Overview
ISO/TR 22281:2018 is a technical report from ISO (prepared by the International Institute of Welding, IIW) that addresses the use of trace element analyses in welding consumable specifications. Based on IIW round‑robin interlaboratory studies, it evaluates the reproducibility of measuring trace elements in steels and weld metals and provides guidance on applying accept/reject criteria (for example when using ISO 14344 or API RP 934‑A).
Key topics
- Trace element measurement and reproducibility
- Defines trace elements as species normally measured in ppm (parts per million) and relevant to weld performance.
- Reports interlaboratory reproducibility data from IIW round‑robins on Cr‑Mo steels and their weld metal.
- Bruscato factor
- A weighted sum of P, Sb, Sn and As used as an acceptance criterion in some procurement specifications.
- Manufacturing limits such as API RP 934‑A reference a maximum Bruscato factor of 15 ppm.
- IIW results: interlaboratory standard deviation ≈ 1.0 ppm (at a mean of 12.0 ppm). A 95% confidence uncertainty band around 15 ppm is approximately ±2 SD → values between 13 and 17 ppm should be treated as uncertain.
- Hot‑cracking (Kf) chemical risk factor
- A weighted sum (Pb, Bi, Sb) intended to predict weld metal hot‑cracking susceptibility.
- Analytical reproducibility for Pb and Bi at ~1 ppm is challenging; only ICP‑MS and GD‑MS showed acceptable reproducibility in the studies.
- When limited to ICP‑MS or GD‑MS, the 95% confidence interval is about ±0.5 ppm around the interlaboratory mean → values between ~1.0 and 2.0 ppm are uncertain relative to a proposed 1.5 ppm acceptance criterion.
- Recommended handling of uncertainty
- Acceptance/rejection decisions must account for analytical uncertainty.
- For results within the uncertainty zone, the report recommends repeat testing in independent laboratories before definitive acceptance/rejection.
Applications
- Procurement and quality control of welding filler metals and fluxes
- Material acceptance decisions for pressure vessels, petrochemical, hydrogen service, and high‑temperature Cr‑Mo welds
- Laboratory method selection and QA/QC planning (favoring ICP‑MS or GD‑MS for low‑ppm Pb/Bi)
- Dispute resolution between suppliers and buyers over batch acceptability
Who should use this standard
- Welding consumable manufacturers and suppliers
- Fabricators and end‑users specifying filler metal chemistry
- Materials and welding engineers, QA/QC personnel, and testing laboratories
- Procurement and inspection teams using ISO 14344 or API RP 934‑A criteria
Related standards
- ISO 14344 - Welding consumables: procurement of filler materials and flux
- API RP 934‑A - Materials and fabrication guidance for Cr‑Mo pressure vessels
Keywords: ISO/TR 22281, welding consumables, trace element analyses, Bruscato factor, hot‑cracking risk, interlaboratory reproducibility, ICP‑MS, GD‑MS, ISO 14344, API RP 934‑A.