A105 vs A105N: what is the difference?
ASTM A105 is the standard specification for carbon steel forgings for piping — flanges, forged fittings and valve parts. "A105N" is not a separate standard: it means A105 supplied in the normalized condition.
What normalizing does
Normalizing heats the forging above its critical temperature (around 900 °C for this steel) and lets it cool in still air. This refines the grain coarsened by forging, evens out properties through the part and improves toughness. A105 itself requires heat treatment in certain cases (for example flanges above Class 300); otherwise forgings may be supplied as-forged. Ordering A105N makes normalizing mandatory for every piece, and the "N" is marked on the flange.
Mechanical properties (both)
| Property | Requirement |
|---|---|
| Tensile strength | 485 MPa (70 ksi) min |
| Yield strength | 250 MPa (36 ksi) min |
| Elongation | 22% min (2 in) |
| Hardness | 187 HBW max |
When to specify A105N
Many oil, gas, refinery and power projects specify A105N as standard because properties are more consistent. It is commonly required for sour (H₂S) service alongside the hardness limits of NACE MR0175 / ISO 15156. For impact-tested low-temperature service, use ASTM A350 LF2 instead — A105 has no mandatory Charpy test.
Frequently asked questions
Is A105N a different material from A105?
No. It is the same ASTM A105 steel supplied in the normalized heat-treated condition, marked with an N.
Can A105 be used for low-temperature service?
Not where impact testing is required. Use ASTM A350 LF2, which is Charpy tested to −46 °C.
What is the maximum hardness of A105?
187 HBW per ASTM A105.
Last updated 2026-11-02