The world's largest metallurgical company ArcelorMittal has unveiled its new innovative solution for the production of ultra-light car doors. Global research into steel technology and innovation in the automotive industry has now shown that 27 percent savings in vehicle weight can be achieved without compromising structural requirements and compromising vehicle safety.
Looking ahead to the development of new advanced high-strength steel technologies that will enter the market over the next few years, ArcelorMittal has made a breakthrough in technology with complementary solutions, allowing it to deliver even greater weight savings - up to 34 percent over existing solutions from automotive companies.
Automakers must reduce vehicle weight to meet new environmental standards in the future (European Exhaust Regulations are currently in force, coming into effect in 2015, and US regulations on exhaust emissions and fuel economy, which are coming into effect in 2021). In both regions, all vehicles are subject to rigorous scrutiny and stringent weight standards by 2025, which must be reduced by about 12 kilograms (26 lb) to achieve CO2 emissions of up to 1.6 grams per mile.
Using a combination of existing advanced high strength steels (AHSS) and ultra high strength steels (UHSS), it was possible to reduce the weight of the original C-door segments from 18.3 kilograms (40.3 lb) to 13.3 kg (29.3 lb) subject to standard structural safety requirements. This is the most significant reduction in weight since the car was introduced, especially if you remember that such reduction is usually measured in grams. This short-term solution is realized with UHSS grades such as MS 1500 and Usibor 2000 for structural parts and double phase steel products such as FF280DP for external panel. These grades have already become available and are used today in the production of vehicles.
In the redesigned exterior panel, the short-term solution is the 0.6mm FF280DP door with the addition of local reinforcements to improve rigidity. This solution also includes the use of a new laser welded workpiece (LWB) inner panel with a very fine gauge.
Short and medium term solutions save partly weight by using thin steel for the outer door panel. This method is only used for steels that have improved ductility, high resistance to denting and meet industry measurement standards.
The mid-term solution is to move forward in weight reduction while maintaining the same level of performance. Local properties are optimized using LWB. There are several options for matching different types of doors. New high-strength steels and technologies will enter the market in the next few years and will be available by 2017.
The front and side doors are C-segment compliant and can withstand the stresses in an accident. ArcelorMittal offers an evolution of the short term solution to reduce weight by up to 34 percent, resulting in a total door weight of around 12 kilograms (26.4 lb). This is possible thanks to innovative steel grades of the Usibor class, from which the company is currently developing some invisible parts of the outer door panel to reduce the outer panel thickness to 0.5 mm. The requirement for a larger D-segment door does not include frontal crash loading options, allowing lighter doors with limited weighing capacity to be used.
The result of the existing solution is a car door that is 30 percent cheaper than an aluminum door. Innovative solutions for ultra light steel car doors are further proof that steel is by far the most resilient, versatile and affordable material for making lighter cars.
