Heat Treatment Effects on Microstructure and Hardness of Low-Carbon AISI 1020 Steel

Heat treatment can change the properties of any metal by changing its size and orientation of grain structure. Structural steel is particularly sensitive to heat treatment. The material’s microstructural orientation can change the material’s mechanical properties. The current study provides 7 different heat treatment methods that drastically vary cooling rates to allow for detailed microstructural analysis. In order to analyze the microstructural changes in heat-treated samples, one additional sample was kept in “original” or “as received” state. An optical microscope was used to observe the variations in the grain structure. In addition, FESEM (field emission scanning emission microscope) was used to observe the highly magnified images. Using X-ray diffraction (XRD), the crystal structure in each sample was also studied. The stepped cooling procedures (e.g., sand + water, sand + oil) followed in this work are effective in preventing the formation of martensite. Also, a substantial reduction in hardness was achieved after the stepped cooling process done in the sand + water medium.