ISO 18735:2026

Overview

ISO 18735:2026 sets the international foundation for specifying minimum requirements for high-manganese austenitic steel castings intended for use in cryogenic temperatures-notably for pressure-containing components like valves and flanges, as well as non-pressure retaining parts in ships and marine technology. Developed by the International Organization for Standardization (ISO), this standard aims to align with relevant codes adopted by the International Maritime Organization (IMO), including the IGC and IGF Codes, ensuring robust performance for metallic materials under extremely low temperatures.

High-manganese austenitic steel castings are favored in marine and cryogenic applications due to their superior mechanical properties and consistent performance at ultra-low temperatures, fulfilling stringent strength and safety requirements for ships’ cargo tanks, fuel tanks, and piping systems.

Key Topics

• Material Designation and Composition
  • Defines the designation “HMC xxx” for high-manganese steel castings, where “xxx” denotes the specified minimum yield strength (SMYS).
  • Specifies required chemical compositions and tolerances for elements like manganese (Mn), silicon (Si), chromium (Cr), and boron (B).
• Manufacturing and Heat Treatment
  • Outlines acceptable manufacturing processes, including electric furnace or open hearth, with precise guidelines for moulding, casting, and test coupon preparation.
  • Details heat treatment requirements, including temperature uniformity surveys and controlled cooling, ensuring uniform mechanical properties.
• Mechanical Properties and Testing
  • Requires extensive mechanical property testing, including tensile tests, Charpy impact tests, and bend tests, with clear minimum criteria for acceptance.
  • Addresses preparation, extent of testing, alternative testing standards, and retesting procedures in case of non-compliance.
• Inspection and Quality Assurance
  • Emphasizes rigorous inspection requirements: visual, liquid penetrant, radiographic, and ultrasonic testing, based on international and industry-recognized standards.
  • Mandates thorough traceability, documentation, and quality management processes in line with ISO 9001 principles.
• Health and Safety
  • Requires manufacturers to comply with statutory health and safety legislation, providing protective equipment and monitoring.

Applications

ISO 18735:2026 is critical for stakeholders involved in the specification, manufacture, and procurement of steel castings used in:

• Marine Engineering and Shipbuilding
  • Valves, flanges, and pressure-retaining components for gas carriers, LNG/LPG fuel systems, and other vessels operating at cryogenic temperatures.
  • Piping systems, including those processing liquefied hydrogen, when agreed upon by the purchaser.
• Pressure Systems
  • Any pressure-containing system, such as storage tanks and piping, requiring steels with verified performance at low temperatures to ensure operational safety and regulatory compliance.
• Manufacturing, Testing, and Certification
  • Provides foundries, ship owners, manufacturers, and certifying bodies with a unified, consistent standard for high-manganese austenitic steel casting production, testing, and inspection.

By standardizing materials and processes, ISO 18735:2026 enhances the reliability and global interoperability of marine and cryogenic equipment, supporting marine safety and efficiency.

Related Standards

For comprehensive implementation, users of ISO 18735:2026 should also be familiar with the following standards and codes:

• ISO 148-1: Charpy pendulum impact test - Methodology for impact testing of metallic materials.
• ISO 2566-1/2: Conversion tables for elongation values of steel.
• ISO 4990: General delivery requirements for steel castings.
• ISO 6892-1: Tensile testing methods for metallic materials.
• ISO 5173: Destructive bend tests for welds in metals.
• ISO 5208: Pressure testing of metallic valves.
• ISO 9606-1 / ISO 9712: Qualification testing of welders and NDT personnel respectively.
• ISO 10474: Inspection documentation for steel products.
• ASME B31.3 / BPVC: American Society of Mechanical Engineers codes for process piping and pressure vessel construction.
• API 598 / ASME B16.5: Alternative pressure testing and mechanical property standards.

Aligning with these documents ensures comprehensive compliance and safety for all stakeholders in the marine and cryogenic sectors.

By implementing ISO 18735:2026, companies across the supply chain can assure consistent product quality, safety, and performance-meeting both regulatory and operational demands for high-manganese austenitic steel castings in cryogenic and marine environments.