“When stainless steel and aluminium-coated steel are welded together, a reaction can occur that compromises sealing integrity in the finished part,” explains Thorsten Schäfer, global engineering manager rigid heat shields, Federal-Mogul Powertrain.
“A recent design optimisation opened the door for this new welding process thereby eliminating the issue.”
The gasket in question comprises a thick steel distance layer aluminium-coated for corrosion resistance and to reflect heat, sealed on both sides by functional stainless steel layers, each with a sealing bead.
To avoid handling separate parts, all three layers are welded up, but this can create known issues with sealing uniformity because the aluminium coating can react during welding.
Federal-Mogul Powertrain’s solution is to have three holes blanked out of the distance layer and three dimples created in both of the sealing layers.
This ensures accurate location of the components, allowing the functional outer layers to be spot-welded directly through the dimples without affecting the material in the distance layer.