The compressor is a Demag Delaval and I have the material of the stud bolts listed as 26 NiCrMoV 11-5 in the OEM's parts listing. A German colleage gave me a copy of a Werkstoff chart which listed 26 NiCrMoV 11-5 as DIN 1.6948 as well as SEW 555. I was trying to find an equivalent alloy in North America. From the chemistry, A-471 looked to be the closest match. A-471 lists classes 1 to 6, 10, 11 to 13, and 14. I think the closest match is class 1 to 6. Thanks