MAG Welding - Plug Welding
1. Plug Welding
1.
Plug hole drilling:
Drill holes for plug welding in the upper work panel.
To ensure adequate weld strength, the proper hole diameter must be chosen based upon the metal thickness.
Use 0.8 mm (0.031 in) MAG welding wire equal to or greater than lowest tensile strength of the parts being welded to ensure adequate weld strength.
Plug hole diameter (reference)
Thickness
mm (in)
Less than
1.0 (0.039)
1.0-1.5
(0.039-0.059)
1.6-2.3
(0.063-0.091)
Hole
diameter
? mm (in)
6.0 (0.24)
8.0 (0.31)
10 (0.39)
2.
Clamping weld location:
Use vise grip type pliers to tightly clamp the upper and lower panels together.
Use a hammer to correct any deformation and ensure a tight fit between the panels.
3.
Making the plug weld:
Hold the torch firmly at a right angle to the plug welding hole.
Move the torch in a circular motion along the hole inner diameter to weld it closed.
Check penetration depth and ensure adequate penetration of the bottom panel.
4.
Plug weld inspection
If the ripples (round marks) appear on the bottom panel due to the welding heat, weld penetration is sufficient.

2. Bead Shape
Bead shape
Example of typical faults:
Lack of penetration resulting in insufficient strength.
Insufficient welding current.
Though penetration is sufficient, if the beads protrudes from the panel too far, it will take longer to grind smooth.
<Good Example>
A moderate bead height