Tutorial for Lecture 12: The heat-treatment of plain-carbon steels
QUESTIONS
Higgins Ch12
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Define all the glossary terms.
Why are isothermal heat treatments of carbon steel limited to thin sections?
Why are there a range of different quenching fluids?
When a carbon steel is quenched, which grain structure causes hardness?
If a quenched steel is too hard, what process can be used to toughen it?
On the TTT curve for a particular carbon steel, what advantage is there in avoiding
the ‘nose’ of the curve – as isothermal heat treatments do?
7. List iron grain structures that are super-saturated with carbon.
8. Describe the difference between heat treatment of hypo and hyper-eutectoid
steels. Why is hyper-eutectoid more complicated?
9. Describe the Jominy test. What does it measure?
10. Describe how Critical Cooling rate can be modified by %C or alloys elements.
11. An injection mould tool is made from thick steel sections that must be hard.
Explain why you would choose a carbon or alloy steel. Give an example of a suitable
alloy from this chart.
12. Summarise the advantages and disadvantages of the three carburising methods
shown in the video: Pack carburising , cyanide and plasma.
Glossary
Martensite
Bainite
Super saturated solution
Critical cooling rate
Tempering
Martempering Austempering
Ruling section
Jominy Test
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