Annealing is a process by which steel is reheated and thencooled to make it less brittle. Consider the reheat stage for a100-mm-thick steel plate (Ï= 7830 kg/m3, c= 550 J/kg·K,k= 48 W/m·K), which is initially at a uniform temperature of Ti=120°C and is to be heated to a minimum temperature of 550°C.Heating is effected in a gas-fired furnace, where products ofcombustion at ∞T∞= 800°C maintain a convection coefficient of h=250W/m2·K on both surfaces of the plate. How long shouldthe plate be left in the furnace?
