At the start of sintering, a cylindrical powder metal high-speed-steel (HSS) green-compact (destined to become a machining
Question:
At the start of sintering, a cylindrical powder metal high-speed-steel (HSS) green-compact (destined to become a machining tool) with length 20cm and diameter 2cm, is placed from storage at 20o C into a furnace at 1250o C. Use the dimensionless temperature distribution graph estimate:
(a) How many seconds it takes for all of the interior of the green-compact to be heated to at least 1000o C (ignoring any heat flow into the two ends of the cylindrical compact). [8 marks]
(b)The temperature 2mm below the surface after 4 seconds? [8 marks]
(c) A surface coating is often applied to HSS machining tools to reduce in-use wear and so extend tool lifetime. The coating makes the tool appear golden. Suggest what coating has been applied, explain how such coating reduces wear for HSS, and name a technique you could use to deposit the coating. [4 marks]
(d)Describe, with the aid of a sketch, the process of forward extrusion of aluminum, and explain the role of the dead-metal zones. [5 marks] Data for steel powder compact: Thermal conductivity = 5 W m-1 K-1 Density = 7000 kg m-3 Specific heat capacity = 650 J kg-1 K-1
Cost Accounting A Managerial Emphasis
ISBN: 978-0133392883
6th Canadian edition
Authors: Horngren, Srikant Datar, George Foster, Madhav Rajan, Christ