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[MW:4999] RE: 4998] mode of metal transfer in mig welding

By Materials & Welding
AWS welding handbook says the following for CO2 with GMAW:
 
. . . "With a CO2 shield, the metal transfer mode is either short circuiting or globular.  Axial spray transfer requires an argon shield and cannot be achieved with a CO2 shield.  With globular transfer the arc is quite harsh and produces a high level of spatter."  (implied if transfer is globulr then) "This requires that CO2 welding conditions be set to provide a very short "buried arc" (the tip of the electrode is actually below th surface of the work in ordre to minimize spatter."
 
In the US, when CO2 is used as a shielding gas, the transfer mode is nearly always short circuiting arc transfer (dip).  My understanding is that in Europe globular transfer is not uncommon, but I have little experience with it in actual welding.  If your process is short circuiting transfer, and ASME Sc IX is to be applied you will need to take into account essential variables QW-403.10 and QW-404.32 which may limit the qualified thickness of base metal and filler metal.  For QW-409.2 you willhave to list the transfer mode as short circuiting (dip).
 
Hope this helps.
 
John

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of durga bala suresh
Sent: Thursday, April 29, 2010 10:43 AM
To: materials-welding@googlegroups.com
Subject: [MW:4998] mode of metal transfer in mig welding

Dear Members,
we are going to qualify MIG welding process.
How to differentiate metal transfer like dip, globular & spray?
we are using IS 2062 material with 99.9% CO2 shielding gas,1.2 dia filler wire,12mm thick in single '' V'' Grove  butt Joint.
what is the desired testing requirements ? depending of metal transfer as per section IX 

thanks and regards,
Suresh

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