Cromodora Wheels SPA has installed a chip recycling furnace with a capacity of 10,000 tons per year for wheel production in Ghedi, Italy. Since 1962 Cromodora Wheels has produced high pressure and low pressure cast magnesium and aluminum alloy wheels for standard production and competition. Cromodora Wheels is an official supplier to luxury automotive manufacturers, such as BMW, Jaguar Land Rover, Daimler (including AMG and Smart), Porsche, Audi, Volkswagen, Skoda, Fiat, Maserati, and Alfa Romeo.
According to Cromodora, they were the technological innovators of low pressure casting, heat-treated aluminum alloy wheels. Their wheels are manufactured in the low-pressure casting process by using flow forming technology, which helps to obtain lighter wheels. When manufacturing wheels, large quantities of chips are typically produced along with relatively low portions of piece scrap.
Chip recycling is challenging because the unfavorable ratio of surface area and volume cause significant material loss through burn-off. The traditional method of recycling chips is to compact the chips before melting, which reduces metal loss. However, this method requires additional work and consumes more energy, and the chips are frequently contaminated with adhering cooling lubricant during the process.
Modernizing the Recycling Process
With the installation of the new melting furnace, Cromodora is modernizing the recycling of its processing scrap while improving their financial flow. The furnace with a capacity of 10,000 tons per year was successfully supplied and commissioned by Hertwich Engineering, a part of the SMS group. Hertwich Engineering’s recycling system offers an economical solution for large volumes of chips. Using a combination of the company’s Ecomelt concept (based on the internal use of the energy content of organic impurities removed from the scrap) and a special tailor-made furnace technology, low metal loss values are achieved during operation. The system guarantees cost savings for recycling for specific wheel production versus the long-used traditional methods.
In addition to the melting furnace, the system includes chip-pretreatment with a bypass system for conveying in separate transport containers. During pre-treatment chips are centrifuged. To ensure stable processing afterward, unfavorable chip shapes are shredded in a chip crusher. Next, a separator removes undesirable elements.
The prepared chips are then fed into the melting furnace. In the furnace, the charged chips are heated to approximately 400°C within a few seconds using an intensive hot gas flow, removing moisture and organic contaminants. Hot gas from the melting furnace provides energy, and the flue gases from the dryer support the heating of the furnace.
The preheated and cleaned chips are continually fed into the downward directed melting flow and immediately drawn under the bath surface to the furnace floor. Most of the typical metal loss due to oxidation is avoided because of the fast melting, resulting in very low dross formation. The heat is removed largely from the flue gases in a regenerative combustion system and thus the combustion air is preheated to around 900°C.
According to Cromodora, the system provides several advantages. Since it is mostly automated, the complete furnace system can be operated by just one employee per shift. Metal loss during the operation results in values below 0.01%, exceeding the value of conventional furnace units melting ingots. Sustainability wise, low energy costs are achieved with values less than 600 kWh/t (taking into account chip drying and combustion). The system is also ecologically compatible, meeting strict central European emission regulations. An objective inspection was carried out on metal quality that determined that the untreated melt from the chip recycling furnace was already ready for casting again.