[MW:10883] RE: 10879] Duplex Claded Eqipt PWHT

Dear Mr. Hedge,

 

When executing PWHT at 600 °C your corrosion resistance will be reduced because of the formation of Sigma phase (FeCr precipitates) in the microstructure of the cladding. Sigma phase can occur in the temperature range from 450 °C – 850 °C so if you will discuss lowering the PWHT temperature you should go for 400 max. but I would choose to propose withholding PWHT and take care of controlling welding parameters during production.

You may propose executing portable MicroVickers hardness tests after weld completion in order to demonstrate no high hardness values are present at the HAZ near weld surface.

Most important is to convince your client to withhold PWHT because of the corrosion resistance of the cladding. When client insist on any kind of stress relieve treatment you perhaps can convince them to use high frequency hammering of the cap layer and HAZ. This will introduce compressive stresses in the surface up to 2 mm instead of the tensile stresses present after welding.

 

Met vriendelijke groeten / Best Regards

 

Herman Pieper

 

Pieper Quality Support & Inspection

Phone: +31 (0)521 380083

Fax:     +31 (0)84 7539225

Cell:     +31 (0)6 51691215

www.pieper-qsi.nl

 

Van: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] Namens Prakash Hegde
Verzonden: vrijdag 29 april 2011 6:31
Aan: materials-welding@googlegroups.com
Onderwerp: [MW:10879] Duplex Claded Eqipt PWHT

 

Dear Friends

I have a query about The Duplex  cladded E quipment having base material SA 516 Gr70 of 50mm thk and clad of Duplex (3mm )

The eqipment require to undergo PWHT at 600C The Joint is clad restored by Duplex weld

 

i) Does the PWHT at 600C will affect  the Corrosion properties of Duplex weld (Corrosion test like IGC,Pitting corrosin,etc  as per GS8)

ii) If yes do we require to carry out PWHt at lower Temp.

 

Regards

Hegde P.B.

08805593046

 

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