Ιone only reviews the electrified vehicles currently in the market, it could be concluded that there is no clear link between powertrain and material choice. Around 10 years ago there was a view in some quarters that to accommodate very expensive battery packs needed for BEVs especially, the vehicle structure must be constructed from low density materials such as aluminium, carbon fibre and magnesium. However, on the whole, this has not happened. Many partially or fully electrified systems such as hybrids, fuel cells and full battery systems on the roads today have been retrofitted to existing, mainly steel intensive vehicle structures. The reason for this is partially related to rapid improvements in battery technology and also lightweighting achieved through the deployment of new and advanced steels, but the major reason is cost or affordability.

Car manufacturers have had to factor that the mass market consumer will not pay a premium for their vehicle. The early adopters who are driving around today in BEVs or even PHEVs have paid a premium, despite the many subsidies available. Early adopters typically pay for the privilege of being first but when a technology becomes mainstream, the majority of consumers will not. It is likely that once the sales reach a critical volume, existing subsidies will be unaffordable and will stop. The average consumer will not want to pay any more than they are paying today.

There also remains significant challenges with electrified vehicles: batteries remain expensive, bulky, heavy, have limited range, are relatively slow to charge and offer significant challenges end-of-life. Lightweighting will help with some aspects but not all and it is far more efficient to spend money on battery technology than significant spend on saving a few kilograms of body mass through the application of non-ferrous materials.
There are examples where OEMs have utilised non-steel vehicle structures for their electrified systems. The much publicised BEVs from Tesla are currently constructed from a mixture of aluminium, titanium and steel. However, the new model from Tesla (model 3) which will be produced in relatively high volume will be constructed from steel. The reasons are linked to lower cost, improved quality, faster build times and for their customers, reduced insurance premiums.
Whilst many OEMs view material strategies in different ways, they all anticipate that whilst ICE systems – either full or hybrid – are dominant, the need for lightweighting will remain a high priority. Lighter vehicles can be powered with smaller, more efficient engines, or as in the case with hybrids, lighter vehicles can directly help increase electric-only powered range.
The steel roadmap considers the what materials and technologies are needed to meet tomorrows lightweighting goals.

end-of-life.Steel has a significant advantage over alternative materials – it is easily segregated, it is easily disassembled, it is infinitely recyclable – and can be upcycled. Materials such as CFRP perform poorly during end-of-life; they are difficult to segregate, cannot be recycled and need to be scrapped as land fill.

Today, our customers are building environmental models in preparation. They are starting to view the trade-off of adopting low density, non-ferrous materials for increased lightweighting potential to help reduce running emissions against the significant penalty inflicted at the cradle and grave of a vehicles life. Our customers are confirming that steel has compelling propositions throughout the full life cycle.

For the steel market size assessment detailed later in the report, a conservative set of assumptions have been adopted regarding steel context. It has been assumed that the overall level of steel content will reduce in the vehicle structure over the midterm. This reduction will be a consequence of an increased use of advanced high strength steels for substitutional lightweighting, but also partial migration towards non-ferrous materials.

Long-term, it is expected that steel content will plateau or even marginally increase as a consequence of LCA benefits and also much lower pressure on lightweighting due to infrastructure recharging improvements.

Electric propulsion system

All electrified vehicles will require one or more electric motors as either the primary or secondary means to drive the wheels. Electrical steel is an essential material in the construction of electric motors. By tailoring the electrical steel grades, different motor performance can be achieved. This will become extremely important to the OEM as they look to differentiate their powertrains from those of their competitors. Higher performing electrical steels can improve the motor efficiency which will help to either extend the range of the car or increase the dynamic performance of the car. For a given range, efficiency improvements can help to take out tens of kilograms of battery pack mass and therefore system cost.

Engineers are now working with Tata Steel to deploy our advanced electrical steel grades to tailor motor performance. The steel market size and mix therefore factors a change in qualities of electrical steel grades used in electric motors.
 

