Code-Based Explanation (ASME Section IX)
1. Base Material Grouping – P-Numbers
ASME Section IX groups materials by P-Numbers to control essential variables.
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Duplex Stainless Steels (e.g., UNS S31803 / S32205)
→ P-No. 10H -
Super Duplex Stainless Steels (e.g., UNS S32750 / S32760)
→ P-No. 10I
📌 Since P-No. 10H ≠ P-No. 10I, they are treated as different base material groups.
2. Essential Variable for Base Materials
ASME Section IX clearly states:
QW-403.11
A change from one P-Number to another P-Number is an essential variable and requires requalification of the WPS.
✅ Therefore:
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A WPS qualified on Duplex (P-No. 10H)
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Cannot be used for Super Duplex (P-No. 10I)
-
Without a new PQR covering P-No. 10I
3. Mechanical and Metallurgical Differences (Supporting Rationale)
Although not strictly required by code, this reinforces why the rule exists:
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Super Duplex has:
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Higher PREN
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Higher yield and tensile strength
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Tighter control on heat input, interpass temperature, and ferrite/austenite balance
-
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Welding Super Duplex with a Duplex-qualified WPS risks:
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Loss of corrosion resistance
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Sigma phase formation
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Improper phase balance
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Codes intentionally separate these alloys due to these risks.
4. Filler Metal Consideration (Additional Control)
Even if a Super Duplex filler metal is used, the limitation still applies, because:
QW-404 (Filler Metal Essential Variables)
Filler metal control does not override base material P-Number limitations.
Final Conclusion (Code-Compliant Answer)
❌ A Duplex WPS cannot be used for Super Duplex welding.
✅ ASME Section IX requires requalification, because:
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Duplex = P-No. 10H
-
Super Duplex = P-No. 10I
-
Change in P-Number is an essential variable per QW-403.11
Can we use Duplex WPS for Super Duplex, kindly quote with the help of codeThanks--
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