Hardening is a metallurgical metalworking process used to increase the hardness and strength of a metal. The hardness is directly proportional to the uniaxial.
Hardening is a way to make the steel knife harder by first heating the steel knife to between 1050 and 1090 ° C (1922 and 1994 ° F) and then immediately cooling it will be called quenching it, making the steel knife much harder but also more brittle.
The hardening process has three steps :
The hardening process has three steps :
- The specimen to heat depends upon the carbon content.
- Sock at that temperature for sufficient time.
- Quenching is called fast cooling.
The hardness of metal at the location of the imposed strain is directly proportional to the uniaxial yield stress.
For hardening of steel required a change in structure from the body-centered cubic structure to the face-centered cubic structure while BCC structure found at room temperature and FCC structure found in the austenitic region.
- If suddenly quenched, the Martensite is formed. This
is a very strong and brittle structure.
- If slowly quenched, it would form Austenite and
Pearlite which is a partly hard and partly soft structures.
- It would mostly be extremely soft Pearlite if the cooling rate is extremely slow.
Purpose of hardening?
- The main purpose is to develop high hardness.
- To improve wear resistance for steel tool.
- To improve tensile strength for structural steel.
- To improve yield strength for spring steel.
Factors affecting the hardening process
- Chemical composition
- Hardening cycle
- Size and shape of steel part
- Homogeneity and grain size of austenite
- Quenching media
- The surface condition of the metal
Applications of hardening
- High-strength construction material
- Machine cutting tools like drill bits, taps, lathe tools
- Knife blades
- Bearings
- Armor plating
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