Increase Hardness and Strength: To prevent screws from stripping (head rounding off) or becoming elongated/ fractured under tensile loads.
Achieve Good Toughness: To avoid sudden brittle fracture of screws when subjected to impact or vibration.
Improve Fatigue Resistance: To enhance the screw’s ability to withstand repeated cyclic stresses (e.g., in vibrating environments) and reduce the risk of fatigue cracking.
Relieve Internal Stresses: To eliminate stresses induced during processes like cold heading or machining, thereby preventing future deformation or cracking.