New methodologies and material concepts are helping OEMs to find opportunities in lightweighting
The task carmakers face is to create affordable, environmentally friendly, and safe mobility solutions. Without a shadow of doubt, steel is still the most affordable material to meet the challenge. It’s also one of the most innovative.
At the beginning of the 1990s, OEMs used steels with strengths around 300 megapascals (MPa). With the upcoming introduction of ArcelorMittal’s Usibor 2000, carmakers will soon have access to steels of 2000 MPa, over six times as strong. Yet the freedom of vehicle designers to create innovative lightweight mobility solutions is not impacted. While it’s not ArcelorMittal’s job to design vehicles, we can bring OEMs the products and knowledge they need to create the best solution. We develop generic solutions under the S-in motion brand name and pass these on to OEMs.
One such example came with at Honda where we worked with the carmaker directly to co-engineer specific parts and modules. This ensured that the best solutions from ArcelorMittal were applied as soon, and as efficiently, as possible.
In 2014, Honda launched its new Acura MDX model which featured the automotive industry’s first single-piece, hot-stamped door ring. Made from hot stamping steel in various grades and thicknesses, the door ring reduced the overall weight of the Honda Acura, reduced fuel consumption, and improved safety significantly for the vehicle’s occupants.
The highly innovative solution has led to widespread industry recognition for both Honda and ArcelorMittal, and has seen the Acura MDX achieve the highest ratings from vehicle safety bodies.
Lightweighting opportunities with steelSteel remains one of the most cost-effective solutions for the automotive industry. Alternate materials offer good lightweighting potential, but are more energy-intensive and expensive to produce and implement into a production line. They can also be harder to recycle at the end of the vehicle’s life.
Automotive steels are, like all steels, 100% recyclable at the end of their useful life. Steel can also be readily extracted from waste streams with the use of a simple electro-magnet. This ensures the average recycling rate for steel and iron in cars is close to 100% and makes steel the most recycled material used in mobility.
Over the past 50 years, the steel industry has demonstrated the versatility of steel and its ability to overcome the challenges society faces. No other material has evolved as dramatically as steel. The industry’s ability to innovate will ensure steel remains the most cost-effective material of the future, and that it will play a critical role in making mobility solutions lighter and safer.
Lightweighting is a major challenge for carmakers as they seek to meet more restrictive regulations on vehicle emissions. Achieving a lower weight for a part requires a trade-off between its geometry (design), thickness, and the properties of the material it is made from. The main goal is to decrease the thickness of the part while increasing the strength of the steel to ensure safety levels are maintained. But increasing the tensile strength of the metal decreases its formability potential. ArcelorMittal has developed a number of new methodologies and material concepts to solve these issues.
One of these solutions is Usibor 1500, an advanced high strength steel (AHSS) developed by ArcelorMittal for use in the structural and safety components of vehicles. Usibor hot stamped parts are noted for their uniform mechanical properties. This ensures exceptional fatigue strength and impact resistance which allows the weight of the part to be reduced significantly and safely. Weight savings of 30% to 50% can be achieved compared to conventional cold forming grades.
Putting the right steel in the right placeTo complement Usibor 1500, ArcelorMittal offers Ductibor 500. As the name suggests, it is a much more ductile steel. Ductibor 500 is offered in association with Usibor 1500 for use in laser welded blanks (LWBs). Also known as tailored blanks, an LWB is a sheet of steel which combines two or more grades of steel. The individual steel parts can be in various thicknesses.
The different parts are laser welded together so that the right steel is in the right place, creating a tailor-made solution for the customer. In this way, the crash deformation of specific vehicle parts (for example, the B-pillar reinforcement) can be tightly controlled while eliminating excess weight. After hot stamping, the tailored blanks are typically applied for the body-in-white (BIW) and closures of a car.
In the coming months, ArcelorMittal will further enhance the strength and ductility of LWBs with the launch of Usibor 2000 and Ductibor 1000. Usibor 2000 has been under development by ArcelorMittal for some time and is compatible with standard press hardening technologies and processes. It is an aluminium-silicon coated AHSS which is even stronger than its popular predecessor Usibor 1500. It could typically bring 10% to 15% weight savings when compared to existing hot stamping solutions.
By contrast Ductibor 1000 has excellent crash ductility at a strength of 1000 MPa. The properties of Ductibor 1000 complement those of Usibor 2000 when the two steels are combined into a single LWB. LWBs created from this combination of steels offer several significant advantages including weight savings, improved crash behaviour, and cost savings through material and manufacturing optimisation.
ArcelorMittal’s ongoing S-in motion programme has identified the lightest steel solutions for key parts of vehicle ranging from passenger vehicles to pick-up trucks. The range launched in 2010 with a set of steel solutions for C-segment vehicles. Since then S-in motion now covers many other types of vehicles and vehicle parts.
One of the latest S-in motion studies looks at the lightweighting potential of steel in mid-size sedans and SUVs (see main image above). S-in motion solutions for these vehicle types can help carmakers achieve a 20% to 26% reduction in body structure weight, compared to representative 2015 North American models. These new S-in motion solutions can be implemented globally and have already been rolled out to individual OEMs.
New ways of building vehicles on a global scaleAs the Honda Acura example demonstrates, OEMs are also working directly with ArcelorMittal to create the new concepts which will revolutionise the way vehicles are built.
Multi-vehicle platforms are a relatively new development in automotive manufacturing, and a major focus for OEMs. They enable OEMs to build vehicles for different segments on a common ‘platform’. This reduces development and engineering costs significantly, particularly compared to the early automotive industry where vehicles were designed locally to meet the needs of consumers in one country or region.
Today, some OEMs are going further and creating vehicles in ‘modules’. Each module can be interchanged to create different models (for example, a mid-size sedan and a pick-up truck) or tailored to meet local customer preferences. By using modules, OEMs can quickly take advantage of the additional strength and lightweighting potential of new steels. When a new steel becomes available, the module can be redesigned almost immediately. The OEM does not need to redesign the entire vehicle or wait a few years for the next model to go into production. With its global presence and its full range of high-quality automotive steels, ArcelorMittal is uniquely positioned to supply carmakers around the world.
Moving with the mega trendsFor more than 50 years, the automotive industry provided mobility solutions using a tried and tested method of developing and manufacturing vehicles. With the advent of mega trends including sustainability, connectivity, and globalisation, mobility is changing and so is the way OEMs make cars. One thing that hasn’t changed, however, is the critical role steel plays in helping carmakers to create safe and affordable mobility solutions which address today’s trends.