chris collister Jun 18, 2013:

By definition, welding requires two solid (ice, plastic, metal,...) surfaces to be in the liquid state such that perfect mixing occurs between the two liquids. On freezing, the two surfaces are "welded" together. In this sense you could argue that "bord fondu" is a bit redundant, though there are many types of weld: spot welds, friction welds, gas, electric, etc. on many types of material and in many mechanical configurations.
Maybe it is indeed just an edge joint, as mchd suggests.