Re: [MW:26770] Pitting corrosion in Duplex material

Dear Goswami sir,

The temperature of test was 40 degree celcius. Heat i/p for TIG was from 1.5 to 2.2 and for MAG 0.65 to 0.9. Pitting corrosion was observed both on root and in cap. But more in cap.

Regards,

Aby

On Wed, Aug 30, 2017 at 2:48 PM, pgoswami <pgoswami@quickclic.net> wrote:

What's the  temperature for pitting corrosion test? What're the recorded welding parameters including heat input?

Appreciate your response. 

Thanks. 

Pradip Goswami. 

Sent from my Bell Samsung device over Canada's largest network.

-------- Original message --------

From: Aby Jose <abycscec@gmail.com>

Date: 2017-08-30 03:40 (GMT-05:00)

To: materials-welding@googlegroups.com

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

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