Steel giant on a mission to cut emissions

Michael Nash talks to Jean-Luc Thirion of ArcelorMittal about the company’s expanding portfolio of solutions that could help make battery electric vehicles more enticing for the consumer It’s an exciting time to be involved in the automotive industry – a period of significant change and considerable disruption. A throng of megatrends is currently sweeping across …

Michael Nash talks to Jean-Luc Thirion of ArcelorMittal about the company’s expanding portfolio of solutions that could help make battery electric vehicles more enticing for the consumer

It’s an exciting time to be involved in the automotive industry – a period of significant change and considerable disruption. A throng of megatrends is currently sweeping across the market, each of which is having a considerable influence on OEMs and Tier 1 suppliers alike.

“The rising popularity of car-sharing, the imminent introduction of highly autonomous vehicles, and the growing role for 3D printing in vehicle manufacturing are among the key trends that come to mind,” Jean-Luc Thirion, ArcelorMittal’s Head of Global R&D, Automotive, told Megatrends. “They are having a big impact on everyone, but for steel producers like ArcelorMittal, these trends are encouraging us to come up with new ideas.”

A fourth trend, and arguably the most pertinent at present, is electrification. Several OEMs have recently launched new plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs), while numerous studies point to considerable growth in the two segments over the next ten years.

ArcelorMittal’s mill at St-Chély d'Apcher, France
ArcelorMittal’s second-gen iCARe electrical steel product range offers improved power density over the first-gen range, which translates into less weight for the same motor performance, in turn improving driving range (Pictured: ArcelorMittal’s mill at St-Chély d’Apcher, France)

This rising popularity is partly due to future regulations that are starting to take shape. In November 2017, the European Commission (EC) presented a legislative proposal for CO2 targets of passenger cars and light commercial vehicles (LCVs) across the continent post-2020.

Under the proposal, fleet-wide emissions of new cars in 2030 will need to be 30% lower than the 95g of CO2 per kilometre target that is set for 2021. This would prevent around 170 million tonnes of CO2 from being emitted, and could save consumers around €18bn (US$20.99bn) per year in fuel costs.

Although it is meant to encourage a technology-neutral approach to vehicle development, the proposal is likely to ensure that OEMs increase their efforts in electrification. “The targets are so severe that the conventional evolution of vehicle manufacturing with classic powertrains and weight savings just won’t suffice,” Thirion warned. “It’s clear that electrification will be necessary, at least at some level.”

As a result, the market share of mild hybrid vehicles, PHEVs and BEVs will likely grow. Expectations vary, but ArcelorMittal thinks that around 25% of all global vehicle sales will be electrified by 2025.

Different architectures, different impacts

Each of the three architectures – mild hybrids, PHEVs and BEVs – will have varying impacts when it comes to design and manufacturing. For mild hybrids, the impacts are likely to be relatively minimal, while PHEVs will require a certain level of sophistication between the internal combustion engine (ICEs) and electric motor.

Emissions targets are so severe that the conventional evolution of vehicle manufacturing with classic powertrains and weight savings just won’t suffice. It’s clear that electrification will be necessary, at least at some level

The latter, Thirion claimed, could be the most noticeable in terms of impact on design and manufacturing. “Firstly, there is an important change in terms of mass because the battery can weigh as much as 700kg,” he noted. “This changes the way that we need to distribute the mass, which, in turn, will have an impact on the chassis and the wheels.”

BEVs on the market today typically contain lithium-ion battery packs located beneath the floor of the vehicle. This generally has a positive impact when it comes to handling, as a low centre of gravity in a vehicle reduces the load that is shifted to the front during braking and to the rear during acceleration.

However, the inclusion of a battery also has an impact on performance and responsiveness, and also comes with safety implications. “As the battery adds a significant amount to the overall weight of the vehicle, we have to find a way to offset this through lightweighting, otherwise it could be very sluggish off the mark,” Thirion noted. “Furthermore, the BiW plays a double role in terms of safety – protecting both the vehicle occupants and the battery.”

