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iCARe®: ArcelorMittal’s range of electrical steels for automotive

About iCARe®

iCARe® is ArcelorMittal’s range of innovative electrical steels for the automotive market. Our iCARe® steels help automakers create environmentally friendly mobility solutions for a greener world.

These values are at the core of the name iCARe®. Finding innovative (i) and environmentally friendly (e) solutions is essential for the CAR of tomorrow.

Introduction

ArcelorMittal’s iCARe® steels are a combination of standard and high performance electrical steel grades which have been specifically designed to meet the particular needs of electric and hybrid vehicle makers. Our iCARe® steels exhibit high permeability, low loss levels and have excellent yield strength.

The large number of products in the iCARe® range provides technical solutions for automakers which achieve:

  • Lower CO2 emissions and better fuel consumption for hybrid vehicles
  • Longer drive range with existing battery technology
  • Lower total cost of electrification
  • Better power density of electric machines, to reduce the size and weight of electrical drive trains.

The iCARe® offer

There are three steel types included in ArcelorMittal’s iCARe® offering: Save, Torque and Speed. Each has been specifically designed for a typical electric automotive application. ArcelorMittal also offers advanced technical support to manufacturers, enabling them to realise the full potential of our iCARe® offer.

Save

A steel with very low losses, Save is ideal for the efficiency of the electrical machine. Its key role is to optimise the use of current coming from the battery. See our iCARe® Save datasheet to discover more about the range.

Torque

Torque is a range of steels with high permeability which can achieve the highest levels of mechanical power output for a motor or current supply for a generator. Minimum polarisation at 5,000 A/m is above 1.65 T. See our iCARe® Torque datasheet to find more about the full offering.

Speed

A group of specific high strength electrical steels for high speed rotors which maintain high levels of magnetic performance. These grades allow the machine to be more compact and have a higher power density. The grades come with guaranteed yield strengths, and guaranteed magnetic properties. The iCARe® Speed datasheet contains full details of the offering.

Coatings for iCARe®

Electrical steel varnishes for non-oriented grades are designed to enhance the behaviour of fully processed electrical steels. Their main purpose is to provide inter-laminar insulation and to improve the punchability of these steels. ArcelorMittal offers two coatings for its iCARe® electrical steels: C3 and C5. The coatings are suitable for fully processed grades for hybrid and electric traction machines and compressors. For alternators, uncoated solutions can be used. More information about the use of these coatings can be found in the Coatings for iCARe® datasheet.

Advanced technical support

For automakers who wish to exploit the full potential of ArcelorMittal’s iCARe® steels, we can offer advanced technical support in many areas including modelling, prototyping and material handling.

  • ArcelorMittal’s machine modelling services
    As a steel provider, ArcelorMittal also offers our customers all the help they need to choose the most suitable steels. We can also help to design the electrical machine. This level of assistance is possible thanks to our advanced R&D know-how and the high-tech equipment available in our research centres. For more information see our iCARe® Advanced technical support datasheet.
  • Prototyping services
    Our modelling services enable design engineers to make precise machine calculations. This allows them to reduce the number of prototypes needed before pre-series begin. A minimal amount of prototyping is still needed to prove the machine’s performance. ArcelorMittal can offer small quantities of sheets for first stage Epstein and tensile testing, and for the next stage of laser cutting. In the industrial validation phase, ArcelorMittal can provide small slit coils for punching and machine assembly development.
  • Material handling issues
    The production of prototype or series machines can involve production processes that have the potential to degrade the properties of the fully processed steels we have supplied. Advanced R&D support is available to help customers quantify the impact of material handling processes on the magnetic performance of the machine’s lamination stack. Our iCARe® Advanced technical support datasheet contains more information.

