Carbon Steel Flanges
Flanges join pipes, valves, pumps and equipment with a bolted, gasketed joint that can be taken apart. Dimensions and pressure-temperature ratings follow ASME B16.5 (NPS ½"–24") and B16.47 Series A/B (NPS 26"–60"), in classes 150 to 2500.
Choose a grade below for specifications, composition, sizes and weight charts.
Carbon Steel flanges by grade
| Grade | Specification | Key characteristic | Typical use |
|---|---|---|---|
| ASTM A105 Flanges | ASTM A105 | ASTM A105 is the standard specification for carbon steel forgings for piping components (flanges, forged fittings, valves) for ambient- and high-temperature service. | |
| ASTM A350 LF2 Flanges | ASTM A350 | ASTM A350 LF2 covers carbon steel forgings for low-temperature service |
How carbon steel flanges are made, sized and tested
How it's madeFlanges are forged from billets (or cut from plate for some blind and plate flanges), heat treated to the material specification, and machined: bore, face, raised face or ring groove, bolt holes and hub bevel.
- Size range
- NPS ½" – 24" (B16.5), 26" – 60" (B16.47 Series A/B); Class 150, 300, 600, 900, 1500, 2500; EN 1092-1 PN 6 – PN 100 on request
- Finish
- Raised face (RF), flat face (FF) or ring-type joint (RTJ); serrated spiral or concentric face finish (typically 3.2 – 6.3 µm Ra)
- Ends
- Weld-neck bevel matched to pipe schedule; socket bore; threaded
Testing & documents
- Chemical and mechanical tests of the forging
- Dimensional inspection to ASME B16.5 / B16.47
- Hardness, impact and IGC tests as specified
- Ultrasonic testing of forgings on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Frequently asked questions
What does flange class 150 or 300 mean?
It's the pressure-temperature rating class under ASME B16.5. The allowable working pressure depends on the material group and temperature, not simply "150 psi".
RF or RTJ?
Raised-face flanges with spiral-wound or sheet gaskets are standard. Ring-type joint (RTJ) flanges with metal ring gaskets are used for high pressure and temperature.
Which carbon steel grades are available as flanges?
ASTM A105 Flanges, ASTM A350 LF2 Flanges.
Which specifications cover carbon steel flanges?
ASTM A105, ASTM A350, depending on grade.
Need carbon steel flanges?
Send grade, size, quantity and destination.