1. Material Definition and Composition Characteristics
07Cr25Ni21NbN is a niobium-nitrogen-strengthened austenitic heat-resistant steel, a specialty ultra-high-temperature stainless steel. Its composition features:
High-chromium nickel base (Cr 24.0-26.0%, Ni 20.0-22.0%): Provides extreme oxidation resistance (temperature resistance up to 1200°C);
Strengthening Elements:
Nb: 0.30-0.60% (carbide stabilization, anti-sensitization);
Number: 0.15-0.25% (solid solution strengthening, improving high-temperature strength);
Ultra-low carbon (C ≤ 0.07%): Completely eliminates the risk of intergranular corrosion.
Compliant Standards: ASTM A213/A312 (American Standard), GB/T 5310 (National Standard for Boiler Tubes).
2. Core Performance Advantages
Ultimate Temperature Resistance:
Continuous operating temperature 1100°C, short-term resistance 1250°C;
Oxidation weight gain at 1100°C <1.0 mg/cm² (100-hour test);
High-Temperature Strength:
Tensile strength ≥120 MPa at 900°C (50% better than 310S steel);
Creep resistance reaches HR6W level (endurance strength ≥60 MPa at 800°C/100,000 hours);
Processing Characteristics:
Welding requires ER383 wire (preheat temperature 200-250°C);
Solution treatment temperature 1150-1200°C, followed by rapid cooling.
3. Typical Applications
Energy Equipment:
Ultra-high temperature heat exchange tubes for fourth-generation nuclear power plants;
Main circuit piping for molten salt reactors;
Extreme Industrial Environments:
Radiant section tubes for petrochemical cracking furnaces;
Heat-resistant rails for billet heating furnaces;
Special Applications:
Aerospace engine combustion chamber liners;
Semiconductor single crystal furnace thermal field components. 4. Comparison with Similar Materials
vs. 07Cr25Ni21 (310S):
Niobium-nitrogen composite strengthening, 40% higher high-temperature strength;
Carburization resistance tripled (suitable for reducing atmospheres);
vs. Inconel 617:
Lower nickel content, 1/3 the cost;
Comparable performance in pure oxidizing environments.
5. Quality Control and Procurement Key Points
Key Tests:
Delta ferrite content ≤ 3% (to prevent high-temperature embrittlement);
1100°C/100-hour oxidation weight gain test;
Processing Warnings:
Hot forming requires a final rolling temperature ≥ 950°C;
Sulfur-containing cutting fluids are prohibited (can cause hot cracking).
