BeginnerTopic 19 of 100Materials & Chemical
Heat treatment of steel
Annealing, normalising, quenching and tempering tailor properties.
In depth
Annealing and normalising soften and refine; quenching austenite rapidly forms hard brittle martensite; tempering (150–650 °C) trades hardness for toughness; case hardening (carburising, nitriding), induction hardening treat surfaces. Distortion and quench cracks are risks.
Key points
- Austenitising temperature
- Quench media: oil, water, polymer
- Tempering colours
ExampleA hardened chisel is tempered to reduce brittleness.
What is Heat treatment of steel?
Annealing, normalising, quenching and tempering tailor properties.
Why is it important to understand heat treatment of steel?
Heat treatments tailor the properties of steel after shaping, so the same steel can be soft for machining or hard for wear.
What is the difference between annealing and normalising?
Annealing gives the softest and most uniform structure with slow cooling, while normalising uses air cooling and gives a finer, slightly stronger structure.
Why temper after quenching?
Quenching makes steel very hard and brittle, and tempering reduces brittleness while keeping much of the strength.
How is Heat treatment of steel used in practice?
Typical applications include annealing a steel bar to soften it before machining, quenching and tempering a shaft to get strength and toughness and normalising a forging to refine the grain structure.
What should I learn before Heat treatment of steel?
Study "Steel types" first (topic 18 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Heat treatment of steel?
Austenitising temperature. Quench media: oil, water, polymer. Tempering colours.
Can you give an example of Heat treatment of steel?
A hardened chisel is tempered to reduce brittleness.
What comes after Heat treatment of steel?
The next topic is "TTT and CCT diagrams", which builds directly on this one.
How difficult is Heat treatment of steel?
It is classed as Beginner in Materials & Chemical (topic 19 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.