904L is recognized globally under multiple standards:
- UNS N08904 (U.S. Unified Numbering System)
- 4539 (DIN/Werkstoff Germany)
- X1NiCrMoCu25-20-5 (EN Europe)
- F904L (ASTM/ASME specifications) 12.
2. Material Properties
Corrosion Resistance
- Resists pitting, crevice corrosion, and stress corrosion cracking (SCC) in chloride-rich environments 12.
- Superior performance in sulfuric, phosphoric, and nitric acids due to 19-23% Cr, 23-28% Ni, and 4-5% Mo 26.
Mechanical Properties
- Tensile Strength: ≥490 MPa | Yield Strength: ≥215 MPa | Elongation: ≥35% 34.
- Density: 8.0 g/cm³ | Hardness: ~200 HB (solution-annealed) 36.
Fabrication Advantages
- Excellent weldability with 904L filler rods and compatibility with TIG/MIG methods 6.
- Non-magnetic and retains ductility after cold working 56.
3. Standards and Specifications
904L nuts comply with:
- ASTM A194/A194M: Standard for stainless steel nuts for high-pressure/temperature service.
- ASME SB649: Bars and forgings for piping components 36.
- DIN 934/936: Metric hex nuts and flange nuts 4.
4. Types of Nuts Produced with 904L
- Hex Nuts (ASTM A194 Grade 904L)
- Lock Nuts (Nylock, all-metal prevailing torque)
- Flange Nuts (SAE J995)
- Wing Nuts and Cap Nuts for specialized equipment 36.
5. Key Applications
Chemical & Petrochemical
- Reactors, heat exchangers, and piping in sulfuric acid production 13.
Pharmaceutical
- Non-reactive containers and sterile equipment 56.
Marine & Offshore
- Seawater handling systems and subsea fasteners 25.
Power Generation
- Flue gas desulfurization (FGD) scrubbers and ductwork 35.
Primary Keywords:
- 904L Stainless Steel Nuts
- UNS N08904 Fasteners
- ASTM A194 904L Nuts
- High-Corrosion Resistance Nuts
Long-Tail Keywords:
- “904L Hex Nuts for Chemical Processing”
- “Super Austenitic Stainless Steel Lock Nuts”
- “Marine-Grade 904L Flange Nuts”
Suggested Tables
Table 1: Chemical Composition of 904L (wt%)
| C ≤0.02 | Cr 19-23 | Ni 23-28 | Mo 4-5 | Cu 1-2 | Fe Balance | 24
Table 2: Mechanical Properties
| Tensile Strength | Yield Strength | Elongation | Hardness | |
| ≥490 MPa | ≥215 MPa | ≥35% | 200 HB | 34 |
Conclusion
904L stainless steel nuts offer unmatched corrosion resistance and mechanical stability for critical applications. By adhering to ASTM/ASME standards and leveraging their unique alloy composition, these nuts ensure reliability in the most demanding environments. For industries prioritizing longevity and safety, 904L remains the material of choice.
Keywords: 904L nuts, UNS N08904 fasteners, ASTM A194, chemical processing nuts, marine-grade stainless steel nuts.
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