Mode of Transfer for GMAW

Date 11-29-2018 12:50

Hey ARE Aye,
Generally, you need 80% or more Argon to get into the spray mode.

Go to any of the wire manufacturer and look up their recommended V & A to see the expected mode of transfer.

By pipewelder_1999 (****)

Date 12-02-2018 13:29

There are a great many resources to help with study questions besides just looking for the "answer". The parameters that you list are ones that very few including myself would be familiar with.

These research questions are for learning typically. Understanding the topics related to the question are the "goal".

If I am wrong in my interpretation, please let us know the applications where you use 4.0 mm solid electrode and 170 cfh of CO2.

One of the best ways to answer this query is to setup using the parameters and test them out...unless this is a question for your learning. Then the study of some theory related to GMAW transfer modes is suggested.

By Are Aye (*)

Date 12-11-2018 11:50

The application is for Spiral and Straight-seam pipe manufacturing process.

Even the welding machine supplier can not give answers regarding mode of transfer.

A 4.0 mm electrode is the best size for pipe thickness from 0.500 in.~ 1.2 in. with GMAW process.

The ABOVE parameters has been adopted through series of trials conducted.

By pipewelder_1999 (****)

Date 12-11-2018 14:51 Edited 12-11-2018 15:12

That is very interesting. my experience with Spiral Welded pipe has ben SAW only. 4.0 MM GMAW would be interesting to see.

The transfer mode is best established by observation as opposed to the theory since you are there to observe what is happening. An oscilloscope or even high-speed video could be used to observe what is happening if you are undecided between short circuit and globular. Because you are using 30% CO2 only then theoretically, spray does not occur. I, however, have never used 4MM GMAW so I am only speaking from knowledge of information read. I have observed metal transfer that looked like, sounded like, and welded like spray using 75/25 Argon/Co2.

Spray is pretty obvious when it occurs also.

A paper on the subject of transfer mode sensing can be read at http://files.aws.org/wj/supplement/WJ_1991_04_s91.pdf which may lead you to more information other than opinions.

In my mind, your options are globular and short circuit if you are sticking to accepted "theory" but verification using theory is not as strong as verification using observation. There are variations of our standard "textbook" modes and many research papers on the process.

If you are trying to use the transfer mode as a basis for qualifcation ranges related to thickness, I strongly suggest verification of suitability on all thicknesses to be welded. I know that could be an expensive process on a spiral weld setup but for straight seams, it could be a little easer.

By Are Aye (*)

Date 12-12-2018 11:58

Thank you pipewelder_1999!

Yes it is interesting to see. It is actually a 2-step welding process where the initial weld (Tack welding) done during forming (for Spiral) with the GMAW process and then it is finally welded with an offline SAW process. What you've experienced I think is the conventional process (direct SAW during forming).

Short-circuiting mode has been used since then (reflected in the WPS).

By pipewelder_1999 (****)

Date 12-12-2018 16:23

You are correct. I was involved with the process performing inspection. They used FCAW-G if my memory is correct.

If the WPS states Short Circuit, is there a reason to doubt that? The Oscilloscope or High-Speed video would be a way to confirm that. Some 1200 FPS cameras can be inexpensive. They will not record the arc in high resolution but you can see the darkening around the area easily.