Spray arc with FCAW

Date 03-08-2002 12:47

Brian, EXXT-1, EXXT-2, EXXT-3, EXXT-6, EXXT-11 electrodes have a spray type arc. We have used the EXXT-11 extensively and it operates in ranges normally associated with spray transfer. FCAW is an excellent alternative to low hydrogen SMAW electrodes.

Mike Sherman
Shermans Welding

By Niekie3 (***)

Date 03-08-2002 22:46

Hi Brian

The FCAW process is something of a strange beast in that it is actually a combination between the SMAW and GMAW processes. Depending on the flux used, the transfer mode can resemble spray transfer. This is however not really of much importance because FCAW wires are designed to operate at certain current ranges and able to weld out-of-position, or not. These characteristics you are not really able to manipulate by changing the current settings as is the case with GMAW.

As such, I prefer to think of FCAW as an "inside-out" SMAW process. You get what you get in the electrode, so you need to choose this for the appropriate conditions under which you will be welding. Don't buy any old electrode and try to manipulate it to do different types of jobs.

Hope this helps

Regards
Niekie Jooste

By bmaas1

Date 03-09-2002 13:12

The company I work for uses astm a514 material extensively and FCAW 95 percent of it. They want to reduce spatter. They use esab wire .045 diameter with c-25 gas(75/25). Any ideas would be appreciated.

Brian Maas

By boilermaker (**)

Date 03-09-2002 14:34

Brian, I have found using FCAW-G that the electrode to puddle length has a very profound effect on spatter. Normally I too run a similar wire and shielding combination....when you dial in the voltage get your wire to "spray" off at about 1/8" off the puddle....or maybe a little longer arc. Also you could try the "anti-spatter" spray in the spray cans....I've found that they work pretty good even on stainless FCAW...

By Seldom

Date 03-09-2002 15:55

Hi Brian,
Boilermaker has given you a good tip on the voltage/amp setting to help minimize spatter but I would offer a word of caution. Be cognizant of the voltage/amp balance while attempting to do this! As Niekie stated previously, FCAW (specifically gas shielded) has an arc that “resembles” spray.

If you watch the end of the wire with the proper voltage/amp settings you’ll notice that the arc (not the wire) is quite square and focused toward the puddle. There’ll be a steady hiss with a slight crackle once in a while (slightly globular) and little spatter. It’s been my experience that if the amps are too high in comparison to the voltage by setting or nozzle length, the arc will have developed a soft, “paint brush” appearance (widen out) with all hiss and no crackle. In addition, the weld’s appearance will have a very “savvy” look to it and admitttedly, less spatter.

In many cases though, due to this imbalance (and it doesn’t take much), will allow slag to roll under the puddle’s leading edge. I’ve found this to be one of my most common discontinuities I find when dealing with multi-pass, FCAW weldments and it’s usually traceable back to voltage/amp imbalance and very seldom to operator technique! Interestingly, I’ve observed this phenomenon at all locations around a circumferential weld instead of just at the 12:00 o’clock position of a 5G weld and it’s very, very prominent throughout out 2G’s.

The last example that I was involved in personally in,occurred with a nationally recognized pressure vessel fabricator, field erecting several large diameter 5/8” SS pressure vessels and all of the welds were 2G. Immediately I noticed the scenario I’ve just described and questioned the voltage/amp imbalance after watching with my glass and seeing the “paintbrush arc”. They (the QC inspector & QA mgr.) professed to be within the confines of the WPS and that their welders were using the appropriate technique (granted they were but nozzle length was too close) and no QA was going to tell them anything. They cut out over 250’ of 5/8”SS weld after the required radiography showed unacceptable amounts of slag inclusions between passes! All that just for a savvy appearance and little spatter cleanup!

Please excuse me if I've rambled a little too much on this topic.

By Niekie3 (***)

Date 03-09-2002 22:22

Some of the most user friendly wires I have seen are ESAB FCAW-G wires. Generally, if you use the correct gas recommended by ESAB and the correct Amps and Volts, the rest works quite well.

Are you using one of ESAB's new wires? If not, give it a try. With them you can use high currents and still weld in all positions with very little spatter. Just make sure you have the right gas for the wire being used. (As recommended by ESAB in their datasheets.)

