Automotive Industry

Electromobility Has No Viable Future Without Foundries

| Author / Editor: Gerd Krause / Rosemarie Stahl

How will the supplier industry develop once the combustion engine becomes obsolete? Experts give the all-clear: Electric motors continue to rely on castings. Yet foundries and die-casting companies still need to prepare themselves for the transformation.

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The combustion engine has been standard for a long time now. Electric and hybrid engines present new challenges but also chances to suppliers and manufacturers of engines and engine parts.
( Source: Schaeffler; ©Kybele - stock.adobe.com_[M]_Vogel Design_Werkstatt )

At the moment, there are several possible concepts regarding what drive systems will look like in future. Electric engine? Hybrid drive? Fuel cell? Or the good old combustion engine after all — powered by CO2-neutral e-fuel, that is, with synthetic fuel produced with the help of renewable energy?

Electromobility is broadly considered to be the key to CO2-neutral private transport in the long term. How long the combustion engine will continue to be the transitional solution depends not only on political decision-makers but also and above all on progress in the development of battery technology and on the widespread availability of charging infrastructure. After all, users require a longer range at economic cost.

In the meantime, experts think that combustion engines will be continuing to play a role for a long time in the transition period and afterwards as well. FEV (Foschungsgesellschaft für Energietechnik und Verbrennungsmotoren), an independent development service provider in the automotive field, has conducted a study on e-mobility. According to the results, less than one percent of all vehicles sold globally in 2016 were primarily driven by electricity. The experts expect that the majority of vehicles sold in Europe in 2030 will still have a combustion engine (75 to 85 percent), although most of them (about 90 percent) will be in hybridised powertrains. The global situation does not look any different. Even if there is a strong increase in electrification of the powertrain, most drives will still have combustion engines in 2030 as well. The experts at FEV emphasise that these combustion engines will need to operate in very varied drive topologies.

Professor Hermann Rottengruber from Magdeburg University is certain: “The switch to purely electrical vehicles will be taking place via hybrid drive systems.” He expects a hybrid powertrain with a combustion engine and an electric motor to remain the optimum solution for many different applications and types of vehicles in the long term as well. The motor expert issues a warning, however: “It is nevertheless time to think about how the market for vehicle drive components will be transformed in view of these changes”.

Aluminium die-casting on the outside, a lot of steel on the inside: This electronic axle drive with two-speed transmission was presented at IAA 2017 by Schaeffler.
Aluminium die-casting on the outside, a lot of steel on the inside: This electronic axle drive with two-speed transmission was presented at IAA 2017 by Schaeffler.
( Source: Schaeffler )

Nevertheless, traditional production processes will not be obsolete: Electromobility will not have a viable future without foundries and steel mills. Major components of the engine, the powertrain and the body of electric vehicles are made from steel or aluminium — either moulded or cast.

Electrification of the powertrain

The experience of driving an electric vehicle is powered by a great variety of systems. The reduction in fuel consumption and CO2 emissions, which are the aims of electrification, begin with the comparatively simple automatic start-stop systems based on 12 V electrics and end with a completely battery electric vehicle (BEV) with high-voltage technology.

All of these systems have consequences for the design: Electrification leads to a fundamental change in the powertrain. Consequently, entire supply chains for engine manufacturing need to be rethought completely. While combustion engine drives are dominated by manual and automatic transmissions with up to ten gears, an exclusively electric vehicle manages without complex engines and transmissions. While the engine and transmission of a conventional car consist of about 1,400 parts, an electric motor plus transmission have no more than about 200.

The consequence for foundries of the elimination of combustion engines: no cylinder blocks, no cylinder heads, no pistons, no exhaust and other manifolds. Steel manufacturers lose forged crankshafts, camshafts and complicated transmissions. Yet steel mills and foundries have every reason to be relaxed about such developments. Classic combustion engines and new electric motors will need to be manufactured alongside each other for many more years anyway, which will initially even lead to an increase in components. Moreover, electric vehicles include forged and moulded steel parts and castings as well, so that new opportunities will be created. No battery vehicle moves without highly complex cast and steel components. The battery, electric motor, powertrain and power electronics are the crucial components in electromobility.

