1. Specifications & Capability
FUSHUN METAL forges nuclear flange rings in SA-508 Gr.3 and 20MnMoNi5-5, produced from vacuum-cast ingots up to 114 t. Final outside diameter is established through project-specific process qualification, since these are the closure flanges of the reactor pressure vessel (RPV).
The flange ring is forged as a single piece with the adjacent shell section where specified, eliminating the weld seam at the highest-stress closure region. Every ring receives full-section ultrasonic testing and third-party surveillance.
| Grade | Standard | Typical Use |
|---|---|---|
| SA-508 Gr.3 | ASME SA-508 | RPV flange rings |
| 20MnMoNi5-5 / 1.6310 | EN 10222 | European RPV steel |
| 16MND5 | RCC-M | French RPV steel |
2. Components & Service Conditions
These forgings are the RPV flange rings of a pressurised water reactor – the heavy closure flanges that seal the vessel head to the shell under operating pressure and temperature. They form part of the primary pressure boundary, so their integrity is safety-critical.
Because the flange sees neutron irradiation near the core, the steel must control copper, phosphorus and vanadium to resist irradiation embrittlement over the reactor’s life. Forging the flange integrally with the shell removes the weld seam in the highest-stress region, and the vacuum-cast ingot with full-section ultrasonic testing provides the internal soundness the nuclear code requires.
3. Grade Equivalents – SA-508 Gr.3 / 20MnMoNi5-5
| Designation | Standard | Notes |
|---|---|---|
| SA-508 Gr.3 | ASME SA-508 | US RPV steel |
| 20MnMoNi5-5 / 1.6310 | EN 10222 | European RPV steel |
| 16MND5 | RCC-M | French RPV steel |
| SA-508 Gr.2 | ASME SA-508 | Lower-strength RPV grade |
| 20MnMo | JB/T | Reference only, not used in certification |
| Grade | C | Si | Mn | Cr | Mo | Ni |
|---|---|---|---|---|---|---|
| SA-508 Gr.3 | 0.25 max | 0.15-0.40 | 1.20-1.50 | 0.25 max | 0.45-0.60 | 0.40-1.00 |
| 20MnMoNi5-5 (1.6310) | 0.17-0.23 | 0.40 max | 1.20-1.50 | – | 0.45-0.60 | 0.40-0.80 |
Copper, phosphorus and vanadium are tightly controlled to resist neutron irradiation embrittlement over the reactor’s service life.
4. Manufacturing Process
Melting & casting. FUSHUN METAL produces the steel to nuclear cleanliness limits and vacuum-casts large ingots up to 114 t, with controlled copper and residual elements for irradiation resistance.
Forging. The flange ring is forged as a single piece, integrally with the adjacent shell section where specified, on a large forging press.
Heat treatment. Quenching and tempering set the strength and toughness, followed by full-section ultrasonic testing and third-party surveillance to the nuclear code.
Testing. UT, mechanical and impact tests, and third-party surveillance with complete traceability.
5. Standards & Certification
Nuclear flange rings are supplied to ASME SA-508 and RCC-M, with EN 10204 3.2 certificates and third-party surveillance. FUSHUN METAL holds ISO 9001 and AS9120B certification.
Related forgings: large seamless rings and nuclear RPV forgings.
6. Typical Applications
RPV flange rings
Closure flanges of pressurised water reactor vessels.
Integral flange-shell
Flange forged integrally with the shell section.
Closure heads
Head flanges for reactor closure heads.
Primary boundary
Forgings for the primary pressure boundary.
7. Inquiry Essentials
To quote your nuclear flange ring, please provide the flange dimensions, the required grade, the certificate level (3.2) and the surveillance or third-party inspection requirements.
