After a difficult start in 2024, the e-car market is picking up significantly in 2025: With over 40,000 new registrations per month, twice as many e-cars are hitting the roads as in the previous year. The market share has risen to 16.6% (January 2024: 10.5%).

The driving force behind this development is the EU’s stricter CO₂ fleet limits. This transformation is fundamentally changing the demand for wire products and requires specialized qualities for completely new applications.

Wire Products for Electric Vehicles: Application Areas

Tire Reinforcement through Steel Cord: Electric vehicles pose new demands on tires due to their higher weight and instant torque. The growing demand for high-quality steel cords for tires is driven by the higher weight of electric vehicles and research into longer-lasting tires. Companies like ArcelorMittal and Bekaert have optimized their steel cord products: Modern steel cords for EV tires offer higher tensile strengths with improved fatigue resistance.

Steel cord is a wire rope made of brass-plated or galvanized steel wire used in car tires for elongation limitation. The brass plating plays a central role: During vulcanization, the brass is attacked by sulfur, creating copper sulfide, which is crucial for the adhesion of rubber to the steel wire. Bead wire technology has also been further developed to withstand increased loads.

Battery Technology: Battery systems require high-precision connecting elements under extreme temperature conditions. Companies like Bulten are developing specialized fastener solutions that absorb mechanical loads, ensure electrical insulation, and compensate for thermal expansion. voestalpine Wire Austria offers EPD-certified cold heading wires with reduced CO₂ footprints and optimized recyclability.

Suspension Systems: Mubea has developed special coil springs for electric vehicles that account for the increased loads from battery weight. Using Ansys simulations, spring characteristics are precisely tuned to EV platforms — with a focus on mechanical durability and NVH properties (Noise, Vibration, Harshness). The higher weight and altered weight distribution of electric vehicles pose new requirements for springs and damper components made from high-strength spring steels.

Welding and Joining Technology: The assembly of EV components requires specialized welding wires. voestalpine Böhler Welding develops solid wires and cored wires for welding different materials, integrating lightweight construction materials, and ensuring electrical insulation. Steel battery housings require high-precision welding technologies with defined chemical compositions.

Heat Treatment Processes for Wire Products

Heat treatment is a crucial process step for adapting wire products to the requirements of e-mobility. Different processes are used depending on the application:

Patenting

During patenting in a lead bath, the wire structure is homogenized. This process is particularly relevant for spring steel wires that are predominantly subjected to static loads. The wire rod is first patented and then pickled and phosphated. During wire drawing, the required wire diameter and tensile strength are then established.

The patenting process creates a sorbitic structure — a fine lamellar pearlite structure that is very well suited for subsequent cold forming. A special heat treatment, patenting, gives the drawn wires high uniformity and good processability. Alloying elements such as silicon and chromium improve relaxation and temperature resistance.

Quenching and Tempering

During quenching and tempering, the steel is first heated above the GSK line into the austenite region, then rapidly quenched and subsequently tempered at higher temperatures in the range between 550 °C and 700 °C. The goal of quenching and tempering is to achieve maximum toughness at a specific strength.

For spring wires, an oil-hardened and tempered version is often used. Here, the wire is subjected to heat treatment after drawing to the final diameter. Quenching and tempering creates a finely distributed carbide structure with an optimized combination of strength and toughness — ideal for dynamically highly stressed EV components.

Low-Pressure Carburizing with High-Pressure Gas Quenching

In the carburizing process, the components are heated in the furnace to temperatures around 900° C, allowing carbon from the process gas to diffuse into the component surface. The component is then rapidly cooled to fix the diffused carbon atoms in the surface structure. The geared components used in transmissions are subject to very high mechanical stresses and must be heat treated. This is achieved with heat treatment technologies such as low-pressure carburizing with high-pressure gas quenching in flexible, production-integrated system installations.

New Standards and Requirements

The standards “AMS2750” (aerospace industry) and “CQI-9” (automotive industry) require regular inspection of industrial furnaces. The results must be documented traceably. There is increasing demand for CQI-9 compliant heat treatment for wire. Heat treatment systems must achieve a high degree of temperature accuracy and temperature uniformity to meet the demands of the automotive industry.

E-mobility is establishing its own quality standards that have direct implications for wire production:

Electrical Properties: Wire products in electric vehicles must exhibit defined electrical conductivities or insulation properties depending on the application. Components near battery systems require extended thermal resistance and must withstand thermal cycling loads.

Sustainability Documentation: EPD certifications and CO₂ footprints are becoming decisive quality criteria in supplier selection. Comprehensive documentation of material origin and properties is becoming a prerequisite for integration into EV production lines.

Mechanical Requirements: Wire products are characterized by high dimensional accuracy, fine-grained microstructure, freedom from cracks, and uniform material properties — ideal for safety-critical and highly stressed applications. An average mid-size vehicle uses up to 90 kg of processed wire.

Opportunities of the Transformation

The e-mobility transformation offers the steel wire industry considerable opportunities:

Product Differentiation: Specialized wire products for e-mobility applications enable higher margins and stronger customer loyalty.

Innovation Leadership: Companies that invest early in e-mobility technologies can establish themselves as innovation leaders in new segments and secure competitive advantages.

Sustainability Image: Supporting the e-mobility transformation strengthens the sustainability image of steel manufacturers. Since e-mobility is a global trend, new export opportunities are opening up in global markets.

Conclusion

Successfully navigating the e-mobility transformation requires strategic foresight, technical innovation, and operational excellence. Heat treatment plays a key role in producing wire products with the required mechanical, thermal, and electrical properties.

Companies that invest early in e-mobility-specific competencies will benefit from long-term growth prospects. The German steel wire industry must combine its traditional strength in precision manufacturing with the innovation requirements of e-mobility — through intensive cooperation with automotive manufacturers, consistent sustainability orientation, and continuous development of future-oriented wire solutions.

Further Information and Sources

• Ansys: Mubea optimizes coil spring design for EVs

• Bulten: Annual and Sustainability Report 2023

• Mubea: Coil Spring Systems

• voestalpine: Wire Technology: Mobile Industry

• ArcelorMittal: Bars & Rods / WireSolutions Europe

• Hyperion Materials & Technologies: Understanding steel cord mechanics for longer-lasting tires

• inggo.com: Manufacturing of Spring Steel Wires

• Graphite Materials: Vacuum Heat Treatment in the Automotive Industry

• Kraftfahrt-Bundesamt: New Registrations