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Up Topic Welding Industry / Technical Discussions / 75/25 Gas on Structural Steel
- - By SWN1158 (***) Date 04-28-2023 19:20
I'm reviewing an AWS D1.1 WPS.for fillet welds...

WPS                                                                                            ELECTRODE MANUFACTURER

Process:  FCAW                                                                          Same

Electrode Diameter:  .045 (Hyundai Supercored 71MAG)          Same       

Shielding Gas:  75% Argon, 25% CO2                                        Ar-20% CO2 (Note 2)

Filler Class:  E71T-1                                                                    Same

Current:  DCEP                                                                           Same

Amps or WFS:  200-300                                                              Same

Volts: 26-34                                                                                  26-32

Note 2: Use Ar-20~25% CO2 gas.

There's a table in one of the AWS Everyday Pocket Series indicating that short circuit transfer uses 75% argon, and indicates 80% argon is needed to get out of the short circuit transfer mode and into the spray transfer mode. We all know that short circuit transfer is not a prequalified mode of transfer in D1.1, and what concerns me with this WPS is using it to weld thicker base metals, as my experience with 75% argon is that it's been primarily used on handrails and stairs, and even though in this case, the user is referred to Note 2, using it on structural steel concerns me. Any thoughts and comments are greatly appreciated.

Parent - By tlw Date 04-28-2023 22:48
The short circuit with 75/25 applies to solid wire and you are using flux cored wire.  Is that the difference?  Almost all of the gas shielded fcaw wires I've been around use 75/25 or straight co2 .
Parent - By Lawrence (*****) Date 05-01-2023 11:58
Good to see you Scotty !

Agreeing with TLW here.

While 200-300 amps is an excessively wide range for a prequalified WPS the energy represented is likely adequate for .045 FCAW even at the low end.

Some manufacturers state the transfer mode for FCAW is globular, some say spray.  Both are prequalified transfer modes for FCAW.

Some of their data
Parent - By Jim Hughes (***) Date 05-18-2023 18:17
I agree. This WPS indicates they are not using Short circuit mode due to it being FCAW and the WFS. 75-25 is very common in struct. Steel and pipe welding in the spray transfer mode. (and before I get inundated with comments about not being able to get into spray transfer mode with 75-25) I don't care.  I would be very concerned if they wanted to use Short Circuit for something this thick. Not a good idea.
Parent - By jwright650 (*****) Date 05-19-2023 11:25
I think the rule of thumb regarding the percentage of argon to get into spray mode relates to GMAW with solid wire, rather than with FCAW cored wires.
Parent - By welderbrent (*****) Date 06-13-2023 02:46
Good Day Scott,

I agree with all the rest here.  Mode of transfer is applicable for GMAW, not to FCAW.  75/25 is a common shielding gas for FCAW as long as the electrode is classified as an 'M' and not 'C'. 

Have a Great Day, Brent
Up Topic Welding Industry / Technical Discussions / 75/25 Gas on Structural Steel

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