ISO 21028-1:2016

Overview

ISO 21028-1:2016 - "Cryogenic vessels - Toughness requirements for materials at cryogenic temperature - Part 1: Temperatures below −80 °C" specifies toughness criteria and test requirements for metallic materials intended for service below −80 °C. It defines when impact testing is required, minimum acceptance levels for steels, specimen size and location, and acceptance/retest rules. Unalloyed steels and cast materials are excluded.

Key topics and requirements

• Scope: Applies to metallic materials for cryogenic vessels at temperatures < −80 °C; excludes unalloyed steels and cast materials.
• Toughness verification: Material producers or vessel manufacturers must guarantee toughness or verify it by impact testing per the standard.
• Steels - minimum values:
  • Ferritic steels: 34 J/cm² (corresponds to 27 J for full-size specimen)
  • Austenitic steels: 40 J/cm² (corresponds to 32 J for full-size specimen)
  • Minimum lateral expansion: 0.38 mm
• Lower-temperature service (colder than −196 °C):
  • Base metal, HAZ and weld metal must be tested.
  • Testing at −196 °C is acceptable provided either:
    • 48 J/cm² minimum, or
    • 40 J/cm² if welding procedure tests show similar values at the lower temperature, or
    • 0.53 mm lateral expansion.
• Aluminium and copper alloys: Generally have sufficient low‑temperature toughness; impact testing is not required (references: ISO 6361 series, EN standards).
• Specimen and test rules:
  • Standard test cross-section 10 × 10 mm V‑notched (reduced sections allowed for thickness 5–10 mm per ISO 148‑1).
  • No impact testing on plates < 5 mm thickness.
  • Orientation: specimens taken transverse to rolling and parallel to rolling direction (notch perpendicular to plate surface).
• Weld and HAZ test piece locations:
  • e ≤ 10 mm: 3 from weld centre + 3 from HAZ (6 total)
  • 10 < e ≤ 20 mm: 3 weld + 3 HAZ (6 total)
  • e > 20 mm: two sets of 3 from upper and lower surfaces (12 total)
• Acceptance criteria:
  • Minimums are averages of three specimens; single value may be as low as 70% of specified value.
  • Failed initial series may require a second series of three; combined acceptance rules apply (average of six ≥ min; max two values below min).

Applications and users

• Who uses it: Designers, material suppliers, vessel manufacturers, welding engineers, QA/QC inspectors, and regulatory bodies involved in cryogenic storage and transport (LNG, industrial gases, laboratory cryostats).
• Why use it: To ensure materials and welded joints maintain adequate toughness at cryogenic temperatures, reduce brittle fracture risk, and comply with product or regulatory standards for cryogenic vessels.

Related standards

• ISO 148-1 (Charpy impact test method)
• ISO 6361 series (wrought aluminium)
• EN 10028‑4 / EN 10028‑7 (steel for pressure purposes)
• EN 1652 / EN 1653 / EN 1981 / EN 12163 (copper/copper alloys)
• ASME BPVC Section II (materials)

Keywords: ISO 21028-1:2016, cryogenic vessels, toughness requirements, impact test, weld testing, minimum working temperature, cryogenic materials.