Introduction
Commercially pure titanium is commonly divided into four ASTM grades: Grades 1, 2, 3, and 4.
These grades are unalloyed titanium materials with different permitted levels of interstitial elements and impurities. Their mechanical properties vary accordingly.
The general trend is straightforward: Grade 1 offers the highest ductility and lowest strength, while Grade 4 provides the highest strength among the four standard CP grades.
Understanding this progression helps buyers and engineers select the right material for forming, fabrication, and corrosion-resistant industrial applications.
1. What Does Commercially Pure Titanium Mean?
Commercially pure titanium is not chemically pure titanium.
It contains controlled amounts of elements such as oxygen, iron, nitrogen, carbon, and hydrogen.
These elements influence the strength, ductility, and processing behavior of the material.
Grades 1–4 are defined by specified chemical composition and mechanical-property requirements. They are not simply different levels of purity.
2. The Four Grades
Grade 1
Grade 1 has the lowest strength and highest ductility among the four standard CP grades.
It is commonly selected for applications requiring extensive forming and good corrosion resistance.
Grade 2
Grade 2 is the most widely used general-purpose CP titanium grade.
It offers a practical balance of strength, ductility, corrosion resistance, and availability.
Grade 3
Grade 3 provides higher strength than Grades 1 and 2, with reduced elongation.
It is selected when additional strength is needed while retaining the characteristics of unalloyed titanium.
Grade 4
Grade 4 has the highest strength among Grades 1–4.
It is used where stronger CP titanium is required, although its lower ductility may limit some forming operations.
3. Chemical Composition and Strength Relationship
Oxygen is an important interstitial element in titanium.
Within the CP titanium grade family, higher permitted oxygen levels are associated with higher strength requirements and lower ductility.
Common maximum oxygen limits are:
| Grade | Oxygen Maximum | |---|---:| | Grade 1 | 0.18% | | Grade 2 | 0.25% | | Grade 3 | 0.35% | | Grade 4 | 0.40% |
Other elements, including iron, nitrogen, carbon, and hydrogen, are also controlled.
The table is a general reference. The complete chemistry requirements must be checked against the applicable specification and edition.
4. Mechanical Property Comparison
Commonly published minimum tensile-property requirements for annealed CP titanium include:
| Grade | Minimum Tensile Strength | Minimum Yield Strength | Minimum Elongation | |---|---:|---:|---:| | Grade 1 | 240 MPa | 170 MPa | 24% | | Grade 2 | 345 MPa | 275 MPa | 20% | | Grade 3 | 450 MPa | 380 MPa | 18% | | Grade 4 | 550 MPa | 483 MPa | 15% |
These figures are reference values commonly associated with ASTM material data. Actual acceptance values depend on the relevant product form, thickness, condition, and specification.
Do not apply plate values automatically to bars, tubes, or other product forms.
5. How to Select the Right CP Titanium Grade
The selection should begin with the component's actual requirements.
| Requirement | Grade Often Considered | |---|---| | Extensive forming and high ductility | Grade 1 | | General industrial service | Grade 2 | | Higher strength than Grade 2 | Grade 3 | | Highest strength within CP Grades 1–4 | Grade 4 |
This is a preliminary selection guide, not a substitute for engineering review.
Corrosion resistance, design stress, thickness, fabrication method, and applicable codes must also be considered.
6. Common Applications
CP titanium Grades 1–4 are used in:
- Chemical processing equipment
- Heat exchangers
- Industrial tanks and vessels
- Piping and fabricated components
- Marine equipment
- Corrosion-resistant sheet components
- Selected medical material applications
The appropriate grade depends on the intended service and governing specification.
7. Important Purchasing Considerations
When ordering CP titanium, confirm:
- Grade and UNS designation
- Product form
- Dimensions and tolerances
- Applicable standard and edition
- Delivery condition
- Mechanical-property requirements
- Chemical composition requirements
- Testing and inspection
- Material traceability
A material designation without a product specification is not a complete purchasing requirement.
Frequently Asked Questions
Which CP titanium grade is most commonly used?
Grade 2 is widely used as a general-purpose commercially pure titanium grade.
Which grade has the highest ductility?
Grade 1 generally offers the highest ductility among Grades 1–4.
Which grade is strongest?
Grade 4 has the highest specified minimum strength among the four standard CP grades.
Are Grades 1–4 titanium alloys?
They are generally classified as unalloyed or commercially pure titanium, not conventional alloyed titanium grades.
Conclusion
Grades 1–4 provide a useful range of strength and ductility within the commercially pure titanium family.
Grade 1 is suited to applications emphasizing formability, Grade 2 is a versatile general-purpose choice, and Grades 3 and 4 provide progressively higher strength.
The final selection must match the product specification and actual service requirements.
Discuss Your CP Titanium Requirements
Feinuotai supplies titanium materials and coordinates processing solutions for industrial requirements.
Please specify the grade, product form, dimensions, quantity, applicable standard, and delivery condition when requesting a quotation.
Internal Link Suggestions
- RES-002: Grade 1 vs Grade 2 Titanium
- RES-011: Titanium Corrosion Resistance
- RES-015: Plate, Sheet, Strip and Foil
- Titanium Plates & Sheets product page
References
- ASTM International, ASTM B265.
https://store.astm.org/standards/b265
- Fort Wayne Metals, Commercially Pure Titanium.
https://fwmetals.com/what-we-do/materials/titanium/commercially-pure-titanium
- ESPI Metals, Commercially Pure Titanium Composition and Properties.