Effect of Heat Treatment on Microstructure and Properties of 304/Q235 Composite Round Steel

During the heat treatment of stainless steel (SS)/carbon steel (CS) bimetal composites, the carbon in the CS diffuses into the SS, and carbides precipitate on the grain boundary and in the grains, affecting the microstructure and properties of the composite steel. In order to change the precipitation and distribution of the carbides seen on hot-rolled 304/Q235 after cold drawing (HR), the microstructure and properties of composite round steel were investigated by optical microscopy, SEM/EDS, and hardness, tensile, fatigue, and electrochemical tests while changing the temperature of the full annealing and aging treatments. The results showed that dispersed chromium carbide particles precipitated at the grain boundaries, and intragranular and slip lines promoted simultaneous dispersion strengthening and fine-grain strengthening and greatly improved the hardness, yield strength, tensile strength, and fatigue strength of the composite round steel. However, the increase in chromium carbide particles leads to the formation of stress concentration points and accelerates the creation of fatigue cracks, resulting in a decrease in the fatigue strength of the steel. Simultaneously, the corrosion resistance of the composite round steel samples was reduced due to the precipitation of a large amount of chromium carbide.