ISO 23515:2022

Overview

ISO 23515:2022 defines a unified designation system for titanium and titanium alloys based on chemical composition and impurity content. The standard establishes clear naming rules - covering unalloyed titanium grades, alloyed titanium designations and alloys containing micro‑alloying elements - enabling consistent material identification across specifications, procurement and international trade.

Keywords: ISO 23515, titanium designation system, titanium alloys, chemical composition, impurity limits

Key topics and technical requirements

• Prefix and symbols
  • All ISO designations use the prefix “ISO” (may be omitted for brevity where obvious).
  • International chemical symbols are used for element notation (e.g., Ti, Al, V).
• Unalloyed titanium designation
  • Format: Ti + single digit representing the maximum allowable impurity class (examples: Ti1, Ti2, Ti3, Ti4).
  • Impurity limits (examples from Table 1): nitrogen (0.03–0.05 %), iron (0.20–0.50 %), oxygen (0.18–0.40 %), with each figure tied to specific maxima.
  • Special suffixes: “H” (higher guaranteed offset strength) and “L” (lower guaranteed offset strength) indicate modified mechanical guarantees with slightly different impurity levels.
• Titanium alloy designation
  • Format: Ti‑<whole number><Element>‑<number><Element>…, where whole numbers indicate nominal percentage amounts (e.g., Ti‑6Al‑4V).
  • Alloying elements are listed in decreasing content or alphabetical order when contents are equal. Ranges or minima are rounded as specified.
  • Abbreviations like ELI (extra low interstitial) may be appended for alloys with lower limits on iron and interstitials.
• Micro‑alloying and impurity-level combined designation
  • Alloys with low‑level micro‑additions (Pd, Ru, Mo, Ni, Cr, Co) combine the impurity class notation and alloy notation (e.g., Ti1‑0.15Pd). Micro‑alloy ranges are reported to up to two decimal places.

Applications and users

ISO 23515 is practical for:

• Material specifiers, metallurgists and R&D teams designing or classifying new titanium alloys.
• Manufacturers and fabricators that need consistent material marking and traceability.
• Procurement and quality assurance teams creating or enforcing purchase specifications.
• Aerospace, medical, chemical process and marine industries where material identity, corrosion resistance and interstitial controls are critical.
• Standards bodies and test laboratories creating harmonized product standards and certificates.

Related standards (context)

• The standard was prepared by ISO/TC 79 (Light metals and their alloys), Subcommittee SC 11 (Titanium). ISO 23515 is intended to work alongside testing, metallurgy and product standards that specify mechanical, chemical and inspection requirements for titanium products.

By adopting ISO 23515:2022 users gain a consistent, internationally recognized system for naming titanium materials - improving specification clarity, supply chain interoperability and global trade of titanium and titanium alloy products.