The right amperage for a 7018 welding rod depends on the rod’s diameter. As a general rule, you need about 1 amp per thousandth of an inch of rod diameter: a 3/32″ rod runs at roughly 70 to 110 amps, a 1/8″ rod at 110 to 150 amps, and a 5/32″ rod at 140 to 200 amps. These ranges give you room to adjust based on joint position, material thickness, and your machine’s output.
Amperage Ranges by Rod Diameter
Each 7018 rod size has a usable amperage window. Running at the low end of the range gives you a cooler, more controllable arc that works well for vertical and overhead welding. Running at the high end produces deeper penetration and faster travel speeds, which suits flat and horizontal fillet welds on thicker material.
- 3/32″ (2.4 mm): 70 to 110 amps. Best for thin material, root passes, and out-of-position work where you need a smaller puddle.
- 1/8″ (3.2 mm): 110 to 150 amps. The most commonly used 7018 size. Versatile enough for general structural work, plate welding, and most shop fabrication.
- 5/32″ (4.0 mm): 140 to 200 amps. Used for heavier plate and fill passes where you want to deposit more metal per pass.
- 3/16″ (4.8 mm): 180 to 250 amps. Reserved for thick structural steel in flat or horizontal positions where high deposition rates matter.
Start in the middle of the range for your rod size, run a test bead on scrap material, and adjust from there. The sweet spot produces a smooth, consistent arc with minimal spatter and a flat to slightly convex bead profile.
How Polarity Affects Your Settings
The 7018 rod runs on DCEP (direct current electrode positive, also called reverse polarity) about 90% of the time. Most structural welding procedures specify DCEP because it produces a stable arc, good penetration, and a smooth bead. Some 7018 rods are also rated for AC, which is useful if you’re running a transformer-style buzz box that doesn’t have DC output.
DCEN (direct current electrode negative, or straight polarity) is occasionally specified for certain open-root pipe welds using 7018 or 7016 rods, but those are specialty situations. If your welding procedure sheet doesn’t say otherwise, default to DCEP.
When running on AC, the arc tends to be less stable than on DC, and you may need to bump your amperage up slightly to maintain a smooth puddle. AC-rated 7018 rods contain extra arc stabilizers in the flux coating to compensate, but the experience still feels rougher than DCEP.
Signs Your Amperage Is Too High
Excessive amperage shows up in several ways. The most obvious is undercut, where the arc melts a groove along the edges of the weld that doesn’t get filled in by the deposited metal. You’ll also see more spatter scattered around the joint. In some cases, the weld pool freezes before shielding gas from the flux can fully escape, trapping gas pockets inside the bead and creating porosity you may not see on the surface but that weakens the joint.
If your bead looks wide, flat, and has visible grooves running along either side, dial the amperage down 5 to 10 amps and try again.
Signs Your Amperage Is Too Low
Too little amperage causes the opposite problem: lack of fusion and poor penetration. The arc doesn’t generate enough heat to melt into the base metal, so the weld bead sits on top of the surface without actually bonding to it. The bead often looks tall, narrow, and ropey. You may also notice the rod sticking to the workpiece frequently, because the arc keeps snuffing out.
If the rod feels sluggish and the puddle won’t flow smoothly, increase amperage in small increments until the arc sounds like a steady frying bacon and the puddle wets out to both edges of the joint.
Adjusting for Weld Position
Position changes how gravity affects your molten puddle, which means you need to adjust amperage accordingly. For flat and horizontal welds, you can run at the higher end of the range for your rod size because gravity holds the puddle in place. For vertical-up welding, drop your amperage 10 to 15% from your flat setting. A smaller, cooler puddle is easier to control when you’re fighting gravity. Overhead welding calls for a similar reduction, keeping the puddle tight so it doesn’t drip.
Material thickness matters too. On 1/4″ plate, a 1/8″ rod at 130 amps works well. On 3/8″ or thicker plate, you might use a 5/32″ rod at 170 to 180 amps for fill passes to get adequate penetration and reasonable travel speed. For root passes on thicker joints, many welders drop back to a 3/32″ or 1/8″ rod at lower amperage to maintain control, then switch to a larger rod for the fill and cap passes.
Dialing In Your Machine
The amperage ranges above are starting points. Every welding machine has slightly different output characteristics, and factors like lead length, cable condition, and even the brand of rod affect how the arc behaves. The best approach is to set your machine to the middle of the recommended range, strike an arc on a piece of scrap that matches your project material, and listen. A properly set 7018 arc produces a smooth, steady crackling sound. If it sounds harsh and loud, you’re probably too hot. If it sputters and pops, you’re too cold.
Check your bead after each test pass. A good 7018 bead has a flat to slightly convex profile, uniform ripples, and clean tie-in at both toes of the weld with no undercut. Once you find the setting that gives you that result, note it for future reference. Small adjustments of 5 amps at a time are all you need to fine-tune from there.