Low heat input and a solution for the brittle intermetallic phase

Steel and aluminum are an ideal combination in lightweight construction. Where strength is required, steel is used. Wherever weight is to be saved, aluminum takes over. Particularly in the automotive industry, lightweight yet safe car bodies can be produced in this way.

The challenge of the intermetallic phase

There is, however, one crucial point in the welding of aluminum and steel: the two materials tend to form a brittle intermetallic phase. Cracking and component failure may be expected particularly when, for safety reasons, steel is used in automobiles instead of aluminum.

The heat input is a key factor

The size of the brittle intermetallic phase depends directly on the heat input: The higher the heat input, the greater the intermetallic phase. And because of the different physical properties of the metals, a high heat input causes further problems. Component distortion is just one example.

New approaches needed

At this point, many otherwise proven joining processes reach their limits, so that mechanical joining processes with the corresponding disadvantages have, so far, primarily been used for joining steel and aluminum. For this reason, we have been looking for new approaches together with our research partner ISF. Our experience and numerous tests led us to a low-energy controlled short-arc process.

Include the intermetallic phase

But the process itself is only part of the solution. The filler material used is at least as important. We use a low-melting, zinc-based wire. It not only allows low heat input but also ensures that the brittle intermetallic phase is detached from the steel sheet and deposited in a ductile zinc matrix.

Robust process and high strength

The process which we developed in cooperation with the ISF achieves a joint strength that is on the same level as the aluminum base material. Moreover, the process is more robust when using a zinc filler material, compared to aluminum-based filler materials. It is less sensitive to fluctuations and offers a significantly larger usable process window.

Integration into the automotive industry – feasible without large investment

With all its strengths, the process can also be integrated into production without major investments - especially in the automotive industry. The zinc-based filler material can also be used for steel-steel joints, also attaining the base material strength. This way, different materials and material combinations can be joined on one system - even with only one-sided accessibility.

Ready to be used in your production

The complex and extensive series of tests in the joining technology laboratory have proven: Steel and aluminum can be joined reliably and with high strength using the controlled short-arc process and a zinc-based filler material. Therefore, secure your competitive advantage and resort to the know-how of the technology leaders.

Together with you, we would be pleased to check where you can safely join even lighter constructions in your production using the new process. We then select the suitable system with you and determine the optimum process parameters for your joining task between steel and aluminum.