Question: Our company has understood that NACE MR0175/ISO 15156, Table A.2 required the maximum specified hardness for austenitic stainless steels be satisfied at any location on bar stock (e.g., at locations considered significant by the user). Since cold-finished bars frequently have surface hardness values above the maximum specified in MR0175, we have declined to certify these products as compliant to the specification. We appear to be in the minority, or perhaps the only stainless bar producer that interprets the standard in this way. We routinely find competitors’ cold-finished stainless bar in the marketplace certified to MR0175 based on a mid-radius hardness even though the surface hardness is above the maximum permitted in the standard. We realize this is a long-standing issue, but would like to clarify the hardness requirements of the Table A.2. We understand the logic in requiring the material meet a hardness maximum at any location (e.g., surface) in order to provide a predictable level of stress corrosion cracking resistance. Yet the standard does not clearly state, for example, that meeting surface hardness is a requirement. Please clarify the hardness requirements of MR0175 to allow all stainless bar producers to provide a uniform product to this standard.
NACE cannot provide assistance in specifying where to take hardness impressions and readings for this alloy or for any other alloy. This is because NACE MR0175/ISO 15156 is not a quality assurance document. It is the responsibility of the alloy supplier to meet the hardness requirements and metallurgical requirements of the austenitic stainless steels in Table A.2.
This question is in relation to NACE MR0175/ISO 15156-3 Clause 6.2.1
Reference: ISO 15156 Maintenance Panel Inquiry #2003-06
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