Overview
ISO 18496:2020 - Brazing - Fluxes for brazing - Classification and technical delivery conditions defines a clear classification system and delivery requirements for brazing fluxes. The standard covers two main classes:
- Class FH: fluxes for brazing heavy metals (steels, stainless steels, copper and its alloys, nickel and its alloys, precious metals, molybdenum, tungsten).
- Class FL: fluxes for brazing aluminium and its alloys.
The document characterizes fluxes by effective temperature range, chemical basis, typical residues and removal method, and specifies technical delivery conditions, packaging/marking and health & safety precautions.
Key topics and requirements
- Flux classification and codes: Types FH10–FH40 and FL10–FL30, with descriptive codes (e.g., FH20) indicating intended use and properties.
- Effective temperature range: Mandatory determination for each product. Annex A provides an example test method for FH fluxes; manufacturers define methods for FL fluxes.
- Chemical basis and residues:
- FH fluxes often contain boron compounds, fluorides, chlorides, borates, phosphates or silicates. Residues can be corrosive (require washing/pickling) or non‑corrosive (may be removed mechanically).
- FL fluxes use hygroscopic chlorides/fluorides or non‑hygroscopic fluorides (some include caesium fluoroaluminates); residue behavior and alloy compatibility (e.g., up to 0.5 wt-% Mg for FL30) are specified.
- Forms of delivery: powder, paste, liquid (additional forms referenced in Annex B).
- Designation and marking: Standardized designation (e.g., “Flux ISO 18496 - FH20 B”), mandatory labeling items (supplier, trade name, batch number, net weight/volume, hazard warnings).
- Health & safety: Users must consult manufacturer Safety Data Sheets (SDS); national regulations may apply for transport, storage and disposal.
Applications and who uses it
ISO 18496:2020 is used by:
- Flux manufacturers for product classification, test documentation and correct labeling.
- Brazing engineers and metallurgists to select the right flux type for parent materials and brazing temperature ranges.
- Procurement and quality managers to specify fluxes in purchase orders and acceptance criteria.
- Fabrication shops and maintenance teams for safe handling, residue removal and compliance with technical delivery conditions.
Typical applications include brazing of steels, stainless steels, copper alloys, nickel alloys and aluminium components in automotive, aerospace, heat‑exchanger, and precision metalwork industries.
Related standards
- ISO 17672 (brazing filler metals) - referenced for related material codes and practices.
- ISO/TC 44 (Welding and allied processes) provides the technical committee context for brazing standards.
Keywords: ISO 18496:2020, brazing fluxes, flux classification, FH flux, FL flux, effective temperature range, flux residues, technical delivery conditions, brazing aluminium, brazing heavy metals.
