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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 
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)        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)

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