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What is Multi Part Integration (MPI)?

Multi Part Integration (MPI) is a new concept from ArcelorMittal Tailored Blanks which is designed to incorporate many parts into one laser welded blank (LWB). MPI uses press hardenable steels (PHS) and hot stamping LWB technology to create the single part. The goal is to simplify production for OEMs.

What are the benefits of Multi Part Integration?

The MPI concept brings significant benefits for OEMs including:

  • Radical simplification of the vehicle production process
  • One common and modular solution for multiple powertrains
  • Enhanced crash management
  • Considerable sustainability gains including a lighter finished vehicle
  • Potential cost savings of up to 10 percent.

Building on our experience

The MPI concept builds on the success of ArcelorMittal projects such as S-in motion® and the single-piece door ring. The door ring has been adapted for different vehicle segments and successfully introduced into several vehicles by the global automotive industry.

To help prove the practical viability of the MPI concept, teams from ArcelorMittal Tailored Blanks and ArcelorMittal Global R&D have completed an MPI analysis for the rear, underbody, and rails of an S-in motion® SUV vehicle. Known as the ‘rear H-frame’, the concept replaces 11 separate parts with one. The solution can be applied to almost any powertrain simply by adding patches to reinforce local areas.

Further projects are already in development and will be announced later in 2021.

A simplified production process

Combining multiple parts into one greatly simplifies the part production process and associated costs. Advantages include:

  • Only one stamping tool needs to be produced, and it can be used in one stamping operation.
  • Just one blank is produced. The only finishing work that needs to be done is trimming the part and applying patches to enhance strength and accommodate different powertrains. As there is only one final part, less assembly steps are required.
  • A reduced shopfloor footprint as the OEM needs fewer process steps to manufacture the MPI module.
  • Almost unlimited design freedom to create complex geometries which optimize the advantages of the hot stamping process.
  • A finished part with excellent geometric accuracy.

One common modular solution for multiple powertrains

Using Multi Part Integration, one modular solution can be developed for multiple powertrains. The part shape and distribution of material is similar for every powertrain.

Patches can be applied to the part to add reinforcement for a specific powertrain without increasing costs.

Multi Part Integration solutions can be used with a variety of powertrains including:

  • Internal combustion engine (ICE)
  • Hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV)
  • Battery electric vehicles (BEV)
  • Future powertrains based on technologies such as hydrogen and fuel cells.

Improvements in safety

The use of hot stamped press hardenable steels (PHS) in a single LWB is key to Multi Part Integration. The LWB ensures that the right PHS steel, in the right thickness, is in the right place. LWBs have continuous weld lines which enhance energy absorption and the behaviour of the part during a crash. LWBs also eliminate weak points in the part.

ArcelorMittal PHS families such as Usibor® and Ductibor® are ideal material choices. Usibor® offers the strength and anti-intrusion properties required to protect the vehicle’s occupants and power system. Ductibor® provides ductility, enabling crash energy to be controlled and directed away from the passenger compartment and fuel source. Working in combination these grades enable engineers to dramatically enhance safety while reducing mass.

Sustainability gains from the MPI approach

By integrating multiple parts into one, OEMs can reduce the overall mass of the part. This approach offers many sustainability benefits including:

  • Lower CO2 emissions from reduced steel production:
    • Less steel is required to achieve the same functionality. This avoids emissions from steel production.
    • Even further reductions in steel usage are possible with the deployment of advanced nesting techniques which enhance material utilization. Advanced nesting optimises the amount of steel used and reduces the amount of scrap steel that must be shipped back to the steel plant for recycling.
  • Less CO2 emissions during the vehicle’s life. A lighter finished vehicle will have lower emissions over the use phase of its life.
  • Reducing the plant footprint required to manufacture and store parts for different powertrains of the same model. Depending on the part, the space required can be reduced by almost half.

Cost reductions in production

ArcelorMittal has contracted an independent external partner to calculate the cost savings from every MPI project. The methodology uses an ideal, virtual plant which produces 150,000 vehicles annually. The calculation assumes that the same vehicle – in different powertrain versions – is produced for five years.

Each MPI study will contain more information on potential cost reductions.

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.

Integrating 11 parts into one

The new rear H-frame integrates 11 separate parts – including the rear rails and rear crossmember – into one LWB. 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’s 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.
  • Cuts costs by around three percent per vehicle for the sub-assembly.

Why hot stamping?

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.

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

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