Article
ASTM A105 is the most widely used material for forged carbon steel flanges, fittings and valve components. It covers ambient and higher temperature service in pressure systems, and it is the default material when a piping specification simply calls for "carbon steel flanges".
Chemistry and strength
| Property | Requirement |
|---|---|
| Carbon | 0.35% max |
| Manganese | 0.60–1.05% |
| Tensile strength | 485 MPa (70 ksi) min |
| Yield strength | 250 MPa (36 ksi) min |
| Hardness | 187 HB max |
A105 and A105N
Heat treatment is not mandatory for all A105 forgings, but flanges above Class 300 and certain other items must be heat treated. Many buyers specify A105N, meaning the forging has been normalised. Normalising refines the grain and gives more consistent toughness, so A105N is often requested for oil and gas projects.
Temperature limits
- Low temperature – A105 is not impact tested, so it is generally not used below about −29 °C. For colder service, use ASTM A350 LF2 (impact tested at −46 °C).
- High temperature – A105 flange ratings in ASME B16.5 decline as temperature rises; above about 425 °C prolonged exposure can lead to graphitisation, so Cr-Mo grades such as A182 F11 or F22 are preferred.
When to choose something else
| Service | Better choice |
|---|---|
| Low temperature | ASTM A350 LF2 |
| High-yield pipelines | ASTM A694 F42–F70 |
| High temperature | ASTM A182 F11, F22, F91 |
| Corrosive fluids | ASTM A182 F304L, F316L, F51 |
Corrosion protection
Carbon steel flanges rust quickly in storage. Suppliers usually apply rust-preventive oil or black varnish, and protect faces with caps or wooden covers. Galvanising or coating can be specified for outdoor service.
Frequently asked questions
What does A105N mean?
It is ASTM A105 forged carbon steel supplied in the normalised condition.
Can A105 flanges be used at low temperature?
Not below about −29 °C without impact testing. ASTM A350 LF2 is used for low-temperature service.
What is the minimum tensile strength of A105?
485 MPa (70 ksi), with a minimum yield of 250 MPa (36 ksi).
Key takeaways
- A105 is the standard forged carbon steel for flanges.
- A105N (normalised) gives more consistent properties.
- Use A350 LF2 for cold service and A182 for corrosive or high-temperature service.
Need these products?
Sawariya Metal Industries supplies stainless steel pipes, flanges and buttweld pipe fittings from Mumbai to buyers in India and overseas. Send your size, grade, standard and quantity through our enquiry form and we will reply with a clear quotation and the test documents you need. You can also browse our stainless steel pipes, flanges and buttweld fittings.