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Leaving Cert Engineering: Hardening, tempering & annealing

How often Hardening, tempering & annealing comes up on the Engineering papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

OL Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

June 2028 is the first exam on the new Engineering course. These come from the 2016–2025 papers, so read them as a guide.

Hardening, tempering & annealing, Higher Level(7 marks)

Quick ones on Hardening, tempering & annealing.

(a)Why is hardened steel tempered?
  1. To make it as hard as possible for cutting tools
  2. To reduce brittleness and increase toughness
  3. To add carbon to the surface for wear
(b)To harden a 0.5% carbon steel, it is heated to what temperature before quenching?
  1. About 230 °C (pale straw)
  2. Just below the lower critical temperature
  3. 30–50 °C above the upper critical temperature
(c)Temper colour usually used for springs?
  1. Blue (about 300 °C)
  2. Dark straw (about 250 °C)
  3. Pale straw (about 230 °C)
Show the answers

(a) To reduce brittleness and increase toughness

(b) 30–50 °C above the upper critical temperature

(c) Blue (about 300 °C)

Your turn: Higher Level questions on Hardening, tempering & annealing.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q4
2024Q4
2023Q4
2022Q4
2021Q1(i), Q4
2019Q1(h), Q3
2018Q3
2017Q3, Q4
2016Q1(b), Q3

Links open the State Examinations Commission’s paper for that year.

More Hardening, tempering & annealing questions

Hardening, tempering & annealing, 3 marks

Why is brine a more severe quench than plain water?

  1. Brine is kept colder than plain water, so it cools faster
  2. Salt adds carbon to the steel surface as it cools
  3. Salt stops a vapour blanket forming, so it cools faster
Show the answer

Salt stops a vapour blanket forming, so it cools faster

In plain water a layer of steam forms round hot steel and slows cooling. Salt breaks this vapour blanket, so heat is removed faster and more evenly.

Hardening, tempering & annealing, 3 marks

Why should a hardened part be tempered soon after quenching?

  1. Rust will stop it being tempered
  2. It could crack from its internal stresses
  3. It will lose its hardness if left
Show the answer

It could crack from its internal stresses

Quenching leaves high internal stresses in brittle martensite. Left untempered, the part may crack. Tempering promptly relieves the stress and adds toughness.

Hardening, tempering & annealing, 3 marks

Process annealing of cold-worked mild steel is done at?

  1. A temperature below the lower critical temperature
  2. 30–50 °C above the upper critical temperature, then quench
  3. About 230 °C, then air cool
Show the answer

A temperature below the lower critical temperature

Process (sub-critical) annealing heats below 723 °C so the deformed grains recrystallise and soften. No phase change is needed, so there is less scaling and distortion.

Ordinary Level

Asked on 9 of the last 9 Ordinary Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q3
2024Q3
2023Q3
2022Q3
2021Q3
2019Q3
2018Q3
2017Q3
2016Q3

Links open the State Examinations Commission’s paper for that year.

More Hardening, tempering & annealing questions

Hardening, tempering & annealing, 2 marks

How is medium carbon steel hardened?

  1. Heated, then cooled slowly inside the furnace
  2. Heated above upper critical, then cooled slowly in still air
  3. Heated above upper critical temperature, then quenched
Show the answer

Heated above upper critical temperature, then quenched

Rapid quenching in water, brine or oil traps a hard structure. Slow furnace cooling is annealing; cooling in still air is normalising.

Hardening, tempering & annealing, 2 marks

What is the main purpose of annealing steel?

  1. To add carbon to its outer surface
  2. To soften it and make it easier to work
  3. To make it as hard as possible for tools
Show the answer

To soften it and make it easier to work

Annealing heats the steel above its critical temperature, soaks it, then cools it very slowly in the furnace. This relieves stress and leaves it soft and ductile.

Hardening, tempering & annealing, 2 marks

How is steel cooled when it is normalised?

  1. In still air
  2. In cold water
  3. Slowly inside the furnace
Show the answer

In still air

Normalising heats steel above its critical temperature and lets it cool in still air. This refines the grain and removes stresses left by forging or welding.

Other Engineering topics

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