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[MW:20360] Black Spot Issues on the SDSS Weld.

By Materials & Welding
Hi Billy,
 
Thanks for your follow-up  email on this issue. I did remove our  ongoing correspondences on the failure analysis of the SDSS PQR(to keep the confidentiality).
 
Attached are my correspondences with the gentleman ,who originally posted this query. I did not hear from him since then. However seeing feedback sent to you by the reputed filler wire manufacturer (as we had discussed over the phone ), I see that our analysis was on the right track.
 
I did discuss this issue with your manufacturer's Canadian counterpart. Their answer was, the causes could be ,filler lubricants, any lubricant if used during pipe  manufacture and some effects of the purity of shielding gas.  Also their answer was  austenitic stainless steel is tolerant  to such , black pock marks , due it's higher alloy content and easier weldability.
 
While explaining the  formation of oxides on DSS ,LDSS & SDSS welds the , extracts from this research paper is quite interesting. Hotter arc caused by Nitrogen could add to complexity of surface oxides.
 
Regards.
 
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Specialist
Ontario, Canada
pgoswami@quickclic.net
pradip.goswami@gmail.com
pradip_goswami@yahoo.ca
 

From: BILLY TAN [mailto:bil19875539@hotmail.com]
Sent: Monday, March 17, 2014 10:08 PM
To: pgoswami
Subject: RE: SDSS Weld Procedure Failure issues.

Hi Pradip,
 
Below will be the response from our wire supplier. For him, this is normal.
 

-------------------------------------------------------------------------------------------------- ----------------------------------------

 


The small black spots are coming from the TIG rod and will not effect any chemical / mechanical / corrosion property .


 


During manufacturing of TIG rods need to apply a very smooth surface coating / lubricating for smooth operation & also this will protect from atmosphere during storage of TIG wires .


 


To avoid these kind of small black spots some fabricator use a suitable emery paper to apply once / twice before welding , since this operation helps to remove the surface coating and hence no black spot 

 

------------------------------------------------------------------------------------------------------------------------------------------

Best Regards
Billy Tan
 

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