Increased deformation and formation of light-colored corrosion bands and dark etched sections

The local plastic deformation near the non-metallic inclusions increases, and the color is brighter after pickling. In addition, under the condition of plastic deformation, the crystal lattice changes, all of which promote the further development of the diffusion process, and often cause different types of organizational changes in the vicinity, including the decomposition of retained austenite, martensitic tempering. And the formation of ferrite, carbides, etc.

The formation of dark corrosion segments depends on the tempering of the martensite. During the rolling process, the sliding band moves along the entire raceway as the moving contact area increases. In some sections, the product falling into the sliding band is not as stiff as the surrounding material. Causes the deformation to increase and forms a light-colored corrosion zone and a dark etched zone.

A greater degree of deformation in the vicinity of hard non-metallic inclusions promotes plastic depletion and microcracks, and finally the microcracks are joined together to form macroscopic cracks that cause fatigue spalling, ie, pitting. After the first spalling pit was formed, the cracks continued to expand along the edge of the pit, and small pieces of metal fell off, resulting in an increase in the area of ​​separation.