In a solution heat treatment process, long cylindrical pieces of an aluminium alloy of radius r = 5 cm are placed inside a radiant oven. The initial temperature of the cylinders is 25°C. The walls of the oven are maintained at a temperature of 800°C. The oven is evacuated such that the surface of the cylinders is exposed only to radiation heat exchange with the oven walls. The emissivity of the cylinder surface is 0.95. The solution heat treatment process is considered to be completed when the temperature of the alloy reaches 520°C and is left in the oven for another hour.
(1) What is the time taken to complete the solution treatment process for the aluminium pieces?