Question:

Can postweld heat treatment be skipped for weld overlays on low-alloy ferritic steel valves?

This webpage features a question regarding weld overlays applied to low-alloy ferritic steel valves using Inconel 625 filler metal with SAW process. The valve is used on wet gas wellhead production platform with operating temperatures at 93°C, operating pressure of 145 bar, and vapor fraction of H₂S and CO₂. The as-welded hardness test results comply with the requirements of Table A.1 of NACE MR0175/ISO 15156-2, and the client wants to know if postweld heat treatment is required.

Answer:

The answer confirms that provided the weld procedure qualification complies with the hardness requirements in A.2.1.4 and A.2.1.5, no postweld heat treatment is required. Paragraph A.2.1.4 states that as-welded carbon steels, carbon manganese steels, and low-alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment. Paragraph A.2.1.5 allows for overlays applied by thermal processes such as welding and are acceptable if they comply with the specified conditions.

This question pertains to NACE MR0175/ISO 15156-2 Annex A.2.1.4 and A.2.1.5.

Reference: ISO 15156 Maintenance Panel Inquiry #2004-11.

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