How can the quality of the weld seam of ERW welded pipe be ensured?

A reliable weld seam is the keystone of ERW pipe performance. Shijiazhuang Faith Machinery Co.,Ltd builds ERW lines to support consistent seam quality, and manufacturers can adopt a structured set of engineering controls, inspection practices and maintenance regimes to ensure the seam meets mechanical and service requirements.

Process and equipment controls

1. Proper strip preparation

·Clean, deburred and dimensionally consistent strip edges reduce inclusions and irregular heating. Edge trimming, scarfing and edge-milling (if required) should be specified for sensitive grades.

2. Stable and matched forming geometry

·Progressive forming rolls must track and maintain the designed seam gap and edge overlap. Rigid machine frames, precision roll alignment and closed-loop roll position control reduce edge mismatch.

3. Welding power stability and control

·Use solid-state HF/ERW power supplies with fast feedback control. Monitor and log welding current, voltage and frequency continuously. Adaptive control that modulates power with speed changes helps maintain consistent heat input.

4. Controlled forging pressure and welding roll condition

·Correct roll pressure and clean, well-profiled welding rolls produce the mechanical forging needed for full fusion. Worn rolls or surface damage will change contact conditions and can cause defects.

5. Thermal management

·Manage local temperatures at the seam with proper cooling circuits and control of cooling water flow. Overheating and too-rapid cooling can both produce undesirable microstructures.

6. Seam alignment and tracking systems

.Las Maintenance and reliability measures

1.Regular roll and tooling inspection

·Scheduled inspection and replacement of welding rolls, guides, and contact surfaces

prevent progressive degradation that can cause seam flaws.

2. Coolant and hydraulic system maintenance

·Water quality and flow rate affect coil temperature and weld head cooling; hydraulic

systems that set roll pressure must be leak-free and responsive.

3. Electrical system upkeep

·Transformers, power modules, and connections require thermal monitoring and preventive replacement of aged components.

Inline and post-weld inspection

1. Surface inspection (visual and camera systems)

·High-resolution surface cameras detect bead irregularities, undercut, surface cracks or excessive flash immediately after welding.

2. Ultrasonic testing (UT) / Phased array UT

·UT detects volumetric defects such as lack of fusion, porosity or internal discontinuities.

Phased array UT provides higher resolution and more rapid coverage for production lines.

3. Eddy-current testing (ECT)

·ECT identifies surface and near-surface defects, particularly useful on conductive materials like carbon steel.

4. Hydrostatic testing and pneumatic tests

·Hydrostatic tests verify overall pipe strength and seam integrity to a specified pressure. For production sorting, segmental hydrostatic tests or burst testing of sample lengths are common.

5.Destructive sampling and metallography

·Periodic destructive testing (tensile, bend, Charpy impact where applicable) and metallographic cross-sections of the seam verify mechanical properties, fusion and HAZ characteristics.

6. Automated rejection and trimming

·Integrate automatic defect marking and diversion so that defective lengths are removed without stopping the line.

Qualification and documentation

1. Welding procedure specification (WPS)

·Create and maintainWPS documents that define acceptable ranges for current, voltage, roll pressure, coil speed, and pre/post treatments.

2. Procedure qualification records (PQR) and operator qualifications

·Validate procedures with PQRs and ensure operators are trained and certified for their roles.

3. Material traceability and mill test records

·Link each coil’s mill test report (chemical and mechanical data) with the production data for every pipe length (time-stamped weld parameters, NDT records).

4.Statistical process control (SPC)

·Apply SPC to key variables (weld current, seam temperature, seam geometry) to detect drift and trigger preventive interventions.

Summary checklist to ensure seam quality

·Clean and dimensionally consistent strip edges

.Stable forming geometry and weld head alignment Controlled, logged welding power and roll pressure

·Inline NDT (UT/ECT) plus surface cameras and automatic rejection·Periodic destructive testing and metallography

·Formal WPS/PQR,operator training and SPC monitoring·Rigorous preventive maintenance and spare-parts readiness

Implementing layered controls across process, inspection and documentation significantly reduces the risk of seam-related failures and supports the reliable use of ERW pipe in demanding applications.