OK, in the 9th Edition, the applicable sections are
7.7.1 a),
Grades M65, L80 all types, C90, T95 and C110 – Through-wall hardness
The hardness numbers and/or mean hardness numbers obtained shall comply with the requirements in Table C.5
or Table E.5.
and
10.6.2
Frequency of testing — General
The frequency of hardness testing for all products is specified in Table C.40 or Table E.40. When more than one
test is required the test specimens shall be from different lengths.
Additional hardness testing on the outside surface and through-wall hardness testing of pipe and upsets may be
carried out as agreed between purchaser and manufacturer. Test procedures for this additional testing shall be
agreed between purchaser and manufacturer.
The requirements from E.5 say the Max Hardness is either 23 HRC or 241 HBW, but with a footnote that in case of dispute, the HRC test will be the referee method.
The requirements from E.40 say two through-wall tests per lot (from different lengths), with lot size of 200 lengths or 100 lengths, depending on OD size, with at least one heat control test, each taken at the same location as the tensile test.
So, a surface hardness test is not required by the standard. When agreed between purchaser and manufacturer, surface hardness testing may be performed, but the details of such testing are outside the scope of the standard. This is to recognize that some applications may require a more strict requirement than simply the through-wall hardness and allow such testing in the standard, but leave the details to be worked out between the purchaser and manufacturer. There are many reasons the surface hardness may be different, which the standard does not try to define; these details are left to the purchaser and manufacturer. Finally, manufacturers will often perform surface hardness tests as a process control check, not to qualify the product, and this wording allows the manufacturer to do that.
So, to answer your question, I would say you can accept the through-wall results (provided the test methods, results, and frequencies meet the requirements).
Look at it this way; if you were to reject the material, what would you reject it for? There is no clause in the standard that requires a surface hardness test or what the results would need to be if one was performed. If you have questions whether the results on the certification are representative of the material, you can perform another test. If those results meet the requirements of the standard, you can't really say the material does not meet the requirements.
rp
