Carbon Steel Forgings: A105 vs. A105N

Carbon steel forgings, manufactured in accordance with ASTM A105, are generally used for piping applications. These forged carbon steel piping components (including flanges, fittings, and valves, etc) are used for ambient- and higher-temperature service in pressure systems. The A105N, which is designated with a suffix “N”, denotes that the A105 forging shall be furnished in normalized condition. If the forgings are used for piping applications of ASME BPVC or ASME B31, the material shall be its identical equivalent of SA-105 or SA-105N. In short, the heat treatment of normalization distinguishes A105N from A105, or SA-105N from SA-105.

Although normalization is a prevalent heat treatment procedure for ASTM A105 forgings, it is not a mandatory requirement except for the following piping components:

• For ASTM A105 flanges manufactured in accordance with ASME B16.5 or ASME B16.47, if the pressure rating is above Class 300, normalization is a must.
• For A105 flanges of special design where the design pressure at the design temperature exceeds the pressure-temperature ratings of Class 300, Group 1.1, or special design where the design pressure or design temperature are not known, normalization is also required.
• For piping components other than flanges that are made from A105 forgings, if the size is over NPS 4 and the pressure rating is above Class 300, normalization is required. If the working pressure at the operating temperature exceeds the tabulated values for special Class 300 of Group 1.1, ASTM A105N shall be applied.