My son’s welding class has me 2nd guessing polarity

[scaredsuccotash20]

My kid's taking a welding course and asked me why some rods run better on DC+ and others on DC−. I thought current was current no matter the direction, so why does flipping the leads change how hot the weld gets

 

[SparkyCool]

Good question! Switching the leads changes the heat. With DC+, the workpiece gets hotter for deeper welds. With DC−, the rod gets hotter, melting it faster but without as much depth.

What rods is your kid using? Some work best with one polarity. Also, what kind of welding is he doing?

 

[Cov3ll.WG]

My kid's taking a welding course and asked me why some rods run better on DC+ and others on DC−. I thought current was current no matter the direction, so why does flipping the leads change how hot the weld gets

Just to add to @SparkyCool's answer.. so basically, the direction of the electron flow dictates where the majority of the arc's heat gets concentrated. That's why flipping the leads makes a noticeable difference in how a rod performs vs how the weld metal behaves!

 

[scaredsuccotash20]

Perfect! Understanding the electron flow finally makes the difference in heat concentration click for me. He's just running beads on a flat plate with 6013 and 7018 rods. So, does welding with AC alternate the heat focus between the rod and the workpiece?

 

[Bumblebee]

Perfect! Understanding the electron flow finally makes the difference in heat concentration click for me. He's just running beads on a flat plate with 6013 and 7018 rods. So, does welding with AC alternate the heat focus between the rod and the workpiece?

Yep, AC keeps flipping the arc direction, so the heat sorta balances out between the rod and the metal. It's not as focused as DC, but it's more forgiving for dirty or rusty steel.

 

[scaredsuccotash20]

So AC's like the middle ground when you're not chasing depth or speed. He's mostly practicing indoors on clean stock. DC's been working fine but they do throw in AC sessions too. Do you find AC makes a messier bead or just more spatter in general?