Quality levels for imperfections in fusion-welded joints (steel, nickel, titanium and their alloys)

What it does

It covers fusion-welded joints in steel, nickel, titanium and their alloys (beam welding — electron and laser — is out of scope). It lists imperfection types — cracks, porosity, inclusions, lack of fusion, undercut, excess weld metal, misalignment and the rest — and for each gives permitted limits at three quality levels: B (stringent), C (intermediate), D (moderate). The current edition is EN ISO 5817:2023, superseding the 2014 edition.

That is all it does, and it is why it is referenced everywhere. It gives an inspector a number instead of a judgement.

Choosing the level

The level is not chosen by the inspector; it comes from the design or the application standard. EN 1090-2 assigns levels by execution class. A drawing that says “weld quality to ISO 5817” without stating the level has not said anything actionable.

Where the arguments happen

Undercut and excess weld metal, almost always. They are the imperfections most visible to a client walking the shop and most likely to be within limits at level C and outside at level B. An argument about whether a weld passes is usually an argument about which level applies, and that argument is settled by the contract — if the contract was read.

What has to be recordable

• The quality level required for each joint, and where that requirement came from
• The imperfections found, with type, size and location
• The evaluation against the applicable limit
• The disposition where the limit was exceeded

The value of recording the level per joint rather than per project is that projects are rarely uniform. One structure can carry level B welds and level C welds, and an inspector working from a project-level assumption will get one of them wrong.