Mechanical Engineering - Engineering Materials - Discussion

The correct answer is: Annealing.

Annealing is a heat treatment process used to soften hardened steel by:

1. Heating the steel to a specific temperature (usually between 800°C to 900°C) to relieve internal stresses and reduce hardness.
2. Holding the temperature for some time to allow the steel to fully transform into a softer microstructure.
3. Cooling the steel slowly to prevent re-hardening.

Annealing is often used to:

- Soften hardened steel for machining or forming.
- Relieve internal stresses and prevent cracking.
- Improve ductility and toughness.

The other options are not used for softening hardened steel:

- Carburising: A surface hardening process that adds carbon to the steel surface.
- Normalising: A heat treatment process that refines the microstructure and relieves internal stresses, but does not significantly soften the steel.
- Tempering: A heat treatment process that reduces the hardness of quenched steel, but is not used to soften fully hardened steel.

=> Note that the specific heat treatment process and parameters may vary depending on the steel grade and application.

Tempering: Tempering reduces the hardness in the martensite by transforming it into various forms of tempered martensite. Tempering is a heat treatment technique applied to ferrous alloys, such as steel or cast iron, to achieve greater toughness by decreasing the hardness of the alloy.

Annealing/Normalising: Annealing is a heat treatment process which alters the microstructure of a material to change its mechanical or electrical properties. Typically, in steels, annealing is used to reduce hardness, increase ductility and help eliminate internal stresses.

There is some confusion, we know that annealing is done for softening a piece of steel, but in question mentioned that what is done to soften a hardening steel?

That means after hardening, we must go for tampering, it is also done for the expanse of hardness.

The process of heat treatment of steel is in order of = annealing - normalizing (equilibrium condition) and hardening-tempering (non-equilibrium condition). So option D is correct.

Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.

Annealing is a primary hardening process while tempering is a secondary hardening process. Tempering is done to increase the toughness of the steel by reducing the hardness of the alloy.

It is done after hardening the steel in order to remove the brittleness. Since it it mentioned that hardened steel, tempering would be the answer.

Answer is correct.

Annealing is used to relieve stress caused by rolling, extruding etc.

Though the final product is ductile and soft, it is not used for hardened steels.

Tempering is used to increase toughness of hardened steel. So the final product from tempering is soft and tough steel.

Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.

So it is right answer.

Tempering is a heat-treatment process consisting of reheating the hardened steel to a temperature below 400°C, followed by cooling. Steel in its hardened condition is generally too brittle to be used for certain functions. Therefore, it is tempered.

After the hardening of steel is completed that hardened steel is softened by Tempering but normally steel is soften by the annealing process of heat treatment.

Here the answer will be tempering as it asks hardened steel is softened by the process.

So annealing is the process to improve ductility, relieve the residual stresses H annealing < H tempering so we can say that annealing process is the softening process by which we can achieve more ductile material than tempering.