Pre-welding is a critical step in the manufacturing of LSAW pipes (Longitudinal Submerged Arc Welding pipes). However, several issues may arise during this process, affecting the final product quality. This article discusses the most common pre-welding problems and their solutions.
Edge misalignment is one of the most frequent issues in pre-welding. Excessive misalignment can lead to pipe downgrading or rejection. Key causes include:
· Improper open seam adjustment – The gap between the plate edges must be precisely controlled.
· Incorrect seam press roller setup – If the circumferential angle is wrong, rollers are asymmetrical, or radial extensions are uneven, misalignment occurs.
· Insufficient edge pre-bending – Straight edges due to improper pre-bending can cause misalignment at the pipe’s head or tail.
Solution: Ensure proper roller alignment, adjust seam pressure, and verify edge pre-bending quality.
Excessive weld bead on the backside or burn-through can disrupt production and affect internal weld quality. Common causes:
· Poor seam closing – Low hydraulic pressure or improper clamping force.
· Poor forming – Excessive ovality (roundness deviation).
· Incorrect pre-welding parameters – High heat input or slow speed leads to excessive penetration.
Solution: Optimize clamping pressure, improve pipe roundness, and adjust welding current, voltage, and speed.
Porosity in pre-welding can cause defects in the final weld. Possible reasons:
· Low-quality shielding gas – Moisture contamination or insufficient gas flow.
· Clogged welding nozzle – Uneven gas coverage allows harmful gas intrusion.
· Rust or oil on the bevel – Contaminants lead to gas entrapment.
Solution: Use high-purity gas, maintain proper gas flow, and clean the bevel before welding.
Irregular weld shape affects tracking in subsequent welding stages. Causes:
· Incorrect heat input – High speed with low current/voltage reduces penetration and width.
· Porosity presence – Often linked to poor weld formation.
Solution: Balance welding parameters (current, voltage, speed) and ensure proper gas shielding.
Spatter can damage the pipe surface and bevel, impacting weld quality. Causes:
· Wrong shielding gas mixture – Insufficient argon content.
· Incorrect welding parameters – Unstable arc increases spatter.
Solution: Adjust gas composition (increase argon ratio) and optimize welding settings.
Proper pre-welding ensures high-quality LSAW pipes. By addressing misalignment, weld bead issues, porosity, poor weld formation, and spatter, manufacturers can enhance efficiency and reduce defects. Regular equipment checks and parameter optimization are key to success.
English