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[MW:14502] MW-14496-root causes for failing Pitting test in Duplex SS

By Materials & Welding


Hi Ankit,

ASTM G48 testing in ferric chloride solution allows a quick assessment of pitting corrosion resistance of stainless steels. The t effective ways of improving pitting performance and hence increasing the likelihood of passing the test as follows:-

  • Remove the  weld oxides, improve surface finish, such as by pickling, grinding, brushing.
  • For 22%Cr duplex stainless steel, use  superduplex filler  as an alternative to a matching 22%Cr duplex.
  • Check the Nitrogen content in the SMAW electroede MTR and Test pad. Any Nitrogen loss from the weld pool may be problematic and would definitely impair the pitting resistance. Nitrogen is the "singlemost" important element to improve or lower the pitting resistance.
    •
  • Monitor the welding parameters, such that heat imput (1.2-1.5 KJ/mm) and the IPT (125-150 Deg C Max) is just withinn the recomemnded range -as per the best practices followed for this metal.
  • Ensure the Ferrite/Astenite balance is claose to 50:50 or 60:40 or 55:45 range.
If the process is SMAW as per the description below, what's the value of Oxygen content in the arc environment or on the root side? Higher oxygen in the weld would affect "notch toughness" and may cause  lowre pitting resisatnce also.
Hope the clarifications above and the atatchements would help to you to make the test pass , next time.
 
Thanks.
 

     

     

    Pradip Goswami,P.Eng.IWE
    Welding & Metallurgical Specialist
    Ontario, Canada.
    Email-pgoswami@sympatico.ca,
    pgoswami@quickclic.net

    -----Original Message-----
    From: materials-welding@googlegroups.com [    mailto:materials-welding@googlegroups.com] On Behalf Of khatri ankit
    Sent: Friday, June 08, 2012 2:56 AM
    To: Materials & Welding
    Subject: [MW:14496] root causes for failing Pitting test in Duplex SS

    Dear Expets,

    What will the root causes for failing the pitting corrosion resistance test for duplex SS (22% Cr grade).

    What should be the remedies or how to improve my welding or welding quality, so the duplex SS test coupon will passes for pitting test?

    (I made the weld test coupon for PQR to do the Pitting test, but the results have failed it.the electrode that we used for welding is
    E-2209)

    Kindly send ur reviews, so i can improve it the same.

    Regards,

    Ankit Khatri

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