A never-ending story—the life cycle of a steel beverage can12 December 2018
A never-ending story—the life cycle of a steel beverage can
We have become so accustomed that we barely notice them in detail: beverage cans. In Germany alone, billions of cans cross store counters every year. How are such incredible numbers even possible? What is behind it all? And how is it possible to produce a product of such high quality in a sustainable and efficient manner? Let’s take a look at the key stages in the “life” of a steel beverage can—including the most important numbers and facts surrounding this popular and robust tinplate container.
The life of a steel beverage can commences in an oxygen steel mill, for example at thyssenkrupp Steel Europe in Duisburg. Here, liquid raw iron is made from iron ore, coking coal, additives such as limestone and reducing agents like coal, oil or gas at high temperatures in a blast furnace. At the steel mill scrap steel is added and melted, which has the advantage of lowering the temperature to the required temperature range of 1600°C. This temperature is the optimum value for the production of crude steel from raw iron. Crude steel is the starting product for hot rolled strip, which is transferred to Germany’s only manufacturer of packaging steel, thyssenkrupp Rasselstein GmbH in Andernach, for further processing.
Thinner than a human hair
At this site, thyssenkrupp processes the steel band into ultra-thin, cold-rolled blackplate, which is tin-plated for the subsequent production of beverage cans. Once rolled up into coils, this so-called tinplate or packaging steel is shipped to beverage can manufacturers.
Benjamin Liebscher is a development engineer for applied technology at thyssenkrupp Rasselstein GmbH and knows the production process like the back of his hand: “Thanks to decades of research and development, today’s tinplate is a high-tech material with special properties that are not necessarily obvious at first sight. Among other things, steel beverage cans are light, airtight, robust and easy to stack, with a wall thickness of only 65µ—thinner than a human hair!”
A 0.33 liter steel beverage can weighs only 19 grams; that’s more than a third lighter than in 1985. thyssenkrupp’s vast experience as a long-time supplier of D&I packaging steel for beverage cans ensures high quality products combined with reduced resource use: steel ranks highly in terms of sustainability due to the development of new steel grades and ongoing research into the manufacturing processes. Each newly produced steel beverage can contains a share of recycled steel scrap. Each ton of steel scrap used approximately accounts for a ton of CO2 emissions savings.
In order to achieve maximum efficiency in the supply chain, thyssenkrupp ensures that its material has what it takes to be processed into beverage cans: a high degree of steel purity enables maximum formability and reduces waste during processing. Furthermore, tribologically optimized surface characteristics and friction properties facilitate further processing and protect the machines and tools.
Once the packaging steel has reached the packaging manufacturer it is processed into two-part D&I beverage cans, primarily in 330 and 500 milliliter sizes. D&I is short for “drawn and wall-ironed”, which refers to the manufacturing process.
In a first step, open cups are stamped from the tinplate coil and deep-drawn. Then they are pressed through four deep drawing rings of a special forming machine, the so-called “bodymaker”. The diameter of these rings is smaller than the tinplate cup’s diameter, which means the steel is not only elongated, but also made thinner with each step—until it finally reaches the desired thickness of a mere 0.065mm. “A cooling lubricant absorbs the heat resulting from the process. Additionally, the surface of the tinplate has a lubricating effect which is necessary for rapid throughput,” Liebscher explains. On average, the bodymaker produces 250 cans per minute! During the final step of the forming process, the can is stamped using a customized tool to create the typical, dome-shaped base, which provides stability. Once washed, painted and printed, the opening of the can is tapered during the “necking” process. Now the can is essentially finished and ready to be filled.
30 percent less material than 30 years ago
“Over the course of 30 years, the amount of steel required per can has gone down by approximately 30 percent. This is in no small part due to the close collaboration with our material technology colleagues in Duisburg. This cooperation sees the continuous development of new material grades and the non-stop refinement of production processes. These steel grades can then be tested in a bodymaker in Andernach in real-life conditions. The potential of steel as a packaging material is far from fully exhausted”, Benjamin Liebscher is convinced.
After the cans are palletized, filled and sealed, it is time for consumers to have a drink! The consumption stage is certainly very short compared to processing stages so far, and the subsequent stages. Once emptied, the can finds its way back to the steel mill by way of recycling schemes and the scrap trade: the life cycle is thus complete. This cycle can be repeated indefinitely without a change in material properties, making packaging steel a permanent material. Each ton of recycled steel saves approximately 1.5 tons of iron ore, 0.65 tons of coking coal and 0.3 tons of limestone in raw materials. Consequently, every ton of recycled packaging steel and every recycled steel beverage can contribute to the conservation of limited resources.
Europe’s material cycle is impressively efficient. Out of all the different packaging materials, steel has the highest recycling rate – as high as 79.5% in 2016. The recyclability of a steel beverage can is also high: over 90% of the can is recyclable, corresponding almost exactly to the total share of steel content. Eventually, the compacted beverage can, along with other steel scrap, reaches a steel mill again. Of course, a beverage can will not necessarily become a can again. Quite the opposite - depending on fate, it could also be “reborn” as part of a car, a bicycle or ship propeller.
 Assessment of the recyclability of commercial tinplate packaging conducted by the scientific institute cyclos-HTP on behalf of thyssenkrupp Rasselstein GmbH.