MIG terms, globular, spray, short circuit

[Teeps]

Alex, could you send me a copy of that pdf?

[email protected]


and I gotta figure out out that coffee statement from Paul, LOL.

Thanks in advance,

Don

[Alex]

Hey Slagindaboot,
Bro that is one fantastic website. Thanks for the link.

Alex

[paulrbrown]

Slagindaboot, I see how you got you name now, Ed Craig taught me something great when I was really trying to Dial in my MIG welding and understand just how to set the machine up, 17 cups of coffee at 10 o'clock. You can weld about 90% of anything needed in steel with that setting according to him and I believe it, for those not in the know, go there, he has some great info, if you can't find that reference, I will elaborate if asked... Thanks Ed Craig!!!! Slagindaboot, try wearing long pants instead of shorts while welding!!!!BTW, I have earned a few White spots on the Tattoo on my Leg from setting down to weld with no leather apron even with thick denium. Best regards, Paul 'DocBrown' Brown

[slagindaboot]

Alex has provided you with a very good explanation of mig welding metal transfer. There's a wealth of additional information on Ed Craig's site, www.weldreality.com If I'm not mistaken even high speed video of the metal transfer.

I've put the SS mode to good use on sheet metal down to 20 gauge, and the spray mode to good use on heavy plate. When set up properly both will give excellent results for their respecive applications with almost no spatter. Globular transfer, on tlhe other hand, always produces considerable amounts of spatter and the only good use that I've found for this mode is to find holes in my gloves...or boots.

[hankj]

Walker,

Pick up a copy of "Welding Essentials" by Marlow and Galvery. Great reference book. It covers a lot of topics, including all of the current welding processes.

Be well.

hank

[Alex]

Hey Walker,
I don't think that booklet is available from Praxair anymore. I have a PDF of it that I've linked most all of the subjects to the table of contents. I don't know how much you know about PDF files, but if it's linked, you can just click on the topic and it will take you right to it. The file is just a little over 1MB. If you're up for it, I can email it to you. It's really informative. Covers not just GMAW, but also SMAW, GTAW, plasma welding, and plasma cutting. 70 pages. Wouldn't be of much interest to the Pro welders around here, but it's pretty useful for us amateurs. Heck, if anybody else wants a copy, let me know.

Weld on,
Alex

[walker]

Wow, Alex! That was a great explanation. I also just read a new post on spray transfer. I was just unclear on when it changed from shortcircuit to globular to spray, that really clears things up. I have never seen that book from praxair, I'll have to bug them about it next time I am in there.

[Alex]

Walker,
Saw your post this morning. Frankly, I'm surprised that no one has jumped on this. Let me excerpt some reading material for you (this is gonna look like the "great American novel):

In the short-circuiting mode, metal transfer occurs when the electrode is in direct contact with the weld pool. In this mode of metal transfer, the relationship between the electrode melt rate and its feed rate into the weld zone determines the intermittent establishment of an arc and the short circuiting of the electrode
to the workpiece. Specifically, the electrode is fed at a constant
speed at a rate that exceeds the melt rate. When it contacts the molten pool a short circuit occurs, at which time there is no arc.
The current then begins to rise and heats the wire to a plastic state. At the same time, the wire begins to deform or neck down due to an electromagnetic pinch force. Eventually, the current value and resulting pinch force causes a drop of metal to transfer into the weld puddle. At this point, an arc is established. This sequence repeats itself approximately 50 to 250 times per second. Since there is less “arc on time” established during the short circuit, the overall heat input is low, and the depth of fusion is relatively
shallow; thus, care must be exercised in selecting the procedure and weld technique to assure complete fusion when welding thicker materials. Due to its low heat input characteristics, the process produces a small, fast-freezing weld puddle which make it ideal for
welding in all positions. Short-circuiting transfer is also particularly adaptable to welding sheet metal with minimum distortion and for filling gapped or poorly fitted parts with
less tendency for burn-through of the part being welded.

Globular Transfer is characterized by the transfer of molten metal in large drops across the arc. This transfer mode takes place when
the current and arc voltage are between the short-circuiting and spray transfer current and voltage levels; it occurs with all types of shielding gas. Carbon dioxide yields this type of transfer at all usable welding currents above the short circuiting range. Globular
transfer is characterized by a drop size approximately two to four times greater than the diameter of the electrode. With carbon dioxide, the droplet is not propelled across the arc, due to the repelling forces acting upward toward the wire tip. These forces tend to hold the droplet on the end of the wire. During this time the drop grows in size and eventually either transfers by gravity due to its weight, or short circuits across the arc gap.

In Spray Transfer, the molten metal is propelled axially across the arc in small droplets. In a gas blend of at least 80% argon, when combined with the proper operating conditions, the electrode
metal transfer changes from globular to a spray or spray-like mode. The minimum current and voltage levels required vary for any given electrode diameter. The change takes place at a value called the globular-spray transition current. Spray transfer in argon is
characterized by a constricted arc column and pointed electrode tip.
Molten metal transfers across the arc as small droplets equal to or less than the electrode diameter. The metal transfer is axially directed to the workpiece. Since the metal droplets are small, the transfer rate can be as high as several hundred droplets per second. Due to puddle fluidity, spray transfer is limited to the flat or horizontal welding position.

This information was taken from my Praxair "Welding Tips" booklet.

Hope this helps,
Alex

[walker]

I seem to have missed out on something in my MIG welding glossary. Could someone please share what the differences are in globular transfer, spray, and short circuit. Do they differ in polarity, amperage, and wire speed? Also, do the different blends of shielding gasses make a difference in these processes?
Thanks, I just seem to have missed this part of my education.