All forms of arc welding use electric current to generate the intense levels of heat necessary to weld metals together. You don’t need to be an electrician to understand the process, but the greater your knowledge, the safer and better off your welding will be.
A Quick Science Lesson
Electric current is created by the flow of electrons from a high electron concentration (positive charge) to a low electron concentration (negative charge). The flow of electricity though a conductor generates heat, the level of which is based on the amount of resistance offered by the conductor.
An arc welder discharges electricity into the air (via the gap between the electrode and the metal being welded). Air offers heavy resistance to electrical conduction, and therefore generates a great deal of heat.
Units of Measure
Electricity is measure by voltage, amperage and wattage.
Voltage (Volts) measures the potential electric pressure. Voltage determines the distance an arc can travel across the gap between the electrode and the metal – the higher the voltage, the further the gap.
Amperage (Amps) is the volume of electrons flowing through a conductor, and controls the size of the arc.
Wattage (Watts) measures the amount of electrical power in the arc, and determines the depth and width of the weld
Welding Power is supplied by:
- Constant Voltage (CV) maintains the arc’s voltage, despite changes in the current flow
- Constant Current (CC) maintains the same output, despite the changes in the currents flow
- Open Circuit Voltage determines the voltage at the tip of the electrode before the arc is activated
Welding power is sourced through the following three processes:
- A mechanical generator produces power from a gasoline or diesel fuel engine.
- A step down transformer changes high voltage alternating current into low-voltage high-amperage current.
- An inverter changes current with solid state electronics, minus the heavy weight of a transformer.
Currents used for welding include:
- Alternating Current (AC), which changes the positive-negative electron flow twice per cycle and creates an even current build-up
- Direct Current (DC), in which electrons flow one direction – a rectifier is used to convert DC current into AC current, and direct current is specified by one of two polarity options:
o Direct Current Electrode Negative (DCEN), in which the electrode is negative and the workspace is positive
o Direct Current Electrode Positive (DCEP), in which the electrode is positive, and the workspace is negative (widely considered to be the best option for arc welding purposes)
Duty Cycle is the level of continuous running time for a given power out-put of a welding machine, measured in ten minute intervals. Welding machines produce high internal heat, and require cooling time. A 60% duty cycle indicates a machine can run continuously for six minutes, and then requires a four minute cooling period.