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MIG Welding Basics - Gas Metal Arc Welding (GMAW)

Shielding Gas Metal Arc Welding (MIG)

Introduction

Gas Metal Arc Welding (GMAW) also known as Metal Arc Welding (MIG).MIG Welding is used extensively in the industry due to it being easily operability, its ability to weld any kinds and any thickness of metal.MIG welding also is often used in manufacturing, automotive including aeronautic industries, aside from carbon steel.MIG welding also can be used to weld aluminium and stainless steel.MIG electrodes are provided in the form of different wire loops with different welding electrodes in the shape of rods.
Shielding Gas Metal Arc Welding
Picture: MIG Welder Machine

Basic Principles of MIG Welding

In MIG welding, electric arc is formed when the end part of the electrode wire touches the base metal.The arc create heat that will melt the base metal and electrode’s end.The melted electrode mixes with the base metal, shaping the molten pool and infused when cold to form a welding notch.Electrode wires without covering is continuously provided ( in the form of loops) through the wire feed unit.The shielding gas protects the arc and the molten weld pool from the atmospheric air.

Welding Machine and Accessories

Among the parts and functions of MIG welding machine: 
  • Control Panel

control panel
Picture: Control Panel
The control panel placed the adjustment knob to adjust the output speed of the electrode wires and shielding gas.The volt and current adjusters are also on the control panel.
  • Torch (Gun)

Torch or “gun” functions in sending electrode wires, shielding gas, and current to the welding area. There is a switch to start and stop the arc, cutting of the shielding gad an welding electrodes.
MIG torch
Picture: MIG Torch

Welding Nozzle

Torch Nozzle
Torch nozzle
The torch’s nozzle assign the electrode wires and shielding gas to the welding area.It is mae of stainless steel and can be detached from the torch.There are two kinds of nozzles, that is water-cooling torch nozzle and air-cooling torch nozzle.Air-cooling torch nozzle is used for light works with current less than 200 Ampere, while water-cooling torch nozzle is used for heavier works with current more than 300 Ampere.

There are two kinds of wire feed mechanism used by the torch nozzles, which are the push-type and the pull-type.While welding, observation must be made on the torch nozzle especially the orifice, nozzle and chip as there might be sparks that sticks to the torch nozzle until it fills the nozzle, which will affect the smoothness of the welding process.
applying gel


Anti-stick gel spray used on the torch nozzle can help making the sparks easier to rub off.

Wire Feed Unit

The motors in the wire feed unit will automatically procure the electrode wire from the wire loops into the arc nozzle blowpipe.There are several speeds for the wire procurement, which can be alter using the adjustment switch on the control panel. There are two kinds of wire feed; one that is built within the power source or as a different unit from the welding machine. The separated unit is best used to weld in wide areas.

Shielding Gas

wire feed unit
Picture: Wire feed unit
Shielding gas used in MIG welding are argon, helium, mixture of argon and helium, and carbon dioxide.

Control Panel Adjusters, Controllers and Flow Meter with its adjustments


The flow of shielding gas from the cylinder to the welding are is adjusted from the control panel, controller and flow meter. Inert gases continuously flow out to protect the molten create area of the welding even when the nozzle switch is at ‘OFF’ when the welding stops.The duration of the gas production is adjusted on the MIG welding machine’s control panel.The shielding gas cylinder controller contains the pressure gauge that shows the gas pressure.


gas flow meter
Picture: Gas flow meter
The adjustment knob on this controller will determine the pressure of the gas coming out of the cylinder. The rate of gas flow on the welding area is measured in litre per minute. The rate of production is adjusted by turning the adjustment knob on the flow meter. The ball bearing will float and the metered glass tube to show the rate of flow for the produced gas.





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