What does the letter behind the standard mean?

There is no difference in material composition between A105N and A105 in the ASTM A105/A105M standard. The difference is only in the standard and mechanical properties.

When the order has an auxiliary requirement for heat treatment, a letter is added after A105, and the letters are expressed as: A-annealing, N-Normalizing, NT-Normaling+Tempering, QT-Quenching+Tempering.

In addition, A105 and A105M in ASTM A105/A105M are not much different. Don’t think that there is a change in materials. In fact, the units are not the same when supplied. The indication without M is supplied in English units, and the indication with M is supplied in metric units.

Other standards such as ASTM A193/A193M, A351/A351M, etc. are all relevant.

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