The mainstream welding process for ASTM A252 Gr.3 steel pipe is straight seam double-sided submerged arc welding (LSAW), supplemented by gas shielded welding or manual welding for supplementary repair. The core process parameters and technical points are as follows:
1. Mainstream process: straight seam submerged arc welding (LSAW)
Process principle: The arc burns under the flux layer, melts the welding wire and the edge of the tube blank, and double-sided welding ensures penetration.
Key parameters:
Current: 400–800A
Voltage: 28–35V
Speed: 20–50 m/h .
Material matching:
Welding wire: H08A (special for low carbon steel)
Flux: HJ431 (anti-oxidation, stable arc).
Advantages:
The weld has deep penetration, no pores/slag inclusions, and is suitable for large-diameter thick-walled pipes (outer diameter 406–1422mm, wall thickness 7.9–50.8mm).
2. Auxiliary process
Gas shielded welding:
Applicable scenarios: local repair or thin-walled pipe welding 1;
Parameters: CO₂ flow rate 10–25 L/min, speed 10–30 m/h;
Material: ER50-6 welding wire (matching Gr.3 low-carbon composition).
Manual arc welding:
Applicable scenarios: small-diameter pipes or on-site repair;
Key points: preheating 100–150℃, J507 electrode short arc operation
3. Process control core
| Item | Require |
|---|---|
| Groove treatment | Remove oil and rust within 20mm on both sides of the groove to reveal the metallic luster |
| Weld inspection | 100% ultrasonic/X-ray inspection (to ensure no unfused or cracked parts) |
| Elongation guarantee | Strictly control the interlayer temperature, and the elongation should be ≥20% when the wall thickness is ≥7.9mm. |
