Trumpf and Gestamp have collaborated on developing a new industrial welding processThe demands placed on modern vehicles are increasing. Components need to be lighter, production and investment costs more efficient. At the same time, production processes are becoming increasingly complex, especially in car body construction.
Spanish multinational automotive component company
Gestamp has taken up this challenge. Thanks to
Trumpf technology, Gestamp has developed an innovative, industrial-grade laser welding process that addresses the very areas where conventional methods reach their limits — the fast and flexible joining of large, coated structural components.
Miguel Ángel Ferrández, material joining and R&D Tokyo and Bilbao director at Gestamp, said: "We rely on large structural components instead of many individual components in order to simplify industrial processes. This reduces complexity in final assembly, which implies more cost efficiency.”
Why larger components?In automotive production, the fewer components a vehicle needs, the more efficiently it can be manufactured and assembled. Gestamp is pursuing this strategy with its Ges-Gigastamping family – large-format structural components using hot forming from high-strength steels. These parts offer enormous advantages in terms of weight, stability, and crash safety, but place high demands on the joining process.
Mr Ferrández explained: “The challenge starts with the material. We process press-hardened steels with an aluminium-silicon coating (AlSi). This protects the component from corrosion but makes welding rather difficult. It was therefore necessary to replace traditional welding processes with an industrial laser welding process that offers greater speed and flexibility.”
Gestamp had already done the groundwork by developing the new G-Weld laser welding process. At the heart of the development is a G-shaped overlap seam specially designed for overlapping blanks and assembly components after forming. The welding process is more efficient, ensures more stable seams, and enables welding speeds up to five-times faster. However, unlike spot welding, laser welding required the AISi coating to be removed before joining. This additional process step negated the time savings. To achieve this Gestamp turned to the laser experts at Trumpf.
Mr Ferrández continued: “Our goal was to weld the components securely and efficiently without having to remove the coating in a previous process step. This was the only way we could streamline the process and improve component quality.”
Multi-focus makes the difference The challenge in laser welding coated components is that the two different materials do not bond homogeneously. During the melting process, intermetallic phases and alpha ferrite form, which are structural components that negatively affect the seam quality and the resulting structural mechanical properties of the component.
Marc Hummel, global business development manager of mobility at Trumpf, said: “The key to the solution lies in laser beam shaping – in Gestamp’s case, in the multi-focus optics option.”
With the multi-focus option, the laser beam is split into four individual beams, each with the same energy input. Each beam has a core beam and a ring beam — the latter calms the melt pool with its additional energy and prevents spatter formation.
The four individual beams mix the AlSi coating in a controlled and homogeneous manner in the melt pool, thus preventing the formation of intermetallic phases and alpha ferrite. The result is a stable seam with high strength and tensile hardness. Mr Hummel added: “You can compare it to stirring dough. The more stirrers mix the dough, the better it is at breaking up any lumps.”
For Gestamp, the new industry-compatible process strategy brings a number of advantages. Mr Ferrández said: "Thanks to Trumpf’s laser beam shaping, we achieve significantly higher speeds and better seam quality during welding. In addition – and this is very important for large structural components – we benefit from significantly better accessibility with the laser at unreduced process speeds. And last but not least, single-sided welding with the laser also gives us an advantage known as a semi-visible surface. The seam is no longer visible on the outside of the component.”
The new laser welding process has now been validated internally and for Mr Ferrández, one thing is clear: “The close cooperation with Trumpf was an important factor. From the very beginning, Trumpf was more than just a technology provider. Together, we developed a solution that has the potential to revolutionise the production of structural components.”