Troubleshooting Porosity in Submerged Arc Welding: Why It Happens and How to Fix It
1. The #1 Culprit: Damp Flux (Moisture)
Water is the enemy of welding. When flux absorbs moisture from the air, the intense heat of the arc breaks the waterogen and Oxygen. The gas gets trapped as the metal freezes.
The Fix:
· Agglomerated Flux (SJ Series):Because it is bonded at lower temperatures, it is hygroscopic. It must be re-dried at 300°C–350°C for 2 hours before use.
· Fused Flux (HJ Series):While more resistant, it should still be dried at 150°C–250°C if stored in humid conditions.
· Tip:Never leave flux in the hopper overnight. Return unused flux to the oven.
2. Insufficient Flux Burden (Layer Height)
In SAW, the flux layer protects the molten pool from the atmosphere (Nitrogen and Oxygen). If the flux layer is too thin, you might see "flash-through" (arc light visible). This allows air to penetrate the arc zone, causing nitrogen porosity.
The Fix:Ensure the flux depth is sufficient to completely cover the arc, typically 25mm to 35mm depending on the current. If you see the arc light, add flux immediately.
3. Contaminated Base Material
SAW is known for deep penetration. If your steel plate has oil, rust, paint, or moisture on the surface (or on the groove edges), these impurities will vaporize into gas during welding.
The Fix:
· Clean the joint area (20mm on both sides) with a wire brush or grinder.
· Preheat the steel plate if the ambient temperature is low to remove surface condensation.
4. Improper Flux Recycling
Recycling flux is essential for cost control, but it carries risks. Over time, recycled flux accumulates fine dust and slag particles. Too much dust reduces the permeability of the flux layer, trapping gas inside the weld.
The Fix:
· Always mix new flux with recycled flux (e.g., ratio of 1:1 or 1:2).
· Use a sieve to remove fine dust and slag crusts from the recovered flux before reusing it.
5. Voltage and Current Imbalance
Excessive voltage creates a longer arc length. If the arc is too long, the flux cavity becomes unstable, potentially drawing in outside air.
The Fix:Follow the parameter recommendations on our Gujin Flux Data Sheets. Keep the arc length consistent.
Conclusion
Passing the X-ray inspection starts with proper storage and handling of your consumables. At Jinan Gujin Welding Materials, we ensure our flux is packaged in moisture-resistant bags, but your on-site handling is the final defense against porosity.
Need a flux with high resistance to moisture absorption?
Check out our SJ101 and SJ414 series at www.gjflux.com.
