What do the letters at the beginning of an ASTM standard signify?

Every ASTM standard is identified by a unique designation. It includes a capital letter (A – G), followed by a serial number ranging from one to four digits, a dash, and finally the year of issue. For example, a common bolt specification is A449 – 07a, although when specified the standard’s year designation is usually not included.

The alphabetical letters represent general classifications. Outlined under each classification are a number of standards for a variety of products, materials, testing processes, and many other topics.

General ASTM Classifications

A—Ferrous metals and products

B—Nonferrous metals and products

C—Cementitious, ceramic, concrete, and masonry materials

D—Miscellaneous materials and products

E—Miscellaneous subjects

F—End-use materials and products

G—Corrosion, deterioration, weathering, durability, and degradation of materials and products


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    Can you please tell that why ASTM A494 (Nickel Alloy castings) is covered under A series eventhough Nickel comes under a Non ferrous? However, Nickel Alloy forgings are covered under B series- ASTM B 564.

    Hi Dane,
    Could you please tell me what the h stands for in the material letter code, for instance A479 TP 304H?. Also i have this material code which is Inconel 625H which i suspect if it really exist or not.

    @Arun- In the A479 304H I believe the H stands for High Carbon. The opposite of that is 304L which is low carbon. As for your Inconel 625H, we don’t do much with the Nickel based alloys are are not as familiar with that one.

    could you please tell , when to use ‘TYPE’ and when to use ‘Gr’

    For example, in case of SA 240 GR304 OR SA240 TYPE 304. I have seen both the designations. Is there any specific criteria?

    Expect your reply.

    @Ajith Kr – I do not believe that one or the other is correct nor incorrect, however in the ASTM A240 standard, the specific alloys are referred to as “Types”, so I believe that to be more common.

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