Syllabus Dot Point
heat treatment of ferrous Metals
– annealing
– normalising
– hardening and tempering
– changes in macrostructure and microstructure
changes in properties
Case Hardening
Metal must be pliable to be suited to a variety of applications. However, a metal must also be durable, especially when it comes to surface strength. These two characteristics are integral to ensure optimum function and reduce the effect of excessive wear and tear. That’s where case hardening, which is also referred to as surface hardening, comes in. This process enhances surface strength while allowing the core to remain flexible.
In carburizing, the surface hardness of the steel is increased by adding carbon to the component. The component that requires hardening is heated to 9000C and exposed to a carbon environment. The carbon penetrates the surface of the metal and strengthens it.
Nitriding steel is steel treated by a highly specialized surface hardening process known as nitriding, which is a heat-treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface.
Flame hardening in its simplest form is the heating up of steel to its hardening temperature by a flame and then quenching in water or oil. It is used to produce a hard case on the surface of a wide range of mechanical components.
With induction hardening, the workpiece is heated by induced eddy currents. The hardening depth is controlled by the frequency of the alternating current!
The flames during flame hardening generally lead to a large heat-affected zone. With small geometries, this can lead to undesired full hardening over the entire cross-section. In order to harden even such thin-walled workpieces only on their surface in the range of a few tenths of a millimetre, so-called induction hardening can be used.