1. Material Definition and Standard Specifications
S34779 is an improved niobium-stabilized austenitic stainless steel (corresponding to the Chinese designation 07Cr18Ni11NbN). Its core features include:
Composition Upgrade:
Base composition (Cr 17.0-19.0%, Ni 9.0-12.0%, Nb 0.30-0.60%);
Nitrogen addition (N: 0.10-0.20%) enhances strength, while carbon content is more strictly controlled (C ≤ 0.06%);
Compliant Standards: ASTM A312/A358 (American Standard), EN 10216-5 (European Standard). 2. Performance Advantages and Strengthening Mechanism
High Strength: Room-Temperature Tensile Strength ≥ 620 MPa (15% higher than S34770);
Corrosion Resistance:
Passes ISO 3651-2 intergranular corrosion test;
Precision Resistance Equivalent (PREN) ≥ 20 (better than ordinary 347 steel);
High-Temperature Stability: 800°C Endurance Strength 20% higher than S34770.
3. Typical Industrial Applications
Chemical Extreme Environments:
Concentrated Nitric Acid Evaporator Tubes;
Urea Synthesis Tower Liners;
Energy:
Supercritical Boiler High-Temperature Headers;
Nuclear Power Secondary Circuit Heat Exchange Tubes (Non-Nuclear Grade).
4. Comparison with S34770
Advantages: Nitrogen strengthening increases strength and narrows weld heat-affected zone;
Limitations: Higher cold work hardening rate, requiring intermediate annealing (HB ≤ 250).
5. Procurement and Processing Considerations
Testing Key Points: Nitrogen content verification + grain size testing (≥ Grade 5);
