FCAW Mode of metal transfer

[Nashanas]

Hello,

In my WPS for FCAW the mode of metal transfer is listed as "Spray arc". My client is telling me in a condescending way that its impossible to have spray arc metal mode transfer in FCAW. I am new to the field, so I did some research, and to my understanding from ASM Handbook, there is a mode of metal transfer in FCAW and it can be of the same types as mentioned for GMAW. So it can be globular, spray, streaming or short circuit.

Am I understadning it wrong? What is the mode of metal transfer in FCAW?

 

[weldstan]

There are FCAW electrodes that produce spray transfer and those that produce globular transfer.Some of the electrodes that had acidic fluxes and produced spray transfer have been modiied with more basic fluxing agents and produce more of a mixed mode of spray and globular transfer.

 

With argon mixes transfer looks more like spray; with 100% CO2 more like globular. If it looks like spray transfer and sounds like spray transfer, it's spray transfer. It is what it is.

Your client is technically correct but also pedantic about a non-issue. It's a messy and I feel pointless discussion, and on this one the Code should just get out of the way. I review a lot of welding procedures and have long since given up on correcting on this point.

(While they are at it, ASME should separate FCAW process from GMAW completely, because really this question is generated from trying to shoehorn FCAW in with GMAW. There will always be at least one essential variable that separates them.)

End of rant.

Signed, a flux-cored arc lover.



"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DVWE]

Have a look at Annex A in SFA-5.20, from ASME Section II, Part C.

Many descriptions of the electrodes (starting on A7) are characterized by "spray" or "spray-type" mode of transfer.

You might want to point that out to your client.

The devil is in the details; she also wears prada.

 

[kingnero]

its impossible to have spray arc metal mode transfer in FCAW

@ IM, what exactly is not correct here?
I have been putting "Spray" on all of my FCAW-G procedures since I started doing this, FCAW-S often have a more globular transfer mode.
I'm also a Fülldraht-afficionado, so even if it's being pedantic, I'd appreciate your insight.

I fully agree that FCAW and GMAW are two different processes, metal cored arc welding and GMAW are much more similar than FCAW and GMAW are.

EDIT: @ Nashanas, what is streaming transfer? Never heard the term before.

 

[gtaw]

It is somewhat dependent on the applicable welding standard.

AWS does not apply transfer mode to FCAW. In the case of FCAW, the transfer mode may be spray like or globular like. The size of the droplets are primarily a function of the flux system and to a lesser extent on the type of shielding gas if a shielding gas is used. The range of welding parameters of FCAW are not as "wide" as they are with GMAW.

The transfer mode when welding with GMAW is pretty well defined and dependent on the welding parameters and shielding gas used. In the case of short circuiting, the gas is prodomantely carbon dioxide, low voltage, low wire feed speed, low amperage, and low heat input.

Globular transfer with GMAW uses higher voltage, higher wire feed speed, higher current, and a high proportion of carbon dioxide.

Spray transfer with GMAW uses the same parameters as globular transfer, only the shielding is changed to about 80% or more argon.

Pulse spray, while every manufacturer thinks they have a better way to produce pulse spray transfer, but it uses the same shielding gas as spray transfer.

This isn't the case with FCAW. The flux used plays the major roll in the way the metal droplets transfer through the arc. To a lesser degree, the shielding gas used influences the size of the droplets, but the transfer mode is not as well defined or discrete as it is with FCAW.

I do not list transfer mode when the welding process is FCAW with either ASME, NAVSEA, or AWS.

Best regards - Al

 

[Nashanas]

@kingnero

From ASM Handbook:

In streaming transfer, a well-developed liquid column extends from the solid electrode down into the arc and
breaks into small droplets before contacting the weld pool (see the discussion on spatter below). Streaming transfer can
involve 1000 drops/s, and the arc has a characteristic "cone" shape.

It all depends on drops/sec. In spray mode there are 100 drops/sec, while in stremaing mode 1000 drops/sec. In globular mode 1-10 drops/sec.

 

[kingnero]

Nice. Didn't know that - but I'm not used to working with ASME/AWS standards - I don't even know about the ASM handbook.
In EN/ISO, there's only dip, globular and spray transfer. And sometime pulse is used for metal transfer, sometimes it's used as waveform.

 

[kingnero]

@ IM, could you give some info on why "spray transfer" isn't technically correct on FCAW ?

 

Spray transfer was defined on the basis of GMAW process using solid wire, within a certain amperage and voltage range.
It is unrealistic to apply that same definition for a steel sheath containing flux and metal powder to have arc transfer defined in the same way.
But as I said, if your FCAW arc transfer looks like spray and sounds like spray, you can call it spray and I won't reject your WPS.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[kingnero]

Thx for the clarification.
Spray transfer must be otherwise defined under AWS or ASME standards, as under ISO, apparently.
I'd be severely pissed off if someone would reject an (otherwise fine) WPS solely based on linguistics.
But - I also don't like making mistakes - I'll have a look at ISO codes for this...

 

I've become the same way about parameters for manual GTAW and manual SMAW. Filler metal diameter and position pretty much define the parameters within a fairly narrow, consistent range, and an intelligent WPS designer just needs to reproduce that on the document (or risk looking silly and ignorant in front of his welders).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."