Zirconium Pipes and Tubes: Zr 702 vs. Zr 704 vs. Zr 705

Introduction

Zirconium (Zr) is widely used in various industries due to its exceptional corrosion resistance, high strength, and excellent thermal properties. Among the commercially available zirconium pipes and tubes, Zirconium 702 (Zr 702), Zirconium 704 (Zr 704), and Zirconium 705 (Zr 705) are the most commonly used grades. This article provides an in-depth comparison of these three zirconium grades to help you determine which one is best for your needs.

Chemical Composition

The main difference between Zr 702, Zr 704, and Zr 705 lies in their chemical composition:

• Zr 702 (UNS R60702): Commercially pure zirconium with very low impurity levels.
• Zr 704 (UNS R60704): Contains a small amount of niobium (Nb) to enhance mechanical properties.
• Zr 705 (UNS R60705): An alloy with 2-3% niobium, significantly improving strength and corrosion resistance.

The addition of niobium in Zr 704 and Zr 705 increases their mechanical strength while maintaining excellent corrosion resistance.

Mechanical Properties Data Table

To better understand the differences in mechanical performance among these zirconium grades, the following table summarizes their key mechanical properties:

From the table above, we can see that Zr 705 has the highest tensile strength and hardness due to its niobium content, making it ideal for high-stress applications such as aerospace and nuclear industries. However, Zr 702 has superior ductility and elongation properties, making it easier to form and fabricate in applications requiring complex shaping. Zr 704 offers a balance between the two, providing moderate strength and good corrosion resistance.

Corrosion Resistance

One of the primary reasons zirconium is used in various industries is its outstanding corrosion resistance.

Zirconium 702 exhibits exceptional resistance to most acids, including hydrochloric acid (HCl) and sulfuric acid (H2SO4). It also demonstrates high resistance to seawater and other chloride-containing environments. Zirconium 704 offers slightly enhanced corrosion resistance compared to Zr 702 due to the addition of niobium, making it more effective in high-temperature environments. Zirconium 705 provides the highest level of corrosion resistance among the three, particularly in harsh chemical and nuclear environments.

Further reading: Something You Should Know About Zirconium Pipes

Workability and Fabrication

• Zr 702 is the easiest to machine and form due to its high ductility.
• Zr 704 has moderate workability but requires more effort in machining compared to Zr 702.
• Zr 705 is the hardest to machine due to its higher hardness and strength, requiring specialized tools and techniques.

Cost Considerations

• Zr 702 is generally the most cost-effective option due to its widespread availability and ease of processing.
• Zr 704 is slightly more expensive due to its enhanced properties.
• Zr 705 is the most expensive among the three, given its higher strength and specialized applications.

Applications of Zirconium Alloys

Different zirconium alloys are utilized across various industries due to their distinct mechanical properties and exceptional resistance to corrosion.

--Zirconium 702

With its excellent corrosion resistance, particularly in acidic and chloride-rich environments, Zirconium 702 is commonly used in chemical processing industries. It plays a crucial role in manufacturing acid storage tanks, heat exchangers, and piping systems that handle aggressive chemicals. Its ability to withstand seawater exposure makes it a preferred choice for marine applications, including seawater-resistant components. Additionally, its biocompatibility allows for use in medical implants and prosthetics, ensuring durability and compatibility with the human body. The aerospace and defense sectors also incorporate Zr 702 in select components where corrosion resistance is critical.

--Zirconium 704

Due to the addition of niobium, Zirconium 704 exhibits enhanced performance in high-temperature environments, making it particularly valuable in nuclear reactor applications. It is widely used for fuel rod cladding and coolant pipes, ensuring structural integrity under extreme conditions. Its superior resistance to thermal and mechanical stress also makes it ideal for high-temperature heat exchangers, where efficiency and durability are essential. In the aerospace industry, Zr 704 is employed in components that must withstand extreme heat and oxidative conditions. Additionally, it is utilized in specialty chemical processing equipment where standard materials might degrade under prolonged exposure to corrosive substances.

--Zirconium 705

Offering the highest strength and corrosion resistance among the three alloys, Zirconium 705 is a key material in nuclear power plants. It is commonly used in structural components and reactor core parts, where material integrity is crucial for safety and longevity. The aerospace and military industries rely on Zr 705 for applications that demand both high strength and resistance to extreme environmental conditions. In industrial sectors dealing with highly aggressive chemicals, Zr 705 is an essential choice for equipment exposed to extreme chemical environments, ensuring prolonged service life and reliability in harsh operating conditions.

Conclusion

Choosing the right zirconium alloy depends on the specific requirements of your application:

• Zr 702 is best suited for applications requiring high corrosion resistance and ease of fabrication.
• Zr 704 is ideal for environments with high temperatures and moderate mechanical stress.
• Zr 705 is the best choice for high-strength applications, particularly in nuclear, aerospace, and chemical industries.

Advanced Refractory Metals (ARM) offers a wide range of zirconium pipes and tubes in various sizes and grades. Three distinct grades are available to suit different application needs. ARM also manufactures zirconium strips, pellets, powder, pieces, and wires. Zirconium alloys and compounds are also available for specialized applications. For custom zirconium pipes or further information, please contact us for more details.