1. Specifications & Capability
FUSHUN METAL forges high-pressure gas cylinders and pressure hull sections in AISI 4340 ultra-clean steel, vacuum-degassed for maximum cleanliness, to custom sizes for deep-sea and defence applications. Components are forged as single pieces, quenched and tempered, and full-section ultrasonically tested.
Forging a pressure shell from one piece removes the weld seams that are the weak points under cyclic pressure, giving the integrity a deep-sea hull or high-pressure cylinder demands.
| Grade | Standard | Typical Use |
|---|---|---|
| AISI 4340 | AMS / MIL | Pressure hull, gas cylinders |
| 1.6957 / 26NiCrMoV14-5 | EN 10250-3 | European equivalent |
2. Components & Service Conditions
These forgings are the pressure hull sections of submersibles and the bodies of high-pressure gas cylinders, holding internal pressure against external water depth or containing gas at several hundred bar. Both are fatigue-critical pressure boundaries.
The ultra-clean, vacuum-degassed 4340 gives the strength and toughness for these thick sections, while forging from a single piece eliminates the weld seams that limit fatigue life. Quenching and tempering sets the ordered strength, and full-section ultrasonic testing confirms freedom from the internal defects that could fail under cyclic pressure at depth.
3. Grade Equivalents – AISI 4340
| Designation | Standard | Notes |
|---|---|---|
| AISI 4340 | SAE J404 / AMS | Ni-Cr-Mo high-strength steel |
| 26NiCrMoV14-5 / 1.6957 | EN 10250-3 | European equivalent |
| 30Cr2Ni4MoV | GB/T 8732 | Reference only, not used in certification |
| Grade | C | Si | Mn | Cr | Ni | Mo |
|---|---|---|---|---|---|---|
| AISI 4340 | 0.38-0.43 | 0.15-0.35 | 0.60-0.80 | 0.70-0.90 | 1.65-2.00 | 0.20-0.30 |
The 1.65-2.00% nickel gives the deep hardenability and toughness needed for thick pressure sections; the vacuum degassing keeps inclusions low for fatigue life.
4. Manufacturing Process
Melting. FUSHUN METAL produces ultra-clean steel with vacuum degassing, keeping inclusions low for maximum fatigue life.
Forging. The shell is forged as a single piece, eliminating weld seams and aligning grain flow with the pressure boundary.
Heat treatment. Quenching and tempering set the ordered strength and toughness.
Testing. Full-section UT, mechanical tests, and pressure verification, with full traceability.
5. Standards & Certification
Pressure shells are supplied to AMS and military specifications, with inspection certificates under EN 10204 3.1. FUSHUN METAL holds ISO 9001 and AS9120B certification.
Related forging: gun barrels.
6. Typical Applications
High-pressure cylinders
Bodies for high-pressure gas cylinders.
Pressure hull sections
Hull sections for submersibles and deep-sea craft.
Defence
Pressure forgings for defence applications.
Deep-sea equipment
Pressure vessels for deep-sea equipment.
7. Inquiry Essentials
To quote your pressure shell, please provide the shell drawing, the design depth or pressure, and the material specification.
