Heat Treatment Flashcards
(18 cards)
What is Heat Treatment?
Heat Treatment process is the controlled heating or cooling of plain carbon steel or alloy steel
Why is Heat Treatment done?
Heat Treatment of steel is done to change its molecular structure, in order to obtain certain mechanical properties. (like: hardness, strength or ductility)
What are the Types of Heat Treatment processes?
- Annealing
- Normalizing
- Quenching
- Tempering
Describe the process of Annealing
In Annealing, steel is heated to a temperature which is slightly above the critical temperature, followed by slow cooling
What are the results of Annealing?
- Reduced hardness
- Improved grain structure
- Increased ductility
Describe the process of Normalizing
Normalizing is the process of heating steel and cooling it in air.
Normalizing is used to remove the effect of all the previous heat treatment processes.
What are the results of Normalizing?
Normalizing relieves internal stresses in the material and refines the grain structure. It also improves machinability of the material.
Describe the process of Quenching
In Quenching, steel is heated to the critical temperature and then cooled rapidly in water or air.
What are the results of Quenching?
Quenching is used to increase hardness and wear resistance. In this process, steel becomes brittle and its ductility is reduced. To remove some of the brittleness of the quenched material, tempering can be performed.
Describe the process of Tempering
Tempering is reheating of Quenched component to a temperature which is below transformation range, followed by cooling at a desired rate.
What are the results of Tempering?
Tempering is used to restore ductility and reduce the brittleness due to quenching.
What are some defects of Heat Treatment processes? (6)
- Decarburization
- Over heating
- Oxidation
- Soft spots
-Quenching cracks - Warping
What is Decarburization?
Decarburization is loss of carbon from the metal surface due to prolonged heating
What is Over heating?
Loss of ductility and impact strength due to heating metal for a long period of time at high temperature
What are Soft spots?
Localized decarburization and bubble formations in metal
What are Quenching cracks?
Cracks arising in metal surfaces due to higher cooling rates
What is Warping?
Non-uniform heating or cooling of the metal
What are some benefits of Heat Treatment?
- Reduce stresses in the metal
- Can increase the strength of metals
- Can make metals more ductile
- Can make metals more flexible
- Can increase wear resistance (hardness) of metals
- Can increase or decrease brittleness of metals
- Can improve electrical properties of metals
- Can improve magnetic properties of the metals
