1. What is this material?
07Cr25Ni21NbN is a high-alloy, austenitic, heat-resistant stainless steel designed for use in extremely high-temperature environments. Its core components are chromium (25%) and nickel (21%), with niobium (Nb) and nitrogen (N) added to enhance high-temperature stability and creep resistance. Similar international grades include ASTM A213 TP310HNbN, and the older domestic designation is 0Cr25Ni21NbN (GB/T 20878).
2. What are its core properties?
Ultra-high-temperature performance: It can withstand long-term temperatures up to 1150°C and short-term temperatures up to 1250°C, making it suitable for applications such as furnaces and heat treatment equipment.
Oxidation and corrosion resistance: The high chromium and nickel content forms a dense oxide film, while niobium and nitrogen inhibit carbide precipitation, resulting in excellent resistance to intergranular corrosion.
Mechanical strength: Nitrogen solid solution strengthening results in significantly superior high-temperature creep strength compared to standard 310S stainless steel.
3. Typical Applications?
Energy Industry: Ultra-supercritical power plant boiler superheater tubes, gas turbine combustor components.
Petrochemical Industry: Ethylene cracking furnace tubes, high-temperature piping for reformers.
Heat Treatment Equipment: Annealing furnace rollers, high-temperature kiln linings.
4. How does it differ from standard 310S (25Cr20Ni)?
07Cr25Ni21NbN significantly improves its high-temperature strength and creep resistance through the combined addition of niobium and nitrogen. 310S, on the other hand, relies solely on chromium and nickel for oxidation resistance, resulting in a lower upper temperature limit (approximately 1000°C) for long-term use. Furthermore, 07Cr25Ni21NbN offers superior weldability, eliminating the need for complex post-weld heat treatment.
5. Processing and Procurement Considerations
Standard Certification: Prefer steel pipes conforming to ASTM A213 or GB/T 5310 to ensure safety in high-pressure boiler applications.
Welding Process: Welding consumables containing niobium (such as ENiCrFe-7) are recommended, with interpass temperatures controlled at ≤150°C.
Testing Requirements: High-temperature tensile testing (≥600°C), intergranular corrosion (ASTM A262-E), and ultrasonic testing reports are required.
