Duplex WPS for Super Duplex

[Alex Kumar Antony]

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

Thanks

[Karunakaran Karan]

Sir,

 Not using .because filler,interpass temp.,etc are not same.DSS. 

DSS. ER2209 

SDSS ER2594

   Thanks and regards,

     S.KARUNAKARAN,
      karu...@gmail.com

      91-6382279754

      

On Mon, 15 Dec 2025, 16:29 Alex Kumar Antony, <alexk...@gmail.com> wrote:

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

Thanks

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[Anandhapadmanabha pillaim]

As per ASME Section IX, the use of SDSS filler wire is permitted even when impact testing is not specified or required, provided the essential variables are met.

However, beyond the code requirements, from a metallurgical and performance standpoint, DSS and SDSS differ significantly in their ferrite-austenite phase balance requirements. Achieving the correct phase balance is critical and is strongly influenced by welding heat input. SDSS, in particular, has a higher PREN (Pitting Resistance Equivalent Number) requirement compared to DSS.

To achieve the required PREN and phase balance in SDSS weld metal, nitrogen is commonly added to the shielding and backing gas. Nitrogen is a strong austenite stabilizer and also contributes to an increase in PREN, thereby improving corrosion resistance.

If a WPS is qualified for DSS using pure argon as the shielding gas, and it is later proposed to use an argon–nitrogen mixture (for Eg: Ar + 2% N₂) for SDSS welding, this change would require requalification of the PQR. This is because the addition of nitrogen significantly affects weld metal chemistry, phase balance, and mechanical and corrosion properties, making it a metallurgically significant change even if not explicitly listed as an essential variable in all cases.

That said, if the required mechanical properties, corrosion resistance, and phase balance are successfully achieved using the same gas composition qualified for DSS (i.e., pure argon), ASME Section IX permits its use, as long as all applicable essential and supplementary essential variables remain within the qualified range.

On Mon, 15 Dec 2025, 5:29 pm Alex Kumar Antony, <alexk...@gmail.com> wrote:

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

Thanks

--

[syed kauser ahmed]

As per ASME Section IX – QW-403.5:

No, a change from one Group Number to another Group Number within the same P-Number shall be considered an essential variable and requires requalification of the WPS.

On Mon, 15 Dec 2025, 16:29 Alex Kumar Antony, <alexk...@gmail.com> wrote:

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

Thanks

--

[Mohd Siraj]

yes, provided that you have revised drawing.

[venkateswara reddy Desireddy]

Yes you are right, shielding gas also one of the essential variables. Along with P number and F number other parameters also we have to consider before choosing WPS.

To view this discussion visit https://groups.google.com/d/msgid/materials-welding/CAJ90KGR%2BWjiOTHjPf4mNLed34QHj4QP3_KD%2BzfeckX20tFydUA%40mail.gmail.com.

[Marco Nunes]

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.

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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 <alexk...@gmail.com> wrote:

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

Thanks

--

[Anandhapadmanabha pillaim]

Base material grouping is a supplymentary essential variable, even though it's a supplymentary essential variable, both DSS & SDSS have P 10H and Gr. 1. As per ASME SDSD WPS is permitted to write with DSS PQR, still impact testing is not there you want to use SDSS wire itself, yes it is permitted, if impact testing is there and you want to use SDSS wire, it's not permitted and requalification is required, 

Below consideration I have addressed previous need to be taken into consideration, 

However, beyond the code requirements, from a metallurgical and performance standpoint, DSS and SDSS differ significantly in their ferrite-austenite phase balance requirements. Achieving the correct phase balance is critical and is strongly influenced by welding heat input. SDSS, in particular, has a higher PREN (Pitting Resistance Equivalent Number) requirement compared to DSS.

To achieve the required PREN and phase balance in SDSS weld metal, nitrogen is commonly added to the shielding and backing gas. Nitrogen is a strong austenite stabilizer and also contributes to an increase in PREN, thereby improving corrosion resistance.

If a WPS is qualified for DSS using pure argon as the shielding gas, and it is later proposed to use an argon–nitrogen mixture (for Eg: Ar + 2% N₂) for SDSS welding, this change would require requalification of the PQR. This is because the addition of nitrogen significantly affects weld metal chemistry, phase balance, and mechanical and corrosion properties, making it a metallurgically significant change even if not explicitly listed as an essential variable in all cases.

That said, if the required mechanical properties, corrosion resistance, and phase balance are successfully achieved using the same gas composition qualified for DSS (i.e., pure argon), ASME Section IX permits its use, as long as all applicable essential and supplementary essential variables remain within the qualified range.

To view this discussion visit https://groups.google.com/d/msgid/materials-welding/CADkb7FDnfAUxq4kw9%3DUhUQrskiz5oSv1%2Bdh1yqHMs3ygzx-Epg%40mail.gmail.com.

[Anandhapadmanabha pillaim]

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

To view this discussion visit https://groups.google.com/d/msgid/materials-welding/CAHXTn13GP75Hk7hisbt4yD5v5brzSvKEUfseobmjDxGf6JqYNQ%40mail.gmail.com.