Three grades, three positioning strategies.

In titanium bar procurement, the three most frequently requested grades are TA2, TC4, and TC4 ELI. Although their names appear similar, their material properties and application scenarios differ significantly.

TA2 represents industrial pure titanium, offering excellent corrosion resistance, weldability, and moderate cost. It is the most widely used titanium grade in chemical processing, marine applications, and general industrial equipment. TC4 belongs to the Ti-6Al-4V system of high-strength titanium alloys, featuring superior specific strength. It is the preferred material for aerospace structural components and downhole oil & gas tools. TC4 ELI reduces interstitial elements to minimal levels compared to standard TC4, significantly enhancing fracture toughness and damage tolerance. It serves as the core material for orthopedic implants and high damage-tolerance structural components.

Standard Correspondence: GB/T vs. ASTM Designations

Titanium grades have different designations under Chinese and American standards. The table below shows the correspondence between three grades across both systems:

Please note that "correspondence" does not mean "equivalence." GB/T and ASTM standards have subtle differences in chemical composition ranges and mechanical property requirements. Final acceptance must be based on the standard specified in the contract. For example, national standard TC4 may have different upper limits for aluminum content compared to ASTM Gr.5. Do not simply interchange these materials during procurement.

Regarding the GB/T specification for TC4 ELI: "TC4 ELI" is not a formal GB/T grade designation; it is the common industry term used domestically for low interstitial Ti-6Al-4V materials. In GB/T 2965, this material is designated as TC4, with ELI characteristics (lower interstitial element content and higher fracture toughness) typically specified via supplementary technical agreements. When procuring, we recommend explicitly referencing the target standard number (e.g., ASTM F136, ISO 5832-3, or customer technical specifications) rather than using only "TC4 ELI."

Regarding the relationship between ASTM F136 and Gr.23: ASTM F136 is the product specification for Ti-6Al-4V ELI forged material used in surgical implants, while Gr.23 denotes an alloy grade within the ASTM system. The two are not equivalent; F136 incorporates the chemical composition and performance requirements of Gr.23, along with additional specifications tailored for medical implants. Industrial ELI bars typically reference ASTM B348 Gr.23, whereas implant-grade bars reference ASTM F136.

Chemical Composition Comparison: How "Ultra-Low Interstitial" in ELI Actually Compares

The core difference among the three grades in terms of chemical composition lies in the control levels of interstitial element content.

TA2 Characteristics: Contains no aluminum or vanadium, belonging to the pure titanium family. It offers excellent corrosion resistance and weldability but has the lowest strength among the three grades. Oxygen content can be controlled within 0.25%, while a moderate iron content ensures a good balance of ductility and toughness.

TC4 features aluminum and vanadium as primary alloying elements, significantly boosting strength. Compared to TA2, it maintains good corrosion resistance in most environments but requires stricter process control during welding. The maximum oxygen content is 0.20%, placing it at an intermediate level among the three grades.

TC4 ELI features: The core of ELI lies in reducing oxygen content to below 0.13% and tightening iron content to within 0.25%. Although these "ultra-low interstitial" levels slightly reduce material strength, they significantly improve fracture toughness and resistance to fatigue crack propagation. For applications subjected to cyclic loading or requiring high damage tolerance, the added cost of ELI delivers a substantial increase in performance safety margin.

Mechanical Property Comparison: Balancing Strength and Toughness

The mechanical property differences among the three grades directly determine their respective applications. The following data represent typical properties for annealed bars; actual values may vary based on product standards and specifications.

Strength: Both TC4 and TC4 ELI have tensile strengths more than twice that of TA2, making them suitable for load-bearing components, fasteners, and downhole tools. Due to its lower oxygen content, TC4 ELI has slightly lower strength than TC4 but remains in the high-strength category among the three grades.

Toughness Dimensions: TA2 exhibits the highest elongation (≥20%), offering superior ductility and cold-forming performance. Although TC4 ELI shows elongation comparable to TC4, its fracture toughness and damage tolerance are significantly better, making it safer under service conditions where cracks or defects may be present.

Fatigue Performance: For components subjected to cyclic loading (e.g., aerospace rotating parts, orthopedic implants), TC4 ELI offers superior fatigue crack growth resistance compared to TC4. TA2 is suitable for non-load-bearing or low-stress applications.

Product Form and Supply Specifications

Common supply forms for titanium bars include hot-rolled, cold-drawn, and forged bars. The following outlines typical commercial availability; actual supply capabilities vary by grade and specification.

TA2 offers excellent ductility and cold-forming capability, enabling production of cold-drawn bars in small diameters for fasteners and small components. The annealed condition is the most common delivery state.

TC4 can be produced as large-diameter hot-rolled and forged bars to meet the requirements of aerospace structural components and large-scale oil and gas equipment. In addition to the annealed condition, some applications may require solution treatment and aging to achieve higher strength. Note that TC4's long-term service temperature is typically limited by design conditions, stress levels, and oxidation environment; it cannot be defined by a single temperature value across all use cases.

TC4 ELI has a specification range similar to TC4 but is typically supplied in the annealed condition. For medical implants, TC4 ELI bars are commonly available in diameters ranging from 6 mm to 50 mm, depending on the specific implant device requirements.

Material Selection Logic

The following material selection decision framework is based on typical industrial procurement scenarios and can be adjusted according to actual operating conditions:

Select TA2 (Gr.2) when:

Primary requirement: corrosion resistance (seawater, chlor-alkali, general chemical media)

Requires excellent weldability due to extensive welding in manufacturing.

Low load, low strength requirements

Cost-conscious, seeking the best overall value.

Typical Applications: Heat Exchanger Supports, Chemical Fasteners, Marine Seawater Pipe Flanges, General Industrial Corrosion-Resistant Structural Components

Select TC4 (Gr.5) when:

Requires high specific strength and high load-bearing capacity.

Components for aerospace structures, downhole oil and gas tools, and high-performance sports equipment

Requires some fatigue performance but is not a damage-tolerance-critical component.

Typical applications: aircraft structural components and fasteners, oil and gas well strings and tools, high-performance racing cars and motorcycle parts

Select TC4 ELI (Gr.23) when:

Components for orthopedic implants, spinal fixation devices, or dental abutments

Extreme requirements for fracture toughness and damage tolerance

Service environments involving low temperatures, high-cycle loading, or high-reliability requirements

Application scenarios require materials with strict control of interstitial elements.

Typical applications: surgical implants, high damage-tolerant aerospace critical components, cryogenic engineering, and deep-sea equipment key parts

Supplement on the Russian Market: If the customer is from Russia or a CIS country, their inquiry may reference GOST grades. TA2 corresponds approximately to ВТ1-0, and TC4 corresponds approximately to ВТ6 (these are approximate matches, not exact equivalents). TC4 ELI has no direct GOST equivalent; confirm against the customer's technical specifications. When procuring, clearly specify whether acceptance will be based on GOST or ASTM/GB/T standards.

(Yucheng Haitai Industry | TA2 / TC4 / TC4 ELI Titanium Rods |yuchenghaicompany.com）