Zirconium Zr 702 (UNS R60702) – Composition, Properties, and Uses

UNS R60702, also known as Titanium Grade 7, is a corrosion-resistant alloy primarily made of titanium and palladium. This alloy is widely used in the aerospace, marine, and chemical industries, thanks to its high tensile strength, low density, and excellent corrosion resistance. If you want to learn more about UNS R60702, including its composition, physical and mechanical properties, uses, hardness, heat treatment, welding, and corrosion resistance, this ultimate guide is for you.

R60702 Composition

UNS R60702 is an alpha-beta titanium alloy that contains 0.12-0.25% palladium and trace amounts of iron, carbon, oxygen, nitrogen, and hydrogen. The palladium increases the alloy’s resistance to corrosion, particularly in acidic environments, and improves its strength and flexibility. The low levels of interstitial elements make UNS R60702 suitable for applications that require high purity, such as medical implants and equipment.

UNS R60702 Physical Properties

UNS R60702 has a 4.48 g/cm3 density, lower than most other metals. It also has a melting point of 1670°C and a boiling point of 3287°C, making it suitable for high-temperature applications. The thermal and electrical conductivity of UNS R60702 is lower than those of copper and aluminium but higher than those of stainless steel. Moreover, UNS R60702 exhibits a unique property called super elasticity, which means it can return to its original shape after being deformed up to 2-3% strain.

R60702 Mechanical Properties

UNS R60702 has a minimum tensile strength of 345 MPa and a minimum yield strength of 275 MPa. Its modulus of elasticity is 105 GPa, and its elongation at break is 20-25%. The fatigue strength of UNS R60702 is excellent, and it can withstand cyclic loading without cracking or fracturing. The combination of high strength and low density makes UNS R60702 suitable for weight-sensitive applications, such as aircraft parts.

R60702 Uses

UNS R60702 is used in various applications, including reactor vessels, heat exchangers, desalination plants, chemical processing, marine equipment, and medical implants. Its excellent corrosion resistance and biocompatibility make it suitable for dental implants, pacemakers, and joint replacements. It is also used in the aerospace industry for structural components, landing gear, and engine parts.

R60702 Hardness

UNS R60702 has a Brinell hardness of 125 to 215, depending on the heat treatment and processing. Cold working can increase the hardness, while annealing can decrease it. The higher the palladium content, the higher the hardness and strength of the alloy. The hardness of UNS R60702 also affects its wear resistance, which is beneficial for applications that involve sliding or abrasion.

R60702 Heat Treatment

UNS R60702 can be heat treated to improve its properties, such as strength, flexibility, and corrosion resistance. Annealing at 704-760°C for 1-2 hours can soften the alloy and improve its formability. Solution heat treatment at 850-900°C followed by quenching can increase strength and hardness. Age hardening at 482°C for 4-8 hours can further increase the strength and toughness of the alloy.

R60702 Welding

UNS R60702 can be welded using various techniques, such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and electron beam welding (EBW). Preheating the parts and using a protective welding atmosphere can prevent oxidation and contamination of the weld. Post-weld heat treatment can relieve residual stresses and improve the mechanical properties of the weld.

R60702 Corrosion Resistant

UNS R60702 has excellent corrosion resistance in various environments, such as strong acids, seawater, and chlorine. The presence of palladium makes the alloy resistant to crevice corrosion, which can occur in stagnant or low-oxygen areas. UNS R60702 can also resist stress corrosion cracking, which can occur under continuous tensile stresses in corrosive environments. The corrosion resistance of UNS R60702 makes it a reliable and durable material for critical applications in harsh conditions.

Conclusion

UNS R60702 is a versatile, high-performance alloy with a unique strength, weight, and corrosion resistance combination. Whether you need a material for medical implants, aircraft parts, or chemical processing equipment, UNS R60702 can meet your requirements. This ultimate guide has covered the composition, physical and mechanical properties, uses, hardness, heat treatment, welding, and corrosion resistance of UNS R60702, giving you a comprehensive understanding of this valuable material.