Your boss is given a new cylindrical aluminum part to be sand cast. The part is a disk 50 cm in diameter and 20 cm thick to be cast of pure aluminum in a closed

mold system containing a gating system and riser volume that is 50% of the mold

cavity volume. Assume that a superheat of 100°C is used and that the aluminum

properties are as follows:

▪ Melting temperature of aluminum = 660°C

▪ Latent heat of fusion = 389.3 J/g density

▪ Density = 2.70 g/cm3

▪ Specific heat = 0.88 J/g-°C. Assume the specific heat has the same value for

solid and molten aluminum.

Q1:Compute the amount of heat (in MJ) that must be added to the metal to heat it to the pouring temperature, starting from a room temperature of 25°C.

Q2: Assume the same part in Q2 is being made with the same method. Based upon past experience when poured from the same temperature, the mold constant for sand casting an aluminum part was found to be 5 min/cm2. Determine the total solidification time (in minutes) for the part.

Q3:Assume that the sand mold downsprue is 25 cm long and the cross-sectional area at the base is 2.5 cm2. The downsprue feeds a horizontal runner leading into a mold cavity. Assume also that the part has the same dimensions as described in Question 22 and that the volumetric contraction for the cast metal in the mold is 4.3%. Finally, assume that using the current superheat, it takes 28 seconds before solidification begins. What is the mold fill time (in seconds)?

Q4: Will the mold fill before the start of freezing?

Q5: Assume that a part with unknown dimensions uses a permanent mold casting process with a mold constant of 1 min/cm2 and that the part solidifies in 60 min. Calculate the dimensions (in cm) of an effective riser assuming that the riser is a cylinder with a height/diameter ratio H/D = 1 and that the riser will take 10% longer than the casting to solidify. H = D = ?