For round bar stock 304/316 SS material, does the NACE MR0175 Rockwell C 22 max hardness requirement refer to the hardness anywhere on the raw material or does it refer to the hardness measured at mid-radius, which is the location where ASTM standards require the hardness measurement to be made? For 304/316 austenitic stainless steel MR0175 indicates that the hardness must be Rockwell C 22 max as long as the material was not hardened to enhance mechanical properties. The hardness on 304/316 SS round bar typically varies with radial position. The material typically has the highest hardness readings at the outer surface and lowest in the center. ASTM standards define hardness measurements for bar stock to be taken at mid-radius. In purchasing raw material, the hardness readings reported are at mid-radius.
The Maintenance Panel cannot comment on the hardness test locations specified in ASTM standards.
These materials, when used for sour service, must comply with all the requirements of NACE MR0175/ISO 15156-3, Table A.2. The definition of the hardness testing location is outside the scope of the standard, but hardness requirements must be met regardless of the chosen test location.
This question is in relation to NACE MR0175/ISO 15156-3 Table A.2
Reference: ISO 15156 Maintenance Panel Inquiry #2006-05
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