Ac / Dc

[larrynjr]

I remember a thread that mentioned that having the ability to stick weld on DC helped in magnetic applications. I was wondering how often those situations might occur or what other applications you'd want / need to use DC for. I was at Lowe's the other day and they had a Lincoln 225 tombstone for around $269 which seems like a decent price to me but it is only AC.

[Thomas Dean]

Welding on magnetic material use AC.

[larrynjr]

OK, bad memory on my part but what are the applications that you'd want / need DC +/- for?

[Jose Gomez]

Direct current provides a much quieter, more stable arc, with much less spatter on the finished weldment. It is the preferred setup for most serious welding, aside from a few odd situations (such as severe arc blow), and tig welding on aluminum (where the positive side of the AC cycle is needed in order to break through the oxide layer covering the surface of the aluminum). The popularity of AC only machines is due to their low price tag and near indestructibility, which are both great if you don’t burn rod all day. The price of an AC/DC machine is typically 1.5 to 2 times that of an AC only unit, but if you plan on welding all day you might appreciate the increase in control provided by A DC machine. Don’t get me wrong... AC machines work, but DC is a whole lot friendlier.

[irnsrgn]

the advantage of a DC machine, especially an engine driven one like the SA200 Lincoln Pipeliner is the abiltity to use High Amperage and Low Open Circuit Voltage or Low Amperage and High Open Circuit Voltage to get basically the same heat, but with completely different Arc Characteristics.


And Arc Blow is not that big a problem, any old time welder usually knows how to counteract it. see http://www.iforgeiron.com/forum/f64/...-welding-4398/ post #15

[larrynjr]

Thanks, Jose and irnsrgn that was exactly the info I was looking for!

[Dave M]

Some types of rods are AC. or DC. only. I am a bit rusty on stick welding but I think that DC. reverse polarity for welding over head and out of position with 5 P rod was the best way. I thought that it penitrated rust and paint better and that DC. the welds are cleaner with less splatter and you have better arc control and start. Lastly I think that DC. straight polarity welds thinner stock better. The down side is stick machines and tig machines that do both AC/DC are almost always twice as much money. The good thing about AC. only machines they are almost imposible to kill.

[arftist]

These day there are ac versions of most rods ( 7018, 308-16,etc) and 6011 runs great on ac and is a good all purpose easy to use rod, But If possible, with the dc machine, a tig torch can be hooked up for scratch start tig. Good for most tig exept Al. Look for a torch with a gas valve in the handle. The extra money for the dc machine will be paid back in cheaper rod cost.

[Pipeliner32]

Good info, Thanks, I have been thinking about the AC and DC issues myself