ISO 636:2017

Overview - ISO 636:2017 (Welding consumables classification)

ISO 636:2017 defines a classification system for welding consumables (rods and wires) used in tungsten inert gas (TIG/GTAW) welding of non-alloy and fine‑grain steels. It covers consumables and their all‑weld metal properties in the as‑welded and post‑weld heat‑treated conditions for steels with minimum yield strength up to 500 MPa or minimum tensile strength up to 570 MPa. The standard provides two combined classification systems: one based on yield strength + 47 J impact energy and another based on tensile strength + 27 J impact energy.

Key topics and technical requirements

• Classification structure: Designations are built from four parts - product/process symbol, strength/elongation symbol, impact properties symbol, and chemical composition symbol. The process symbol for TIG is “W”.
• Two classification systems:
  • System A: yield strength with 47 J Charpy average impact requirement.
  • System B: tensile strength with 27 J Charpy average impact requirement.
• Impact testing rules:
  • For 47 J: three specimens tested; average ≥ 47 J; one value may be ≥ 32 J.
  • For 27 J: five specimens tested; discard highest and lowest; remaining three average ≥ 27 J; one of the three may be ≥ 20 J.
  • An optional “U” suffix indicates supplemental compliance with the alternate impact level.
• Strength and elongation: Symbols indicate yield/tensile strength and elongation in the as‑welded or PWHT condition (see Tables 1A/1B).
• Chemical composition: Consumables are classified by characteristic alloying elements and limits (see Tables 3A/3B).
• Mechanical and chemical test conditions: Includes preheat/interpass guidance, welding parameters, PWHT conditions, rounding and retesting procedures.

Practical applications and users

ISO 636:2017 is used where consistent selection and specification of TIG filler materials is required:

• Welding engineers selecting consumables to meet joint mechanical and toughness requirements
• Filler‑metal manufacturers classifying products for market and technical data sheets
• Fabricators and inspectors verifying that delivered rods/wires meet contractual and code requirements
• Procurement and quality managers creating purchase specifications and acceptance criteria for TIG consumables Its focus on all‑weld metal properties makes it especially relevant for structural, pressure‑equipment and fabrication work where weld toughness and strength need to be matched or controlled.

Related standards

• ISO 15792‑1 (all‑weld metal test methods)
• ISO 14175 (shielding gases)
• ISO 544, ISO 13916, ISO 14344 (delivery and welding guidance)
• EN 1668 (related classification background)