The foundry in Tuttlingen is a practically perfect recycling facility. Annually more than 50,000 tons of steel scrap are processed into brake discs. Extremely high specifications are placed on the scrap. It is initially smelted in a cupola furnace together with coke and thereafter fed into an inductive duplicate furnace set specifically to each article and the corresponding elements in the alloy to ensure reproducible conditions.
To meet the high demands of the casting process, all sand moulds are coated prior to casting. This avoids sand inclusions in the casting and also facilitates the separation of the cast from the mould while positively affecting the cooling process of the molten iron.
The brake discs are cast at roughly 1,350°C into sand moulds fitted with cores and filters on two automated moulding machines. To ensure optimum quality of the raw brake discs, the casting and solidification process is simulated in advance.
Once they have cooled, the circumference of the brake discs, which have diameters of up to 420 mm, is deburred. Each ventilation channel is inspected by laser and the surface is inspected as a final step before being packed, often automatically by robots.
Some automobile manufacturers do not have their own foundry but machine the brake discs themselves. Consequently, there is associated demand for quality raw brake discs
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Brake discs are safety components. For this reason, they must meet the most stringent quality specifications and be able to be traced back to production.
During operation, temperatures can reach up to 700°C. To ensure that no cracks develop due to temperature fluctuations, the demands placed on the raw casting are extremely high. The customers of SHW are increasingly shifting to lighter brake discs to reduce CO2 emissions. This pushes the envelope of permitted tolerance constraints, which in turn raises the quality standards placed on a stable process to manufacture reproducible raw castings.
SHW produces a range of raw castings right up to high-alloy, high-strength grey-cast steels for demanding applications, such as in motor sport. Quality is constantly checked during serial production using a spectrometer to determine the relative components of the alloy and this is documented to ensure an audit trail. The same applies to the process parameters of serial production. In this way, SHW ensures constantly high casting quality.