Question

For AISI 1050 Steel at 10 cm in diameter, use case hardening methods to produce a surface hardness of at least 60 HRC. Describe the method that will create a thin, carbon enriched surface layer in order to maintain the ductile properties of the core. Show calculations.

Answer 1

Case hardening methods like induction hardening and carburising are used to increase surface hardness. AISI 1050 is a medium carbon steel with 0.5 wt% carbon.

As it is having 0.5 wt% of carbon content, oil quenching will give it 61 HTC. But the problem is that quenching Make a the core also hard. So in order to get the core ductile carburising is preferred. Here the material is heated to about 900 degree celsius at an atmosphere of gases like methane(CH4). The carbon diffuser into top layer of material creating a harder outer surface and a ductile inner core. The thickness of cte is directly proportional to the time exposed to gas. By this way we can achieve our required hardness value of 60HRC.

The thickness of layer for hardened case can be found out using Ficks second law or fisrt law, depending on the nature of difussion, steady state or non steady state.