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.
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
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.
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.
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
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
That's more like the link I was wanting to pass on to him when I sent
him to
formatting link
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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