Yes, it's weird that a "grade 50" steel is 70 ksi yield strength. HSLA is "high strength low alloy" as TLHS says. The bending stress is 50 ksi - maybe that is why they're calling it "grade 50" in the attached test report.
I didn't see that one can upload files here. I'm attaching the NAAMM...
I was reading this thread about how regular pipe does not satisfy the load requirements of the standard specs used:
http://www.eng-tips.com/viewthread.cfm?qid=405072
I meant to just reply in that thread but it is closed.
My supplier has been selling me HSLA pipe that has a much higher stress...