Weld Passes and Interpass Practices
Hot pass, interpass cleaning, interpass temperature, stringer beads, and multi-pass technique.
- Describe the purpose and technique for root pass and hot pass
- Explain interpass cleaning requirements and slag removal techniques
- Apply stringer bead and multi-pass technique for fill and cap passes
Lección 1
Root Pass and Hot Pass
The Root Pass
The root pass is the first weld bead deposited in a groove joint. It is the most critical pass because it establishes penetration and fusion at the root of the joint.
Root Pass Technique
- Use a smaller diameter electrode (typically 3.2 mm / 1/8") for control
- Maintain a tight arc (short arc length) for maximum penetration
- Stringer bead only - no weaving on the root
- Watch the keyhole - a small hole ahead of the weld pool that indicates full penetration
- Consistent travel speed is critical for uniform root penetration
The Hot Pass
The hot pass (second pass) is applied immediately after the root pass at slightly higher amperage. Its purpose is to:
- Burn out small defects and inclusions in the root pass
- Provide a smooth, clean surface for subsequent fill passes
- Build up the root area to proper thickness
- Must be applied before the root pass cools below interpass temperature
Why "Hot" Pass?
The hot pass is called "hot" because it is applied at higher amperage than the root pass and while the root is still hot. This extra heat helps burn out wagon tracks (small slag lines at the edges of the root bead).
The root pass establishes penetration - watch for a keyhole indicating full penetration. The hot pass follows at higher amperage to burn out root defects. E6010 is commonly used for root passes due to its deep penetration characteristics.