Voltage — What It Is and Why It Matters
Voltage in welding controls arc length and arc characteristics. In MIG welding (constant voltage process), voltage is set on the machine and determines the arc length and heat distribution across the weld bead. Higher voltage produces a wider, flatter bead with a longer arc. Lower voltage produces a narrower, more convex bead with a shorter, more focused arc.
In TIG and stick welding (constant current processes), voltage is not set directly — it varies dynamically with the arc length the welder maintains. Holding a longer arc increases voltage; shortening the arc decreases it. This is why arc length control is a critical skill in stick and TIG welding.
Voltage and amperage together determine heat input. The relationship between voltage and wire feed speed in MIG welding must be balanced — too much voltage for the wire feed produces a long, unstable arc with excessive spatter; too little produces a stubby, sputtery arc with poor wetting. Finding the sweet spot where the arc sounds smooth and consistent is the goal.
Frequently Asked Questions
How do voltage and wire feed speed relate in MIG?
They must be balanced. Increasing wire feed speed (which increases amperage) requires increasing voltage proportionally to maintain a stable arc. If you increase wire speed without increasing voltage, the arc becomes stubby and the wire stubs into the puddle. Too much voltage for the wire speed creates a long, sputtery arc.
What happens if my voltage is too high?
Excessive voltage in MIG welding produces a long arc, wide and flat bead profile, increased spatter, possible porosity from atmospheric contamination, and undercut at the bead toes. Reduce voltage until the arc shortens and the bead profile becomes appropriately convex with a smooth, consistent sound.