1. Specifications & Capability
FUSHUN METAL forges large seamless rings in 16MND5, SA-508 Gr.3 and F304 stainless steel, up to 4000 mm outside diameter, for steam generator shells and reactor internals. Final dimensions are established through project-specific process qualification to RCC-M and ASME.
Seamless rings are ring-rolled or forged as single pieces, eliminating the longitudinal weld seam and its associated heat-affected zone, which is essential for the primary-boundary and internals components of a nuclear plant.
| Grade | Standard | Typical Use |
|---|---|---|
| 16MND5 | RCC-M | Steam generator shells |
| SA-508 Gr.3 | ASME SA-508 | Reactor vessel rings |
| F304 | ASTM A182 | Reactor internals |
2. Components & Service Conditions
These rings are the steam generator shell courses, reactor vessel rings and reactor internals of a nuclear plant. The steam generator shell holds the secondary-side water at pressure, while the reactor internals support the core and must remain dimensionally stable under irradiation.
A seamless forging removes the longitudinal weld and its heat-affected zone, the region most prone to stress-corrosion cracking in primary-water service. The low-alloy 16MND5 and SA-508 Gr.3 provide the strength for the pressure boundary, while the austenitic F304 offers the corrosion resistance and irradiation stability required of reactor internals. Full-section ultrasonic testing confirms the soundness the nuclear code demands.
3. Grade Equivalents – 16MND5 / SA-508 Gr.3 / F304
| Designation | Standard | Notes |
|---|---|---|
| 16MND5 | RCC-M | French steam generator steel |
| SA-508 Gr.3 | ASME SA-508 | US RPV steel |
| F304 / S30400 | ASTM A182 | Austenitic stainless internals |
| 20MnMoNi5-5 / 1.6310 | EN 10222 | European equivalent of 16MND5 |
| 20MnMo | JB/T | Reference only, not used in certification |
| Grade | C | Si | Mn | Cr | Ni | Mo |
|---|---|---|---|---|---|---|
| 16MND5 | 0.20 max | 0.10-0.30 | 1.15-1.55 | 0.25 max | 0.50-0.80 | 0.45-0.55 |
| F304 (S30400) | 0.08 max | 1.0 max | 2.0 max | 18.0-20.0 | 8.0-10.5 | – |
The low-alloy grades give the pressure-boundary strength, while the austenitic F304 provides corrosion resistance and irradiation stability for reactor internals.
4. Manufacturing Process
Melting & casting. FUSHUN METAL produces the steel to nuclear cleanliness limits and vacuum-casts large ingots, with controlled residual elements.
Forging. The ring is ring-rolled or forged as a single seamless piece, eliminating the longitudinal weld seam.
Heat treatment. Low-alloy rings are quenched and tempered; F304 rings are solution annealed.
Testing. Full-section UT, mechanical and corrosion tests, with third-party surveillance and complete traceability.
5. Standards & Certification
Large seamless rings are supplied to RCC-M and ASME, with EN 10204 3.2 certificates and third-party surveillance. FUSHUN METAL holds ISO 9001 and AS9120B certification.
Related forging: nuclear flange rings.
6. Typical Applications
Steam generator shells
Seamless shell courses for nuclear steam generators.
Reactor vessel rings
Seamless rings for reactor pressure vessels.
Reactor internals
F304 rings for reactor internal structures.
Primary boundary
Seamless forgings for the primary pressure boundary.
7. Inquiry Essentials
To quote your seamless ring, please provide the ring dimensions, the required grade, and the certificate level and surveillance requirements.
