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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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)

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 (the German research company for energy technology and internal combustion engines), 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.

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Foundry trade fair Gifa

Many of the presentations and discussions at Gifa, the international foundry trade fair and technology forum held in Düsseldorf, Germany, from 25 to 29 June 2019, will be focussing on the issues of electromobility and new drive concepts. It has traditionally been the case that innovative cast components for automotive applications have been displayed on the exhibitors’ stands.

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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.

Electrical strip – a core material

Both steel and cast products continue to be essential for the engine and powertrain as the switch is made to electric cars. “Electromobility is not possible without steel,” says Andreas J. Goss, CEO of Thyssenkrupp Steel. The company considers itself to be the market and technology leader for electrical strip, the core material for all electric motors. Motor torque depends to a large extent on the quality of the magnetically soft steel product. The iron-silicon alloy determines the efficiency level, which is supposed to be as high as possible, and the energy loss due to remagnetisation, which is supposed to be as low as possible. Only a few manufacturers anywhere in the world supply this expensive special material; the competitors that do so include Arcelor Mittal and the Austrian company Voestalpine.

The electric engine of the first purely electric model by Audi, the E-Tron Quattro.
The electric engine of the first purely electric model by Audi, the E-Tron Quattro.
(Source: Audi AG)

Research and development work in the electrical strip area has not been completed by a long way yet. Vacuumschmelze from Hanau in Germany recently demonstrated just how much potential the electrical strip technology has. Equipped with material from Vacuumschmelze, the world record-holding electric racing car “Grimsel” accelerated from zero to one hundred kilometres per hour in only 1.513 seconds. No car in the world that is produced in series can get anywhere near acceleration of this kind, not even the 1,000-horsepower “Project One” model manufactured by the Daimler subsidiary AMG. This “Hypercar” with Formula 1 technology, which was presented at IAA 2017, took 2.5 seconds to reach 100km/h. The four electric motors in the “Grimsel” have sheet metal packages made from a special material that would be prohibitively expensive for series production. Yet Vacuumschmelze is thinking of launching a modified electric motor material for premium vehicles on the market.

Electromobility is creating additional market opportunities for foundries

Plenty of castings from foundries such as Georg Fischer (GF) or Nemak are also common in electric cars. From 2019 onwards, for example, the GF Automotive Division based at the Mettmann location in Germany will be producing battery housings made of aluminium with an integrated cooling system for a French car manufacturer. Competitor Nemak also confirms that additional growth is being generated by the change in drive concepts and the introduction of new structural electromobility components like battery housings.

Electric drive systems for cars require a large number of new components. Besides housings for batteries, these are, first and foremost, housings for electric motors and power electronics, which are designed preferably as castings due to their complexity, as Christian Heiselbetz, R&D Director Global at Nemak Europe, reports.

The Audi E-Tron Quattro will be available from August 2018.
The Audi E-Tron Quattro will be available from August 2018.
(Source: Audi AG)

Combustion engines made from die-cast aluminium have been standard for a long time now. Electromobility is creating additional market opportunities for foundries. Cast motor parts are premium key components in both partly electrified and battery electric vehicles. Since 2013, Nemak has been supplying the die-cast electric motor housings for the BMW models i3 and i8. Particularly for complex parts and when the integration of functions is needed, casting technology is able to show its strength and meet varied challenges – be it with low-pressure casting and such casting processes as lost foam, sand and investment casting. If complex cooling circuits are necessary then low-pressure casting permits the use of sand cores or the inclusion of tubes in order to be able to carry out optimised cooling, as Heiselbetz emphasises.

Franz-Josef Wöstmann, foundry expert and departmental manager at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, thinks there is a promising future market for foundries not only in lightweight structures or housings for electric motors, batteries and power electronics. He considers rotors with aluminium or copper and even hybrids to be an issue. The foundry expert stresses that coils can be cast and new magnetic casting materials could become a market.

New drive concepts with formed steel and die-casting

Another component that will still be needed for the drive technology of electric vehicles is the transmission, and thus highly complex die-cast aluminium components as well as equally complex steel components manufactured via forming technology. This is confirmed by Astrid Wilhelm-Wagner, Marketing Manager at Voit, an automotive supplier from Saarland in Germany that has its own foundry. The company intends to strengthen the production of conventional transmission parts (primarily for the supplier ZF) and expand the electromobility business at the same time.

“The established manufacturing segment for conventional powertrains is already being substituted in the hybridisation of existing drive concepts up to and including completely integrated electric drive modules,” says Wilhelm-Wagner. In her opinion, some existing components will be eliminated entirely in future, while other components such as control units for power electronics will be integrated directly into the transmission. Wilhelm-Wagner is sure that the product range will be extending more and more in the coming years. The expert lists such components as internal transmission parts, housing structures for electromobility applications, housing structures for power electronics, electric motor housings, energy recovery components and fuel cell stacks.

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