Welding ASTM A871 Grade 60 Corten Steel is not just about joining two pieces-it's about preserving its corrosion resistance, structural strength, and iconic patina. Many fabricators and engineers face avoidable issues: weak welds, patina mismatches, or post-weld corrosion, all because of improper welding techniques. The good news is that correct welding for this Corten Steel grade is straightforward, as long as you follow key guidelines aligned with ASTM standards and practical best practices.
Key Pre-Welding Preparation (Critical for Success)
Proper preparation eliminates 80% of welding issues-focus on cleaning, preheating, and material compatibility:
Clean the Weld Area: Remove all surface contaminants (rust, oil, grease, paint, or dirt) from 25–50mm on both sides of the joint. Use a wire brush or grinder for thorough cleaning-any residue will cause porosity and weak welds.
Preheating (When Needed): For thick sections (over 12mm) or cold environments (below 10°C), preheat to 150–200°C. This prevents cold cracking, a common issue with high-strength Corten Steel. Thin sections (under 12mm) typically don't require preheating.
Match Filler Metal: Use a compatible filler metal-AWS E7018 (for SMAW) or ER70S-6 (for GMAW) works best. Avoid filler metals with high sulfur or lead, as they degrade corrosion resistance and weld strength.
Recommended Welding Methods & Parameters
ASTM A871 Grade 60 Corten Steel is weldable with standard methods, but parameter control is key to avoid damaging its properties:
Shielded Metal Arc Welding (SMAW): Ideal for thick sections. Use AWS E7018 electrodes, 2.4–4.0mm diameter, with current 80–140 amps (adjust based on electrode size). Maintain a short arc length (2–3mm) for minimal spatter.
Gas Metal Arc Welding (GMAW/MIG): Best for thin to medium sections. Use ER70S-6 filler wire, 0.8–1.2mm diameter, shielding gas (75% argon + 25% CO₂), and current 100–200 amps. Keep travel speed steady to avoid undercutting.
Key Parameter Rule: Avoid excessive heat input-high temperatures can damage the alloy's corrosion-resistant properties and cause warping. Keep heat input between 15–25 kJ/mm.
Welding Process Best Practices
Follow these simple steps during welding to ensure strong, corrosion-resistant welds:
Maintain a slight drag angle (10–15°) for SMAW and GMAW to ensure good fusion with the base metal.
Use stringer beads (not weave beads) for better control-weave beads can cause uneven heating and warping.
Allow each weld pass to cool to 150–200°C before the next pass-this prevents excessive heat buildup and preserves the metal's properties.
Post-Welding Treatment (Don't Skip This)
Post-weld steps are critical to restore Corten Steel's corrosion resistance and patina:
Remove weld slag and spatter immediately with a chisel or wire brush-slag trapped on the surface will cause localized corrosion.
Lightly grind the weld surface to match the base metal's texture-this ensures uniform patina formation over time.
Avoid painting or coating the weld area-let the patina form naturally to maintain corrosion resistance.
Common Welding Mistakes to Avoid
Skipping preheating for thick sections: Causes cold cracking and weak welds.
Using incompatible filler metal: Leads to weld failure and reduced corrosion resistance.
Excessive heat input: Damages the alloy's patina-forming ability and structural strength.
In short, welding ASTM A871 Grade 60 Corten Steel correctly comes down to preparation, proper parameters, and post-weld care. By following these guidelines, you'll create strong, corrosion-resistant welds that match the base metal's performance and aesthetic-ensuring your Corten Steel project lasts decades outdoors.