By the way, I do not work for ESAB.

Regards
Niekie

By bmaas1

Date 03-11-2002 07:11

We use .045 and 1/16 inch ESAB Dualshield T-95M (E90T5-K2 class) wire for welding ASTM A514 material.

Brian Maas

By GRoberts (***)

Date 03-11-2002 15:58

Bill,
The EXXT5-X means that you are using a wire with a basic slag. These tend to have more spatter than the wires that use an acid slag such as the EXXT1-X. We use both here, and there can be a big difference with regards to splatter, depending on the particular brand. Some are worse than others. We only use the basic slag wires when we need the extra tougness to pass Charpy Vee Notch tests. (You can see in the ESAB catalog, the E90T5-K2 gets 68 ft-lb as welded at -60F, while the E91T1-K2 only gets 22ft-lb as welded at -60F). The easiest way to reduce your spatter would be to switch to an acid slag wire, if you can find one that will give you the properties that you need. Also, I have noticed that when using some basic slag wires, (which are usually only classified to run flat and horizontal), that spatter increases greatly when run out of position.

G Roberts

By Niekie3 (***)

Date 03-11-2002 19:07

I have personally never used this wire before, so I can not vouch for how much or little spatter you can expect. The ESAB catalogue gives the following welding parameters: (Incase you do not have these.)

Ar/CO2 mixtures up to 75% Ar.

Amps Volts WFS(IPM) S/Out Polarity
250 30 469 1" DCEP
300 32 606 1" DCEP
350 32 740 1" DCEP

The more Ar you use, the less the spatter should be, because the Ar results in a greater effect to "spray" the moulten metal off the front of the wire. The more CO2, the greater the effect to cause a "globular" type of transfer, which is usually associated with more spatter.

Essentially this wire is purely for flat and horizontal welding. If you want to perform out-of-position welding, you can try using DCEN with 19V and 170A with a 3/4" S/Out and 285 IPM WFS.

All the above info is for 0.045" wire. For 1/16" wire, use 28-34V and 250-500A with 3/4 - 1" S/Out.

Hope this helps.

Regards
Niekie

By bmaas1

Date 03-12-2002 07:12

Thank you all for your input. It is greatly appreciated.

Brian Maas

By dee

Date 03-14-2002 02:05

Niekie,
I am just a bit confused over the purpose and use of this flux core wire, and although I don't like to advertise how much I don't know, my school taught me the only stupid question was one left unasked... and I hate it to be proved wrong :)

I am under the impression flux is intended to shield the molten metal from atmospheric components that would harm the weld. Why would we want to use a flux core wire in an inert gas shield... isnt it kind of redundant-redundant? I understand the need for the Ar; it's easier to ionize than air or CO2 and lowers the energy requirement making spray transfer attainable (also effecting penetration profile), but wouldn't the flux/slag inclusion issues be akin to silicon issues in spray transfer with ER70-s6000 (not 6, but six thousand, if it were produced) with all that unnecessary & redundant flux floating around in the weld pool waiting to be cleaned off?

I understand flux core is designed for all position welds and provides various benefits, but I spray transfer and it yields a very nice but fluid high energy bead which cannot be run in all positions; I become doubly confused. Why not merely use a solid wire for spray or shut off the gas valve, use flux core and enjoy the cost savings in either case?

I have never used the stuff, and I'm not being critical... I would just like to know when, where, and if I should consider it for whatever benefits it may provide. I feel like I missed a point somewhere. Can you please help?

Regards,
D

By Niekie3 (***)

Date 03-14-2002 18:17

Hi D

The evolution of the FCAW process was, as you pointed out, to be able to have a continuous wire feed process without the need for the gas shielding. (I heard a story that old man Lincoln (Lincoln introduced the FCAW process to the world.) was dead set against the GMAW process when it was introduced by a competitor. Instead of also trying to bring out GMAW consumables and machines, he got his development people to invent the self shielded FCAW process.) As with everything however, improvements occur once people get to use it a lot. So what are the advantages of flux core, that is not related directly to the fact that you do not need gas shielding?

