SS GTAW Welding without Back purging.

[Anand Elankumaran]

Dear experts,

Could you please check and advise the below query.

• Whether the back purging is a quality requirement or the ASME code is insisting on back purging on SS material while doing the GTAW process.
• Whether we can qualify SS -GTAW PQR without back purging or the ASME code does not allow doing PQR for austenitic steels without a back purge?
• Kindly advise how to do it without purging in SS GTAW Welding . Planning for PQR as well 

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Thanks and Regards,

E. Anand,

Lead QA-QC,

Sohar,

Oman.

[Vishwas Keskar]

Are you intending to qualify PQR in 

Single Vee butt weld - No welding from Root side ?

Double Side Weld with back grinding DPT from root side ?

This will decide the PQR  purging requirement

Thanks

Vishwas

IWE 

Sent from my iPhone

On 22-May-2023, at 8:40 AM, Anand Elankumaran <email2...@gmail.com> wrote:



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[Kannayeram Gnanapandithan]

Except for Reactive metals, others are optional, while qualifying PQR, u have to keep it in about referring codes requirements. As general engineering practice, if Cr is more than 3%, it is always better to have back purging to avoid oxidation.

THANKS & BEST REGARDS,

KG.PANDITHAN, BE, IWE,  CSWIP 3.1,

ISO 9712 Level 2 in VT,

ASNT-Level II in PT,MT,RT & UT,

LA ISO 9001-2015,

International Welding Engineer. 

CONSULTANT-WELDING & QUALITY

Mobile no: +919940739349

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[srinivas rao]

There are some articles with  GMAW -RMD process on stainless steel without purging gas , even with GTAW by using flux coated wire and flux paste u can do welding without  without purging gas in place , but client acceptance to be taken by using qualified PQR'S in place before procedding for this and it takes time for approval.

in common SS to SS welds always required back purging .

there are some cases of CS# SS doesnot required any back puring during root welding. 

Thanks & regards, 

Srinivas Rao

welding Engineer 

[SHANMUGA PERUMAL]

 Hi, 

Check  with kobelco  they have some TG-X series filler wire without purging that may be used for Rootpass.

Thanks and Regards, 

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[Anand Elankumaran]

Hi Mr. Vishwas Keskar,

Single Vee butt weld  - Root/Hot/fill/cap-  full GTAW

pipe OD -33.4 mm

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/089B4A0A-1805-4EF9-BAF3-AC2527879802%40gmail.com.

[Vishwas Keskar Welding Manager WELDING]

For GTAW welding  -Single Vee - 33.4 OD, Full GTAW welding  - 

SS TO SS Welding   or Cr > 3 %  , backing gas is required to get sound root without any Oxidation.

The Oxygen is excluded by  purging Argon/Helium or other Inert mixtures  at root side to avoid Oxidation .

The root side is inaccessible  due to small diameter in your above case.

Backing gas shall be continued till 6mm deposit is welded . This is not a Code requirement but followed  as a good engineering practice across industries 

Thanks 

Vishwas