Abstract: The outer folding problem of 60Si2Mn spring steel was studied by means of metallographic observation and scanning electron microscope analysis.The results of the metallographic study showed that the outer folding of 60Si2Mn spring steel originated from the surface crack defects of the round steel. Due to the processing rotation characteristics, the macroscopic rotation distribution and the microscopic dislocation shape were formed. The results of the electron microscope analysis showed that SiO2,SiO2-MnS-FeO,SiO2-MnO-FeO inclusions were distributed in the root, near surface and inside the defect . By tracing the process of smelting, it is inferred that the late addition of ferrosilicon in the process of smelting is the reason for the surface crack defects of round steel.

Key words: 60Si2Mnspring steel, outer fold, inclusion