🔩 Macroscopic and microscopic examination of welds — transverse cross-section, etching, visual and microscopic assessment
In short
The prepared (usually transverse) cross-section of the joint is assessed with the naked eye or at a magnification below ×50 (macroscopic examination) or with a microscope at a magnification usually of ×50 to ×500 (microscopic examination), before or after etching. The test is performed according to PN-EN ISO 17639:2022-07; Macroscopic examination: With the naked eye or at a magnification usually below ×50. The procedure comprises 8 steps; it is used for: Welding procedure qualification — assessment of the structure of the test joint (macrostructure, number and arrangement of runs), Detection of welding imperfections: gas pores, slag inclusions, lack of fusion, incomplete penetration, cracks, Measurement of geometric quantities of the joint: penetration depth, width of the weld and of the heat-affected zone.
At a glance
- Standard: PN-EN ISO 17639:2022-07
- Category: Materials and NDT
- Procedure steps: 8
- Macroscopic examination: With the naked eye or at a magnification usually below ×50
- Microscopic examination: With a microscope, magnification usually ×50 to ×500
- Designations: A — macro, I — micro, E — etched, U — unetched
Overview
The standard gives recommendations for the preparation of test specimens, the procedures of macroscopic and microscopic examination of welded joints and their main objectives. Macroscopic examination is the examination of a test specimen with the naked eye or at low magnification (usually below ×50), with or without etching; microscopic examination is the examination with a microscope at a magnification usually from ×50 to ×500, also with or without etching. The person carrying out the examination is the examiner — the person performing the macroscopic or microscopic examination.
The standard uses abbreviated designations: A — macroscopic examination, I — microscopic examination, E — etched, U — unetched. Parent materials are designated according to the material grouping system of ISO/TR 15608, and the same system is used for the weld metal; filler materials not classified in ISO/TR 15608 are identified in the report. Abbreviations of etchants are to be taken from ISO/TR 16060 where applicable. The classification of geometric imperfections revealed in the examination is given in ISO 6520-1.
The edition ISO 17639:2022 replaced the first edition of 2003. Macroscopic examination is a standard element of destructive tests on test joints: in the presentation of the Lublin University of Technology, for butt joints and T-joints 1–2 test specimens for macroscopic examination are specified alongside tensile, bend, impact and hardness tests.
Method principle
Macroscopic and microscopic examination serves to reveal the macroscopic or microscopic features of a welded joint, usually by examining transverse cross-sections. It is carried out by visual or optical examination of the prepared surface, before or after etching. Macroscopic examination is carried out with the naked eye or at low magnification (usually below ×50), and microscopic examination with a microscope at a magnification usually of ×50 to ×500. The result is described with the abbreviations A (macro) or I (micro) and E (etched) or U (unetched), stating the material group according to ISO/TR 15608 and the etchant according to ISO/TR 16060.
Applications
- Welding procedure qualification — assessment of the structure of the test joint (macrostructure, number and arrangement of runs)
- Detection of welding imperfections: gas pores, slag inclusions, lack of fusion, incomplete penetration, cracks
- Measurement of geometric quantities of the joint: penetration depth, width of the weld and of the heat-affected zone
- Examination of the microstructure of the weld and the heat-affected zone (microscopy)
- Failure analysis and expert assessments of welded structures
Key parameters
| Parameter | Value |
|---|---|
| Macroscopic examination | With the naked eye or at a magnification usually below ×50 |
| Microscopic examination | With a microscope, magnification usually ×50 to ×500 |
| Designations | A — macro, I — micro, E — etched, U — unetched |
| Type of cross-section | Usually a transverse cross-section of the joint |
| Material groups | According to ISO/TR 15608 — for parent materials and weld metal; filler materials outside the system are identified in the report |
| Etchants | Abbreviations according to ISO/TR 16060 where applicable; a trade name is acceptable where ISO/TR 16060 does not apply |
Standard
- Standard number
- PN-EN ISO 17639:2022-07
- Title (PL)
- Badania niszczące spawanych złączy metali — Badania makroskopowe i mikroskopowe złączy spawanych
- Title (EN)
- Destructive tests on welds in metallic materials — Macroscopic and microscopic examination of welds
Step-by-step procedure
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Taking the specimen
Cut a specimen covering the welded joint, usually as a transverse cross-section; determine the number of specimens in accordance with the product standard or the test programme for test joints (e.g. 1–2 specimens for macroscopic examination for butt joints and T-joints).