It is understood that in order to improve the efficiency of future electrified vehicles, new vehicle architectures will be tailored around the propulsion systems. These architectures will still need to meet core design parameters such as external package limitations, safety requirements, occupant and luggage space. However, cost-effectiveness will remain important – alternative propulsion systems are expensive and consumer affordability needs to be factored. Steel has very relevant cost-effective lightweighting propositions and it is our view that steel will remain the material of choice over this period.
What if we look further into the future, what next for lightweighting?
Today, the need to save mass for the battery electric vehicle is clear. The consumer is used to achieving a few hundred kilometre range from a conventional gasoline powered car. Historically, to achieve a comparable range using a BEV, a very large, expensive and heavy battery pack is needed. A lighter vehicle structure will help reduce the associated mass spiral – heavier battery pack leading to increased secondary mass effects such as larger brakes. But what about when the charging infrastructure takes away the need for long range capability?
Imagine the scenario where your future BEV has been fast-charging overnight at home, you take your journey to work and the road system wirelessly trickle charges your vehicle and when you reach your place of work, your car is again automatically charged. In effect your vehicle is continuously charged. Why would you need the vehicle to have a 500 kilometre range? Why would you need a heavy and expensive battery pack? Does the need for lightweighting remain as high as it does today? This future is fast approaching and it offers many opportunities.
This scenario could have a significant impact on material selection. However, there is a driver on the horizon that could arguably have an even bigger effect on what materials are chosen in the future. This driver is environmental sustainability.

Today’s vehicle are judged on tailpipe emissions. However, there are many experts arguing that to achieve a more sustainable transport sector, simply measuring tailpipe emissions is insufficient.
The most complete method of assessing sustainability is through Life-Cycle Assessment (LCA). LCA maps the full cradle to grave environmental impact of a vehicle – environmental impact to make the car – including raw material production, the fuel or energy production impact and the running impact and the disposal impact at the end-of-life.
The production of electric vehicles is typically more energy-intensive than for conventional vehicles. Large amounts of energy are needed to make systems such as the battery pack, but also electrical systems can contain high levels of rare earth metals.
Different material families also have varying environmental impact. For example, to produce the material needed for a functionally equivalent automotive component, compared to AHSS, the level of greenhouse gases emitted during raw material production is around four times higher for aluminium and six times higher for carbon fibre reinforced plastic (CFRP). Material production and processing could therefore significantly contribute to the final, combined environmental impact of a vehicle.
End-of-life vehicles create many millions of tonnes of waste each year. Existing EU legislation, including the EU directive on end-of-life vehicles, aims to reduce waste and encourage recycling of scrap vehicles. The large batteries and additional electrical components available for recycling, including the electric motor and its magnets, are challenging to sustainably dispose or recycle. The choice of material mix also has implications for
 

A key part of the electrified propulsion system will be the energy storage. Since 2010, manufacturers have coalesced around lithium-ion batteries in virtually every electrified vehicle application with a few notable exceptions from Toyota (who now look likely to adopt this technology rather than nickel metal hydride). Lithium-ion batteries are currently manufactured in three different physical battery cell formats; cylindrical, prismatic and pouch. Cylindrical cells are the most relevant to steel as prismatic and pouch are generally packaged in a non-ferrous casing, whereas cylindrical cells are packaged within a nickel-coated ‘can’. Cylindrical cells are the preferred solution for many OEMs. The reason why these cells are likely to be the most common, especially in the immediate future is that they offer one of the lowest costs in terms of energy storage, have good reliability, are relatively easy to manufacture with good mechanical stability. Steel has an important role to play in this technology, certainly in terms of cost effectiveness and sustainability.

