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One-part rear H-frame

To prove the validity of the MPI concept, teams from ArcelorMittal Tailored Blanks and ArcelorMittal Global R&D have developed a new LWB H-Frame solution for the rear of an SUV vehicle. The S-in motion® SUV was used as the basis for the design.


The hot stamped rear H-frame turns 11 parts (left) into one single component (right)

Integrating 11 parts into one

The new rear H-frame integrates 11 separate parts – including the rear rails and rear crossmember – into one LWB. Patches have been added to adapt the H-frame for different powertrains. The solution makes maximum use of hot stamping technology and PHS grades such as Usibor® and Ductibor®.

The rear H-frame concept has also been adapted for different vehicle powertrains including BEV and PHEV cars. The solution meets all relevant safety requirements for the global market and has been tested against both European and North American rear-crash load cases.

Advantages for OEMs

The solution offers key advantages for OEMs as it:

  • Converts 11 parts (weighing a total of 14.45 kg) into one single component (weight 13.05 kg). The total weight saving on the part is just under 10 percent.
  • Can be used for a variety of powertrains including ICE, BEV, HEV, and PHEV. Patches are added to the front of the part to add strength for specific powertrains.
  • Has been assessed against all relevant safety requirements for the global market including the IIHS Rear Impact and Full Width Rear Impact tests. The simulations demonstrate that there is no contact with the battery pack or fuel tanks on the S-in motion® SUV PHEV or BEV models.
  • Uses advanced nesting to increase material utilisation. For example, the 11 parts in the baseline can be achieved with a material utilisation rate of 74 percent. By contrast, the one-part MPI rear H-frame has a material utilisation rate of 86 percent. That is a saving of 4.3 kg of material per vehicle.
  • Cuts the working space required. ArcelorMittal estimates that the factory footprint needed to produce the 11 parts in the baseline vehicle would be just over 400 m2. By contrast, the MPI single-part concept requires just over 200 m2, a reduction of almost half.

Costs are reduced by around three percent per vehicle for the sub-assembly.

Watch our VLOG to find out more about the MPI H-frame:


Hot stamping has been chosen as it offers the best geometric possibilities for large parts. An MPI part can be obtained with cold stamping technology, but PHS for hot stamping offer the best mechanical properties for optimal crash performance. They are also the best option to achieve significant weight savings.

More details of the MPI one-part rear H-frame will be published in 2021. Further studies are in development.

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