1. Common Stainless Steel Grades for ASME Flanges
| ASTM Material | UNS Number | Common Name | Key Characteristics |
|---|---|---|---|
| A182 F304 | S30400 | 304 SS | Standard austenitic, 18% Cr, 8% Ni |
| A182 F304L | S30403 | 304L SS | Low-carbon version (≤0.03% C) |
| A182 F316 | S31600 | 316 SS | 2-3% Mo for improved corrosion resistance |
| A182 F316L | S31603 | 316L SS | Low-carbon with Mo |
| A182 F321 | S32100 | 321 SS | Ti-stabilized for weldability |
| A182 F347 | S34700 | 347 SS | Nb-stabilized for high-temp |
| A182 F904L | N08904 | 904L SS | High Mo (4-5%), Cu-added |
| A182 F6a (Duplex) | S31803 | 2205 Duplex | 22% Cr, 5% Ni, 3% Mo |
2. Temperature Performance Limits
| Grade | Min Temp | Max Temp (Continuous) | Max Temp (Intermittent) |
|---|---|---|---|
| 304/304L | -425°F | 1500°F | 1650°F |
| 316/316L | -425°F | 1500°F | 1650°F |
| 321 | -425°F | 1600°F | 1700°F |
| 347 | -425°F | 1650°F | 1750°F |
| 2205 Duplex | -50°F | 600°F | 750°F |
3. Corrosion Resistance Comparison
| Environment | Best Choice | Alternative | Avoid |
|---|---|---|---|
| Seawater | 316L | 2205 Duplex | 304 |
| Chloride >1000ppm | 2205 Duplex | 904L | 304 |
| Sulfuric Acid (conc.) | 904L | 316L | 304 |
| Nitric Acid | 304L | 316L | - |
| Caustic Solutions | 304 | 316 | - |
4. Pressure Ratings by Class
316L SS Flange Example (psi @ 100°F):
| Class | 150# | 300# | 600# | 900# |
|---|---|---|---|---|
| Rating | 275 | 720 | 1440 | 2160 |
*Note: Ratings decrease with temperature - consult ASME B16.5 Table 2-1.3*
5. Mechanical Properties
| Grade | Yield Strength (ksi) | Tensile Strength (ksi) | Hardness (Brinell) |
|---|---|---|---|
| 304 | 30 | 75 | 201 max |
| 316L | 25 | 70 | 217 max |
| 2205 | 65 | 90 | 290 max |
| 904L | 35 | 71 | 220 max |
6. Welding Considerations
304/316: Require low-carbon filler (ER308L/ER316L)
Duplex: Must maintain 30-70% ferrite/austenite balance
Post-Weld Treatment:
Solution annealing (1900-2100°F) for severe service
Pickling/passivation required for corrosion resistance
7. Cost Comparison (Index)
| Grade | Relative Cost |
|---|---|
| 304 | 1.0 (baseline) |
| 304L | 1.05 |
| 316 | 1.35 |
| 316L | 1.40 |
| 2205 | 2.10 |
| 904L | 3.50 |
8. Industry Applications
Food Processing: 316L (polished finish)
Pharmaceutical: 316L electropolished
Marine: 2205 Duplex or 6% Mo alloys
Chemical Plants: 904L for harsh acids
Power Generation: 347 for high-temp steam
9. Special Requirements
NACE MR0175: Required for sour service (H₂S environments)
3-A Sanitary: For food-grade applications
PED Certification: Needed for EU pressure equipment
NORSOK M-630: Offshore oil/gas standards
10. Inspection & Testing
Material Certs: Mill test reports (MTRs) with:
Chemical composition
Mechanical properties
Heat treatment records
NDE Requirements:
PT (Liquid Penetrant) for surface defects
RT (Radiography) for critical welds
PMI (Positive Material Identification)
Dimensional Checks:
Bore concentricity (±0.5% of diameter)
Face flatness (0.03" max deviation)
Key Selection Criteria:
Match corrosion resistance to process media
Verify temperature limits for service conditions
Consider welding requirements for installation
Account for thermal expansion differences
Specify proper surface finish (e.g., 32Ra for hygienic)
For critical applications, always consult with materials engineers and review ASME B16.5/B16.47 tables for exact pressure-temperature ratings.
