New ArcelorMittal lightweight car door solutions; up to 34% weight savings over existing steel doors in medium-term
|ArcelorMittal lightweight door. Click to enlarge.|
ArcelorMittal, the world’s largest steel and mining company, unveiled its new ultra-lightweight car door solutions. Using steels and technology currently available, ArcelorMittal’s global R&D automotive team has demonstrated that a 27% weight and cost saving can be achieved without compromising safety and structural requirements.
By looking ahead to new advanced high strength steels and technology that will come to market over the next few years, the team has identified additional solutions that will deliver even greater weight savings of up to 34% compared to existing steel car door solutions.
Carmakers need to reduce the weight of their vehicles in order to meet future regulations; currently-enacted regulations in Europe (tailpipe emissions) come into full force in 2015 and those for the USA (tailpipe emissions and fuel economy) come into full force in 2021. With even tougher standards being considered for the years ahead to 2025 in both regions, every part of the vehicle is being studied to determine where weight can be reduced. By reducing the weight of the vehicle by around 12 kg (26 lbs), one gram of CO2-equivalent emissions per kilometre (1.6 g/mile) is saved.
Using a combination of existing advanced high strength steels (AHSS) and ultra high strength steels (UHSS) it is now possible to reduce the weight of the baseline C-segment door from 18.3 kg (40.3 lbs) to 13.3 kg (29.3 lbs) while meeting standard structural and safety requirements.
This is a significant weight reduction for one automotive application, especially considering automotive weight savings is typically measured in grams. This short-term solution uses UHSS grades such as MS 1500 and Usibor for structural parts, and Dual Phase steels such as FF280DP for the outer panel. These steels are available now and are already being utilized in production vehicles today.
In the redesigned outer panel of the short-term front door solution, a 0.6 mm FF280DP grade is used and local reinforcements (patches) are added to improve stiffness. This solution also includes a new laser welded blank (LWB) inner panel concept with a very thin gauge.
Part of the weight savings in both the short- and medium-term solutions is achieved by using thinner steel for the outer door panel. Known as down-gauging, this technique is only possible with steels that exhibit increased yield strength while ensuring the doors will pass industry standards for dent resistance.
The medium-term solutions go further in lightweighting while maintaining the same performance levels. Local properties are optimized by the use of LWBs. Several options are possible in order to match the different types of doors to each customer’s need. The new high strength steels and technology will come to market in the next few years, making these solutions available by 2017.
The requirements of a C-segment door include the management of both frontal and lateral crash load cases. ArcelorMittal proposes an evolution of the short-term solution toward lighter doors with up to a 34% weight reduction, resulting in a total door weight of about 12 kg (26 lbs). This involves innovative steel grades which are currently under development such as Usibor 2000 for some non-visible parts and other AHSS for the outer panel in order to reduce the outer panel thickness to 0.5 mm.
The requirements for larger D-segment doors do not include the frontal crash load cases, allowing lighter doors with more limited light weighting potential.