Overview
EN ISO 3690:2018 - Welding and allied processes: Determination of hydrogen content in arc weld metal specifies sampling and analytical procedures for measuring diffusible hydrogen in weld metal produced by arc welding of martensitic, bainitic and ferritic steels. The standard defines how to produce controlled weld specimens, preserve hydrogen content, collect released hydrogen, and quantify diffusible hydrogen in deposited or fused weld metal.
Key Topics and Requirements
- Scope: Applies to arc welding processes with filler material for steels that are susceptible to hydrogen-induced cracking.
- Specimen production and handling: Deposition of a single weld bead on standard test coupons, rapid quenching and storage (note: chilled specimens can be stored at −78 °C or lower) to prevent hydrogen loss, cleaning and controlled unclamping procedures.
- Hydrogen collection techniques:
- Displacement of mercury: Collected hydrogen displaces mercury; amount is determined by displaced volume.
- Inert-gas headspace with detector: Hydrogen collected into a headspace (e.g., argon) and quantified by detectors such as thermal conductivity.
- Temperature control: Collection temperature is specified to avoid thermal activation of non-diffusible hydrogen, ensuring measurement reflects diffusible hydrogen only.
- Calculation and reporting: Results are expressed as diffusible hydrogen per mass of deposited metal (HD) or per volume of fused weld metal (HF). Calibration, linearity and accuracy provisions are included.
- Normative guidance and annexes: Annexes provide recommendations on older methods (glycerine/mercury comparisons) and information on accuracy and reproducibility.
Applications and Who Uses It
EN ISO 3690:2018 is used by:
- Welding engineers and fabricators to validate consumables and welding procedures against hydrogen control requirements.
- Metallurgical and materials testing laboratories performing weld hydrogen analysis and quality control.
- Welding consumables manufacturers assessing diffusible hydrogen in electrodes and wires.
- Inspection, certification and R&D organizations concerned with hydrogen-induced cracking risk mitigation in structural steels.
Practical uses include procedure qualification, consumable specification, failure investigation, and production quality assurance where hydrogen control is critical.
Related Standards
- ISO 14175 - Welding consumables: gases and gas mixtures (referenced for shielding gases).
- ISO/TR 17671-1 - Recommendations for welding metallic materials (general arc welding guidance).
- Annex C of EN ISO 3690:2018 provides accuracy/reproducibility guidance; Annex B discusses comparisons with older glycerine methods.
Keywords: EN ISO 3690:2018, hydrogen content, diffusible hydrogen, arc weld metal, welding standard, mercury displacement method, thermal conductivity detector, martensitic steel, bainitic steel, ferritic steel.