Overview
ISO 18487-1:2025 - "Aerospace series - Titanium tube for 35 MPa operating pressure - Part 1: Inch series" is an international standard that specifies technical requirements for seamless circular titanium-alloy tubing intended primarily for aerospace systems with a design operating pressure of 35 MPa (5 080 psi) (Pressure Class J). Published in 2025 (second edition), the standard harmonizes dimensions, material composition, mechanical properties and test methods for inch-series tubing while presenting dimensions in SI units with inch equivalents for industry convenience.
Key topics and technical requirements
- Scope and sizing: Applies to seamless titanium tubing of circular cross-section; nominal sizes are the aerospace “inch series” (document uses SI units with inch equivalents).
- Chemical composition: Limits and reporting requirements for key elements (Al, V, Fe, O, N, H, C, Y, Ti). Analytical methods referenced include ASTM E1447, ASTM E1409, ASTM E1941 and ASTM E2371.
- Melting practice: Multiple melts required; inert gas flooding mandatory; vacuum arc remelting (VAR) required for second and subsequent melts; open-air furnace melting prohibited.
- Heat treatment: Cold-worked and stress-relieved in vacuum or inert atmosphere at a minimum of 370 °C for at least 30 minutes; rotary straightening after final heat treatment is not permitted.
- Mechanical properties: Tensile testing at 15 °C (longitudinal direction), with specified tensile strength, proof stress and elongation ranges depending on diameter. Test methods per EN 2002‑001 / ASTM E8 and sample gauge lengths specified.
- Microstructure and inspection: Microscopic examination (≥400×) of longitudinal and transverse sections; grain size and contractile strain ratio (CSR) requirements; ultrasonic inspection and other non‑destructive tests referenced (EN 3718, AMS 2634).
- Forming and service tests: Requirements and procedures for flaring, bending, flattening, deformation-under-pressure, impulse pressure fatigue testing (including proof and pressure impulse tests), and burst/ultimate testing.
- Quality assurance and delivery: Batch testing rules, marking, packing and conformity documentation. Dimensional tolerances to ISO 12573; surface texture references updated to ISO 21920‑2.
Practical applications and users
- Who uses it: Aircraft and spacecraft designers, hydraulic system engineers, tubing manufacturers, procurement/specification teams, quality assurance and testing laboratories, and MRO organizations.
- Typical applications: High-pressure hydraulic and fluid systems in aircraft and space vehicles where reliable, lightweight, corrosion‑resistant titanium tubing is required at 35 MPa operating pressure (actuation systems, flight controls, landing gear hydraulics, fuel and pressurization lines).
Related standards
Relevant references include ISO 8575:2024 (hydraulic system tubing), ISO 12573 (tolerances - inch series), ISO 21920‑2 (surface texture), ISO 6772 (impulse testing), and several ASTM/EN test method standards cited in the document. These should be consulted together with ISO 18487-1:2025 for full specification and test protocols.