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Surface preparation
Prepare the cross-section surface by grinding and polishing in accordance with the recommendations of the standard so that visual or optical assessment is possible.
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Examination before etching
Where necessary, examine the unetched surface (designation U) — it reveals, among others, gas pores, cracks and inclusions.
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Etching
Etch the surface with an etchant selected for the material (designation E); take the abbreviation of the etchant from ISO/TR 16060 and, where it does not apply, give the trade name.
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Macroscopic examination
Assess the cross-section with the naked eye or at a magnification usually below ×50: the structure of the joint, the arrangement of runs, the penetration, the heat-affected zone and any imperfections (classification according to ISO 6520-1).
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Microscopic examination
Where necessary, examine the microstructure with a microscope at a magnification usually of ×50 to ×500, in selected areas: the weld, the fusion line and the heat-affected zone.
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Documentation
Take photographs or make sketches of the cross-section with a description of the observed features; apply the designations A/I and E/U and state the material group according to ISO/TR 15608.
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Report
In the report give the identification of the joint, the type of examination and the magnification, the etchant, the parent and filler materials and the result of the assessment.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Metallographic cut-off machine | For cutting the transverse cross-section of the joint with cooling | — |
| Metallographic grinding and polishing machine | Abrasive papers and polishing discs for preparing the section surface | — |
| Etching station | Fume hood, chemically resistant vessels, rinsing and drying of the specimen | — |
| Magnifier or stereo microscope | For macroscopic examination at a magnification below ×50 | — |
| Metallographic microscope | For microscopic examination at a magnification of ×50 to ×500, with image recording | — |
| Specimen mounting press | Embedding small cross-sections in resin for reproducible grinding | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Etchants | — | Selected for the material group; abbreviated designations according to ISO/TR 16060 where applicable |
Health and safety (OHS)
- Etchants (acids, alkalis, alcohols) — fume hood, chemically resistant gloves, goggles; never pour water into concentrated acid
- Cutting and grinding — wheel guards, goggles, coolant; extract metal dust
- Mounting resins and their hardeners — work under a fume hood, gloves
- Waste after etching — collect as chemical waste, not into the sewer
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 17639:2022-07 — “Destructive tests on welds in metallic materials — Macroscopic and microscopic examination of welds”.
How does this method work?
Macroscopic and microscopic examination serves to reveal the macroscopic or microscopic features of a welded joint, usually by examining transverse cross-sections. It is carried out by visual or optical examination of the prepared surface, before or after etching.
What is the measuring range and accuracy?
Macroscopic examination: With the naked eye or at a magnification usually below ×50; Microscopic examination: With a microscope, magnification usually ×50 to ×500; Designations: A — macro, I — micro, E — etched, U — unetched; Type of cross-section: Usually a transverse cross-section of the joint.
How long does the test take?
The procedure comprises 8 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Metallographic cut-off machine, Metallographic grinding and polishing machine, Etching station, Magnifier or stereo microscope, Metallographic microscope, Specimen mounting press.
Where is this test used?
Welding procedure qualification — assessment of the structure of the test joint (macrostructure, number and arrangement of runs); Detection of welding imperfections: gas pores, slag inclusions, lack of fusion, incomplete penetration, cracks; Measurement of geometric quantities of the joint: penetration depth, width of the weld and of the heat-affected zone; Examination of the microstructure of the weld and the heat-affected zone (microscopy); Failure analysis and expert assessments of welded structures.
What safety precautions apply?
Etchants (acids, alkalis, alcohols) — fume hood, chemically resistant gloves, goggles; never pour water into concentrated acid; Cutting and grinding — wheel guards, goggles, coolant; extract metal dust; Mounting resins and their hardeners — work under a fume hood, gloves; Waste after etching — collect as chemical waste, not into the sewer.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 17639.