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Re: RES: ASTM A36

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On Feb 3, 2006, at 11:52 AM, Mario Velez Nauer wrote:

But there are not a indication of minimum contend of carbon. I understand that the strength of material depends upon the carbon contents, so you will have a very different mechanically properties with different contents of carbon. (I assume al other elements are according to the Standard). If ASTM has a yield point of 248 MPa it seems to me that this mean there must be a minimum carbon content to obtain this value.
The chemistry I quoted you came from an older version of ASTM A-36 and a minimum carbon content wasn't specified. Very likely the reason is that the required minimum yield strength implies a certain alloying content--whatever the actual carbon content, it's sufficient that you meet the minimum allowable yield and ultimate strength. Although not specified, the chances are that the carbon content is about 0.20% The maximum carbon content specified is for weldability. Carbon contents higher than about .33% make poor weldability. The remaining specified alloy content (Mn, Si P & S) have to do with toughness and formability. It's very important that you have everything in addition to carbon and that the steel be manufactured as specified in the ASTM specification.

It is not practical if you must verify (test) all the material you get in order to know what are the mechanical data.
Absolutely wrong. ASTM A-36 also specifies minimum yield and ultimate strengths that absolutely must be met. When you purchase A-36, you should require mill certification that the material will meet the mechanical property requirements. That doesn't mean you need to test it yourself, just that t you obtain proof that the material coplies with A-36 in all respects. If you don't do this you're asking for trouble. I've been involved in a number of failures where someone tried to pull a fast one and _assumed_ he knew what he was getting. Order material to the specification and send it back if it doesn't meet all the requirements.

You cannot be sure that you're getting comparable material if you only match the chemistry. SAE 1020 does in fact have the same specified carbon content as A-36, but the manganese isn't the same and it won't weld the same. You also have no guarantee of the toughness or microstructure.

(I assume al other elements are according to the Standard)
Never assume this without proof. Once again--never assume materials with the same chemistry are the same in all other respects, and never accept someone's estimate of the chemistry without material certification. I'm speaking from hard and bitter experience.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/


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