Resources / Technical Specifications
Material Grade Quick Reference
A complete steel flange specification needs the standard, the class, the facing, and the material grade. The first three are usually obvious from the project documents. The material grade is where the rookie mistakes happen. The reference below is the same quick-lookup the inside sales group uses on bid days.
Forged Carbon Steel
| ASTM Grade | Typical Use | Min Yield | Temp Range |
|---|---|---|---|
| A105 | General service forged | 36 ksi | -20 F to 800 F |
| A350 LF2 Cl 1 | Low-temp service, impact tested | 36 ksi | -50 F to 650 F |
| A350 LF3 | Deep cryogenic, 3.5 Ni | 37 ksi | -150 F to 650 F |
| A694 F42-F70 | High-yield transmission pipeline | 42 to 70 ksi | -20 F to 400 F |
A105 is the default forged carbon grade and the workhorse of general process and refinery service. A350 LF2 takes over below minus 20 F. LF3 is the cryogenic grade. A694 carries the high- yield designation for transmission pipeline applications where the flange has to mechanically match the line pipe.
Plate-Cut Carbon Steel
| ASTM Grade | Typical Use | Min Yield | Notes |
|---|---|---|---|
| A516 Grade 70 | Pressure-vessel plate, AWWA flanges | 38 ksi | Notch toughness available |
| A516 Grade 60 | Lower-pressure waterworks | 32 ksi | Used where Grade 70 strength is not needed |
| A36 | Structural blank flanges | 36 ksi | Non-pressure structural only |
| A283 Grade C | Mild service waterworks | 30 ksi | Lower-grade structural plate |
A516 Grade 70 is the dominant pressure-vessel plate for plate-cut AWWA C207 work. A36 is structural only and should never appear on a pressure-rated flange. Confirm the plate grade on the order so the right material ships.
Alloy Steel (Chrome-Moly)
| ASTM Grade | Chemistry | Max Temp | P-Number |
|---|---|---|---|
| A182 F11 Cl 2 | 1-1/4 Cr - 1/2 Mo | 1100 F | 4 |
| A182 F22 Cl 3 | 2-1/4 Cr - 1 Mo | 1200 F | 5A |
| A182 F91 | 9 Cr - 1 Mo - V | 1200 F | 15E |
| A182 F5 | 5 Cr - 1/2 Mo | 1200 F | 5B |
Chrome-moly grades all require preheat before welding and PWHT after. The P-Number column corresponds to ASME Section IX welding procedure qualification. Mixing P-Numbers across a joint requires additional procedure qualification work.
Stainless Steel
| ASTM Grade | UNS | Typical Use | Max Temp |
|---|---|---|---|
| A182 F304 | S30400 | General stainless | 1500 F |
| A182 F304L | S30403 | Low-carbon, welded fab | 800 F |
| A182 F316 | S31600 | Chloride resistance | 1500 F |
| A182 F316L | S31603 | Welded chloride service | 850 F |
| A182 F321 | S32100 | Stabilized for high-temp | 1500 F |
| A182 F347 | S34700 | Niobium stabilized high-temp | 1500 F |
The L grades cap at lower temperatures for sustained service because the low-carbon chemistry sensitizes more slowly but also softens at high temperature. For continuous service above 800 F, the standard grades (304, 316) or the stabilized grades (321, 347) are the correct choice.
ASME Class to DIN PN Crosswalk
| ASME Class | Cold Rating | Closest DIN PN | Bolts Interchange |
|---|---|---|---|
| Class 150 | 285 psi | PN 16 / PN 20 | No |
| Class 300 | 740 psi | PN 40 / PN 50 | No |
| Class 600 | 1480 psi | PN 100 | No |
| Class 900 | 2220 psi | PN 150 / PN 160 | No |
| Class 1500 | 3705 psi | PN 250 | No |
| Class 2500 | 6170 psi | PN 400 | No |
Bolt patterns and outside diameters do not match between ASME and DIN even when the cold pressure rating is similar. Mixing standards on the same joint requires a qualified transition flange or matched pairs on both sides.
Bolt Material Quick Reference
The flange is half the joint. The bolts are the other half. For carbon and alloy steel flanges, ASTM A193 covers most stud bolt grades.
- A193 B7: Chrome-moly heat-treated, the default stud grade. 105 ksi yield up to 2-1/2 inch diameter, 95 ksi above. Temperature range minus 50 F to 750 F.
- A193 B7M: Same chemistry as B7 but tempered to lower hardness for NACE sour service compliance. 80 ksi yield. Required wherever NACE MR0175 applies.
- A193 B8: Stainless 304 stud. 30 ksi yield. Used in stainless piping and chemical service.
- A193 B8M: Stainless 316 stud. Same yield as B8 but with the chloride resistance of 316.
- A320 L7: Low-temp version of B7. Same yield, with impact-tested toughness for service below minus 50 F.
Matching nuts come from ASTM A194: 2H for B7, 2HM for B7M, 8 for B8, 8M for B8M, 7 for L7.
Need a Spec Confirmed?
Call (281) 484-8325 or email sales@texasflange.com with the grade callout from your project spec. We will confirm availability, lead time, and the matching documentation.
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