So far many of the batteries used in Europe’s electrified vehicles are imported from the Asia. This is likely to change as demand grows with the need to make batteries much closer to the vehicle assembly plants for reasons relating to cost and most importantly, safety. Industry sources have estimated that globally there will need to be around 24 battery gigafactories to serve the 2030 global electrified vehicle demand, with at least six needed in Europe alone. This represents a significant growth opportunity for steel in this area of the vehicle where traditionally there has been negligible demand.
Another overlooked area is infrastructure needs to support the recharging of battery packs and the hydrogen refuelling of fuel cell electric vehicles. It is clear that although the rate of infrastructure improvements is speeding up, there is a long way to go to meet the future demand. This report does not detail this opportunity so further work should be undertaken. However, there will be significant steel demands to support the infrastructure construction ranging from charging points or stations and grid furniture through to transformers and powerstations but also ‘mega city’ developments where zero emission connected and autonomous vehicles will surely be needed.
Impact of transport electrification on steel demand
The steel demand has been estimated using the baseline roadmap combined with the associated assumptions on vehicle structure weight reduction, electrical and plated steel consumption in motors and batteries, respectively, combined with European vehicle production growth.
It is projected that the demand for ultra-low emission vehicles (ULEV) will drive growth in steel supply to the European automotive industry by
4.2 million tonnes between 2015 and 2050. A significant proportion of
this growth is expected in steels needed for battery and electric motors (1.6 million tonnes). However, there will also be an increasing demand for advanced high strength grades needed to cost-effectively, and sustainable achieve vehicle safety and lightweighting targets.

The volume progression is reflective of the anticipated effect of rapid growth in electric propulsion systems – affecting electrical steels and plated steels for battery casings, and also short-medium term pressure on lightweighting before environmental sustainability factors start to significantly influence material selection in the vehicle structure.

It can be concluded that the steel demand will increase, albeit at marginally lower growth levels compared to the vehicle production, but the overall value of this steel demand will increase substantially.
What opportunities will there be for Tata Steel?
There are four areas where Tata Steel offers compelling propositions in the field of vehicle electrification: vehicle architecture, batteries, motors and infrastructure.
■ Vehicle architecture: vehicle lightweighting will remain essential irrespective of propulsion systems. However, lightweighting must be affordable and Tata Steel’s current strategy to develop cost-effective advanced and ultra high-strength steels products along with supporting services will remain essential.
■ Battery pack: battery technology continues to develop at a rapid rate. There are different battery technologies being deployed, and steel has an important role to play in one of these technologies; cylindrical batteries, which is likely to be the dominant form. Tata Steel has developed solutions to current and future issues around cylindrical batteries including advanced coatings or plated steels for the steel cans and thinner layers for improved battery packaging.

Conclusions
It can be concluded that when combining the estimated OEM electrification roadmaps into a single European level roadmap, there will need to be a significant acceleration in cars made and sold with propulsion systems that are capable of running zero tailpipe emissions. By 2021 approximately 25% of vehicles sold in Europe must be ULEV, but with the bias towards ICE-hybrid systems. By 2030, this proportion could be over 40% with fully electric vehicles having a significant contribution to this mix.
Material choice will support any rapid growth in transport electrification. Vehicle structure lightweighting will remain relevant, certainly in the short to medium term, but mass saving must be achieved cost-effectively. The vehicles must be affordable to the mass market to realise the roadmap. Looking longer-term, it is expected that the environmental performance of vehicles will be judged on Life-Cycle Assessment rather than tailpipe. Steel has the most compelling proposition in this assessment, especially compared to low density alternative materials.
As the demand for conventional internal combustion engines diminishes, so will the demand for engineering steels typically required for the manufacture of ICE components such as connecting rods, cam-shafts, transmission shafts, etc. But this drop in engineering steel demand will be compensated through the growing demand for new flat steel automotive products. Electric propulsion systems need advanced electrical steel grades for electric motors, and for energy storage, advanced plated steels for battery casings.
We are facing a fast-moving and exciting time in the road transport sector. Tata Steel is well prepared for this future, and will continue to develop relevant and compelling solutions. We truly believe that steel will remain the material choice as we take the journey towards full transport electrification.