ArcelorMittal has identified higher total vehicle mass on BEVs and PHEVs due to their higher overall powertrain system mass (including battery cells). This increases requirements on the structure, and the need for high strength materials such as AHSS for passenger protection

However, the solution to these problems is not necessarily unique to BEVs. On the contrary, ArcelorMittal has been working for many years on developing lightweight but strong body-in-white (BiW) solutions in vehicles that contain ICEs.

In November 2016, ArcelorMittal expanded its portfolio of third-generation advanced high-strength steels (AHSS) with the introduction of Ductibor 1000, Usibor 2000 and MartINsite M1700 and M2000. The new steel grades were designed to further reduce BiW weight and therefore improve fuel economy without compromising on safety or performance.

As a result, the supplier has no plans to develop specific BiW products for EVs exclusively because “the key trends in steel products are very well suited to BEVs already,” Thirion confirmed.

A complex juggling act

Although not currently developing BiW products specific for BEVs, ArcelorMittal is busy working on electrical steels that are used in other parts of the vehicle, notably steels for use within the electric motor. Called the iCARe range, these electrical steels are extremely important when it comes to enhancing the efficiency and performance of BEVs.

“There are several properties that are very important when it comes to electrical steels,” Thirion clarified. “First of all there is polarisation, which is the level of induction reached in the air gap between the stator and the rotor. This determines the torque of the BEV, and is really important at low speeds or when the car has to start.”

ArcelorMittal’s mill at St-Chély d'Apcher, France
iCARe steels are used in conventional as well as electric cars, with even average conventional cars using up to 70 electric motors for power windows, headlight controllers and power seating. (Pictured: ArcelorMittal’s mill at St-Chély d’Apcher, France)

One of the benefits of BEVs is that they are able to provide instant acceleration from standstill, while ICE-powered vehicles have a slight delay due to the time it takes for the fuel to be injected, combustion to take place, and torque to be delivered. “BEVs have this ability because of the level of polarisation in the air gap, and it’s a very clear advantage,” Thirion noted.

The second important property of electrical steels, he continued, is the minimisation of losses. “An electric motor is a system that converts electrical energy into mechanical energy. During this process, the magnetic field is provided by injecting the current in the copper winding around the steels. This field will modify the magnetic structure of steel in the rotor, but there is a delay in this modification, which is called hysteresis. This is responsible for some energy loss, and if you lose some of this energy, you decrease the efficiency and range of the batteries.”

The third important factor when considering electrical steels is thermal conductivity, as electric motors generate heat that must be extracted to avoid lower performance in terms of power and current output. The steel’s mechanical properties are a fourth consideration.

“To make an electric rotor or stator, we must punch very thin electrical steels to create a sharp edge shape,” Thirion explained. “It’s very important that it is sharp, otherwise it may create shortcuts in the magnetic field, which will again limit the efficiency.”

In terms of innovation and technology, I think it is important to highlight that our focus is on developing products with excellent properties, while also making sure they are very thin, very light, safe and cost effective

ArcelorMittal’s range of three iCARe steels – Save, Torque and Speed – has been specially designed to address each of these issues, something which Thirion admitted has been challenging to achieve: “Developing electrical steels consists of finding the right balance between all of these properties: polarisation, losses, thermal conductivity and mechanical properties. With all these properties to consider, development of electrical steels is one of the most complex tasks among all steel grades.”

New grades

Looking ahead, Thirion is positive about the outlook for BEVs, and believes that ArcelorMittal’s current portfolio of lightweight BiW solutions and electrical steels have positioned the company to take advantage of the growth in the segment.

However, more is on the way. As well as the three listed above, ArcelorMittal has developed a further five second-generation electrical steels, and while he did not reveal a launch date, Thirion is confident that these will help to make BEVs an increasingly attractive proposition.

“The five new grades improve on the properties of the previous generation in all aspects,” he stated. “In terms of innovation and technology, I think it is important to highlight that our focus is on developing products with excellent properties, while also making sure they are very thin, very light, safe and cost effective.”

This article appeared in the Q4 2017 issue of Automotive Megatrends Magazine. 

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