Lamelle is normally a slat, which is similar in cross section (but not length) to the strip used in one type of deposition welding. Here, the strip is in the form of a very narrow coil which forms the electrode. The strip is melted by the electric arc (as it is unwound from the coil) and the metal is deposited on the substrate (if this type of welding is being used to build up a surface) or in the V notch of the prepared edges of the two pieces (e.g. plates) to be welded together. In this type of welding, strip electrodes (rather than wire electrodes) are used if there is a very large V notch to be filled.

Having said all that, I have not actually seen "Lamelle" used in exactly this context, hence my medium confidence level.