The 7018 electrode is a staple in structural welding, valued for its low-hydrogen properties and ability to produce strong, crack-resistant welds-especially in thick steel applications. To achieve optimal results, understanding the correct "burning" parameters (current, voltage, and operational settings) is critical. These settings directly impact arc stability, penetration, bead appearance, and overall weld quality. This news release breaks down the key parameters for using 7018 electrodes and provides guidance for adjusting them based on specific welding scenarios.
Current Type: Direct Current Electrode Positive (DCEP) is Preferred
The 7018 electrode is designed to perform best with direct current electrode positive (DCEP)-also known as reverse polarity. In DCEP, the electrode (positive terminal) attracts electrons, focusing arc energy on the workpiece. This creates deeper penetration, which is essential for thick steel, and ensures proper fusion between the weld metal and base material.
While some manufacturers offer specialized 7018 variants for alternating current (AC), standard 7018 electrodes struggle with AC due to inconsistent arc stability. AC can cause sputtering, uneven deposition, and increased risk of porosity, especially in low-amperage ranges. For most applications, DCEP remains the gold standard, providing a smooth arc, steady metal transfer, and reliable fusion.
Current Range: Matching Amperage to Electrode Size
The "burn" current for 7018 electrodes is primarily determined by their diameter. Using too low an amperage leads to a weak arc, poor penetration, and slag entrapment. Too high an amperage causes excessive spatter, burn-through (in thin sections), and overheating, which can degrade the low-hydrogen coating and introduce hydrogen into the weld. Below is a standard amperage guide for common 7018 electrode sizes:
1/8 inch (3.2 mm): 90–160 amps
This size is versatile for medium-thickness steel (1/4 to 3/4 inch). The lower end (90–120 amps) works for vertical or overhead positions, where lower heat reduces the risk of sagging. The higher end (130–160 amps) is ideal for flat or horizontal welding, maximizing deposition rate and penetration.
5/32 inch (4.0 mm): 140–220 amps
Used for thicker steel (3/4 to 1.5 inches), this size requires more heat to ensure fusion. 140–180 amps suits vertical/overhead welding, while 190–220 amps is better for flat positions, where deeper penetration is needed for thick sections.
3/16 inch (4.8 mm): 180–280 amps
Designed for heavy structural work on steel over 1 inch thick. 180–230 amps works for vertical passes, while 240–280 amps delivers the high heat needed for flat-position multi-pass welding, ensuring each layer bonds securely to the base metal and previous passes.
1/4 inch (6.4 mm): 250–350 amps
Reserved for very thick steel (over 2 inches) or high-deposition applications like pressure vessel fabrication. This size requires high heat to melt through thick sections, with 250–300 amps for vertical welding and 310–350 amps for flat positions.
These ranges are general guidelines-manufacturers may specify slight variations, so checking the electrode data sheet is recommended. For example, some low-hydrogen 7018 rods with extra iron powder may tolerate higher amperages for faster deposition.
Voltage: Secondary Parameter for Arc Stability
While current (amperage) is the primary setting, voltage plays a supporting role in maintaining arc stability. For 7018 electrodes, the ideal voltage range is 22–30 volts, depending on amperage and electrode size. Lower amperages (e.g., 90–160 amps for 1/8-inch rods) pair with 22–25 volts, while higher amperages (e.g., 250–350 amps for 1/4-inch rods) require 26–30 volts.
Voltage affects arc length: too low, and the arc becomes short and erratic, causing "sticking" and uneven bead shape. Too high, and the arc lengthens, leading to spatter, porosity, and shallow penetration. Most modern welding machines automatically adjust voltage to match amperage (constant current machines), but welders should monitor the arc visually- a steady, blue-white arc with minimal spatter indicates proper voltage.
Adjusting for Welding Position and Material Thickness
The 7018 electrode's versatility across all positions (flat, horizontal, vertical, overhead) requires parameter adjustments to account for gravity and heat distribution:
Flat and horizontal positions: Higher amperages (toward the top of the recommended range) are acceptable here, as gravity helps keep molten metal in place. This increases deposition rate and ensures deep penetration, critical for thick steel. For example, a 5/32-inch rod in flat welding on 1-inch steel can use 190–220 amps.
Vertical and overhead positions: Lower amperages (toward the bottom of the range) prevent molten metal from sagging or dripping. A 5/32-inch rod in vertical welding might use 140–170 amps, slowing deposition and allowing the weld pool to solidify faster. Travel speed should also increase slightly to avoid excess buildup.
Thin vs. thick material: On thinner steel (1/4 to 1/2 inch), stay toward the lower end of the amperage range to avoid burn-through. On thick steel (over 1 inch), use higher amperages to ensure penetration through the joint, especially in beveled grooves where fusion to the root is critical.
Key Operational Tips for Proper "Burning"
Beyond parameters, proper handling of 7018 electrodes ensures they burn as intended:
Moisture control: 7018's low-hydrogen coating is highly moisture-sensitive. Exposed to humidity, it absorbs water, which releases hydrogen during welding and causes cracking. Store unopened rods in sealed containers, and once opened, keep them in a heated storage oven at 250–300°F. If exposed to moisture for over 4 hours, re-dry them at 500–600°F for 1–2 hours before use.
Clean base metal: Oil, rust, or paint on the workpiece contaminates the weld and disrupts the arc. Clean the area with a wire brush or grinder before welding to ensure the 7018 electrode fuses cleanly.
Arc length: Maintain a short arc (1/8 to 3/16 inch) to minimize spatter and protect the weld pool with the electrode's slag. A long arc allows atmospheric gases (oxygen, nitrogen) to enter the pool, causing porosity.
Consequences of Incorrect Parameters
Using the wrong settings for 7018 electrodes can lead to costly defects:
Low amperage: Weak arc, poor penetration, and slag entrapment. Welds may fail under load due to lack of fusion.
High amperage: Excessive spatter, burn-through (in thin steel), and overheating. This can degrade the low-hydrogen coating, releasing hydrogen and increasing cracking risk. The weld bead may also become convex and irregular, requiring post-weld grinding.
Incorrect polarity (AC or DCEN): AC causes unstable arcs and spatter; DCEN (direct current electrode negative) focuses heat on the electrode, reducing penetration and causing the rod to overheat and melt too quickly.
Conclusion
Burning a 7018 electrode correctly hinges on three core factors: using DCEP polarity, selecting the right amperage for the electrode size and position, and maintaining proper voltage. For most applications:
1/8-inch rod: 90–160 amps (DCEP), 22–25 volts
5/32-inch rod: 140–220 amps (DCEP), 23–27 volts
3/16-inch rod: 180–280 amps (DCEP), 24–28 volts
1/4-inch rod: 250–350 amps (DCEP), 26–30 volts
Adjust downward for vertical/overhead positions and thinner steel, and upward for flat positions and thick steel. Pair these settings with moisture-controlled storage, clean base metal, and a short, stable arc to achieve strong, defect-free welds.
By mastering these parameters, welders can unlock the full potential of 7018 electrodes-delivering the high-strength, crack-resistant welds required in structural fabrication, heavy machinery, and pressure vessel construction.
