Overview
EN ISO 18496:2021 (ISO 18496:2020) defines the classification and technical delivery conditions for fluxes used in brazing. Published by CEN and adopted from ISO, the standard covers two main classes of brazing fluxes - Class FH for heavy metals and Class FL for aluminium and its alloys - and characterizes fluxes by composition, effective temperature range, residues and recommended removal or retention. It also specifies technical delivery conditions, packaging/marking, forms of delivery and health and safety precautions.
Key topics and technical requirements
- Classification of fluxes: Two classes - FH (heavy metals) and FL (light/aluminium metals). Each class is subdivided by type codes (FH10–FH40, FL10–FL30) that identify chemical makeup and intended brazing temperature range.
- Effective temperature ranges: Types are described by typical operating ranges (e.g., FH10 ≈ 550–800 °C, FH20 ≈ 700–1 000 °C, FH30 ≥ 1 000 °C). Annex A defines how to determine the effective temperature range.
- Chemical composition and residues:
- FH types commonly contain boron compounds, fluorides, chlorides, borates, phosphates or silicates. Some (e.g., FH40) are boron‑free for applications where boron is prohibited.
- FL types use lithium chlorides/fluorides or non‑hygroscopic fluorides and caesium fluoroaluminates for aluminium brazing.
- Residues may be corrosive (require washing or pickling) or non‑corrosive (may be left on the workpiece or removed mechanically).
- Technical delivery conditions: Specifies forms of delivery, packaging and marking requirements; Annex B gives typical technical properties and delivery forms.
- Health & safety: Identifies precautions for handling flux chemistries and their residues, including cleaning and disposal recommendations.
Applications and users
- Practical uses: selection and specification of brazing flux for joining steels, stainless steels, copper alloys, nickel alloys, precious metals, molybdenum, tungsten and aluminium.
- Who uses the standard:
- Welding, brazing and metallurgical engineers selecting fluxes for production
- Flux manufacturers and suppliers for product classification and labelling
- Quality managers and procurement teams specifying technical delivery conditions
- HSE officers implementing safe handling, cleaning and disposal procedures
- Standards writers and conformity assessors in welding and brazing industries
Related standards
- Supersedes EN 1045:1997; adopted from ISO 18496:2020. Prepared by ISO/TC 44 (Welding and allied processes), CEN/TC 121. For additional normative context consult national standards bodies and the ISO online catalogue.
Keywords: brazing fluxes, flux classification, FH flux, FL flux, flux residues, brazing temperature range, technical delivery conditions, health and safety.