I went through a similar drill a year or so ago with the NH DOT.
If I remeber correctly, as far as chemistry goes, the material spec simply puts a limit on Phosphorous. The spec is really more like a listing of mechanical requirements, tolerances, weights, etc.
The supplier can use any steel material they want to (within the Phosophorous limits) to make the pile. You need pile with a 45ksi tensile strength.
We had to obtain a sample from the supplier and run a PQR in accordance with D1.1 (at the insistance of the NH DOT).
In other cases, we have been successful in making the case that the real "test of service" takes place as the pile is being driven.
We used E7018 and NR232 for our procedures.
Charles Hall