what is TRAILING SHIELD ?

[aslam khan]

HI FRIENDS,
GOOD MORNING !
IN WPS GAS (QW-408) IT IS WRITTEN TRAILING SHIELD, CAN YOU SHARE YOUR
KNOWLEDGE ,WHAT IS TRAILING SHIELD ?AND
TECHNIQUE (QW-410 ),IT IS ALSO BE WRITTEN MULTIPLE OR SINGLE
ELECTRODE, IS THERE ANY TECHNIQUE BY WHICH WE CAN DO WELDING OF SMAW
AS MULTIPLE ELECTRODES?

THANKS IN ADVANCE
REGARDS
ASLAM

[joshi jaydeep]

Trailing Shield:

 

This is used for welding of highly reactive material like Titanium.

There are chances that these materials are prone to oxidation in hot condition even after solidifaction. To prevent that, a shield is attached to the welding torch in a trailing manner so that shielding gas will prevent the oxidation of the solidified hot weldment.

 

Single / Multiple Electrode technique is for SAW only where you can have two or more wires are being feeded in the same weld pool.

 

Reg,

Jaydeep

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[sujay kumar]

Dear Aslam,

 

Shielding trailing is applicable in GTAW process and SMAW multi electrodes process,according to my knowledge not available.

 

thanks

Sujay

[pgoswami]

Dear Aslam,

Training shield is required for GATW of reactive materials such as Titanium, Zirconium. The purpose is to shield the cooling weld and HAZ from hydrogen and other gas related embrttlement. For these materials weld and HAZ are quite reactive till 400 deg C, hence use of trialing shields are necessary. Usually it consists of the same gas or may be a  different  mixed gas (as proposed in the WPS) to protect the weld and HAZ as stated above.

You don’t require such devices for other materials , both ferrous  and other common  non ferrous materials. See below the illustrations from QW-256 on the trialing shields/gases.

You may engage multiple welders  for SMAW, such as welding of large diameter pipes. However two welders feeding electrodes on the same (common) weld pool would be difficult to implement, due to inconveniences to the welders and the difficulty in separation of slag and weld metal ,this would cause heavy slag entrapment.

Thanks.


Pradip Goswami,P.Eng.,IWE.
Welding & Metallurgical Specialist & Consultant
Email-p...@sympatico.ca,
pgos...@quickclic.net

     

[Nandha]

This NOT for SMAW-....Preferred for SAW only.

Trailing means Shielding gas after first shield gas.

Thanks,

 With Warm Regards,

 K.NANDAGOPAL;
09977729258
09360049258-
Sr.surveyor

Bureau Veritas India Pvt Ltd
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-----Original Message-----
From: material...@googlegroups.com
[mailto:material...@googlegroups.com] On Behalf Of aslam khan
Sent: Monday, December 20, 2010 9:50 AM
To: material...@googlegroups.com
Subject: [MW:8825] what is TRAILING SHIELD ?

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