PDA
View Full Version :

Welding Article: Arc Blow by Scott Miner



LONGEVITY
11-25-2012, 01:58 PM
The topic of today's discussion is arc blow.


Arc blow is a phenomenon that we see primarily when we do shielded metal arc welding
(SMAW) or what some people call stick welding. Arc blow only occurs when we're using
DC or direct-current. Some of us may have experienced arc blow and never really knew
what it was or understood what was going on.


Every conductor that has electrical current passed through it produces a magnetic field.
In our welding world, this means the welding machine, cables, work clamp, electrode
and electrode holder. What many people fail to forget is that the work itself, the metal
that we're welding on is also a conductor of electricity. As we strike the arc and proceed
down the weld joint, the magnetic field builds up in the workpiece. If the part is relatively
large, the magnetic field is evenly dissipated and it's not very noticeable. On the other
hand, if the pieces are small or if we come to where the part narrows, wraps into a
corner, or the part comes to an end, down in a deep groove, that can be a different
story. As we're moving through the center of a large piece, the magnetic field can move
evenly ahead of us and behind us and dissipate relatively evenly throughout the large
mass. As we approach the end of a smaller piece, the magnetic field has no place to go.
Sometimes it tends the fold back on itself or change directions as we get to or enter a
corner, come to the end or exit of a piece, or in a deep groove. When this happens,
what we observe is the droplets of metal from the end of the electrode being repelled or
pushed away from the molten puddle, the actual location you want and need them to
go. What's going on is the fact very similar to what happens if we try to force together
the poles of two magnets. If the poles are different then they are attracted to each other.
On the other hand, if the poles are the same they rappel or push apart. That is what's
going on in the weld puddle when we see arc blow occurring. the droplets of metal are
actually charged in a similar fashion to that of the workpiece and as such, the droplets
of metal are propelled away from where the work or the path of the electricity in the arc
is going. In reality, the droplets seem to go anywhere but where you want the to go.

So how do we solve it?


One of the quickest and easiest ways is to break the arc and stop welding. Restart and
you may see it go away. Some people try to drive the electrode closer or deeper into the puddle with limited
success. Usually this produces more spatter and sparks to clean up later.
On the other hand, some people feel that changing the rod angle abruptly,
approximately 90 in the opposition to the current direction of travel, and then returning
rapidly to that location sometimes is an aid.


Sometimes we need to consider the direction of our travel. Would it have been better to
weld out of the corner instead of into the corner? In general, welding out of the corner seems to have less problems than if we weld into
the corner. Other times, moving the work lead can solve some or all of the problems. Other folks choose to switch to a different electrode and select alternating current which totally eliminates the problem. Always remember the arc blow only occurs on direct-current or DC welding.
Each weldment and part is different, so it may need the application of one or more of these techniques to create a solution that works for you. Always remember, having the proper knowledge, is just as important as the proper equipment.


What do you guys think of articles like these?

undercut
11-25-2012, 02:03 PM
It's a good subject. I've seen it for myself when I was welding too close to my welding magnet. Quite a sight to see(!) and if someone hasn't read about it, they will definitely be puzzled and will probably go through a few different electrodes trying to see if that is the culprit.

Gadget
11-25-2012, 02:37 PM
Good article and more of similar articles would be a good thing.

roberts56
11-26-2012, 06:51 AM
Thanks so much Simon for this very informative and interesting article, specially for me since what I have are two stick welders only, one AC 300 amp and another a DC 200 amp Inverter. I have been reading a lot about SMAW and would sometimes wonder what the heck is that "Arc Blow" that keeps on appearing in some topics. I love using my DC welder now more than the AC welder due to its soft start, deeper penetration, ease of use and portability. I may have or have not experienced this arc blow, I just don't know and haven't seen the difference when I start an arc or start applying welds. Can you perhaps expound more on this topic, I know lots of guys here would benefit from this additional knowledge specially with their DC Inverters.

This thread will bring lots of information direct from the more knowledgeable and expert people. :clap



Again, thanks for creating this thread !!! Two thumbs up for this !!! :2thumbs

undercut
11-26-2012, 10:07 AM
Thanks so much Simon for this very informative and interesting article, specially for me since what I have are two stick welders only, one AC 300 amp and another a DC 200 amp Inverter. I have been reading a lot about SMAW and would sometimes wonder what the heck is that "Arc Blow" that keeps on appearing in some topics. I love using my DC welder now more than the AC welder due to its soft start, deeper penetration, ease of use and portability. I may have or have not experienced this arc blow, I just don't know and haven't seen the difference when I start an arc or start applying welds. Can you perhaps expound more on this topic, I know lots of guys here would benefit from this additional knowledge specially with their DC Inverters.

This thread will bring lots of information direct from the more knowledgeable and expert people. :clap



Again, thanks for creating this thread !!! Two thumbs up for this !!! :2thumbs

I suggest you try it to see what it looks like. For one, it is cool to see. Secondly, it will allow you to recognize it when it happens so that you don't waste time scratching your head (like I did when I first encountered it!)

Put a magnet very close to where you want to put a bead and start welding. Hopefully you will see it right away. Pretty cool stuff!

arandall
11-26-2012, 11:31 AM
Arc Blow is news to me too. Thanks for bringing it up Simon.

LONGEVITY
11-26-2012, 02:19 PM
Arc Blow is news to me too. Thanks for bringing it up Simon.

Thanks to Scott Miner for sharing his expertise! I am hoping to have more from him shortly.