Effects of spheroidization heat treatment and intercritical annealing on mechanical properties and corrosion resistance of medium carbon dual phase steel

Abstract Spheroidization heat treatment and intercritical annealing and their effects on the mechanical properties and corrosion behavior of CK45 medium carbon steel were studied. Increasing the spheroidization time resulted in the decline of strength and hardness of the initial martensitic steel but improved the tensile ductility and corrosion resistance. Intercritical annealing of the spheroidized steels resulted in the formation of austenite at the expense of cementite particles at short intercritical annealing times, which resulted in the development of dual phase (DP) steels after water quenching. Increasing the holding time at the intercritical annealing temperature led to a remarkable increase in the volume fraction of martensite in the microstructure, leading to poor ductility and corrosion resistance. This processing route, however, made it possible to obtain low martensite contents via short intercritical annealing of spheroidized steels, which resulted in the enhancement of strength-ductility balance while maintaining appropriate corrosion resistance.