Advancing Closure Sheet Performance and Beyond

For more than 40 years, Constellium has been at the forefront of aluminum sheet production for closures used in wine, spirits, carbonated drinks, mineral water, and various other applications. Our closure sheets are renowned for their superior quality in formability, flatness, rectangularity, and surface properties, ensuring reliable performance in high-precision applications.

The Role of Deep Drawing in Closure Manufacturing

Deep drawing is a metal forming process used to shape aluminum sheets into cylindrical or complex geometries, such as bottle closures and other container lids. The quality of the aluminum sheet significantly impacts the success and efficiency of our customers’ production processes. Key characteristics such as uniform thickness, fine grain structure, and optimized mechanical properties play a crucial role in ensuring seamless manufacturability.

What Makes Constellium’s Closure Sheet Stand Out?

Constellium’s closure sheet is available in various aluminum alloys tailored to specific applications:

• 8011A (AlFeSi) – Long cap closure primarily used for spirits and wine closures.
• 3105 (AlMn0.5Mg0.5) – Ideal for carbonated drinks and food cans.
• 5052 (AlMg2.5) – Designed for food cans requiring enhanced corrosion resistance.

These sheets, typically around 1 m² in size with thicknesses ranging from 0.2 to 0.3 mm, are lacquered and undergo deep drawing at our customers’ production lines. Critical to performance are surface appearance, lacquer adhesion, and formability, ensuring both aesthetic appeal and functional integrity.

Understanding Formability: The Key Parameters

Formability is a fundamental property of closure sheets, influencing how well they can be shaped without cracking or failure. Three main parameters define drawability:

1. Grain Structure: Fine grains lead to an even surface appearance, particularly in heavily formed parts such as the bottom of bottle caps.
2. Earing Level: Anisotropy in the sheet metal can result in “earing” during deep drawing. Lower earing levels improve drawability and reduce material waste.
3. Technical Properties: Tensile strength (UTS), proof stress, and elongation at break all provide insight into the material’s ability to withstand forming without defects.

At Constellium, our advanced manufacturing processes ensure precise thickness uniformity and tight tolerances, enabling high precision in our customers’ operations.

The Singen Advantage: A Unique Approach to Manufacturing

Constellium’s Singen rolling mill is distinguished by its inline hot and cold rolling process, which plays a pivotal role in ensuring high and stable performance across all critical parameters. The unique water pool concept enables shorter production routes, reducing property variations and enhancing material consistency. Our proprietary hot rolling line design, combined with alloy compositions specifically adapted to our equipment, results in closure sheets with unmatched quality and reliability.

Additionally, we apply a chromate-free titanium-phosphate conversion layer in our finishing lines. This ensures superior lacquer adhesion during deep drawing and sterilization while eliminating the environmental risks associated with toxic chromate sludge.

Beyond Closures: Applying Expertise to Battery Cell Production

The expertise developed in aluminum closure sheets has also been leveraged for a growing application – prismatic battery cells used in electric vehicles (EVs). Prismatic cells are gaining popularity due to their high space efficiency, flexible design, and potential for greater capacity compared to cylindrical cells. As the European EV market expands, major battery manufacturers are ramping up production, and Constellium’s Singen rolling mill has become a preferred supplier of aluminum coils for this application.

Interestingly, the requirements for prismatic battery cell casings share similarities with closure sheets. Both require alloys from the 3XXX series (AlMn), making it possible to apply our knowledge of production parameters and material properties, such as earing levels, to battery applications. Through close collaboration with our C-TEC R&D lab in Voreppe, we developed a dedicated alloy composition and production route to meet stringent customer demands.

By adapting our established closure sheet production process to a new thickness (~1 mm) and fine-tuning temper properties, we successfully addressed challenges such as springback effects in battery cell manufacturing. This synergy underscores Constellium’s commitment to innovation and cross-industry expertise.

Driving Innovation Across Industries

Whether for premium beverage closures or cutting-edge electric vehicle batteries, Constellium’s aluminum sheet technology continues to set industry benchmarks. Our deep understanding of material science, combined with state-of-the-art manufacturing, ensures that our customers receive products optimized for performance, efficiency, and sustainability.

Stay tuned for more insights in the Aluminum Expert Series, where we explore the latest advancements shaping the future of aluminum applications.