Latest generation steels bring new opportunities for carmakers
The single-piece hot stamped LWB door ring can be tailored for different levels of complexity to achieve different weight savings, while improving safety in many different crash scenarios.
While laser welded parts have been around for several years, the evolution of grades suitable for LWBs is making them an even more attractive option than ever before. Some of the most recent innovations have included Usibor® 2000 and Ductibor® 1000 for hot stamping, and Fortiform® 1180 and Fortiform® 980 for cold stamping.
For OEMs who utilise hot stamping, ArcelorMittal offers a range of press hardenable steels (PHS) including the Usibor® and Ductibor® brands. The latest, Usibor® 2000 and Ductibor® 1000 offer some of the best weight saving opportunities. Compared to the earlier Usibor® 1500 and Ductibor® 500 steels, the new PHS grades offer the potential to reduce weight by another 10 to 15 percent, while maintaining or improving existing crash performance.
With the new-generation press hardenable steels, thickness of BIW parts can be significantly downgauged while still maintaining safety and performance.
Usibor® and Ductibor® were developed with LWBs in mind. Ductibor® enhances the energy absorption of an LWB part while Usibor® enhances its strength. The new Ductibor® 1000 absorbs an additional 15 to 20 percent of energy compared to Ductibor® 500, while Usibor® 2000 achieves an additional 10 percent weight reduction compared to Usibor® 1500. The new grades have been designed to use the same welding processes OEMs use today, ensuring that there are no additional processing costs.
ArcelorMittal’s third generation of steels for cold stamped LWBs include high formability (HF) grades such as Fortiform® 1180 and Fortiform® 980. These steels offer weight savings of up to 10 percent compared to existing dual phase (DP) grades. The enhanced formability of these grades ensures that OEMs who choose cold stamping for a specific part can also achieve considerable weight reductions.
ArcelorMittal’s range of steels for LWBs includes emerging Usibor® and Ductibor® grades for hot stamping, and Fortiform® for cold stamping.
The Fortiform® range offers OEMs an excellent compromise between high strength and formability. ArcelorMittal is also developing a range of high strength high formability (HSHF) grades which will be known as Fortiform® S. Now in the final stages of industrialisation, the Fortiform® S range will offer weight savings of up to 20 percent compared to DP grades thanks to their higher strength.