Mash welding is a variant of resistance seam welding in which the sheets to be joined are overlapped by a distance of only about 1.5 times the sheet thickness (t). The face of the welding wheel is wider than this contact width and during welding the material is crushed to a final thickness typically 1.4t. Some melting occurs, but the edges of the joint form a solid phase bond to eliminate the crevice.
This is of particular advantage for production of food or beverage containers through allowing hygiene requirements to be met. Welding current is continuous and higher frequencies are used for welding thinner materials. Welding speeds can be over 70 m/min when this process is applied to 0.2mm tinplate.