A cylinder 6 cm in diameter and 18 cm in height is to be cast from...

 

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A cylinder 6 cm in diameter and 18 cm in height is to be cast from brass alloy using an open sand mould. The melting temperature of brass is 926 C, and the pouring temperature will be 1100 C. Assume the amount of brass heated will be 3% more than what is required to fill the mould cavity. a) Draw a schematic cross-sectional diagram of the cylinder showing the grain structure you would predict; justify your answer. (3) b) Name the two basic mould types that distinguish casting processes? (2) c) If the linear shrinkage of brass is 1.4%, what are the required dimensions of the pattern incorporating shrinkage allowance? (2) d) The specific heat of brass is 0.402 Jg1 C as a solid, rising to 0.411 Jg C in the melt. It has a density of 8.4 g cm. A simplifying assumption is made that its behaviour can be described with a heat of fusion of 168 J g. i. Using a sketch, explain why the use of a single value for heat of fusion is a simplification for an alloy? iv. (3) What is the mass of brass needed for a single casting operation? (2) How much heat energy is needed to raise the brass to the pouring temperature from an ambient temperature of 20 C? (3) Use Chvorinov's Rule (given below) to calculate the solidification time for the casting given a mould constant of 4 min cm. Please assume a reasonable value for any missing parameters. Trs = Cm)" (5) A cylinder 6 cm in diameter and 18 cm in height is to be cast from brass alloy using an open sand mould. The melting temperature of brass is 926 C, and the pouring temperature will be 1100 C. Assume the amount of brass heated will be 3% more than what is required to fill the mould cavity. a) Draw a schematic cross-sectional diagram of the cylinder showing the grain structure you would predict; justify your answer. (3) b) Name the two basic mould types that distinguish casting processes? (2) c) If the linear shrinkage of brass is 1.4%, what are the required dimensions of the pattern incorporating shrinkage allowance? (2) d) The specific heat of brass is 0.402 Jg1 C as a solid, rising to 0.411 Jg C in the melt. It has a density of 8.4 g cm. A simplifying assumption is made that its behaviour can be described with a heat of fusion of 168 J g. i. Using a sketch, explain why the use of a single value for heat of fusion is a simplification for an alloy? iv. (3) What is the mass of brass needed for a single casting operation? (2) How much heat energy is needed to raise the brass to the pouring temperature from an ambient temperature of 20 C? (3) Use Chvorinov's Rule (given below) to calculate the solidification time for the casting given a mould constant of 4 min cm. Please assume a reasonable value for any missing parameters. Trs = Cm)" (5)