Testing

Ultrasonic Testing for Groove Welds Magnetic Particle Testing for Fillet Welds (according to Jim Swanson)

Arc Academy MIG 1

inert gas

An inert gas is one that tends not to react. For this reason, inert gasses are often used as shielding gasses in welding. An inert gas may be made of compounds, whereas a noble gas (also non-reactive) is made of only one element.

open circuit voltage (OCV)

Open circuit voltage is the amount of voltage available when a welding machine is turned on and no welding is being done (50-100 volts). Once welding beings, the arc gap produces resistance, causing voltage to drop (to about 18-36 volts).

duty cycle

Duty cycle is the percentage of time that a welding machine can be on.

filler metal strength

Filler metal strength is classified 3 ways in relation to base metal strength.
(Note that tensile strength Fu, rather than yield strength Fy is compared.)

undermatching: FEXX < Fu

matching: FEXX = Fu

overmatching: FEXX > Fu

electrical characteristics

The size of a welding machine is given by current. 150-200 amps for light duty; 250-300 amps for manufacturing; 400-600 amps for construction.

The higher a welding machine's voltage, the more power output it will have at a given current:

Potential (volts) x Current (amps) = Power (watts)

Most households have 230 volts, single phase. A welding machine will run off of either single or three phase power. Converting phases is very inefficient.

Constant current (CC) machines are used for SMAW and GTAW processes. They can run off of AC, DC, or either, depending on the machine. CC machines keep current constant, even when voltage changes.

Constant voltage (CV) machines (aka constant potential) are used for all wire-feed welding processes, including GMAW and FCAW. They hold a narrow voltage range despite changes in arc length and amperage. CC/CV machines provide the most versatility and can be used with any arc-welding process.