Selection guide

Field

Applications

Substrates

Powertrain machines

High efficiency alternators

Torque

Save

   

Belt driven starter-alternators

Torque

Save

   

High efficiency starters

Torque

Save

   

Permanent magnet synchronous machines (PMSM) for centralised traction

Save

Torque

Speed

D20*

D24*

PMSM for wheel hub motors

Save

D20*D22*  

HPMSM for current generation

Save

Torque

Speed

 

 

Wound rotor synchronous machines (WRSM) for traction

Torque

Save

D22*  

WRSM for current generation

Torque

Save

   

Switched reluctance machines (SRM) for traction

Save

    

Induction machines (IM) for traction

Torque

Save

   

IM for current generation

Torque

Save

D40*  

High performance auxiliary equipment

Heating, ventilation and air conditioning (HVAC) compressors

Save

Torque

   

Ignition coils

Save

D70* D80*

   

Dashboard metering

Save

    

Hybrid controllers

Save

Torque

   

For information on coatings, please check the Coatings data sheet.
For D20, D22, D24, D40, D70 and D80 substrates, please click on the reference to see the corresponding product sheet in the ArcelorMittal Flat Carbon Europe product catalogue for Industry.
See also: http://industry/arcelormittal.com > products > product catalogue for other electrical machine applications.

ArcelorMittal’s electrical steel offering

In order to stretch the amount of power extracted from the battery, every other element in the electric vehicle must be optimised for low weight and high efficiency. This is particularly important for the electric motor and generator which form the heart of the powertrain.

ArcelorMittal’s iCARe® electrical steel solutions can bring significant performance improvements to the core of the electric machine, and improve battery performance. The combination of efficiency and light weight means electric vehicles can go longer between charges, extending the drive range of the vehicle.

ArcelorMittal’s iCARe® range includes specific electrical steels for applications where high power density or high torque are required. iCARe® steels enable the electrical systems in the vehicle to operate more efficiently, maximising power and delivering increased cranking torque. When the machine design is optimised using iCARe® steels, further weight savings can be achieved as fewer magnets and less copper windings are required. This also has the potential to reduce costs.

Importance of polarisation

The level of induction reached in the air gap between the rotor and the stator determines the torque a motor can develop. In the starter motor of a car, this break-away torque is very important. At low car speeds, the quality of the electrical steel used can create large differences in the dynamic behaviour of electric vehicles.

Importance of losses

An electric machine is no more than a system to convert electrical energy to mechanical energy (or vice-versa). The torque generated in the starter motor, is created by a polarisation level created in the steel, due to a magnetic field. The magnetic field can be provided by injecting current in a copper winding around the steel.

The key point is that the magnetic field creates a change in the magnetic structure inside the steel, in equilibrium with the applied field, which leads to a certain level of polarisation.

In an alternating current cycle, the magnetic field is reversed in some point later in time, but the internal magnetic structure of the steel cannot adapt immediately. There is a delayed response, known as hysteresis, which is linked to irreversible processes taking place inside the steel.

Hysteresis is responsible for some energy loss, known as iron loss. As the steel warms up, the motor gets warm as part of the electricity provided to the motor is changed into wasted heat rather than useful mechanical output. With higher cycling speeds, hence higher electric frequencies, these losses become more important. Lowering the iron losses from the machine’s steel laminations increases the amount of battery energy available in an electric or hybrid vehicle.

Thermal conductivity

The heat generated in an electrical machine needs to be extracted to ensure the safe operation of the machine. Failure to adequately remove the heat can lead to lower performance in terms of power or current output.

The heat is generated by the iron losses described above, along with losses from permanent magnets or copper windings. In fact, the insulation of copper windings is critical in the thermal equilibrium of a machine. The heat can be evacuated via the:

  • Rotor laminations towards the rotor shaft
  • Air gap
  • Stator lamination towards the housing. In this case it is important to choose steels with good thermal conductivity for the lamination.

Mechanical properties

The mechanical properties of steels used in electrical applications must be adapted to allow good punchability. The punch should be able to form a sharp edge shape. If the edge is not sharp, shortcuts in the magnetic field may occur between assembled laminations and the edge of the steel may be deformed, reducing its magnetic properties. However, these factors must be balanced against the desired useful life of the punching tool.

ArcelorMittal’s fully processed electrical steels are optimised for punchability. Further reductions in tool wear can be achieved by applying a suitable coating.

For hybrid and electric traction machines, the mechanical needs of the steel go beyond punchability. One method used to obtain higher power density machines is to work with higher speed rotors. This requires the rotor laminations to withstand higher centrifugal, electromagnetic and dynamic forces as the rotors speed-up and slow down. The laminations often have very intricate, lace-like designs. It is a real challenge for mechanical machine designers to meet these strength needs in both standard and exceptional situations.

