Answer:

AISI and ASTM are two kinds of industry standards in the United States, the implementing agencies are different, but the raw material are the same. AISI - American Iron and Steel Institute Standards, ASTM - American Society for Testing and Materials standards.

In the United States there are many other standards, such as, ANSI- American National Standards, ASME- American Society of Mechanical Engineers standards.

Japan also has his own standards, but they are not unified.
Remarks: they may have a tiny difference in composition and properties, so we can't distinguish them. There is also a number of stainless steel grades in ASTM method. The relationship of these two are similar but not identical.

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