Basic Gas Metal Arc Welding Operating Variables

Size and Type of Filler Metal: Dictated by the size and type of the metal being welding. Match the electrode type to the base metal. Use the smallest electrode that is appropriate for the job. Electrode size has a direct effect on the size of the finished weld.

Operating Variables: Factors that can effect the welding arc. Factors that can have a direct effect on the quality of the finished weld. In order to create consistently good welds, the welding operator must know the welding variables at play and the effect of the welding variables on the finished weld. Ultimate goal is to know and control the following variables.

Characteristics of Shielding gas: Type of shielding gas being used has a direct effect on the arc and penetration characteristics. Carbon Dioxide and Argon or Helium based gasses can change the structure and appearance of the finished weld. Choose the shielding gas that best matches the specific application.

Gas Flow Rate: Adequate gas shielding is essential for creating sound welds. A standard setting is 15-20 CFH flow of shielding gas. However, certain conditions may dictate an increase in flow rate.

Travel speed: Has a direct effect on bead size, penetration and appearance. In general, travel speed should be adjusted to keep the welding arc on the leading edge of the molten puddle. At a given current density, slow travel speed will provide greater weld build-up and less penetration. Excessive travel speed will result in less build-up and poor penetration. The goal is to keep the arc at the leading edge of the molten puddle and use a travel speed that produces the desired size weld. NOTE: Finished welds should be 10 times the electrode diameter in width.

Voltage Settings: Arc voltage dictates the mode of metal transfer (type of welding arc). For the short circuit transfer, the voltage setting should be high enough to ensure consistent melting of the electrode, without forming a ball on the end of the electrode. A voltage that is too high will result in “stubbing” or inadequate melting of the electrode which produces an erratic arc, lack of fusion and poor weld appearance. Voltage settings are dictated by the type of transfer desired and the type and size of the electrode.

Wire Feed Speed and /or Welding Current The setting of the wire feed speed dictates the amount of welding current being delivered at the arc. All electrode typed and sizes have a minimum and maximum current density with the best work range falling somewhere in the middle. In general, any change in wire feed speed will effect penetration. Travel speed, bead formation, filler wire burn off rate and weld size and appearance are all effected by current settings. Wire feed/current settings are dictated by the transfer desired and the type and size of the electrode.

Electrode Extension: Also referred to as “stick out” is the amount of wire extending past the end of the contact tip. In short circuit transfer, increasing the electrode extension increases arc voltage and reduces welding current and penetration. Reducing electrode extension reduces arc voltage and increases welding current and penetration. Correct electrode extension is dictated by the type and size of the electrodes and the mode of metal transfer being used.

Gun angle: The angle of the welding gun in relation to the axis of the weld and direction of travel. Welds can be performed using a leading (push) angle or trailing (drag) angle. In general, a trailing gun (drag) will produce welds having greater penetration and a high, narrow bead. A leading (push) angle will produce welds having less penetration and a wider, flatter contour. Maximum penetration is obtained using a 10 degree trailing angle.