ISO standard · reference card
Does ISO 17638 apply to your weld? Scope decision flow for the magnetic particle testing standard, the materials it excludes, and the records that support an MT inspection report.
ISO 17638 is a surface and near-surface method, and its scope is set as much by what it excludes as by what it covers. It applies to ferromagnetic materials only, and it finds discontinuities that break the surface or sit close beneath it — the physics of the method sets that boundary, not a choice a specification could widen.
The recurring mistake is specifying magnetic particle testing on a non-ferromagnetic joint out of habit, usually because a related process step elsewhere in the shop uses it. The result is a test that returns clean indications regardless of what the weld actually contains, which is a worse outcome than no test at all because it looks like evidence. The second mistake is expecting the method to catch internal lack of fusion between passes, which sits below what a surface method can reach.
Therness equipment does not perform magnetic particle testing. It produces the per-weld thermal and process record that helps direct surface NDT to the welds most likely to need it, and ties that record to the same weld identifier the inspection report references.
| Question | If yes | If no |
|---|---|---|
| Is the parent material ferromagnetic? | Magnetic particle testing under ISO 17638 is applicable. | The method will not work reliably; use penetrant testing or another surface method instead. |
| Is the discontinuity of interest surface-breaking or shallow subsurface? | This is the method's strength — proceed with the technique and magnetisation method the standard sets out. | Deeper or volumetric discontinuities need radiography or ultrasonic testing; magnetic particle testing will not find them. |
| Does the contract already name an acceptance level for indications? | Apply that level once indications are evaluated; ISO 17638 governs the test method, not the accept/reject decision. | An application or quality-level standard has to supply the level before a pass/fail call can be made. |
| Is the surface condition or coating thick enough to mask a leakage field? | Prepare the surface first, or use another surface method — ISO 17638 needs a surface that can show an indication. | Magnetic particle testing under ISO 17638 applies as set out for this surface condition. |
Conformity is decided by inspection and testing against the criteria the standard and the contract set. The records below are evidence that the process was held where it was qualified; they support an inspection result, they never replace one.
| Requirement | Record produced | Source |
|---|---|---|
| Flagging welds worth prioritising for surface NDT | Per-weld thermal anomaly record captured before the inspection stage | HeatCam IR-C |
| A production record to accompany the magnetic particle testing report | Weld identifier, operator, timestamp and process parameters exported per weld | WeldTrace |
Therness records what the machine actually delivered on every weld — parameters, thermal signature and a per-weld trail — so a conformity argument rests on measurements instead of recollection.
Progetto cofinanziato nell'ambito del PR Piemonte FSE+ 2021-2027,
Priorità I, Obiettivo Specifico a), Azione 4 – "Sostegno alla nascita delle start up"
