Explain the process of heat treatment in steel manufacturing and its effects on the microstructure and mechanical properties of steel.

Heat treatment is a process used to alter the microstructure and mechanical properties of steel by heating, cooling, and tempering. The process typically involves three stages: heating the steel to a specific temperature (annealing, hardening, or tempering), holding it at that temperature to allow for phase transformations, and then cooling it at a controlled rate. Heat treatment can modify the hardness, strength, toughness, and ductility of steel by adjusting the grain size, distribution of phases, and residual stresses within the material. Common heat treatment techniques include annealing, quenching, tempering, and case hardening, each tailored to achieve specific material properties for different applications.