Magnetic Arc Blow

By likehai Date 03-08-2007 20:38

The abstract of my paper, full paper is avaiable ( likehai@gmail.com) . will be available in Welding Journal

Double-Electrode Gas Metal Arc Welding, referred to as DE-GMAW, is a novel process which decouples the melting current into base metal current and bypass current by adding a bypass torch to a conventional GMAW system to establish a bypass arc. This makes it possible to increase the melting current while the base metal current still be controlled at a desired level. Experiments have been done to find the conditions which can assure a stable bypass arc be established/maintained between the welding wire and the bypass torch. To control the base metal current at the desired level, a group of power resistors is added in the bypass loop. The resistance of the power resistor group is adjusted real-time by changing the combination of the resistors and the change in the resistance results in a change in the bypass current thus a change in the base metal current. A model has been developed to correlate the change of the resistance needed to achieve the desired base metal current to the deviation of the base metal current from its desired level. Experiments demonstrated that the developed control system can adjust the bypass current in a large range to maintain the base metal current at the desired levels.

By js55

Date 03-08-2007 21:18

This seems a very interesting prospect. I have long had an interest in two wire mig applications.
But I do believe than in order to initiate the discussion in this forum we may need to clear some of the specific research vernacular. At least for my sake. When you say melting current you are speaking of arc energy available for material melting? Correct?
And when you say base metal current you are speaking of the wire that is operating in the eletrode positive or negative direction?
And I'm a little confused about the term "decoupled". That would imply a limited amount of energy that has been split, whereas what 'I think" you are doing is adding energy with the addition of another wire, just in an opposing polarity.
And unless I just completely misunderstand, to my knowledge, the only way previous attempts at twin mig have resolved the issue of arc blow was through alternating pulses.
And my final question is, what is the ultimate purpose of the technology. Is there a deposition rate advantage? A solution to previous twin mig applications? Is there a prize upon which you have your eye?

By likehai Date 03-09-2007 01:05

Hi,

This process utilized only one power supply, so it does decouple not add current.
The melting current here is total current through the wire, and the base metal current is current through the base metal. Both currents are real currents that can be measured with current sensors.

The purpose of this technology is to increase the welding productivity by increasing the melting current. thus the deposition rate is high ( double ). This is not a twin MIG ( tandem) process because part of the current does not flow through the workpiece.

If you are interested, I can send you my paper. then we can discuss it in details. My email is likehai@gmail.com.

I may re-open another topic to discuss this double-electrode process since the current subject is confused, I think.

By js55

Date 03-09-2007 14:26

I'll send you an email for the info thanks. And this certainly warrants further discussion. I think we have communication problem. I need to understand better how oyu are using your terminology in your work in order to communicate with you.

By CWI555

Date 03-08-2007 22:52

You may want to do some research into the SAW multiwire techniques. There is likely some good information to be found in that.

By DaveBoyer (*****)

Date 03-09-2007 06:03

About 30 years ago I saw a demonstration using a magnetic field to manipulate a TIG arc. Could You use an external magnetic field to make the arc go where You want it to go?

By js55

Date 03-09-2007 14:39

Dave,
This may be an approach. However, the plant I worked for used a lot of magnetic arc oscillation for hot wire and cold wire Tig applications. This stuff is still used though the technology as it stands is very raw (these are actually very simple devices), to my knowledge, compared to what would be necessary to manipulate the arcs independently for this application. And I believe that, as opposed to a simple switching of polarities or magnitudes to move an arc back and forth this system would intend to stabilize the arc locations in the presence of another arc location magnetic field immediately adjacent, and have to be tied into any current variations in the welding process.
I suspect that the reasearch that would be necessary to impliment the next generation of arc manipulation such as this is a ways off. EWI may have some stuff on this since they did so much with tandem migs, but of course they don't just give that info to anybody.

By js55

Date 03-09-2007 14:30

I'm not sure the available SAW multi wire applications will have much assistance since they either run the same polarities or toss in AC. This would preclude the arc blow issue (the very reason AC is used in these applications) he is having, I believe.
Also, I've seen the tandem migs achieve almost 60 lbs/hr deposition which is astonishing. Though the weld quality suffers (consistent fusion). The pulsing of the two wires whcih prevents the arc blow problem also reduces available melting arc energy. In my opinion.

By js55

Date 03-12-2007 16:55

Likehai,
I've finished a cursory peruse of your paper and find it very interesting, and certainly don't understand alot of it. But I do now understand what you mean by 'decoupling'. And I see, in clarification, that the primary intent of the research is to minimize HAZ impact while maintaining high levels of weld metal deposit (which has been possible for some time from tandem migs).
But, in answer to your original inquiry, I don't have an answer. If it is critical that the GTAW arc occupies the same space as the GMAW arc then I'm not sure technology is available (at least on a practical welding level)to control the arc blow. The only thing that comes to mind is pulsing. A technique used by tandem to eliminate electromagnetic interference. Perhaps this is more primitive than your own discussions, but if it works for two mig arcs why not a tig/mig arc apparatus. And the technology is certainly available.
On the other hand, what Dave had mentioned may work after all. This technology has been around a long time and is used commonly with auto/machine hot/cold tig applicaitons for simple arc oscillations. But maybe if you increase the amplitude of the magnetic field it will act to inundate, stabilize and override the variations of the two seperate GMAWE/GTAW fields.
WOW. Talk about specualation.

By js55

Date 03-12-2007 17:09

Upon further reading:
Here's another thought:
Your horizontal distance (d sub 3)is limited to 5mm based upon GTAW arc start capability. But what about using high frequency to start the GTAW and spreading the distance to eliminate arc blow interference?