Gasless versus normal MIG welders

When I tried out a reel of flux cored wire in my little SIP MIG box I took the cover off the welder and swapped the connections over. Having studied the circuit diagram it was plain that there was no need to do anything with the supply to the wire feed motor.

Regards Mark Rand RTFM

So Mark can you confirm that the polarity IS different then ? Just wondering why this is.

Andrew

: > >Is there any reason that I can't use cored 'gasless' MIG welding wire in : a : > >normal (ie gas equipped) MIG welder pre-supposing that the appropriate : > >diameter tip is used ? : > >

: > >Reason for the question: I have a normal cheepo MIG equipped for gas but : I : > >want to weld a bit of aluminium and don't have any argon to hand so cored : > >wire would be useful for the occasional job. : > >

: > >Is the polarity used the same between the two types as I've seen one : > >advert for a dual machine that implies something has to be changed over : and : > >above just disconnecting the gas bottle. : > >

: > >Andrew Mawson : > >Bromley, Kent : > >

: >

: > When I tried out a reel of flux cored wire in my little SIP MIG box I took : the : > cover off the welder and swapped the connections over. Having studied the : > circuit diagram it was plain that there was no need to do anything with : the : > supply to the wire feed motor. : >

: > Regards : > Mark Rand : > RTFM : : So Mark can you confirm that the polarity IS different then ? Just wondering : why this is. : : Andrew :

I believe you have to change the wire feed rollers as the cored stuff is usually larger than bare wire. Also I got the impression that for non ferrous work you really need argon gas and the cored wires are for Mild steel only Certainly my mini clarke mig welder works ok with gas on alloy and stainless steel but it could do wioth a few more amps and the disosable bottels run out pretty quickly ChrisR

from what i rember about mig welding Aluminium......... from my college days....

the polarity CAN be reveresed, this will put more heat into the wire than the parent metal, thus reducing the risk of blowing holes.

as i said... this info is only from what i rember of my 3 years night school welding classes, so it could be wrong but i did pass all 3 with distinctions.

Can anyone in the group confirm this???

In reality, it would be beter to use an AC tig welder to weld Aluminium, now that i can do...... as long as its big stuff lol

HTH -- From the Keyboard of Tim Bird Home Page

Photo Gallery

Gravity is not just a good idea........ ITS THE LAW!!! How can I soar like an Eagle.... When I am surrounded by Turkeys!!!!

Don't know why it has to be different, just read it in the book! Reversing the polarity does put a lot more heat into the work though.

Mark Rand RTFM

Yes Time I agree - it's just that the pockets are deep enough !

Andrew Mawson

Not sure if you can get cored aluminium checked science and practice of welding and no mention is made of changing polarity to torch nag and earth clamp live the new machine we've ordered for aluminium does cored wire and you don't alter the polarity for that either

the stuff we normally weld is between 1 to 3 mm aluminium I know with tig you can weld with a dc set and change polarity as this helps with breaking down oxidization but the torch gets hot can't say I've tried it mig is quicker and with a pulsed mig the weld looks like tig I had good results with a cheepo mig in my younger days which I think is due to the torch length being short the best person to ask is Ernie Leikuhler on sci.engr.joining.welding he seems to know the answer to most Q

Andrew Bishop

In a DC welding arc roughly 2/3 of the heat goes to the positive terminal and 1/3 to the negative terminal. In MIG welding the wire is normally positive to burn away the wire quicker. I seem to remember the advantage of AC for TIG welding aluminium was to break down the oxide on the surface (but it was a few years ago that I did my HNC in welding!)

Regards

Kevin

PS the term "gasless MIG" always makes me laugh -how can you have a metal inert gas welder without gas?

The Advantage of AC in TIG welding is that it alternates where 2/3 of the heat is going, as the oxide of Al melts at a lot higher temp then the metal its self, this means that the heat is equalised between the filler and the parent metal, reducing the risk of blow outs and giving a more even penetration

HTH

Tim -- From the Keyboard of Tim Bird Home Page

Photo Gallery

Gravity is not just a good idea........ ITS THE LAW!!! How can I soar like an Eagle.... When I am surrounded by Turkeys!!!!

No problems, but you will have to swap polarity

Fluxcore is steel only - ali you either have to get argon and a teflon liner. Tip size is usually next size up for ali, to allow for expansion. Using a small mig with ali is an exercise in frustration, although it can be done. Hard to get good penetration, although preheat helps geoff