1) Extremely deep penetration. - Simmilar to that achievable with SAW. This means that lack of fusion is very rare with FCAW. (Unlike GMAW)
2) As a fluxing process, it can clean the weld pool and result in sound welds even where there are contaminants present.
3) By varying the flux, different compositions can be obtained within the weld pool without having to place these alloying elements in the wire itself.
4) By varying the flux, different welding properties can be obtained, like high deposition rates even out of position.
5) Very high deposition rates. - Higher than with GMAW.

The problem is that it is much easier to improve on the positive points of FCAW, without having to keep on worrying about the self shielding aspect. By allowing the gas to take care of a great deal of the shielding, the makers of the FCAW wire are able to give you a product that optimizes on the advantages of FCAW. In addition, some of the disadvantages of FCAW can be reduced. (e.g. Fumes)

I hope that this tempts you to try the FCAW-G process. Appart from having to remove slag, I believe it is a great process.

Regards
Niekie Jooste

By dee

Date 03-14-2002 19:24

Niekie
Typical of your style you have brought yet another question into focus. (I will try the stuff at first justification; the lengths I sometimes go to to manipulate the work would suggest it would be in the near future).
Thank you, but yet another question remains (or results)

The flux core is essentially a hollow tube filled with flux... naturally it contains less metal than a solid wire of the same diameter; probably a lot less (given PI*R2)
I was cautioned not to assume that faster consumption and higher feed rates necessarily translated to more weld per minute. As I have never used the stuff and my advice comes from someone who was steering me away from it for a particular long forgotten application, please correct me if I misunderstood that you realize higher actual deposition rates than spray arc I compare it to? It was suggested the two are similar. Also worthy of note is the fusion. While I have not seen comparitive profile diagrams of the two I suspect your remarks relating to comparisons of the two processes (GMAW/FCAW G) are presuming short circuit transfer... any problems I had with spray was preventing excessive penetration and traveling fast enough by hand... The right gas helps.

Sure would be nice to make a vertical or overhead with similar profiles regardless of the deposition rate. You can bet I'll give it a try.

Regards,
D

By Niekie3 (***)

Date 03-15-2002 14:48

You are correct that you might have somewhat less metal to deposit per meter of flux core wire compared to the GMAW wire. The deposition rate is however not limited by the amount of wire you can pile into the joint. (How much faster can you set your wire feed speed?)

What greatly affects the deposition rate is the current density on the end of the wire. In the case of the FCAW wire, due to it's smaller cross section, the current density for a given amperage is higher. This means that for any given amps used, you should be able to have a higher deposition rate with FCAW than with GMAW.

Can you weld with GMAW at 280A flat and then just carry on vertical without changing your wire feed speed? You can with something like a ESAB Dual Shield 2 70 Ultra.

Just something even more interesting. You can also get metal cored wires. These are like flux cored wires, only they have mostly metal powder inside. This means you get the advantages of FCAW with an even higher efficiency. (Up to 98%) with very little slag. (e.g. ESAB Coreweld 70)

Regards
Niekie Jooste

By GRoberts (***)

Date 03-15-2002 15:49

Niekie,
I would have to disagree with your comment that "The deposition rate is however not limited by the amount of wire you can pile into the joint. (How much faster can you set your wire feed speed?)"

The amount of metal you deposit by welding is directly proportional to the wire feed speed. You can not get any higher deposition rate without increasing the rate at which the metal arrives at the weld puddle (aka wire feed speed.) I think another way to explain it would be this: Since the current densilty is higher with the flux core wire (as you explained), at the same amperage setting, the flux core will be melting faster than the solid wire, and thus the wire feed speed and deposition rate will be higher, or conversely, at the same wire feed speed, the flux core will require less amperage.

Please let me know if you disagree.

G Roberts

By Niekie3 (***)

Date 03-15-2002 21:25

You are right, that is what I was trying to say.

Just to clarify: When I said that the deposition rate is not limited by the amount of wire you can pile into the joint, I was trying to point out that your wire feeder can usually feed the wire much faster that you would typically use in GMAW. The thing that limits your deposition rate is things like a weld puddle that is too fluid, excess spatter, stubbing of the wire against the work piece or the ability of the power source to deliver the necessary power output.

As such, you can come to the conclusion that your deposition rate is not limited by the speed at which you can supply the wire to the weld puddle. It is other factors that limit your deposition rate.

Regards
Niekie