The Future of Submerged Arc Welding
In Colorado, constant voltage (CV) DC polarity is still used in most submerged arc (sub-arc) applications. It is still used, in large part, because the systems are old and robust, living long lives. Reverse (DC+) polarity is most common because it provides maximum penetration and arc stability. However, its seldom used counterpart, straight polarity (DC-), provides the highest deposition rates but very limited penetration. Since its introduction in 2003, digital square wave AC technology has been slowly but steadily replacing DC. The benefits have been proven and the price of the systems has declined substantially.
Why Digital Square Wave AC is Better Than DC
There are many reasons, digital square wave AC is better than DC. But, the biggest is based on the fact that AC output, which alternates between DC+ and DC-, gives you the benefits of each polarity. You can adjust the amount of TIME spent in each polarity. And even more, offset the current AMPLITUDE on the + and – side. Output frequency is not fixed but, rather, is adjustable to tailor the weld ripple and bead shape. Because the AC wave is square and has no vertical “through the zero point” slope, the switch between the two poles is instantaneous and the arc is remarkably stable. Unlike DC polarity, AC output does not produce a magnetic phenomenon called ARC BLOW that wreaks havoc on both arc stability and bead quality. Lastly, the AC technology comes from a highly efficient inverter power source that will substantially lower your power bill.
What AC Machine Should I Buy?
What AC machine should you buy? It depends. Lincoln Electric’s Power Wave AC/DC1000 SD is more flexible and has more bells and whistles for diehard tinkerers while Miller Electric’s newer 100 & 1250 SubArc Digital Series is more user friendly and easier to tune in as it comes with 12 preset wave shapes with an optimal output frequency attached to each.
Regardless of the system you choose, once you try AC sub-arc you will likely throw your DC system in a corner.