What is the correct answer?
Both annealing and normalising release the internal stresses of the material besides improving the mechanical properties
Low carbon steel does not respond to the heat treatment for hardening of the material, hence it is subjected to case hardening or surface hardening processes like cyaniding, carburising, nitriding etc., which produces high carbon outer layers resulting in increase of surface hardness
Induction hardening and flame hardening techniques are also used for surface hardening
Martempering of a material is a hardening process
C. Induction hardening and flame hardening techniques are also used for surface hardening