FAQ's

For duplex and superduplex stainless steels, what is the NACE MR0175 maximum hardness for HAZ (heat affected zone)?

Question 1:
This request is related to ISO 15156 / NACE MR0175 part 3, A.7.3 Welding of duplex stainless steels. “The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable.”
Q1: In Table A.24 there are is no hardness limit for solution-annealed and liquid quenched or rapidly cooled duplex stainless steels. Does this mean that there is no defined hardness limit for the HAZ to be used for qualification of the welds?

Answer 1:
It is correct that in Table A.24 there is no hardness limit for solution-annealed and liquid-quenched or rapidly cooled duplex stainless steels. Hence, there is no requirements for welds in NACE MR0175 / ISO 15156. It should be noted that NACE MR0175 / ISO 15156 does not list hardness limits for other causes than cracking mechanisms defined in the document. For other properties the team at Oil and Gas Corrosion Ltd can help you define the requirements.

Question 2:
Or, do the hardness limits given in relevant ASTM standards apply? E.g. ASTM A790/A928/A240.

Answer 2:
Advice regarding which other standard(s) that may apply for a particular product is not covered by NACE MR0175 / ISO 15156.

This question is in relation to NACE MR0175/ISO 15156-3/A.7.3

Reference MP inquiry #2018-01

The team at Oil and Gas Corrosion Ltd can help you resolve your queries qualification of duplex and super duplex stainless steel and their welding qualification to meet NACE MR0175 requirements. We can also help you comply with other standards such as DNV RP F112.
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