ISO 3677:2024

Overview

ISO 3677:2024 - "Filler metal for brazing - Designation" defines a standardized naming system for the metallic part of brazing filler materials based on chemical composition and melting range. It applies to metallic filler components used in foils, wires, rods, pastes, flux‑coated rods/wires and flux‑cored rods/wires. The designation explicitly includes solidus and liquidus temperatures to support process control and material selection.

Key topics and requirements

• Designation structure: three parts separated by dashes:
  • First part: the letter B (for brazing).
  • Second part: group of chemical symbols and nominal mass percentages indicating alloy constituents.
  • Third part: solidus/liquidus temperatures in °C, separated by a slash.
• Composition rules:
  • Major element chemical symbol first, followed by its nominal mass percentage (whole number, ±1 accuracy).
  • When an element has a specified range, use the mean rounded to the nearest whole number (round-even on ties); if only a minimum is given, use the rounded minimum.
  • Other elements listed in decreasing nominal percentage; ties resolved by decreasing atomic number.
  • Elements with nominal values <1% are omitted unless they are functional; functional minor elements are shown in parentheses.
  • Only the first six constituents are indicated in the designation.
• Temperature reporting: solidus temperature first, then liquidus (e.g., S 970 °C–L 1 105 °C shown as 970/1105 in the designation).
• Examples:
  • B-Ag72Cu-780 (72 % Ag, 28 % Cu, melting at 780 °C)
  • B-Ag72Cu(Li)-780 (with <1 % Li functional)
  • B-Ni63WCrFeSiB-970/1105

Applications

ISO 3677:2024 is used for:

• Standardized labelling and specification of brazing filler alloys on product data sheets and material certificates.
• Procurement and contract documents requiring unambiguous identification of filler metal composition and melting range.
• Process selection and quality control in brazing operations where melting range (solidus/liquidus) affects joint integrity, heating cycles, and base‑metal compatibility.
• Communicating alloy content between manufacturers, suppliers and end users in industries such as HVAC, automotive, aerospace, electronics and general joining/fabrication.

Who should use this standard

• Welding and brazing engineers, materials and quality managers
• Filler‑metal manufacturers and distributors
• Specification writers, purchasers and testing labs
• Standards committees and regulatory bodies involved in brazing materials

Related standards

• ISO 9453 (soldering materials designations) - soldering designations were removed from ISO 3677:2024 and are now covered separately by ISO/TC 44/SC 12.

Keywords: ISO 3677:2024, filler metal for brazing, brazing filler designation, solidus liquidus, brazing alloys, brazing materials.