Overview of casting in Elkem Sample Clauses

Overview of casting in Elkem. ‌ Elkem uses different techniques for casting molten silicon and other silicon alloys. Some of these are layer casting, ring molds, stationary chill molds, chill mold carousel and chill mold train. These methods differ significantly in terms of equipment complexity, robustness and operating and investment costs. However, there are certain features that are identical for all of the methods. - The mold is covered with fine-crushed Si of the same quality to avoid direct contact between mold and molten Si. - The thickness of the cast can be controlled during casting. - The temperature of the incoming molten alloy is not measured during the casting process. - The duration of the casting process is the time it takes to empty the ladle, typically 15- 20 minutes depending on the volume of the ladle. - The chemistry of the alloy is known at the beginning of the casting process, but no further chemical sampling is done during the casting process. In theory, volatile elements such as Ca could evaporate from the alloy in the ladle during casting. As an example case, we will focus on the casting process currently used at Elkem Thamshavn. The main principles are to a large degree transferable to other variations of silicon casting, as indicated above. At Elkem Thamshavn, the ladle is transported in a crane after refining is completed. The ladle is hanging from the crane at all times, and a secondary lift is used to raise the bottom of the ladle so that the silicon can pour out of the ladle into the 2 by 2 meter casting moulds covered with crushed silicon (Figure 1), typically 1-5 mm size. Four or five moulds are used per ladle, i.e. the crane has to move sideways from one casting mold to the next, see Figure 2. The thickness of the cast Si is about 100 mm. After solidification is complete, the large plates of solidified silicon are removed with a forklift and transported to a storage bin.