Materials and manufacturing

1. You own an aluminium processing plant, and want to hot roll aluminium from a billet to a sheet form. The billet is 5m long, 3m wide and 0.25m thick. Your output sheet is to be 0.001m in thickness by 3m width. You configured your plant as a flexible manufacturing line, with an N-stage rolling mill configuration. Your initial feed rate is 0.005m/s.

Assume that the material does not require reheating from start to finish. The maximum reduction of the cross-section from a single roll is 50%, with negligible post-roll bulging. Side rollers maintain the width at 3m. Use Wikipedia for the data on Al, as needed.

A. What is the total mass of aluminium in the billet?

B. How many roller heads will you need to make this material into 0.001m sheets? You cannot “round down”- rollers and the material dictate the rolling limits.

C. At the final roller, what is the final roll thickness reduction at the output to the take-up spool (in percent)?

D. What is the take-up velocity at the final rolling stage?

E. Since you hot-rolled the aluminium, will it be ductile or brittle?

2. Chromium is critical in manufacturing stainless steel.

A. Why do you need at least 10w/o Cr to ensure “stainless” properties?

3. Cast iron can be ductile. Gray cast iron, however, is more brittle than white cast iron. This is due in part to the shapes of the carbon precipitates.

A. Comment in 2 or 3 sentences why gray cast iron is weaker in tension than white cast iron. Draw pictures, if necessary.

B. Refining cast iron requires removing about 2w/o carbon from the molten iron. How is this accomplished in the processing flow?