ISO standard · reference card
ISO 6520-1: scope, groups and where it applies
Does ISO 6520-1 name the imperfection you are looking at? Scope decision flow for the fusion-welding classification standard, the six groups it defines, and the standards read alongside it.
- Designation
- ISO 6520-1
- Issued by
- ISO
- Title
- Welding and allied processes — Classification of geometric imperfections in metallic materials — Part 1: Fusion welding
- Edition
- Confirm the edition your contract or reporting template cites.
ISO 6520-1 is a naming standard. It gives a geometric imperfection a group and a reference number so that an inspector, a monitoring system and a quality-level standard can all mean the same thing by “2011” or “401” without agreeing on a shop-floor phrase first. It does not say whether an imperfection is acceptable, and it does not tell an inspector how to find one — both questions belong to other standards.
That separation is deliberate and it is where the standard earns its place: a single imperfection can sit under different acceptance rules depending only on the material, and the reference number is what lets ISO 5817 and ISO 10042 use the same vocabulary for steel and for aluminium respectively without duplicating the classification work.
The six groups run from cracks through cavities, solid inclusions, lack of fusion and penetration, imperfect shape and dimension, to a miscellaneous group for what the first five do not cover. Getting the group right before assigning a number is the step most often skipped under time pressure, and it is the step that makes a report searchable later.
Therness equipment does not classify an imperfection. It produces the evidence an inspector classifies from: a continuous per-weld thermal and process record, flagged anomalies worth a closer look, and a traceable identifier that keeps the eventual reference number attached to the weld it describes. See the ISO 5817 and ISO 10042 entries for how the two material routes read these numbers, and ISO 17640 for one of the examination methods that produces a finding in the first place.
Scope: does it apply to your job?
Applies to
- Naming and numbering geometric imperfections found in fusion-welded joints
- Any metallic material and any fusion welding process
- The reference numbers used in inspection reports and in other standards
Does not apply to
- Deciding whether an imperfection is acceptable — a quality-level standard does that
- Pressure-welded joints, classified under a separate part of the same series
- Choosing which inspection method finds the imperfection
Applicability decision flow
| Question | If yes | If no |
|---|---|---|
| Was the joint made by a fusion welding process? | ISO 6520-1 is the classification standard for what an inspection finds in it. | Pressure welding uses a separate part of the ISO 6520 series. |
| Do you need a consistent reference number for a reporting system or a standard's index? | Assign the ISO 6520-1 number; it is the vocabulary other standards, including quality-level standards, are indexed by. | A shop-floor name may be enough for an internal note, but it will not match another report. |
| Are you unsure which of the six groups an imperfection belongs to? | Read the group definitions — cracks, cavities, solid inclusions, lack of fusion and penetration, imperfect shape and dimension, and miscellaneous — before assigning a number. | Assign the specific reference number within that group. |
| Do you also need to know if the finding is acceptable? | Pair the number with the quality-level standard for the material — ISO 5817 for steel, nickel and titanium; ISO 10042 for aluminium. | The reference number alone is enough for classification and reporting. |
What proves conformity, and what only supports it
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 a weld with an anomaly before an inspector ever assigns it a reference number | Continuous thermal and process record per weld with anomaly flags | HeatCam IR-C |
| Tying an eventual classification back to the exact weld, pass and process conditions | Weld identifier joined to the measured process record at acquisition time | WeldTrace |
| A searchable evidence set organised per weld for root-cause work once a number is assigned | Per-weld records exported with identifier, operator and timestamp | HeatCore AI |
Evidence the process, not just the paperwork
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.
