GMAW shielding Gases??

Date 06-23-2010 15:20

david bean
Usually used with 75/25 (argon/CO2) shielding gas or with higher contents of argon, such as 90/10. But can also be used with 100% CO2.
It can be a prequalifiable GMAW procedure if the procedure conforms to all the applicable requirements of Clause 3 AWS D1.1 .
I feel I have more control when welding out of position with the 75/25 Argon vs. the straight C02.
Good Luck
Marshall

By 803056

Date 06-23-2010 15:53

GMAW short circuiting transfer is not prequalified per D1.1. The reason for starting with that comment is that if pulsing is not used, short circuiting is required for welding out of position.

The electrode can be used with CO2 and it is prequalified if globular transfer is used, but not short circuiting.

The welding parameters for globular are on the same order as spray transfer using a high percentage of Argon (80% or more), except the CO2 doe not allow the process to go into the spray mode transfer.

Best regards - Al

By Lawrence (*****)

Date 06-23-2010 17:32

Al,

This is something I've not thought about much until this post came up. (mostly because I'm always skeptical about globular transfer in production). I agree that what you suggest here is possible.. But would like to hear more about practicality as well as what would be required exactly to be fully D1 compliant.

Would it be necessary for the Welder Performance Qualification testing to be carried out in the Globular Mode?

*Must* the Welder Performance and Production WPS's each state "Globular Transfer" ?

Plus; I can see trouble as far as position and progression goes... Unless globular transfer is used for the welder performance testing... If the welders are only qualified with GMAW spray transfer.. they are likely only qualified in the flat and horizontal fillet positions.. Those rails will likely be all position welds eh? Prequalified Vertical progression is limited to uphill and that will be a fun trick on pipe in the globular mode as well.

Frankly, I suspect it would be more time consuming and difficult to be compliant with the code using globular transfer. It's alot easier to qualify personel with short circuiting transfer than with globular when it comes to pipe in all positions (in my opinion)

(also in my opinion) better to do the PQR for GMAW short circuit, or purchase an SWPS with a parameter ranage that you can live with production-wise.

By jarsanb (***)

Date 06-23-2010 18:20

Going to the 100% CO2 over an Argon mix isn't an impovement in my opinion. Not on materials like hand rails with .120" walls. The arc with 100% CO2 just isn't as stable or versatile. Can you make good welds? Sure. But you can aslo expect arc instability and arc sputtering on occassion...just because. It is what it is. Especially on thin wall. You struggle with questions like "what's wrong, is it the gas quality? Are our parameters good? Is the Electrode junk? blah blah blah. Expect it. I promise it will happen. Many suppliers, including the big dogs here, have other clients in other industry, like food and beverage. They (the supplier) test the input quality but cannot gaurentee the quality inside the cylinder. Like if there were a pepsi back purge into it for example. Some managers read - more penetration and pop a boner. Way over hyped when talking Short Arc. The penetration is minimal any way with this process. You're really splitting hairs. All that really matters is fusion with the fillets you'll be welding. Fusion from the weld leg to the base metal. Who really cares how far it penetrated, unless actual throat was engineered, which is hardly ever the case.

By jarsanb (***)

Date 06-23-2010 18:34

I'm mostly referring to out-of-position welds, like these hand rail will be subjected to. I guess you could make an argument if all you had were flat and horizontal welds. But even then, why run not run globular or spray over Short Arc if all the welds are in a good position?

By david bean (**)

Date 06-23-2010 20:38

Thanks Guys
good feedback

Could i qualify short arc to D1.1? given the thickness of the rail .120 wall?

what would you recomend?

By ziggy

Date 06-24-2010 00:49

gmaw-s can be qualified per d1.1. follow the requirements of clause 4.

btw, does your contract specify d1.1 in the misc metal section? some do, some do not.

with the revision to clause 1.2 in the 2008 d1.1, has anyone come across an EOR incorporating any necessary changes to the d1.1 requirements to allow GMAW-S (as it is in d1.3) for base metal less than .125?

ziggy