Heat treatment of steels — identify the incorrect statement Which one of the following statements about spheroidising and annealing of steels is wrong?

Introduction / Context:
Spheroidising and annealing are fundamental heat-treatment processes for steels. Spheroidising is widely used for high-carbon tool steels to transform lamellar cementite (pearlite) into spheroidal carbides for better machinability. Full annealing is used to soften and homogenise steels, removing the effects of cold work. This question asks you to identify if any of the listed statements are incorrect.

Given Data / Assumptions:

• High-carbon tool steels tend to be hard to machine in the as-rolled or pearlitic state.
• Spheroidising aims to produce globular carbide particles in a ferritic matrix.
• Heavily cold-worked steels store significant strain energy and respond to annealing by recrystallising.

Concept / Approach:
Spheroidising is performed by prolonged holding just below or cycling around the lower critical temperature so that cementite lamellae break up into spheroidal particles. This raises ductility and lowers hardness, enabling efficient machining prior to hardening. Full annealing of a severely cold-worked steel involves recovery, recrystallisation, and grain growth, creating a new, strain-free grain structure that restores ductility and reduces hardness.

Step-by-Step Solution:
Check statement (a): Correct — spheroidising is standard for difficult-to-machine, high-carbon tool steels.Check statement (b): Correct — outcome is granular/spheroidal cementite in ferrite.Check statement (c): Correct — full annealing of severely cold-worked steels triggers complete recrystallisation and new grains.Therefore, none of (a), (b), or (c) is wrong. The correct choice is “None of the above”.

Verification / Alternative check:
Metallurgy texts consistently define spheroidising as producing spheroidal carbides for improved machinability and define full annealing as a treatment that restores ductility via recrystallisation in cold-worked steels.

Why Other Options Are Wrong:

• (a), (b), (c): Each correctly states a standard metallurgical fact; none is incorrect.
• (e): Also true, but the question asks which statement is wrong; the correct answer is that none is wrong.

Common Pitfalls:
Confusing spheroidising (to improve machinability before hardening) with tempering (to reduce brittleness of martensite). Also, assuming annealing only reduces hardness without microstructural renewal — recrystallisation is the key for cold-worked steels.

Final Answer:
None of the above statements is wrong.