Thread: Overwelding and distortion

In the correct sub forum this time.
Hi Guys
Here is some more info to help the up and coming welders among us improve the appearance and performance of their beads . The info concerns fillet weld or corner welds as some would call them and butt welds.

Weld metal as it cools shrinks or contracts. The harmful effect is that it can pull a welded component clean out of its intended alignment by many degrees when uncontrolled. It’s a thing one can’t entirely prevent but certainly harmful effects can be can be minimised.
As in any endeavor ,it is possible to over do things and welding is no exception.

The overall potential strength of your weld is limited to the strength of the piece of material it is welded to.In turn it is the thickness of this material that allows a given strength factor.

Building up a weld thickness greater than the thickness of the metal element that that weld adheres to does nothing for it other than to impose greater shrinkage forces and stresses than the metal would ordinarily have to endure from a standard weld

Unfortunately what we have to imbue in a beginner welder is that in the case of deposited weld metal, MORE is NOT STRONGER.

Welding engineers have calculated that the fillet leg lengths of a fillet need only to be the same dimension as the thickness of the metal welded to, achieve equal (or slightly better with some electrodes)

What are the leg lengths ,I hear you ask? The leg dimensions are the vertical and the horizontal dimensions of the triangular fillet bead.

To give you some more welder lingo to use we refer to the outside edges of your bead as the toes. Where the weld metal meets the parent metal is the toe of the weld bead. Draw an imaginary line between the bead toes while looking at it in cross section and you have the recommended shape and amount of bead that needs to be laid.

Any welded material above that imaginary line adds unnecessary volume which shrinks on cooling and pulls the toes and connected parent metals towards each other.

This state of affairs also applies to the other common joint in welding, the butt joint.Causes and cures are the same. To avoid confusion the sizing for butt welds is determined by the plate thickness.

As properly welded material is generally stronger than the parent metals it follows that under overstress the parent metals will fail first.In destructive testing it is seen that the weld deposit tears clear out of the parent metal in most instances.
Therefore if the parent metal is the weak link any amount of strength applied as weld is wasted as the joint will fail in the weakest place.

again see the pic
Grahame