Overview
ISO 23430:2019 specifies requirements for high manganese (Mn) austenitic steel thin strips intended for use in LNG tanks on board ships. The standard covers strips with a thickness range of 0.3 mm to 6.0 mm and focuses on ensuring good weldability, atmospheric corrosion resistance, and mechanical performance suitable for cryogenic shipboard service. It provides material, manufacturing and testing criteria tailored to shipyards, tank manufacturers, steel suppliers and shipping companies.
Key topics and technical requirements
- Scope & purpose: Material specification for thin strip application in LNG cargo and fuel tanks; aims to meet cryogenic strength and toughness needs.
- Thickness and dimensions: Covers 0.3–6.0 mm thin strips; maximum width 1 500 mm (−0/+0.8 mm).
- Manufacture:
- Electric furnace melting with ladle refining to control residuals.
- Hot-rolled plates (ingot or continuous casting), pickling or reducing heat treatment, then cold rolling and recrystallization annealing under a reducing atmosphere.
- Chemical composition (typical limits from the standard):
- Mn: 24.0 to 34.0%
- Ni: up to 3.50%
- Other controls: C, P, S, Si, Cr, Al, N with specific max/min values per Table 1.
- Mechanical properties:
- Minimum yield strength (0.2% offset): 300 N/mm²
- Minimum tensile strength: 670 N/mm²
- Minimum elongation: 40%
- Toughness and cryogenic testing:
- Design temperature: −165 °C; impact test temperature: −196 °C.
- Charpy V-notch requirements: average ≥27 J (transverse); ≥41 J when used as section member (longitudinal).
- Bend and non‑destructive tests:
- 180° bend test per ISO 7438 (no fracture permitted).
- Optional supplementary tests: ultrasonic testing, corrosion tests, macro/microsection, hardness.
- Weldability:
- Steel shall have good weldability; welding procedure specification (WPS) and qualification in accordance with IACS UR W1 rev.3 are required.
- Marking & documentation:
- Manufacturer, grade identification, year, delivery condition; test certificates must document cast ID, chemical and mechanical results and purchaser/hull references.
Applications and users
- Primary use: LNG cargo tanks and LNG-fuel tanks on carriers and gas-fuelled ships where thin strip material is needed (e.g., internal tank components, cladding, lightweight structural elements).
- Typical users:
- Steel producers and alloy suppliers
- Shipyards and tank manufacturers
- Naval architects and ship designers specifying cryogenic-compatible materials
- Classification societies and QA teams for procurement and inspection
Related standards
- ISO 7438 (bend test), ISO 148‑1 (Charpy impact), ISO 6892‑1 (tensile testing)
- IACS UR W1 (material and welding for gas tankers)
- ISO 21635 and IMO IGC/IGF Codes referenced for cryogenic material context
Keywords: ISO 23430:2019, high manganese austenitic steel thin strips, LNG tanks, ships and marine technology, weldability, cryogenic mechanical properties, chemical composition, thickness 0.3–6.0 mm.
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