We have a question regarding the meaning of a sentence in Paragraph 4.4 in MR0175-2003. This same sentence is repeated in Paragraph 10.2.1. 62 The paragraph states: Highly alloyed austenitic stainless steels in this category are those with Ni% + 2 Mo% >30 and 2% Mo minimum. A1. Does the statement mean that there are essentially two groups in this category? Such that . . . One qualifying group consists of materials that contain N% + 2 Mo% >30 Another qualifying group consists of any austenitic stainless steel with 2% Mo minimum (such as 316, 317). A2. Or does the statement mean that there must be a minimum of 2% Mo in the Ni% + 2 Mo% >30 requirement? Since the environmental restrictions in Paragraph 4.4 are the same as in 4.2 (where most austenitics are acceptable), I assume #A1 is the correct interpretation since this would allow for inclusion of 316 and 317.
Your answer A2 is correct. The chemistry requirements are additive.
This question is in relation to NACE MR0175/ISO 15156-3 A.3.2, Table A.8 and Table A.9
Reference: ISO 15156 Maintenance Panel Inquiry #2003-15
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