Reference structure – how steel is getting electric cars into shape
Scalable and weight-optimized: manufacturer-independent and lightweight solutions for electromobility
© Photos: thyssenkrupp Steel
thyssenkrupp Steel bundles its electromobility research and development activities under the selectrify® initiative. Affordable, lightweight solutions for vehicle structure, highly stable safety battery housing, and especially efficient electrical drive motors made from electrical steel all demonstrate the enormous potential of innovative steel solutions for vehicles with electric drives.
“Steel is the most important lightweight material for the automotive industry today,” says André Matusczyk, CEO of thyssenkrupp Steel’s Automotive business unit. “With the help of our selectrify® initiative, we want to show our customers that the material also brings a superior property profile to electric vehicles.”
This begins with an unrivaled price/performance ratio as far as the lightweight construction of the vehicle structure and protection of the sensitive battery is concerned, and extends all the way up to steels with special magnetic qualities without which no electric motor functions.
Worldwide availability, established processing methods, and outstanding repairability and recyclability of steel make it easy for automotive manufacturers to integrate new steel solutions and concepts quickly into marketable electric cars. “Steel makes electromobility safe and easy and contributes to getting electric vehicles out of the small-series model niche and making them affordable for the masses,” says Matusczyk.
selectrify® is also on hand for thyssenkrupp Steel when its customers need support in quickly implementing technologically demanding requirements in mass production.
Giving electric cars a shape: the selectrify® reference structure
thyssenkrupp Steel is once again able to demonstrate its expertise with the selectrify® reference structure. “Before we were able to implement our idea of a manufacturer-neutral electric car structure, we defined a variety of relevant criteria for the target vehicle – from the dimensions to the range,” says Project Engineer Andreas Breidenbach, who’s role is interdisciplinary, working with colleagues from a wide range of departments.
The result is the virtual structure of an electric vehicle in the high-unit-volume compact class, which is designed for a practicable 500-kilometer range, and features seating for a total of five occupants with trunk space. A comprehensive simulation program ensures the technical feasibility of the new development and guarantees that the reference structure meets the requirements set by all standard crash tests. Tools and methods match those used by automotive developers so that results can be compared immediately, and solutions can be quickly put into series production.
The selectrify® reference structure is also based on a flexible platform that is scalable lengthways. Further derivatives and vehicle classes can be extrapolated from this, such as SUVs or coupés. “That also increases the efficiency of our solutions.”
Out with combustion engines, in with a new design
The elimination of conventional combustion engines with auxiliary units and transmissions also fundamentally changes the design of newly developed electric cars. Generally speaking, the front end looks neater, meaning the need for geometrically complex deep-drawn parts drops while the use of simpler structural components and profiles increases.
However, current batteries are still very heavy and the resulting high overall weight of the vehicle continues to place great demand on the strength of the materials used. Now, providing the vehicle’s occupants with extensive protection starts with protecting the sensitive battery in the event of a side-on collision. The acceptable level of intrusion in the battery area reduces to virtually zero. That increases strength and design outlay for rockers, B-pillars, and the surrounding environment.
The most striking changes are the external ones when it to comes to purpose-design electric vehicles – that is, vehicles that are developed from the ground up and exclusively for fully electric operation: “We’re talking about longer wheelbases and short overhangs here,” says Breidenbach. “We have made sure our portfolio of materials matches the new requirements of electric vehicles. The result shows that with steel we’re currently well positioned for electromobility and have the right materials in our portfolio to meet any and all requirements.”
Steel materials: even stronger in the future
But development isn’t standing still. In the long run, it’s conceivable that the traditional development focus, especially in terms of cold-formed steels, will shift from firm and flexible towards higher-strength and more economical alloy concepts. New types of forming technologies such as thyssenkrupp smartform® or hybrid materials are providing new ideas in terms of costs and the performance of steel construction. The increasing trend towards higher strengths will continue since they are especially suitable for weight-optimized and safe vehicles.
“Local strengths have increased significantly in recent years. It’s an enormous growth that nobody had dared hope for,” says Breidenbach. One glance at thyssenkrupp Steel’s broad product portfolio makes it clear to see how much potential there is in the development of steels. The spectrum of dual-phase steels alone ranges from strengths of 500 MPa to 1,200 MPa. When it comes to steels for hot forming such as MBW®, even strengths of up to 2,000 MPa are targeted following press hardening.