Explanation: In this stage, the thermal cycling in the narrow temperature range around lower critical temperature transforms cementite lamellae from pearlite to spheroidal. During heating above lower critical temperature, cementite or carbides try to dissolve and during cooling they try to re-form. This repeated action spheroidises the carbide particles.

Explanation: Spheroidised structures are softer than the fully annealed structures and have excellent machinability. This heat treatment is utilized to high carbon and air hardened alloy steels to soften them and to increase machinability and to reduce the decarburization while hardening of thin sections such as safety razor blades and needles.

Explanation: Recrystallization annealing process consists of heating a steel component below lower critical temperature i.e. at temperature between 625⁰C and 675⁰C (recrystallization temperature range of steel), holding at this temperature and subsequent cooling.

Explanation: This type of annealing is applied either before cold working or as an intermediate operation to remove strain hardening between multistep cold working operations. In certain case, recrystallization annealing may also be applied as final heat treatment.

Explanation: Recrystallization annealing relieves the internal stresses in the cold worked steels and weldments and improves the ductility and softness of the steel. Refinement in grain size is also possible by the control of the degree of cold work prior to annealing or by control of annealing temperature and time.

Explanation: Stress relief annealing process consists of three steps. In the first step, the cold worked steel is heated to a temperature between 500⁰C to 550⁰C i.e., below recrystallization temperature. The second step involves holding the steel component at this temperature for1-2 hours. The final step is to cool the steel component to room temperature in air.

Explanation: The stress relief annealing partly relieves the internal stress in cold worked steels without loss of strength and hardness i.e. without a change in the microstructure. It reduces the risk of distortion while machining and increases corrosion resistance.

Explanation: Since only low carbon steels can be cold worked, the process is applicable to hypoeutectoid steels containing less than 0.4% carbon. This annealing process is also used on components to relieve internal stresses developed from rapid cooling and phase changes.

Explanation: Spheroidised annealing is one of the variants of the annealing process that produces typical microstructure consisting of the globules (spheroid) of cementite or carbides in the matrix of ferrite.

Explanation: Holding the steel component at just below the lower critical temperature transforms the pearlite to globular cementite particles. But this process is very slow and requires more time for obtaining spheroidised structure.