Ken,
I think you are looking at ASTM A588 structural steel shapes which has a minimum yield strength of 50 ksi and a minimum tensile strength of 70 ksi. I believe it is available but I would first check with your local fabricator and/or mill.
Thomas Hunt
Does any one have more information weather structural steel? What is the specification tensile strength or grade? Are they availabe to purchase?No, he's talking about ASTM A 709 plus ASTM A 325 Type III bolts.
TIA