Re: [MW:26768] Pitting corrosion in Duplex material

Dear Sir,

We are also facing this problem than a third party suggest us 98%Ar + 2% N2 for shielding and purging, after use of that mixture you get better result (Corrosion test pass).

Regards,

Muhammad Babur Khan Lashari
Sr. QA/QC Inspector

(CSWIP 3.1 / CWI II From PWI) 

 Khaled Juffali Industrial Company

Mob: + 966 56 2179280 / 58 2774568

PAK : + 92 334 6186285

Skype: babur.lashari

E-Mail: babur.khan@kjgroup.com

On Wed, Aug 30, 2017 at 11:05 AM, 'james gerald' via Materials & Welding <materials-welding@googlegroups.com> wrote:

Please check the Purging Gas purity.

 

Thanks & Regards

J.Gerald Jayakumar

0091-9344954677

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From: Aby Jose <abycscec@gmail.com>
To: materials-welding@googlegroups.com
Sent: Wednesday, August 30, 2017 11:56 AM
Subject: [MW:26765] Pitting corrosion in Duplex material

Dear experts,

Here I am preparing WPS for Duplex material using robotic welding machine. The details are as follows.

Material designation - SA 790 UNS S32205

Pipe dimension - 4",  6 mm thick

Welding process- TIG(Root), MAG(fillup & Cap)

After the PQT while doing the pitting corrosion test it got failed. The pitting corrosion test was done as per ASTM G 48. 

For TIG welding earlier I had used 98% Ar + 2% H2 as shielding gas. Now I have changed it to 98%Ar + 2% N2. 

For MAG welding pulse method is used. Shielding gas used is 98% Ar + 2% CO2. Purging gas used is 99.997 % Ar. 

Heat i/p calculated is within the range 0.6 to 1.5. Also the interpass temperature was below 120 degree. What else can be the reason for Pitting corrosion? It came more in the capping. So I am worried about the shielding gas used for MAG. Which other shielding gas can I use for the MAG welding of duplex material??

Regards,

Aby K Jose

QA/QC Engineer

Qatar

+97430847911

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