Critical Usage Guidelines For E7018

Critical Usage Guidelines for E7018 (Must-Know!)

Low-hydrogen electrodes are sensitive to operating conditions; improper use directly impairs weld quality. Key precautions include:

Strict drying and storage

The coating absorbs moisture easily (moisture increases hydrogen content and reduces crack resistance). It must be dried at 350~400°C for 1~2 hours, then stored in an 80~120°C holding oven for on-demand use.

If exposed to air for more than 4 hours (or >2 hours in humidity >80%) after removal from the oven, re-drying is required (maximum 2 re-drying cycles; otherwise, the coating may become brittle and peel).

Workpiece preparation before welding
Thoroughly clean oil, rust, scale, and moisture from the weld area to avoid porosity, slag inclusions, and loss of low-hydrogen performance.

Welding parameter control

Current: Select based on electrode diameter (e.g., 90~120A for Φ3.2mm electrodes, 140~180A for Φ4.0mm electrodes). Excessive current causes coating overheating/burning; insufficient current leads to shallow penetration.

Polarity: Prefer DC Reverse Polarity (DCRP) (stable arc, deep penetration). For AC welding, ensure the welder's open-circuit voltage is ≥70V (to prevent arc extinction).

Wind speed: Outdoor welding requires wind protection (wind speed >2 m/s needs a windscreen). Low-hydrogen coatings have poor wind resistance; strong winds cause porosity.

Preheating and post-heating (as needed)
For welding thick plates (>16mm), low-alloy high-strength steels, or welding in low-temperature environments (<0°C), preheating (80~200°C) is required. Post-heating (250~350°C for 1~2 hours) after welding helps reduce residual stress and hydrogen content in the weld.

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