EN ISO 17639 Destructive Testing of Welds in Metallic Materials - Macroscopic and Microscopic Examination of Welds

The EN ISO 17639 Destructive testing of welds in metallic materials - Macroscopic and microscopic examination of welds standard, which is based on a European standard and subsequently published by the International Organization for Standardization (ISO) , describes recommendations regarding sample preparation, test procedures, and their basic purposes for macroscopic and microscopic examinations.

For the purposes of this standard, the following terms and definitions apply:

• Macroscopic examination refers to examining a test specimen with the naked eye or under low magnification (usually less than x50), with or without abrasion.
• Microscopic examination refers to examining a test specimen with a microscope, with or without abrasion, usually at x50 to x500 magnification.

Macroscopic and microscopic examination is used to reveal the macroscopic or microscopic features of a welded joint, typically by examining cross-sections. This is done by visual and/or optical examination of the prepared surface before or after grinding.

The purpose of macroscopic and microscopic examination is to evaluate the structure (including grain structure, morphology and orientation, precipitates, and inclusions) either independently or in association with various cracks and voids. Sections can also provide a record of the specimen's shape in the section planes. The table provided within the standard provides guidance on evaluating the properties detectable by macroscopic and microscopic examination.

Test specimens are typically oriented perpendicular to the weld axis (cross-section), including the weld bed and heat-affected zones on both sides of the weld. However, test specimens can also be applied in other orientations. The location, orientation, and number of test pieces should be specified before testing, for example, by reference to an application standard.

In general, the following information is taken into account in the tests:

• Base metals and welding consumables
• Subject of the test
• Composition / name of the abrasive
• Surface quality
• Etching methods
• Additional precautions
• Any additional requirements (e.g. etching time)

The test specimen must be prepared for examination by appropriate cutting, mounting, grinding or polishing, and abrasion. The surface to be examined must not be adversely affected by these operations.

The surface finish requirement depends on the type of inspection (macroscopic or microscopic), the type of material, and documentation (such as photographs). Details of grinding and polishing media and grinding and polishing methods are included in ISO/TR 16060.

Etching methods must be specified before etching. The most common methods are:

• Abrasion of the test sample by immersion in the abrasive
• Abrasion by wiping the surface of the test sample
• Electrolytic etching.

Other methods may be used but should be specified, for example, by reference to a practice standard. Once etching is complete, the test sample should be washed and dried. Precautions can be taken to prevent deterioration of the etched sample, such as storing the samples in a protected atmosphere or, for macroscopic samples, applying a lacquer or varnish to the etched surface.

Typical abrasives for various base metals, weld deposits, inspection purposes, and types are listed in ISO/TR 16060. Depending on the required information, the type and concentration of the abrasive, as well as the abrasion temperature and time, may vary depending on the material and inspection type. Different abrasives can be used for similar joints.

EN ISO 17639 is a critical standard in weld and materials testing because it provides guidelines for the visual inspection of welds. The key reasons for its importance include:

• Ensures consistent quality inspection: This standard standardizes how welds are visually inspected, ensuring that inspections are consistent and comparable across different projects, inspectors, and organizations.
• Defines clear inspection criteria: Outlines:
  • What to inspect (e.g., surface cuts, undercuts, cracks)
  • Lighting requirements
  • Magnification levels
  • Inspection conditions and tools

This clarity helps ensure that all resources meet the same quality expectations.

• Promotes safety and structural integrity: Poorly inspected welds can lead to structural failures, particularly in critical industries such as aerospace, automotive, construction, and pressure vessels. This standard helps prevent dangerous defects from being overlooked.
• Compliance with international requirements: Many industries follow international standards as part of their legal or contractual obligations. EN ISO 17639 ensures that visual weld inspection complies with global quality assurance practices.

Macroscopic and microscopic examination of welds refer to two different levels of weld inspection techniques used to evaluate the internal and surface quality of welds, particularly in materials testing and quality control:

• Macroscopic examination examines weld cross-sections with the naked eye or at low magnification (up to approximately 10x) after preparing and abrading the sample. This examination includes weld geometry (shape, size, penetration), fusion zones, heat-affected zone, surface and near-surface defects (e.g., cracks, porosity, lack of fusion), and layering in multi-pass welds.
• Microscopic examination uses a microscope (typically at 100–1000x magnification) to examine the microstructure of the weld metal, base metal, and heat-affected zone. This examination includes grain structure and grain size, phase composition (e.g., ferrite, martensite, austenite), inclusions or hairline cracks, and changes resulting from the heat of welding (e.g., phase transformations, hardness changes).

In short, macroscopic examination provides an overview of weld quality and structural integrity, while microscopic examination reveals detailed internal changes and metallurgical properties that are not visible to the naked eye.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the EN ISO 17639 standard for "Destructive testing of welds in metallic materials - Macroscopic and microscopic examination of welds."