How does arc welding work

I was just wondering about stick welding, it seems odd that if the
electrode is negative, positive, or AC, the metal from the stick ends
up on the weld, but not the other way around.
I'm guessing that the electrode is smaller and gets much hotter, so
the metal flows off it and to the weld. The tip of the electrode would
get ionized, too, and the metal ions would tend to be repelled from
the electrode surface. Is that true? Is that mostly what makes arc
welding work, or am I missing something?
Jeff P.
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Reply to
Jeff Polaski
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Hmmm. I'm no welding expert, but that web site strikes me as horribly misleading.
"Power is reduced and amperage is increased."?
Surely voltage is reduced, not *power*, unless you're counting the heat losses in the transformer...
"The flux is what is burned and used to fuse the metals."?
Well, on some of *my* welds, the flux is all that joins the metals! But I'd rather the *rod* is melted and used to fuse the metals instead.
"Welders use a lot of electricity because of how much it takes to burn the rod and weld it to the metal. "
Welding the rod to the metal is, again, something I've been doing lots of, but not a desirable feature of the welder!
"It is also important to try and use only one appliance at a time as this can lead to shorting out the unit. "
It's important to do something that can lead to shorting out the unit? I could just run a bit of welding cable between the clamp and electrode terminals on the welding unit - that'd be easier.
And using too many high-current appliances at once is likely to blow a circuit breaker, not short anything out!
"One of the minor drawbacks of an arc welder as compared to perhaps a MIG is that the arc leaves a little uglier weld. This is because the arc welder does not use an inert gas to blow away the left-over flux."
The inert gas in MIG is used to blow away flux, is it? Riiight.
"Once the current from the positive end travels through the metal and completes the circuit it heats up up the flux to an extremely high temperature and melts the rod on the inside. The rod is what is actually "welding" the metals together."
The current heats up the flux, which melts the rod? I always thought it was more that the big fat spark melted the rod AND the flux together :-)
ABS
Reply to
Alaric Snell-Pym
The relative mass of the electrode and the workpiece is a factor, though both increase in temperature, one more than the other. There are other forces at work, however, such as gravity as well as certain magnetic effects which can cause the arc to wander. That's why welding in the flat position is easier than vertical or overhead (upside-down). The repulsion forces that you mention are present, they are simply insufficient to overcome gravity.
Reply to
Thomas Kendrick
hey ! a science fair project ! (This site is rubbish, Im amazed it was posted)
The wire or filler rod melts preferentially because it's hotter, owing to its smaller mass and poor heatsinking along a thin rod, rather than a sheet. The molten metal then sprays in the right direction because it's hotter (easier to strip the surface) and because it's pointier, increasing the field gradient.
DC isn't symmetrical and if you swap polarity around you can indeed control the heat.
Reply to
Andy Dingley
Lots of MIS information comes from people at edu sites who obviously need to spend more time studying and less time on taxpayer provided computers and isps roaming the internet. Although some are already educated beyond their capacity, and are only waiting for their paperwork.
Steve
Reply to
SteveB
What may not be apparent is the role of the coating on the electrode. The metal melts/vaporizes first, and then the coating surrounding the electrode "guides" the vapor/arc stream towards the metal to be welded. Some coatings also help by providing ionizing agents and a protective atmosphere to the arc.
Electrode polarity does have an influence on the shape of weld produced. With the electrode positive, you get deeper, narrower penetration. With the electrode negative, you get shallow, wide deposition. With AC, you get something in between. NOTE: not all electrodes work satisfactorily with all polarities.
Wayne
Reply to
Wayne Bengtsson
That's more like the link I was wanting to pass on to him when I sent him to
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I should have taken time to read what they had to say but it never showed up properly on my screen - yellow or gold writing on a white background, hard to read. I just did a Google search for ["arc welding" & "how it works"]. Got plenty of hits. That one seemed "authentic" at first glance and I passed it on. Sorry about that! :-(
Al
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billh wrote:
Reply to
Al Patrick
odd, especially how welding works whatever the polarity of the electrode is, even if it'sAC. The army welding link helped a lot.
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.
I have a basic idea of what's going on, but there is always more to learn!
Jeff P.
Reply to
Jeff Polaski

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