Background
The general trend of lightweighting in the automotive industry does not wane. On the material level, R&D departments are constantly searching for ways to make components even lighter to help meet the current and coming regulations for CO2 and fuel consumption. As the Body-In-White (BIW) represents a considerable amount of the car’s weight, which is mostly made of steel, the steel industry is developing new material solutions that help to reduce weight further.
Advanced high-strength steels (AHSS) offer a good solution to achieve this goal. Depending on the requirements of a car manufacturer, other factors – such as the end product performance or the production cost per part – need to be taken into consideration. With new steel grades and technology to comprehensively assess their potential, Tata Steel is now able to determine the most suitable steel for a particular component. The company offers an ever-growing range of metals with different properties, plus a set of accompanying services that can show manufacturers their optimal balance between lightweight potential, performance and costs according to their priorities.

Supporting steel selection
To identify an adequate steel grade that can reduce weight in the front and side impact structures, the company conducted several tests with its high strength CP800 complex phase and DP1000LY dual phase steels. These steels are supposed to be able to replace the commonly used DP800 dual phase steels in parts like sills, seat cross members and A-pillars. In addition to the weight reduction potential, Tata Steel compared their performance, manufacturing behaviour and related costs so that manufacturers can consider all these parameters during the selection of the material.

When looking at the lightweighting potential of a material for BIW parts two other material properties remain central: their performance during a crash and their manufacturability during the

deep drawing process. The crash performance of steel largely depends on the bendability of the material – relating to the yield strength – while good manufacturability is related to the stretchability of the material. The higher strength required for the weight reduction, unfortunately, coincide with decreased levels of either the required bendability or stretchability (image 1).
 

To optimally meet the requirements of car manufacturers for various parts, Tata Steel is currently developing and extending its steel families A manufacturer therefore has to define which limitations are acceptable for a particular component.

Crucial crash performance

To support manufacturers in their selection, Tata Steel assessed the crash performance by studying the bending and fracture behaviour of a closed top hat (image 2). Here, bending is very apparent in a crash and the study of the fracture location and appearance indicates that failure through shearing is a common result. For safety reasons, generally as much energy of the crash as possible should be absorbed in the bends.

A three point bend test with a bending VDA angle at 1mm and a shear test measuring the failure strain, in a comparison between DP800 (image 3), DP1000 and CP800, showed that the CP grade offered much better performance for bending and shearing than the DP grades, resulting in a better crash behaviour. This can be related to the different microstructure of CP800.
To further examine the crash performance for sills and seat cross members, Tata Steel simulated and compared the side impact of a crash on components made of CP800 and DP1000LY using the Future Steel Vehicle (FSV) model (image 4). The simulation showed no major differences in the deformation of the components made of CP800 and DP1000LY, so both steel grades show an equivalent crash performance.

Ease of manufacturing
To assess the manufacturability of components made out of CP800 and DP1000LY, a forming analysis for an A-pillar lower, a critical forming part, was conducted for the first draw of the deep drawing process and after flanging/cutting. The simulation showed a slightly better formability of DP1000LY compared to CP800, which is related to the better stretchability of dual phase steels. For the lower A-pillar, this does not have to be critical and can be solved with minor geometric adjustments to the layout if necessary. Nevertheless this indicates that, for components with more complex geometries, DP1000 steel is somewhat better suited to achieve lightweighting in other areas.

Quantifying the costs
To complete the assessment, Tata Steel conducted a cost analysis for the new grades related to each of the tested parts. The analysis showed a clear cost benefit for CP800 compared to DP1000, ranging from 0.03 Euro for floor cross beams, 0.12 Euro for the A-pillar reinforcement, and up to 0.18 Euro for a sill.

Conclusion
Advanced high-strength steels have the potential to reduce weight throughout the entire BIW. However, the variety in steel grades with different properties offer even more than that, and Tata Steel is able to support manufacturers in the assessment of materials to meet the exact requirements in regard to safety, performance, lightweighting and costs for particular components. The present study proves that CP800 can compete with DP1000LY when it comes to lightweight design of crash components. CP800 shows a similar formability and crash energy absorption potential as DP1000LY, but against lower costs, making the steel particularly interesting for mass production applications.