The different between ASTM A105 and A105N

ASTM A105N where the ‘N’ stands for normalized.

It has been heat treated to A105N where the ‘N’ stands for normalized

It has been heat treated to remove the internal stresses caused by casting, forming etc.

If a customer specifically asks for A105N then it will be for a good reason. The normalizing heat treatment will ensure the A105N has superior properties to that of the A105.

The ‘N’ is not a category code, the A105 should be normalized if intended for use below -1 degree C.

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Material treated at 920deg C and then cooling in still air.
So, the marking was not stamped N on the fittings, which fittings are acceptable or not?

Stamping “N” is not required in the code, but make sure that material have to heat treated as normalized.
ASME B16.5 2017 Product marking.
4.2.5 Temperature. Temperature markings are not required on flanges or flanged fittings; however, if marked, the temperature shall be shown with its corresponding tabulated pressure rating for the material.

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As per ASME sec.8 Div.1 2019 Edition we have a major change concerning SA-105 as it turned to be a curve A material while it was a curve b in all of the ASME late editions the point here is that SA-105N occupied curve b that is why this is a big change that every new construction according to ASME sec.8 div.1 or 2 and has a low temperature operating condition and was limited to use a material from curve b not A should be turned into SA-105N (Normalized)

Changing material: design engineering will determine type of material.

of course i am not talking from an inspection point of view i am talking from design point of view