FAQ's

Is there a Fahrenheit to Centigrade discrepancy in NACE MR0175?

Previous Editions of NACE MR0175 Showed Errors in Age Hardening Temperatures and Ranges for Precipitation Hardening Stainless Steels in NACE MR0175/ISO 15156-3

In previous editions of NACE MR0175, there are inconsistencies and errors in the age hardening temperatures and ranges for precipitation hardening stainless steels specified in NACE MR0175/ISO 15156-3 Tables A.27 to A.30. The age hardening temperature midpoint in Centigrade for UNS S17400 and UNS S15500 should be corrected from 620 C to 621 C. The intended range seems to be 1125 – 1175 F, or 1150 +/- 25 F, which converts to 621 +/- 14 C. Table A.28 for UNS S45000 correctly lists the age hardening temperature midpoint as 621 C. This difference of one degree could affect compliance with NACE MR0175-3 service requirements.

Furthermore, there’s an error in Table A.29 for UNS S15700 because c) states 560 C when it should be 565 C to match the value specified in ASTM A564 Table 4. To correct these issues, the necessary changes should be made to the relevant tables in the next revision of NACE MR0175/ISO 15156-3. The correct conversion of 1150°F to Celsius is 621°C, and NACE MR0175/ISO 15156-3 should reflect this correction for UNS S17400, UNS S15500, UNS S15700, and UNS S45000 in Tables A.27 to A.30.

Impact on Compliance with NACE MR0175-3 Service Requirements

The errors in age hardening temperatures and ranges for precipitation hardening stainless steels in NACE MR0175/ISO 15156-3 Tables A.27 to A.30 could have a significant impact on compliance with NACE MR0175-3 service requirements. It is important to correct these errors in the next revision of NACE MR0175/ISO 15156-3 to ensure accurate and consistent data for UNS S17400, UNS S15500, UNS S15700, and UNS S45000.

Conclusion

If you are reviewing older versions of NACE MR0175, the correct age hardening temperature midpoint in Centigrade for UNS S17400 and UNS S15500 is 621 C, and the correct conversion of 1150°F to Celsius is 621°C. The errors in Tables A.27 to A.30 of NACE MR0175/ISO 15156-3 are now amended in the newest versions of NACE MR0175

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