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Confusion about ASTM and AISI/SAE and properly specifying materials

Confusion about ASTM and AISI/SAE and properly specifying materials

Confusion about ASTM and AISI/SAE and properly specifying materials

I am a relatively new engineer and am having some confusion with respect to specifying materials. I have inherited a number of designs from our sister company in the US (we are in Canada) that have unusual material specifications.

I am confused as to what ASTM standards actually dictate. Do they just dictate things like dimensions and tolerances? Do some or all of them dictate everything you need to know about a particular material. For example, ASTM A108 is not a type of steel. I would have to specify a grade to go with it, correct? So I would say, AISI 1018 as per ASTM 108, which would get me a steel with a specific composition (the AISI designation) that meets certain physical characteristics (the ASTM standard). Am I understanding that correctly?

On the other hand, I am getting the impression that there are some ASTM standards that can fully define a steel. For example, ASTM A1018 Class SS Grade 40 is all the information you would need to specify a material, correct? Therefore it wouldn't make any sense to say, "1018 sheet steel per ASTM A1018 Class SS Grade 40" would it?

I apologize for all the questions at once, but I really need to learn the differences between AISI/SAE and ASTM and when and how to use them. I also realize that there are other topics on this, but they have all dealt with specific examples, I am looking for some help in understanding the fundamentals of specifying a material.

Thank you!

RE: Confusion about ASTM and AISI/SAE and properly specifying materials

ASTM standards (consensus standards) can generally be separated into 2 different types. One is a product standard that gives the various different categories of the materials and the other is procedure standard that gives the methods of testing to determine compliance with the individual product standards. These standards have no legal authority until adopted by a code or design standard or by a model or local code or be specified by a designer. the can adopt by reference.

The best way to understand the systems and organization, is to look at the referred standards (usually in one of the first sections of a particular standard) to see what is used to determine the actual references for the standard. Unfortunately the ASTM process is long and slow to update since the standards are written by individual members that spend their time and efforts in the process. There are no "corporate" votes, as far as I can determine, but many individuals are funded or supported by employers or contributing agencies (municipalities, etc.), but it still is a personal vote and there are some restrictions to be a voting member to maintain a consensus committee. It took me 10 years of waiting on a voting list before members resigned.

Membership in ASTM is really very cheap because memberships are generally individual. - It is less than $100 per year and entitles access to on line standards that can be listed and is less than the cost of buying one of the costly individual hard cover standards books (over 100 different books) and reduced cost on PDF reprints on other standards.


Engineer and international traveler interested in construction techniques, problems and proper design.

RE: Confusion about ASTM and AISI/SAE and properly specifying materials

You need to look in the tables of the particular specs that you are using.
The ASTM A general specs say general specification in the title, product specs simply state the applicable products.
In most cases they will have a common name (often the old AISI ones) and then the official name.
The official one will either be an ASTM grade name or the UNS number
The Unified Numbering System gives numbers to each unique chemistry.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Confusion about ASTM and AISI/SAE and properly specifying materials

It seems like you need to read the actual standards before specifying them. There is no need to use the letters AISI on anything, that organization does not specify anything anymore.

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