Casting and steel: prototyping of the prospective fifth generation of electric engines by BMW.
Casting and steel: prototyping of the prospective fifth generation of electric engines by BMW.
( Source: BMW Group )

Lightweight structures are the key

The Tesla electric limousine with the longest range (600 kilometres) incorporates a battery that weighs 750 kilograms. Average electric cars have to move batteries weighing between 200 and 300 kilograms. In order for electromobility to reach the mass market in spite of the weight and expense of the batteries, economic lightweight structures are becoming a key technology in automotive manufacturing. Initially, the electric car pioneer Tesla started with a blend of aluminium, titanium and steel, while BMW chose expensive lightweight carbon fibre-reinforced plastic for its electric car i3. Now, a change is apparent thanks to new lightweight steel materials. The new Tesla Model 3 is based mainly on steel and BMW has in the meantime discontinued its joint venture with the carbon manufacturer SGL Carbon.

The need for lightweight structures and the weight reduction associated with electromobility are an encouragement to foundries. Lightweight cast components made from non-ferrous metal – aluminium and, to a lesser extent, magnesium – are becoming increasingly important as rivals to steel and aluminium sheet and profile components for chassis and body parts. Struts and longitudinal bars made from die-cast aluminium are examples hereof.

Nemak, a leading lightweight metal foundry that supplies automotive manufacturers, thinks that structural components made from die-cast aluminium represent in general a very interesting combination of weight reduction potential, costs and component properties. In the meantime, structural casting is finding its way into higher-volume, mid-sized vehicle platforms that need to be manufactured in identical quality in several different markets all over the world at the same time, Nemak points out.

Economic lightweight design is dominated by a combination of high-strength steel and selected aluminium components. This is also true for lightweight components in electric cars. The car supplier Kirchhoff, for example, presented a concept for a crash-resistant and economic battery housing with an integrated cooling function made from a hybrid steel-aluminium structure at the International Motor Show (IAA) in 2017.

Facelift after four years: The new version of BMW's i3 will be run by an e-machine in a complex, aluminium die-cast housing like its predecessor.
Facelift after four years: The new version of BMW's i3 will be run by an e-machine in a complex, aluminium die-cast housing like its predecessor.
( Source: BMW Group )

According to Professor Christoph Wagener, Vice President Research & Product Development Kirchhoff Automotive, the objective was to produce a battery housing that is as light as possible while still being inexpensive at the same time. He explained that, for corrosion protection reasons, a steel underbody must have a wall thickness of at least 1.5 millimetres, which makes it comparatively heavy. The lightweight structure produced by Kirchhoff with a framework of aluminium profiles satisfies all the requirements, such as passive safety, flat design, thermal management, electromagnetic compatibility, sealing and corrosion protection. Thyssenkrupp Steel also presented its concept for a battery housing at IAA. The module developed from high-strength steel is said to weigh no more than a comparable aluminium version, but costs only approximately half as much.

In the cost-sensitive market of large quantity sales, high-strength steel is the favoured solution. Philippe Aubron, Chief Marketing Officer at the Arcelor Mittal Automotive Europe Corporate Division, says: “Electric cars can be built 50 to 60 kilograms lighter with steel.” The portfolio supplied by the steel manufacturer includes not only flat steel but also long products for exclusively electric cars. According to the company, the demands made on the components are similar, though the transmissions of electric cars are less complex than classic powertrains. The powertrain of a BEV apparently includes, for example, drive shafts and transmission components that are manufactured from special bars and rolled wire. Competitors like Saarstahl and the Georgsmarienhütte steel group are also carrying out similar development work in the long steel sector.

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