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Flanges made from carbon steel offer a strong bolted connection between pipes, valves, pumps, and pressure vessels, ensuring leak-proof joints in various industrial processes. They are produced from common grades such as ASTM A105, ASTM A694, and ASTM A350 LF2 as per ASME B16.5 and ASME B16.47 specifications for pressure classes from 150 to 2500. The high mechanical strength and ease of welding and cost-effectiveness of carbon steel make the material preference over stainless steel and other alloys in oil and gas, power generation, chemical industries, and water treatment systems. Solitaire Overseas manufactures and offers the complete range of carbon steel flanges with full mill test certificates and hydrostatic testing, ultrasonic testing, and quality inspections available upon request.
Request a Quote for Carbon Steel FlangesA carbon steel flange is a forged disc, or a disc cut and machined from a steel plate, with bolt holes arranged around its circumference. Carbon steel is steel in which carbon is the main alloying element, containing up to about 2.1% carbon by weight, though flange grades typically use low to medium carbon content in the 0.10 to 0.35% range for a practical balance of strength, weldability and machinability. The flange faces are sealed with a gasket and drawn together with bolts and nuts, which allows the joint to be opened again for inspection, cleaning or maintenance, unlike a permanent weld.
| Parameter | Specification |
|---|---|
Standard |
ASTM A105, ASTM A694, ASTM A350 LF2, ASME B16.5, ASME B16.47, MSS SP44 |
Size Range |
NPS 1/2 inch to 48 inch |
Pressure Class |
Class 150, 300, 600, 900, 1500, 2500 |
Facing |
Raised Face, Flat Face or Ring Type Joint |
Construction |
Forged, or cut and machined from plate depending on class and grade |
Testing |
Hydrostatic test, ultrasonic test, third party inspection on request |
Certification |
Mill Test Certificate EN 10204 3.1, 3.2 on request |
| Element | A105 | A350 LF2 |
|---|---|---|
Carbon max |
0.35 |
0.30 |
Manganese |
0.60 to 1.05 |
0.60 to 1.35 |
Phosphorus max |
0.035 |
0.035 |
Sulfur max |
0.040 |
0.040 |
Silicon |
0.10 to 0.35 |
0.15 to 0.30 |
| Grade | Tensile Strength (MPa) | Yield Strength min (MPa) | Elongation min (%) |
|---|---|---|---|
A105 |
485 min |
250 |
22 |
A694 F60 |
515 min |
415 |
18 |
A350 LF2 |
485 min |
250 |
22 |
| Class | Approximate Rating at Ambient (psi) | Approximate Rating at Ambient (bar) | Equivalent PN |
|---|---|---|---|
150 |
285 |
20 |
PN20 |
300 |
740 |
51 |
PN50 |
600 |
1480 |
102 |
PN100 |
900 |
2220 |
153 |
PN150 |
1500 |
3705 |
255 |
PN250 |
2500 |
6170 |
425 |
PN420 |
| Point | Forged Carbon Steel Flange | Plate Carbon Steel Flange |
|---|---|---|
Manufacturing method |
Shaped under heat and pressure from a billet |
Cut and machined from flat steel plate |
Grain structure |
Continuous, oriented to the flange shape |
Not optimized for stress |
Typical pressure class |
Class 150 through 2500 |
Class 150 and 300 |
Cost |
Higher |
Lower |
Best suited for |
Critical, high pressure or cyclic service |
General piping, water systems, cost driven applications |
See our Carbon Steel Plate Flanges page for the full plate flange range.
| Grade | Service Range | Typical Use | Related Product Page |
|---|---|---|---|
ASTM A105 / A105N |
Minus 20 to 800 degrees Fahrenheit |
Standard forged grade for Class 150 through 2500, the most common carbon steel flange specification |
Carbon Steel High Pressure Flanges |
ASTM A694 (F42 to F70) |
Ambient to moderate temperature, high yield |
High-pressure oil and gas transmission and wellhead piping |
Carbon Steel High-Pressure Flanges |
ASTM A350 LF2 |
Down to minus 50 degrees Fahrenheit |
Low-temperature service, LNG, cryogenic and cold climate piping |
Low Temperature Carbon Steel Fittings |
Mild Steel Plate |
Class 150 and 300 ambient service |
Cost-driven grade cut and machined from plate |
Carbon Steel Plate Flanges |
A105N indicates normalised heat treatment, which refines grain structure and improves toughness, and is required for flanges above 2 inches in Class 600 and above under ASME B16.5.
A: A carbon steel flange is a forged or plate cut pipe connection component with bolt holes around its circumference, used to create a removable, gasketed joint between pipe sections, valves or vessels, made from carbon steel grades such as ASTM A105.
A: Carbon steel flanges are lower cost and easier to weld but need coating for corrosion protection, while stainless steel flanges cost more but resist corrosion without additional coating. Dimensions are the same for a given standard and class, the difference is material performance and cost.
A: ASTM A105 is the standard forged grade. ASTM A694, in sub grades F42 to F70, is used for high pressure oil and gas transmission. ASTM A350 LF2 is used for low temperature service, and mild steel plate is used for cost driven plate flanges.
A: Forged flanges have a continuous, oriented grain structure and are suitable for Class 150 to 2500 pressure piping. Cast flanges have a less refined grain structure and are generally limited to lower pressure, non critical service, and are not permitted in hydrocarbon or steam piping under most process piping codes.
A: Solitaire Overseas supplies carbon steel flanges from Class 150 through Class 2500 per ASME B16.5 and B16.47, along with equivalent PN ratings for European and Asian projects.
A: Standard ASTM A105 carbon steel flanges are rated for service up to about 800 degrees Fahrenheit (427 degrees Celsius). Higher temperature duty calls for an alloy steel grade rather than carbon steel.
Contact Solitaire Overseas, or see our Carbon Steel Pipe Flanges and Carbon Steel High Pressure Flanges ranges.