Differences Between Chinese GB and American ASTM Grades for Titanium Alloy Plates

Titanium alloy plates are widely used in aerospace, chemical engineering, marine engineering, medical devices and high-end manufacturing worldwide. When selecting materials, buyers often confuse grades under Chinese National Standards (GB) and American ASTM Standards. The two mainstream standard systems differ greatly in naming rules, classification logic, chemical composition, tolerance requirements and application scenarios, though most mainstream grades have equivalent counterparts.

First of all, the naming and classification systems are completely different.

The Chinese GB system classifies titanium products based on metallographic structure. It uses prefix letters to distinguish material types. TA stands for commercially pure titanium and alpha-type titanium alloys, which cannot be strengthened by heat treatment. TC refers to alpha-beta titanium alloys, the most widely used category with balanced mechanical properties. TB represents beta-type titanium alloys featuring ultra-high strength and excellent cold formability. Typical GB grades include TA1, TA2 for pure titanium, TC4 for classic alpha-beta alloy, and TB2 for beta alloy. Each letter directly reflects the material’s structural characteristics, making classification clear for domestic users.

In contrast, the American ASTM B265 standard adopts a simple coding rule of Grade + number, also commonly shortened to Gr. It does not indicate metallographic structure from the grade name. Each grade is also assigned a unique UNS number for global unified identification. For instance, Grade 1 (UNS R50250) and Grade 2 (UNS R50400) are commercial pure titanium, Grade 5 (UNS R56400) is the universal Ti-6Al-4V alloy, and Grade 23 is the extra-low interstitial (ELI) version of Grade 5. This simple numbering rule is easy to remember and has become a common language in international trade.

Secondly, there are distinctions in chemical composition and dimensional tolerances.

Equivalent grades from the two systems have similar main alloy elements, but differ in control of impurity elements such as oxygen, nitrogen and hydrogen. In general, GB standards set relatively looser limits on interstitial impurities and dimensional tolerances, which helps control production costs and meets the demands of general industrial applications. ASTM standards impose stricter requirements on impurity content and machining tolerances. Especially for ELI grades like Grade 23, ultra-low interstitial elements guarantee superior toughness and fatigue resistance, fully adapting to strict working conditions of aerospace and high-precision medical implants.

Thirdly, their application habits and market orientation vary.

GB titanium alloy plates are dominant in domestic projects in China. TA2, TC4 and TA10 are the mainstream choices for chemical corrosion resistance, general structural parts and marine equipment. The supporting standards such as GB/T 3621 for general use and GB/T 13810 for medical titanium also match local manufacturing and inspection specifications.

ASTM grades are the preferred option for international export orders, overseas projects and high-end industries. Global manufacturers universally recognize Grade 2, Grade 5, Grade 7 and Grade 12. Medical-grade titanium follows dedicated ASTM F67 and F136 standards, which are widely accepted by medical regulatory authorities across regions.

For procurement reference, most common grades have direct equivalents: TA1 corresponds to Grade 1, TA2 to Grade 2, TC4 to Grade 5, and TC4 ELI matches Grade 23. For conventional industrial use, GB grades are cost-effective; for export, aviation, medical and high-precision fields, ASTM grades are more recommended.

In summary, GB and ASTM are two mature standard systems with their own characteristics. Understanding their differences helps manufacturers, traders and end-users select proper titanium alloy plates to satisfy different project requirements and market rules.