In my diploma thesis, I found out why in the foundry LIGO.doo, during the casting of the casting AUMA SQ 07 V1, which is used as a part of the reductor, settling errors and shrinkage porosity occur. The casting is cast from gray cast iron with lamellar graphite into a form of bentonite sand mixture. Due to the large inclination of a certain place of the casting to the settling error, the ejection is very large, and the production of circular cast iron is wasteful from the point of view of work and energy. Therefore, the inflow feed system had to be optimized to reduce the ejection fraction. First, I analyzed the place on the casting in the foundry, where the most common settling error occurred, with an optical microscope. Then, at TC Livarstvo, we made a calculation of casting processes in the casting of this casting with the help of computer simulation. We found that the main cause of the settling error is an oversized module just below where the error often occurs. The larger the modulus than the body has, the slower it cools. This means that this spot on the casting hardens last. Ideally, however, the feeder should harden last. Settling and porosity therefore occur because the flow of melt from the feeder to the casting is interrupted when a part of the casting with an oversized module has not yet solidified and shrinkage occurs during cooling. We solved the problem with a different design of the feeder, which was able to power the casting for a longer time, as it had a larger module than the previous power supply. We also lowered the casting temperature to reduce shrinkage during the cooling of the cast iron.
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