DeltaSpot® is primarily suitable for steel and aluminum sheets. It can also be used in combination with commonly used anti-corrosion coatings and for black/white joints. The latter are unalloyed or low-alloy steel joints with non-rusting, high-alloy steels. Different material combinations and thicknesses are also possible. Examples include deep-drawn steels in combination with chrome-nickel steels or Usibor, as well as material combinations with coated steel sheets and aluminum. Development focused mainly on the applicability of the process for high-alloy steel joints as well as magnesium joints. These materials provide the greatest potential in modern lightweight construction. Two-sheet or multi-sheet joining of practically all the above material combinations can also be achieved. The same welding gun can be used to weld different sheet thicknesses and material combinations simply by changing the process tape.
The high efficiency level is produced by additional process heat that arises as a result of the internal resistance and the contact resistances of the process tape. For traditional resistance spot welding of 2 x 1.0 mm AlMg3 sheets, a current of 35,000 A to 40,000 A is required. The process tape reduces the current to 16,000 A. The low welding current and the individual adaptation of the process tape to the welding process permit controlled heat application and allow the position and shape of the welding point to be controlled. This is described in further detail below.
Three-sheet joints (two thick sheets and one thin sheet) are problematic for traditional spot welding. The welding point forms in the area of the thicker sheet and does not cover the thin sheet sufficiently. To compensate for this effect, the additional heat applied by the process tape ensures targeted control of the welding point depth. This means it is possible to compensate for the reduced amount of heat in the area of the thin sheet by using a process tape with greater resistance. In this way, the welding point is displaced sufficiently towards the thin sheet. At the same time, the shape of the welding point is symmetrical and will now show increased volume in the area of the thinner sheet. With aluminum, there is the problem of high electrical and thermal conductivity and a correspondingly low electrical resistance. The accompanying limited heat generation can also be compensated for by selecting the correct process tape. In contrast to traditional spot welding of aluminum that until now has been virtually impossible to achieve, the new resistance spot welding process can successfully weld aluminum for the first time.