Types of Defects in ERW Pipes

ERW pipes are widely used in oil and gas, structural pipes, fluid transportation, and machinery manufacturing due to their high efficiency, stable weld quality, and cost advantages.

However, various defects may occur during the production of ERW pipes due to factors such as raw materials, forming processes, welding parameters, equipment conditions, cooling methods, and operator skill levels.

These defects are generally classified as follows:

Process Defects: Caused by unreasonable production parameters, abnormal welding heat input, or improper post-processing;

Weld Defects: The weld metal does not form a complete, dense, and uniform structure according to standards;

Surface Defects: Caused by the quality of the steel strip or mechanical damage.

ERW Pipe Process Defects

1. No Burrs

The weld has burrs. Generally, external burrs are better in hydrostatic tests. However, weld cracking is more common in bending and flattening tests.

2. Peach-Tip Shape

The weld has no burrs, but it is recessed into the ERW pipe wall, forming a peach-tip shape, which does not seal during hydrostatic tests. However, multiple cracks appeared in the weld after bending and flattening tests.

3. Unilateral Burrs

Burrs on one side of the watertight weld were tested under water pressure and side compression tests. Cracks sometimes appeared during bending and flattening tests.

4. Ablation

Small pits appeared on the outer surface of the weld. There was a lot of sparking during welding. Microscopic observation revealed small pores. Watertightness was good after water pressure, bending, and flattening tests, and most welds did not crack, but this affected the strength and service life.

ERW Pipe Weld Defects

1. Opening

Melt marks or incomplete weld marks appeared at the weld edge. Cracks extended along the weld direction in a two-pointed shape, penetrating the inner surface after water pressure tests, causing leakage.

2. Cracks

Microcracks; fine cracks were visible on the outer surface, while the inner surface remained intact. No leakage was observed after water pressure tests, but cracks appeared under pressure or cold bending.

3. Lap Welding

Misalignment and scraping occur on both sides during welding. Besides burrs, a noticeable protrusion on one side is visible, and the deviation exceeds the wall thickness.

ERW Pipe Surface Defects

1. Scratches

Usually straight scratches along the axial direction, exceeding the wall thickness in depth. Continuous nail-like scratches on both sides of the weld are considered scrap defects. Deviation exceeding the wall thickness is also a scrap defect.

2. Correction Damage

Smoothing spiral indentations significantly exceeding the wall thickness are considered scrap defects.

3. Pitting

Small pits approximately 1mm in diameter exist on the ERW pipe surface.

4. Warping

The ERW pipe surface is warped, causing the part to separate from the metal substrate into fragments, discontinuously, and peeling off—unacceptable phenomena.

ERW Pipe Defect Detection Methods

To ensure quality, large factories perform the following tests:

1. Online Eddy Current Testing (ECT)

This can quickly identify surface cracks, open welds, etc.

2. Ultrasonic Testing (UT)

Detects internal defects such as incomplete penetration, inclusions, and lamellar defects.

3. Hydrostatic Test

Verifies the overall pressure resistance of the ERW pipe.

4. Flattening/Bending Test

Tests weld toughness and metal plasticity.

5. Visual Inspection

Identifies scratches, burrs, dents, surface ablation, etc.

How to Reduce ERW Pipe Defects

1. Select high-quality steel strip raw materials (low inclusions, low segregation).

2. Precisely control the extrusion amount and welding heat input.

3. Regularly maintain deburring tools and forming equipment.

4. Adjust the chamfering and guiding system to ensure steel strip alignment.

5. Monitor weld temperature and frequency online.

6. Establish a strict quality tracking and inspection mechanism.

Read more: ERW Pipe Specifications and Models