Types, classification and acceptance levels for welding imperfections – standardized to DIN EN ISO 5817.

Weld Seam Defects (ISO 5817)

Types, classification and acceptance levels for welding imperfections – standardized to DIN EN ISO 5817.

  • DIN EN ISO 5817 – Evaluation basis
  • Classification according to ISO 6520‑1
  • Definition of acceptable / unacceptable defects

Weld Seams

Weld Seam Defects – Types, Classification & Acceptance Levels

Schematic representation of typical weld seam defects
Fig. Acceptance limits according to DIN EN ISO 5817

Weld seam defects are irregularities or defects in the weld joint that can affect the quality and safety of components. The evaluation and classification of these defects are carried out in accordance with the DIN EN ISO 5817 standard as well as the classification of defect types according to ISO 6520‑1.

The main groups of welding irregularities include, for example, pores, lack of fusion, slag inclusions, cracks, and uneven weld seam geometries. Particularly critical are cracks, which are subdivided into different types, including microcracks and longitudinal cracks, which can significantly impair the strength of the joint.

The standard defines clear acceptance limits for the various defect types to ensure that only weld joints of acceptable quality are used. Standardized documentation and evaluation are essential for quality assurance and traceability.

Internal defects such as lack of fusion or inclusions are detected by ultrasonic testing (UT) and radiographic testing (RT); surface cracks are revealed by magnetic particle testing (MT) and penetrant testing (PT).

If you need weld seam inspection for your components (NDT and destructive tests), see our service page: Weld Seam Inspection.

For further information and individual consultation on weld seam defects, please contact us: Contact us now.

Non-destructive methods for detecting weld seam defects

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Radiographic Testing

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Magnetic Particle Testing
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FAQ

Frequently Asked Questions

How does magnetic particle testing work?

Magnetic particle testing (MT) is a proven method of non-destructive testing. It is used to detect surface and near-surface defects such as cracks, pores, lack of fusion, or shrinkage cavities in ferromagnetic materials (e.g., steel, cast iron, nickel, or cobalt alloys).

Principle of Operation
The test piece is magnetized. When magnetic field lines inside encounter a discontinuity, flux leakage occurs at the surface. Magnetic powder or a suspension of magnetic particles accumulates at these leakage fields and makes the defects visible. Depending on the test medium, the indications appear dark or fluorescent under UV light.
Magnetic Particle Testing Procedure
  1. Cleaning: The surface must be free of oil, grease, rust, or paint and completely dry.
  2. Magnetization: The component is magnetized using a yoke, a coil, or current flow.
  3. Application of test medium: Magnetic powder is applied either dry or as a suspension.
  4. Visualization: The powder accumulates at discontinuities and makes them visible as lines or dots, optionally fluorescent under UV light.
  5. Evaluation and documentation: Indications are evaluated according to standards or customer specifications and documented.
  6. Demagnetization and cleaning: After testing, the component is demagnetized and cleaned.
Suitable Materials
- Ferromagnetic materials: steel, cast iron, nickel, and cobalt alloys. - Not suitable: non-magnetic materials such as aluminum, copper, or austenitic stainless steel.
Advantages
- High sensitivity even for fine cracks at or near the surface. - Fast and cost-effective method. - Applicable to components of different shapes and sizes. - Can be performed on-site or in a testing laboratory.
Typical Applications
- Weld inspections on steel structures. - Testing of castings and forgings. - Safety-relevant components in mechanical engineering, automotive, energy, and railway industries. - Quality assurance in serial production.

Thus, magnetic particle testing is an indispensable method in non-destructive testing of safety-critical components.

Which standards and certifications do you meet in radiographic testing?

Our radiographic testing is accredited according to DIN EN ISO/IEC 17025.
Testing is carried out according to DIN EN ISO 17636-1 and -2 (welds), EN 12681 (castings),
DIN EN ISO 10893-6 (steel pipes), and DIN EN ISO 5579 (fundamentals).
Our inspectors are qualified according to ISO 9712 and guarantee compliant results with legally valid documentation.

What is penetrant testing?

A dye penetrant test is part of surface crack detection methods. The method can make open flaws visible on components or welds. The principle of the method is that the clearly visible penetrant penetrates microfine cracks and pores due to its low surface tension and high capillary action. After cleaning, this becomes clearly visible with the help of a developer.

What is Ultrasonic Testing (UT)?

Ultrasonic testing (UT) is a non-destructive testing method used to detect defects and measure wall thickness in materials. High-frequency sound waves generated by an ultrasonic device are transmitted into a material. When these waves encounter irregularities such as cracks, inclusions, or voids in components or welds, they are reflected. The reflected signals are captured and analyzed to determine the position, size, and type of defects. As a volumetric testing method, UT allows the internal inspection of materials like metals, plastics, and composites and is widely used in quality control.