Welding Rod Guide

How Are Welding Rods Selected?

Welding rod (electrode) selection depends on the base metal, welding position, joint design, and required mechanical properties. AWS classifications use a standardized naming system: E7018 means Electrode, 70 ksi tensile strength, 1 = all-position capable, 8 = low-hydrogen potassium iron powder coating.

The primary goal is to match or slightly exceed the base metal's mechanical properties while ensuring weld quality. For mild steel, E6013 is a general-purpose rod suitable for beginners, E7018 is the workhorse for structural work with low-hydrogen properties, and E6010 provides deep penetration for root passes on pipe.

Electrode diameter selection depends on material thickness: 2.5 mm (3/32") for 1.5-3 mm plate, 3.2 mm (1/8") for 3-9 mm, and 4.0 mm (5/32") for 9 mm and thicker. Current ranges scale with diameter — approximately 30-40 amps per millimeter of electrode diameter for mild steel electrodes.

Formula: Current Range ≈ 30-40 × Electrode Diameter (mm) Minimum Thickness ≈ Electrode Diameter Deposition Rate varies by electrode type Heat Input = (V × I × 60) / (Travel Speed × 1000) [kJ/mm]

Example Calculation

Welding 6 mm mild steel plate in flat position: Select E7018, 3.2 mm diameter. Current range = 80-144 A (typically 120 A). At 25 V and 150 mm/min travel speed: Heat input = 25 × 120 × 60 / (150 × 1000) = 1.2 kJ/mm.

When to Use This Calculator

• A welder or foreman needs to select the correct electrode for a specific base metal and welding position before starting a new job
• Preparing a Welding Procedure Specification (WPS) and needing electrode diameter and current range recommendations
• Training welding apprentices on electrode selection criteria and AWS classification decoding
• Troubleshooting weld quality issues by verifying that the electrode type and current settings are appropriate for the base metal and position

Common Mistakes to Avoid

• Using E6013 for structural work — it is a general-purpose rod with higher hydrogen content; E7018 (low-hydrogen) is required for structural applications per AWS D1.1
• Exceeding the current range for the electrode diameter — too high current causes undercut and burn-through; too low causes poor fusion and slag inclusions
• Failing to store low-hydrogen electrodes (E7018) in heated ovens after opening — they absorb moisture within 4 hours, reintroducing hydrogen that causes cold cracking
• Using all-position electrodes in flat position at slow travel speeds when a high-deposition flat-position electrode (E7024) would be more productive

How to Interpret Results

• Recommendations are starting points keyed to base metal, position, and thickness — final electrode selection for code work must be qualified through a WPS/PQR (AWS D1.1, ASME IX)
• The current range spans roughly 25-45 A per millimeter of rod diameter — start near the middle, then use the low end for vertical/overhead positions and the high end for flat work
• Rod diameter is matched to material thickness — a rod thicker than the plate risks burn-through, while a very thin rod on thick plate causes poor fusion and slow deposition
• Read the notes carefully — preheat requirements (low-alloy steel, cast iron) and heat-input cautions (stainless sensitization) flagged there are essential to crack-free welds
• These are general guidelines, not a welding procedure — verify with procedure qualification and qualified supervision before production welding on structural or pressure-retaining parts

Related Standards & References

• AWS A5.1 — Specification for carbon steel electrodes for shielded metal arc welding
• AWS A5.4 — Specification for stainless steel electrodes for shielded metal arc welding
• AWS A5.5 — Specification for low-alloy steel electrodes for shielded metal arc welding
• AWS D1.1 — Structural welding code — Steel
• ISO 2560 — Welding consumables — Covered electrodes for manual metal arc welding

Frequently Asked Questions

What does 'low hydrogen' mean and why does it matter?

Low-hydrogen electrodes (E7018, E7016) have moisture-resistant coatings that produce less than 4 mL of diffusible hydrogen per 100g of weld metal. Hydrogen causes cold cracking in medium/high carbon steels and is the #1 cause of weld failure in structural applications. These rods must be stored in heated ovens (120-150°C) after opening and used within 4 hours of exposure.

Can I use the same rod for all positions?

Not all electrodes work in every position. The third digit in the AWS classification indicates position capability: '1' = all positions (flat, horizontal, vertical, overhead), '2' = flat and horizontal only. E7018 is all-position, but E7024 (high iron powder for high deposition) is limited to flat and horizontal. For vertical-up and overhead work, use '1'-designated electrodes with appropriate technique.

What are the most common causes of weld porosity?

Porosity is caused by gas entrapment during solidification. The top causes: (1) contaminated base metal — oil, paint, rust, or moisture on the joint surface, (2) insufficient shielding gas coverage — wind, wrong flow rate, or damaged gas nozzle, (3) excessive arc length, (4) damp electrodes, (5) excessive travel speed. Prevention: clean joints, protect from wind, maintain short arc, and store consumables properly.