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Re: [MW:8906] duplex ss pwht

By Materials & Welding

If super duplex material is heat treated  between 300 C to 600 C, Alpha prime phase & 475 C embrittlement phases which has adverse effect on corrosion properties and toughness property.

Heat treatment between 600 to 900 C phases like Sigma phase , chi phase, Cr2N(Chromium Nitrides) etc are generated.This all are detrimental phases.

 

Sigmaphase has prone effect on toughness ( Suddenly decreases) in the super duplex material. It also reduces corrosion resistance Research paper says there is little increase in Hardness and tensile value.

Further,

If PWHT is mandatory for the super duplex ss material, following points are to be taken care;

1. Heating rate, Soaking Time, Cooling Rate should be such that No detrimental phases can be generated.

2. If possible, solution annealing + water quenching shall be advisable after PWHT.

3. While procuring the material, confirm that plate and filler wires has sufficient percentage of Nitrogen and Nickel for proper phase balance.

 
Regards,
Jaydeep


On Thu, Dec 23, 2010 at 12:01 PM, pradip kumar sil <pradipsil@gmail.com> wrote:



Thanx for ur previous help. Here i have one more queries
P No.-10H (duplex SS) PWHT is neither required nor prohobited as per tabel 331.1.1 ASME B-31.3
What is the gain  structurewise / mechanical propertieswise change if i conduct PWHT
regards
Sil

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