LZH and partners develop laser-based joining process for thick mixed joints

Lightweight construction with mixed steel-aluminum compounds is a major topic in the automotive industry.

To reduce fuel consumption and CO2 emissions in the shipping industry, such mixed compounds also are being used increasingly in shipbuilding. With these, however, completely different material thicknesses come to bear. In the joint research project LaSAAS, the Laser Zentrum Hannover e.V. (LZH) and nine partners have developed a laser-based joining process for thick mixed joints.

Ship hulls made of steel and aluminum alloy superstructures are used primarily in yacht construction. Such material combinations reduce the overall weight and lower the center of gravity of the ship, thus stabilizing it. Via an adapter, the two different metals are joined securely and with a high mechanical load capacity. This adapter is conventionally manufactured by explosive plating, a complex and costly joining process. The LaSAAS project has resulted in the development of a laser welding process with integrated welding depth control to manufacture such adapters quickly and flexibly.

Thus, new design options for these connection elements can be realized. Under static load in the tensile shear test, the adapter pieces manufactured in this way achieve similar strength values as the explosion-proofed adapters. For example, the yield strength of the welded aluminum alloy is exceeded by 52 percent.

In the process, the welding depth is actively controlled via the laser beam power, which minimizes the intermetallic phases between the steel and the aluminum alloy. This allows mixed joints to be welded with relatively high seam quality, especially with varying thicknesses of sheet metal.

LZH’s partners in this project were the Fraunhofer Institute for Structural Durability and System Reliability, Druckguss Service Deutschland GmbH, Hilbig GmbH, LASER on demand GmbH, Precitec GmbH & Co. KG, Scansonic MI GmbH, TRUMPF Laser- und Systemtechnik GmbH, Fr. Lürssen Werft GmbH & Co. KG, and Meyer Werft GmbH & Co. KG.