine-tune. If the slag runs ahead of the puddle, you’re too hot. If the rod sticks on initial contact or the bead sits up tall and narrow, you’re too cold. A properly tuned 7018 produces a smooth, quiet arc with fine ripples in the finished bead and slag that peels off in sheets.
Diameter selection rule: Use the largest rod your joint and position allow. A 1/8" rod at 130A deposits significantly faster than a 3/32" at 90A. For vertical up and overhead work, 1/8" is the practical maximum for most welders. For flat and horizontal fill passes, step up to 5/32" or 3/16" to increase deposition rate.
The Low-Hydrogen Problem
Low-hydrogen electrodes have a limestone-based (calcium carbonate) flux that thermally decomposes during welding to produce CO2 shielding gas. The limestone itself contains very little hydrogen. But the calcium carbonate matrix is hygroscopic: it absorbs water vapor from the atmosphere.
Here’s the timeline of moisture absorption:
- Sealed, vacuum-packed: Indefinite shelf life in original packaging
- Opened container, dry shop (under 50% RH): 4-8 hours before reconditioning is recommended
- Opened container, humid shop (over 60% RH): 2-4 hours before moisture becomes a concern
- Outdoor exposure on a humid day: 1-2 hours or less
The moisture doesn’t make the rod unusable in terms of arc behavior. A slightly damp 7018 still strikes and runs. That’s the danger. You won’t notice the moisture during welding, but the hydrogen it introduces causes delayed cracking in the HAZ, sometimes 24-72 hours after the weld cools.
Storage Requirements
AWS D1.1 Section 5.3 sets the storage rules for low-hydrogen electrodes on structural work:
Holding oven temperature: 250-300F (120-150C). This is the temperature you maintain after the rods are removed from sealed packaging. Rods go straight from the sealed can into the oven.
Exposure limits: Once removed from the oven, rods must be used within 4 hours (for H16 classification) or returned to the oven for reconditioning. Many shops use portable rod ovens (quivers) that attach to the welder’s belt, holding 6-10 lbs of rod at 150-200F during use.
Reconditioning: If rods exceed their exposure limit, recondition at 500-800F (260-425C) for one hour. Check the manufacturer’s specific recommendation, as some brands specify narrower ranges. Lincoln Excalibur rods, for example, recommend 700-800F.
Reconditioning limit: AWS D1.1 allows one reconditioning cycle. After that, discard the rods. Repeated heating degrades the flux binder and changes the coating’s melting characteristics, affecting arc stability and slag behavior.
For non-code work: Even if you’re not welding to D1.1, a rod oven improves 7018 performance dramatically. Dry rods arc smoother, produce less spatter, and lay down cleaner beads. A basic rod oven costs $50-150 and pays for itself immediately in weld quality.
Technique
7018 is a drag rod. Hold a 5-10 degree drag angle (tilted back from the direction of travel) and let the flux push the puddle. Don’t weave aggressively; a slight oscillation or straight stringer bead produces the cleanest results.
Arc length: Keep it tight, about 1/8 inch (one rod-core diameter). A long arc on 7018 pulls in atmosphere, increasing hydrogen pickup and causing porosity. You’ll hear the difference: a tight arc has a steady crackling sound, while a long arc sounds hollow and buzzy.
Travel speed: Moderate and consistent. The slag from 7018 is self-leveling and covers the bead uniformly when you maintain steady travel. Erratic speed creates uneven beads and slag inclusion pockets.
Vertical up: Run 7018 vertical up with a slight weave, pausing briefly at each toe to fill the shelf. Keep amperage at the lower end of the range. The iron powder in the coating adds fluidity to the puddle, so too much heat makes the slag run downhill and undercut the toes.
Overhead: Tight arc, lower amperage, straight stringer or very slight weave. Let the arc force and the quick-freezing slag support the puddle. Don’t fight gravity with more heat; fight it with technique and a fast-freezing flux.
7018 vs. Other Structural Rods
7018 vs. 7018-1: The “-1” suffix indicates improved toughness at -50F. Use E7018-1 when the weldment will see low-temperature service (outdoor structural in cold climates, cryogenic support structures). For standard indoor fabrication, regular 7018 is sufficient.
7018 vs. 7018-H4R: The H4R designation means the electrode is moisture-resistant and certified to less than 4 mL hydrogen. These rods (Lincoln Excalibur, ESAB Atom Arc 7018-H4R) can be exposed to atmosphere longer before reconditioning is needed. They cost more but reduce the risk of moisture-related defects in field conditions.
7018 vs. 7024: Both are 70 ksi rods, but 7024 is flat and horizontal only, with a much heavier iron powder coating for higher deposition. Use 7024 for production flat-plate welding and 7018 for everything that requires all-position capability or code compliance.
7018 vs. 6010/6011: The 60xx rods are cellulosic (high-hydrogen), deep-penetrating electrodes for root passes and dirty steel. They complement 7018 rather than replace it. A common procedure uses 6010 for the root pass and 7018 for fill and cap.
Common Brands
Major manufacturers produce 7018 under their own trade names:
- Lincoln Electric: Excalibur 7018 MR (moisture resistant), Jet-LH 7018
- ESAB: Atom Arc 7018, Sureweld 7018
- Hobart: 7018 (in retail-friendly packaging)
- Forney: E7018 (budget option, retail channels)
Price at time of writing ranges from $2.50-4.00 per pound, depending on brand and quantity. Bulk 50 lb cans run cheaper per pound than 5 lb or 10 lb retail packs. For structural work, buy from a manufacturer that provides lot-traceable certificates of conformance.
When NOT to Use 7018
7018 isn’t always the right rod:
- Root passes on open-root pipe: 6010 (DCEP) or 6011 (AC) penetrate deeper and freeze faster for root work
- Sheet metal under 14 gauge: 7018’s minimum amperage is too hot for thin material; use 6013
- Dirty, rusty, painted steel: 6011 tolerates contamination better; clean the metal or switch rods
- Production flat plate only: 7024 deposits faster in flat and horizontal positions
- Stainless steel, aluminum, cast iron: Different alloys need different electrodes entirely
Troubleshooting 7018
Rod sticks on start: Arc starting with 7018 takes a quick, firm scratch or tap. The low-hydrogen coating doesn’t ionize as easily as 6013’s rutile flux. If the rod sticks, pull it free with a sharp twist, not a pull. If it keeps sticking, increase amperage by 5-10 amps. On AC machines, ensure the open circuit voltage is at least 55V.
Porosity in the weld: The most common cause is moisture in the flux coating. Check storage conditions and recondition or replace the rods. Other causes include long arc length (pulling in atmosphere), contaminated base metal, and excessive travel speed that doesn’t allow gas to escape the puddle.
Slag won’t peel: Cold welds cause tight, difficult slag. Increase amperage. 7018 slag should peel in sheets when the bead is properly heated. Also check for erratic travel speed, which creates uneven bead profile and inconsistent slag coverage.
For a complete overview of stick electrode types, check the category guide. Other rods in this category: 6010, 6011, 6013, and 7024.