The biggest reason, of courrse, is to weld aluminum. But other than that, Kevin had to go out and do a little research. The biggest consensus is that it’s the best choice for magnetized steel because the AC isn’t affected by the steel’s magnetic field.
Kevin also said that arc welding rod like 7018 AC, which is specifically made to use when AC welding, welds “like butter.” It also creates a really pretty looking weld. For what he is doing -making art – it’s all about the way it looks.
To test if AC really does work better when welding magnetized steel, Kevin decides to set up a piece of scrap steel with welding magnets on both sides and weld with some 7018 DC and then some 7018 AC and see if it makes any difference if you weld with 7018 AC or DC.
He welds with DC first, then the AC. You can even hear the difference between the two.
Then Kevin shows the welds. The slag is coming up off the welds nearly all in one piece – that’s one of the reasons he really loves welding with 7018 welding rod. He removes the slag and brushes away a little soot and you can see the two welds clearly.
The DC weld is a little misformed, while the AC weld is nice and straight and smooth and pretty looking.
So for magnetized steel and welding aluminum, you’ll want to use AC when stick welding. Otherwise, stick with DC.
Why use DC otherwise? Kevin says it’s theory, but because you’re running a positive and a negative in DC, the positive is going to get attracted to the negative. So when you’re actually welding and the rod is burning away, it’s going to want to attract to the ground, pulling the weld in for better penetration. With AC, the current is going back and forth, back and forth, so Kevin believes you don’t get quite as good penetration as you do with DC.
Don’t miss the ending and Kevin’s shocking revelation!