One of the more difficult welds to make is a fillet weld one which runs along the boundary between two pieces of metal being fastened together at right angles.One piece of metal is mounted edge on to the flat surface of another piece of metal in a tee joint, whereas if the metal pieces are joined at the edges,but with a right angled position rather than a flat position, this is a corner joint, not a tee joint.
Making a fillet weld with a MIG welding machine is a good example of how the settings of these devices need to be adjusted to create the type of weld that is needed for the specific circumstances you are working in.Fillet welds are full-bodied welds with a rounded cross-section they can best be described as “compact” and “stout”,because the weld bead needs to be thick enough to provide equal tension against the pull of both pieces in order to anchor them securely together.
The section of weld in contact with the base metal is known as the “leg”, and in the case of a fillet weld, there are two legs on each weld bead, again at right angles to each other.These legs must be of equal length when a fillet weld on a tee joint is involved.If they are of different lengths, then the strength of the weld’s hold on each piece of metal will be different. This,in turn,will cause stresses to have an unequal effect on the two legs of the weld, possibly causing it to snap under normal work loads.
Adjusting the MIG welder settings
The first adjustment you are going to want to make when welding a tee joint with MIG welding is to increase the voltage.Although this would ordinarily broaden the weld,the special nature of a tee joint makes this necessary even when you want to lay down a fillet of moderate width.
The two pieces of metal in close proximity closer even than in other joints,where the metal lies at different angles and is therefore further from the weld mean that electricity is bled away from the weld bead rapidly.You need more power for this reason in order to produce a joint of ordinary strength a low voltage would produce a cool arc and thus poor penetration and a flabby weld apt to break at the slightest provocation.
A MIG weld on a tee joint fillet should usually be carried out with a pushing,rather than a pulling, angle of welding.When you reach the end of the joint,do not remove the gun from the welding pool too quickly this could expose the still-molten metal to air as the shielding gas is taken away,resulting in oxidation and an ugly,possibly weakened joint.