L4x4x1/2 A36 with 50 ksi rating clarification require?

[marcposada1]

I am working on an upgrade to a self support tower for telecommunication application. My steel shop is telling me that the required angle by the engineer, an A572 grade 50 ksi, they can not get, but instead they could use an ASTM A36 with 50 ksi grade rating. IS this true? If it is what kind of documentation I would need to see from my steel shop in order to make sure that the angle I am getting is actually rated to 50 KSI?

I have read that some steel mills are now dual certifying material to have this type of rating or specifications, how true is this?

Any help will be greatly appreciated.

Marcello.

 

[MiketheEngineer]

You want the mill certs (certifications). A36 at 50 ksi seems like an oxymoron to me. It should just be A50 - or maybe I am all wet.

A36 kind of went the way of the dodo bird about 15 years ago - almost all is now 50 ksi - at least for steel beams. Tube and pipe are different animals.

 

[marcposada1]

Thanks MiketheEngineer. I have been trying to find information on this A36 grade 50 and can't really find anything. Yes A36 went almost the way you describe it.

The only information I could find was an article on Modern Steel Construction MSC magazine dated back from 1999 in which it talkes about dual specs and mentiones table A of ASTM A6/A6M. But then again this is dated back over 10 years ago.

I did get the mill certs and not very happy. the A36 material shows a 48 ksi yield which is no good since I am dealing with an upgrade for a telecommunication tower, and not just that, it has a big "REJECT" note on it...Wonder what that tells me, right!? Fun Friday for me.

 

[stanweld]

Your steel shop seems to think that you will be able to find A36 angles which meet the 50 KSI SMYS (with certified MTR) more easily than the A572 Grad 50. They may well be wrong. They should look harder for the correct steel or request the Engineer to review his requirement as to whether A-36 angles of the specified size are acceptable or which increased A-36 size would be. you may not make the change without the Engineer's approval.

 

[rmw]

What ambient temperature will your tower have to endure? If you are in any kind of cold climate, you should google the terms "A36 DBTT" (without the quotes.)

I think within the results you will find some comparisons of impact testing of the two if you can find one from Lehigh University where A-36, A-572 and A-992 were contrasted.

rmw