GMAW vs. GTAW

Date 07-24-2003 14:53

GTAW will always be slower than GMAW, but there are applications that do not fit GMAW, and then GTAW can be indespensable. There are ways to speed up GTAW though. CK makes a cold wire feeder that can be used with manual welding. Many companies also make orbital GTAW equipment either for overlay or pipe welding.

By jwright650 (*****)

Date 07-24-2003 14:54

Hi Trevor,
Welcome to the forum,
Just the difference in the mechanics of how the filler is added to the weld pool, will have the GMAW out front in a race. GMAW is going to run faster because of the amount of filler being fed into the pool by a machine from a spool.
John Wright

By welder_guy2001 (***)

Date 07-25-2003 04:19

sure, if you have a set of steady hands and an eagle eye and reflexes like a cat, you could GTAW just as fast as GMAW. but since nobody's perfect, GTAW will always be slow.

By thepowerofblue (**)

Date 07-27-2003 00:32

Here is my 2 cents:
Go to your local home depot and buy a little Lincoln AC/DC CrackerBox Stick Welder and Buy a box of 6011's and some 6013's.It runs off of a 220.The reason I say this is Stick Welders offer very little maintenance unless you do a lot of heavy work.Now if you want a good little stick welder is a Miller Thunderbolt AC/DC.The only mainentance it needs is to vacuum it and unscrew the guard off and grease the shunt block with high temperature grease and if the welder is kind of rattling when you weld and while it's running then you tighten those screws by the shunt block 1/4 of a turn and that's it and replace the cables and leads if it needs it and replacing cable or adding cable is easy because you can get cable connectors from lenco because it's not safe just using lugs because the lugs can become active and it's better to use cable connectors.You can weld Aluminum with Aluminum rod and Weld Stainless and you can even cut with a magnesium cutting rod or just a plain ol 6011.Now that is totally easier than Tig or Mig unless you are doing light work or autobody applications.I don't know why you would want to use Mig or Tig but it's your decision.Thanks
John

By brande

Date 07-27-2003 06:58

Depends on the particular weld joint. Manual TIG can be slow, but a cold wire feed TIG can rival some MIG processes in speed.

Cold wire feeders are available from CK Systematics, Profax and others.

Hope this helps
brande

By HappyWelder (*)

Date 07-27-2003 19:01

GTAW is inherently slower than GMAW due to two reasons:

1) In GMAW the filler material is heated by electric resistance before it burns of. IN GTAW You don´t get that additional heating unless You are using a hot-wire preheating device.

2) As the wire-tip burns of additional energy is added to the filler material. That addition is not possible with GTAW, hot-wire or not

Hot-wire GTAW is a process where a wire is heated resistively between 2 poles. The poles may consist on two contact-tips which the wire passes before it enters the arc, or one pole may be the weld-pole itself. It is possible to increse the deposition rate to 6 kg/h with hotwire but problems with fusion and penetration will occur and increase above 3 kg/hour. The higher the deposition rate the cooler the weld pool will be because You can only preheat the wire just below the melting point (range), and everything that is cooler then the average weld-pool temperature of ca 2400 centigrades will reduce the temperature of the pool.

The wire will never cool the weld-pool in GMAW-welding since the molten filler-material will be just as hot no matter what the feeding rate.

Furthermore; by increasing the deposition rate in GTAW You will loose one important benefit with the process, which is the increased toughness in the weld-metal due to the heat-treatment that the many succesive beads produce.

/Happy
EWE

By RonG

Date 07-27-2003 19:57

You might want to look at automated, Hot wire and or Pulse GTAW.
Consider that GTAW uses an none comsumable electrode and you will only get so much life out of it. Other than that, it can compete with GMAW in some applications.

By jon20013 (*****)

Date 07-28-2003 18:48

Okay, here's another spin on the same question and would welcome feedback: We do an awful lot of x-ray quality pipe welds which almost always requires us to deposit a GTAW root/hot pass BUT, we also do a lot of stainless steel SO, my question is this: whats the forums opinion on heat input of GTAW vs. GMAW Spray?

By Niekie3 (***)

Date 07-28-2003 19:01

Hi Jon

There is no straight answer to heat input questions, because the heat input is based on both the "electrical energy" and the welding speed. Because GTAW is a slow process, the heat iput is typically high.

Usually GTAW (spray transfer) is a high heat input process, but again, it depends on the welding speed. What you need to keep in mind when welding pipe is that you can not weld steel out of position with spray transfer. Most pipe welding of GMAW is done in dip transfer.

Regards
Niekie Jooste
Fabristruct Solutions

By RonG

Date 07-28-2003 22:55

Niekie,
Pulse GTAW can reduce heat input significantly. We use it on some finish machined parts to reduce distortion.

By ssbn727 (*****)

Date 07-29-2003 22:04

Hey Jon!

First of all, your going to get more than one opinion on your question because, well - we need more details regarding the material you're welding, the filler, the metallurgical properties you're looking to achieve in the finished weld, and Heat Affected Zone, whether or not you're welding the pipe from a fixed position or out of position, whether or not you're using consumable inserts or not, etc.

Niekie has a point about GMAW spray transfer (even though he wrote GTAW, hmmm - must be that fat fingered virus again!!!).
However, GMAW-P can work well provided that optimal welding parameters are met. So can a good all position FCAW wire for that matter.

In re-reading your question again, GTAW is a process whereby constant current is used, and GMAW spray is performed with a constant voltage power source. therefore, as Niekie stated in his reply, heat input is based on both electrical energy, and the welding speed.

Now RonG gave a good suggestion about using pulse GTAW to significantly reduce your heat input and in fact has been used for quite some time now on some X-ray quality pipe welds.
The other reply's suggestions made sense also.
I'm sure that you'll find an opinion that will help you decide in choosing the best process for your application... Good luck!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By ssbn727 (*****)

Date 07-31-2003 10:35

Hello again Jon!

Just out of curiosity but, did you ever hear of Liburdi's LFX-SS7 GTAW welding flux? These people claim that "Revolutionary Welding results with the Liburdi flux and/or catalyst can improve GTAW quality and productivity by increasing the penetration by 300%! Thus decreasing welding time (fewer passes), Less distortion, no negative effects on the material or weld quality, etc.".
Supposed to work well with Stainless steels, and you mentioned in your post that you weld alot of stainless pipe so, I do'nt think it would hurt to at least get a sample kit from these people, do'nt you think?

This flux and/or catalyst is from the Netherlands.
Innomet B.V. is the esclusive agent of the liburdi welding flux and catalyst in the Netherlands. For more information, a quotation or a sample kit, e-mail: ibthhorst@worldonline.nl Name: "ing. G. ter Horst"
Company name: Innomet B.V., Boekelo

If you've already tried it or if anyone else has, I'd lke to read some opinions on this...

Hope this helps!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

P.S. The Liburdi "Digimetal" website address is:
http://www.digimetal.com/english/

By ssbn727 (*****)

Date 07-31-2003 10:48

Hello Trevor!

Check out my second reply to jon20013 about your question regarding improving production time with GTAW when compared to GMAW.

Just scroll up to my 2nd reply on this thread to "jon20013" and take a look at the info.

I do'nt think it would hurt to investigate a little further, especially if it really works out for your applications.

Hope this helps and Good Luck!!!

SSBN727 Run Silent... Run Deep!!!