It's a mistake to believe that there's a precise relationship between hardness and tensile strength in metals, i.e., that to a given hardness number it corrisponds an exact tensile strength.
Hardness numbers give only a rough idea on what the tensile strength is.
There are several "conversion tables" around showing the relationship between hardness numbers and tensile strength, but the serious ones, like SAE's and ASTM's in the USA and ABNT's here in Brazil (our local ASTM), warn the reader that the conversion is only approximate and MUST NOT be used for calculation purposes. Their intention is to give the reader just an idea.
So, the answer to your question is no, you can not.
Giovanni S. Crisi
Sao Paulo - Brazil
Giovanni is, as usual, exactly correct. Brilliant minds for decades have tried, for obvious NDE reasons, to directly link hardness with tensiles and failed. And I believe for good reason. The deformations are different, and demonstrate differing properties. Though they are very close, as Giovanni again explained with the available conversions.
js55,
thankyou for your kind (and somewhat exaggerated) words. As everybody, sometimes I'm right and sometimes I'm wrong.
Giovanni S. Crisi
Giovanni,
I'm willing to pretend thats not true on your behalf, if you're willing to do so for me. Hah!! Now if we can just bring everyone in on this we'll all be brilliant.
I may be a little out of my league here, but couldn't you use a PMI (possitive material identification) to find out what the material actually is, and then find the stress value in the referencing section of you code book? I'm not familiar with API 510, and not too familiar with PMI and the process used in determining identification.