Re: [MW:35929] Duplex WPS for Super Duplex

Please don't share wrong information both are P 10H Gr. 1 only refer QW/QB- 422

On Tue, 16 Dec 2025, 7:12 am Marco Nunes, <marcovsky82@gmail.com> wrote:

Code-Based Explanation (ASME Section IX)

1. Base Material Grouping – P-Numbers

ASME Section IX groups materials by P-Numbers to control essential variables.

• 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.

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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:

• A WPS qualified on Duplex (P-No. 10H)

• Cannot be used for Super Duplex (P-No. 10I)

• Without a new PQR covering P-No. 10I

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3. Mechanical and Metallurgical Differences (Supporting Rationale)

Although not strictly required by code, this reinforces why the rule exists:

• Super Duplex has:

  • Higher PREN

  • Higher yield and tensile strength

  • Tighter control on heat input, interpass temperature, and ferrite/austenite balance

• Welding Super Duplex with a Duplex-qualified WPS risks:

  • Loss of corrosion resistance

  • Sigma phase formation

  • Improper phase balance

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.

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Final Conclusion (Code-Compliant Answer)

❌ A Duplex WPS cannot be used for Super Duplex welding.

✅ ASME Section IX requires requalification, because:

• Duplex = P-No. 10H

• Super Duplex = P-No. 10I

• Change in P-Number is an essential variable per QW-403.11

On Mon, Dec 15, 2025 at 9:28 AM Alex Kumar Antony <alexkantony@gmail.com> wrote:

Can we use Duplex WPS for Super Duplex, kindly quote with the help of code

Thanks

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