Finding the balance

The limitations of batteries can be mitigated if the available battery energy is optimally utilised. This requires light and highly efficient electrical steels which have low losses as their key property. Finding the balance between losses, permeability, saturation polarisation, thermal conductivity, tensile strength and yield strength, is vital for automotive electrical steels.

ArcelorMittal’s experience as a provider of electrical steels for automotive applications has enabled us to develop steels which meet these challenges. We understand that optimal electrical motor solutions utilise different electrical steels for the stator and the rotor. Electrical steel grades with very low losses and high permeability are required for the stator, while high strength grades are required for the rotor.

Optimising all the electric components of a vehicle

In a process of continuous improvement, different efforts to optimise the electrical applications in vehicles are ongoing. The process started with the re-engineering of auxiliary electrical equipment such as alternators and starter motors. That led to the introduction of electric traction machines, first in hybrid drives and now moving towards vehicles powered fully by electric traction. These changes have led to significant improvements in individual electrical components in vehicles.

Increased demand on alternators

Alternators have always provided the electricity necessary to power the engine pump, the engine cooling system, seat and window motors, and other essential applications. Since the 1970s, there has been an ever-increasing demand for onboard electricity from vehicle safety and comfort features. Meeting this demand has a corresponding impact on the amount of electricity that must be generated by the vehicle.

Thanks to the development of high efficiency alternators, more current can be generated without increasing the amount of mechanical energy drawn from the ICE. Fuel consumption is therefore not affected.

Changes for starter motors

Until recently, starter motors have only been needed once in every drive cycle to crank the ICE into life. This changed with the introduction of stop-start systems which cut the ICE at a red light and restart it immediately the gas pedal is depressed by the driver. Stop-start systems can lead to a 5% drop in both fuel consumption and CO2-equivalent (CO2-eq) emissions.

To accommodate this change in function, starter motors have been completely redesigned to enable them to provide both a cold starting function at the beginning of the drive cycle as well as repetitive hot starts. The starter motors in stop-start systems are extremely efficient.

The challenge of creating electrical traction motors for automotive

The level of electrification of the powertrain has now evolved to the point where the ICE can be replaced with one or more electric machines. These machines provide pure electric traction.

Even when a designer elects to create an electrically powered vehicle, there are further considerations to be made. For example, if the vehicle has a higher power electric machine, more energy can be recuperated during braking. However, the battery must be capable of accepting the transfer of such energy.

In the gap between pure ICE and pure electric vehicles, there are many intermediate powertrain solutions where both the ICE and electric machines are present. In these hybrid configurations, many lay-outs exist and each represents a different set of compromises between the use of fossil fuels and electric energy. These compromises come about because vehicle designers must make choices between the cost of the ICE versus an electric machine. The battery cost and the environmental objectives of the car are the major decision criteria for this choice.

If a hybrid design is selected, the savings in fuel consumption depend on the level of hybridisation. There are generally two options:

  • A mild hybrid which reduces fuel consumption by around 15% using a moderately powered electric motor and smaller battery.
  • A full hybrid which can reduce fuel consumption by up to 30% using a higher powered electric engine and larger battery capacity.

Vehicles powered by electric traction machines are gaining increasing prominence. Unlike vehicles which utilise fossil fuels, pure electric cars produce very few harmful emissions during use. This makes them an attractive option for car makers who are seeking new strategies to meet ever-stricter regulations on vehicle emissions.

However, there are still significant challenges to overcome before electrical vehicles gain widespread acceptance with the general public. There are concerns about infrastructure, particularly the availability of recharging stations; and about the cost, range and longevity of the vehicles themselves.

Many of these concerns can be traced back to the battery in an electric vehicle. Classic batteries utilise a lead-acid technology which is extremely heavy, expensive, slow to recharge and limited in capacity.

New battery technologies have a higher capacity, but the cost and weight of the battery limits the drive range of pure electric vehicles. This is a key focus of electric vehicle development today.

Further information

For more information about ArcelorMittal’s iCARe® range of electrical steels and the support we can provide, please visit: http://automotive.arcelormittal.com/automotive/icare

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