[Maxx]

I've been welding for some time now and always hate losing a great weld to arc blow either on an H beam or wide fillet
weld over head. Ok usual practice. Use run off piece at end of weld, Go left then right and fill in ends, Wrap ground
cable around beam and pass electrode cable through it to counter act magnetic forces, Use AC when you can.
Sometimes these work and sometimes they don't depending on position and item being welded.
I was wondering if anybody had any other unique tricks.

While I'm here I'll add another one. Still related to ark (gas) blow, when welding pipe primarily w/ stick dose it matter which side of slip on flange you weld first? Inside or out to prevent gas build up in weld any size but primarily 4" - 12"

Any tips would be of interest Thanks

[Otto Nobedder]

I'd think "arc blow" a myth, if I didn't know so many people who speak of it.

I'll reserve comment for now, to see what comes up.

As for gas-blow, I always weld the outside of a slip-flange first. That's the critical weld, for structure and integrity.

If I'm required to weld the inside, I'll do 99%, pause a minute for the metal to cool, and "button" the closure.

Steve S

[Coldman]

I don't do a lot of stick welding. I only ever get arc blow on larger square tubing say 4" and upwards.
Going the other way fixes it just about every time. On the odd occasion it doesn't I just cuss and keep going.

[GreinTime]

I have never heard of someone putting the ground around the work lead. Interesting. You've piqued my interest.

[rake]

Arc blow is not a myth. Far from it. Back in my shipyard days I saw joints so magnetized that you could fill them with
MT powder and not a spec fall out. Only guaranteed sure fire way to defeat magnetism is to heat the metal above 1550F.

[weldin mike 27]

Another way is to get a magnetic particle testing yoke and energise it on the joint. then sweep one leg away from the joint in a 90 degree arc. This will change the way the magnetic field flows.

BTW IMHO, heating the metal may work, but doing on the job may result in a pineapple being inserted where you really don't want one. Especially on low alloy quenched and tempered steels.

[jdl66ss]

Being inexperienced doesnt exactly help being able to join in the conversations here. So.......questions it is. Would anyone be able to define or describe this arc blow? Or gas blow?

[weldin mike 27]

Arc blow is caused by disturbance of the welding arc by errant magnetic fields. Naturally occurring mag fields are everywhere, and a generally not a problem. However sometimes, on steels of various types and shapes, and when welding in different areas weldments, the flow of these fields disrupts the DC arc resulting in undercut, excessive spatter, lack of fusion and general poor weld quality. Can be avoided by changing direction, and by some of the methods above. Does not effect AC welding because the polarity is constantly changing.

Gas blow refers to sealing of a closed area by welding, and the enclosed hot air/gasses escaping through the last part of the weld, pushing a blister through the weld.

Hope this helps.

[hillbilly welder]

here's an article from Lincoln
http://www.lincolnelectric.com/en-us/su ... etail.aspx hope this helps

[AKweldshop]

Being inexperienced doesnt exactly help being able to join in the conversations here. So.......questions it is. Would anyone be able to define or describe this arc blow? Or gas blow?

Watch this video mate.
Cover to cover.

Arc blow to me, is an erratic, uncontrollable arc.
https://www.youtube.com/watch?v=CW7I-ymfINU

[Coldman]

Being inexperienced doesnt exactly help being able to join in the conversations here. So.......questions it is. Would anyone be able to define or describe this arc blow? Or gas blow?

I didn't say I was inexperienced. I said I didn't do a lot of stick welding. When I do, it is mostly pipe stands and pipe bracketing on site with RHS square tubing. Any shop fab work for machine bases etc I get out the mig.

There are plenty of methods of dealing with arc blow. If I can't go the other way I just plough on. For pipe stands and brackets it does not matter so I don't waste my time trying.

Anyone can google "arc blow" and get all the definition they need.

You asked for comment, I took the trouble to share mine with you. Maybe its only worth 1c, sorry I misunderstood you but I thought you were interested in real life knowledge not wikipedia definition.

[wheresmejumper]

Lorch,a pretty big German welder manufacturer,have tried to solve this problem,and sell a few dc inverters that have small amounts of ac current superimposed over the dc current,to help nullify the arc blow.
welding pipe mostly,i dont experience arc blow.i was taught by an old hand though to never prep a carbon pipe for a tig root with anything steel.no files,wire wheels or steel based abrasion paper/wheels.repeated contact between the two will very slightly magnetise the pipe,enough to attract the filler rod a little occasionally on open roots.

[Coldman]

Woops, big retraction here. I just realised my response was not to the OP (I though I was being given the finger and got my hackles up).
Apologies to jdl66ss and everyone else.
Time for a chill pill.

[Otto Nobedder]

Yep, Coldman,

Just a discussion, and any one of us can be right or wrong, or some of each...

No apology or retraction required.

Steve S

[Braehill]

I think he was talking about his own inexperience, not yours. I had to go back and check to see if Gamble was at it again.

Len


Sent from my iPhone using Tapatalk

[Maxx]

Thanks for the interesting discussion. Nothing new or earth shattering just an issue we all have to deal with when welding on H beams, Corner joints,and 2" thick veed out braces etc. Especially like the video from GE trying to push there AC welding machine 600 AMP whoa must need a hefty breaker for that baby.
Thanks again for all the input.
MD

[Maxx]

I'd think "arc blow" a myth, if I didn't know so many people who speak of it.

I'll reserve comment for now, to see what comes up.

As for gas-blow, I always weld the outside of a slip-flange first. That's the critical weld, for structure and integrity.

If I'm required to weld the inside, I'll do 99%, pause a minute for the metal to cool, and "button" the closure.

Steve S

Hey Steve Good tip for welding the flange.
Also just for the heck of it whenever I weld with my Miller Air pak at 200 amps or above and cables are laying all over the floor the magnetic forces will draw all the grinding dust to follow those cables where ever they go and if I weld 300 or more amps and I don't unwind the cables off the post their mounted on in the truck they will jump like a son of a gun because of that magnetic force as well as all that current coursing through them but if I lay them on the ground even at 500 amps they don't jump.
They may start to melt - Hah but that's another subject.
I also liked another reply (sometimes all you can do is curse and keep moving on) I'll add and grind weld and grind again till you get it right.
Thanks again for you input hope to talk again.
MD

[DennisZ]

I'd think "arc blow" a myth, if I didn't know so many people who speak of it.

I'll reserve comment for now, to see what comes up.

As for gas-blow, I always weld the outside of a slip-flange first. That's the critical weld, for structure and integrity.

If I'm required to weld the inside, I'll do 99%, pause a minute for the metal to cool, and "button" the closure.

Steve S

Hey Steve Good tip for welding the flange.
Also just for the heck of it whenever I weld with my Miller Air pak at 200 amps or above and cables are laying all over the floor the magnetic forces will draw all the grinding dust to follow those cables where ever they go and if I weld 300 or more amps and I don't unwind the cables off the post their mounted on in the truck they will jump like a son of a gun because of that magnetic force as well as all that current coursing through them but if I lay them on the ground even at 500 amps they don't jump.
They may start to melt - Hah but that's another subject.
I also liked another reply (sometimes all you can do is curse and keep moving on) I'll add and grind weld and grind again till you get it right.
Thanks again for you input hope to talk again.
MD

What on earth do you weld with 500 Amps????

[weldin mike 27]

Maybe its 500 "ants" that's why the cables move around, the ants are messing around with them. @_@