Portfolio of Press Hardening Steels
How material, coating, and joining innovations reshaped automotive steel design from component optimisation to architecture-level performance
Over the past two decades, automotive engineering has focused on improving safety while reducing weight and CO₂ emissions in demanding production environments. As vehicle designs have evolved, and with the shift to electrification, this balance has become more difficult to achieve, with new powertrains and battery systems adding new constraints to body-in-white design and structural performance.
To address this, carmakers adopted a set of complementary technologies that respond to specific limitations in materials, processing, and design. Press Hardening Steels (PHS) provide higher strength while allowing more complex shapes, AlSi (aluminium-silicon) coatings keep the hot stamping process stable, and advanced joining technologies make it possible to use different materials within a single component.
As safety requirements increased and weight targets became more demanding, conventional forming methods reached their limits. Carmakers needed a solution that could produce complex shapes with very high strength while remaining consistent in large-scale production.
Press Hardening Steels (PHS) provide this balance. In the hot stamping process, steel blanks are heated above 900°C, formed while still ductile, and then quenched in the die. This creates a martensitic structure with very high strength. It also reduces springback, improves dimensional accuracy, and ensures consistent material behaviour.
These properties allow engineers to design complex, high-performance structures with predictable crash behaviour. This makes it easier to control intrusion resistance and energy absorption during impact. As a result, PHS became widely used for safety-critical components such as pillars, rails, and other anti-intrusion structures.
While PHS provides high strength and good formability, the hot stamping process introduces a key constraint. Heating blanks above 900°C causes oxidation and scale formation, which can reduce forming quality, increase tool wear, and affect process stability.
To solve this, the industry adopted aluminium-silicon coating. These coatings protect the steel during heating and forming, allowing stable processing without controlled furnace atmospheres or extra surface cleaning. This simplifies production and improves repeatability in high-volume manufacturing.
Within this approach, AS150 became the reference coating. It offers a stable heat treatment window, reliable resistance spot weldability, and consistent behaviour during forming and coating transformation. It also provides effective corrosion protection and good paint compatibility.
As a result, AlSi-coated PHS became the standard for safety-critical body-in-white components, widely used for their reliability and suitability for large-scale production.
As vehicle architectures evolved further, a single PHS grade could no longer meet all structural and crash requirements within one component.
Different zones of the same part must perform different functions. Some areas need maximum resistance to intrusion, while others must absorb energy through controlled deformation. Achieving both within a single structure requires more than uniform material properties.
To meet this need, the material portfolio expanded to support functional differentiation. Usibor® 1500 became the reference for high-strength anti-intrusion zones, while Ductibor® 450 and 500 provide higher ductility for energy absorption. This approach was extended with Ductibor® 1000, which combines strength and ductility for more demanding crash scenarios, and Usibor® 2000, which supports further weight reduction at very high strength levels. More recent developments, such as Ductibor® 1500, continue to extend the available design options.
This evolution allows engineers to define local behaviour within a single component, placing strength and ductility where they are needed instead of using uniform material properties.
Portfolio of Press Hardening Steels
As the material portfolio expanded, the next challenge became structural. Integrating different grades and thicknesses within a single component required a joining solution that could place material accurately, without relying on overlaps or reinforcements.
AlSi-coated PHS introduced a constraint. While the coating is essential, the aluminium in the coating affects weld quality, making conventional laser welding unsuitable for consistent, high-quality joints.
To solve this, a solution based on partial laser ablation was developed. The free aluminium layer is selectively removed from the weld edges, while the intermetallic layer is preserved and the coating remains intact elsewhere. This makes it possible to perform reliable laser welding before hot stamping, without reducing the coating’s protective performance during forming.
With the right filler materials, strong metallurgical control, and precise blanking and nesting, this approach led to the industrial use of PHS laser-welded blanks. It also allows material to be placed exactly where it is needed, reducing waste and improving structural efficiency.
With the ability to integrate different grades and thicknesses within a single blank, optimisation shifts from individual parts to the structure as a whole.
Instead of assembling multiple stamped components with uniform properties, engineers can design a single laser-welded blank that performs several functions. Strength and ductility are placed where needed, based on structural requirements, rather than added through reinforcements or extra parts.
This changes both design and production. The blank becomes a functional sub-component within the vehicle architecture, making it possible to address performance, weight, and manufacturability at the same time and at an earlier stage.
This is the foundation of Multi Part Integration (MPI). By bringing several parts into a single laser-welded blank, MPI reduces part count and simplifies assembly, while shifting optimisation to the level of the overall structure.
In this context, the laser-welded blank is no longer an intermediate product, but a structural module that directly contributes to vehicle performance.
The trend for Door Rings and MPI, a new standard for BEVs
Source: Keynote GDIS 2024
The evolution of PHS, AlSi coatings, and advanced joining technologies shows a consistent response to increasingly complex engineering constraints.
Each step solved a specific limitation and, together, drove the shift from individual parts to integrated structural solutions. MPI builds on this foundation, moving optimisation from part level to vehicle architecture, where performance, weight, and manufacturability can be addressed at the same time.
These results come from deliberate choices across materials, processes, and design. As new constraints emerge, this integrated approach remains essential for turning technical capability into industrial reality.