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Re: How Strong is A7 Structural Steel?

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>A7 steel had a yield of 33 ksi, with a working stress in flexure of 16, 18, 
>or 20 ksi, depending on when the structure was built. (.5, .55, .6 times 
>yield)
My 1961 edition of the AISC spec has chemistry limits of phosphorus of 
between 0.04 and 0.1 depending on the manufacturing process and a sulphur 
limit of 0.05. I bet the success with welding depended a great deal on 
how the steel was made. High carbon and high phosphorus would be the kiss 
of death. The spec required a ladle analysis of percentages of carbon 
manganese, phosporus and sulphur was made from each heat and reported to 
the purchaser evidentloy for reference purposes.

For cultural value I seem to recollect that the specified yield strength 
of A7 was 30 ksi but the spec value was raised to 33 ksi as a metal 
saving measure during World War II--taking advantage of the 15% or so 
margin between minimum and typical yield strength. I know the allowable 
fill pressure for steel gas cylinders was increased 10% both to save 
material and increase storage capacity. After the war the measures were 
continued because of successful service. 

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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