Observation of the fracture of the smashed magnetic trace ferrule showed that the fracture was fine porcelain, indicating that the metal crystal grains did not grow up significantly; through scanning observation, there were holes on the fracture surface. This situation is different from the typical fracture state of forging overburning, and the metallographic inspection found that most of the holes are distributed in the carbide belt, which makes it doubtful that the holes in the ring structure are generated during the forging process.
fter analysis, it was learned that the holes in the FAG bearing ring had appeared in the bar. According to the analysis of the steel supplier, the high temperature during the billet rolling of the steel ingot caused the low-melting material in the segregation part of the steel to melt, resulting in Local overburning is a fundamental cause of microscopic porosity. Because the small holes are distributed in the carbide accumulation position, it indicates that the low melting point substance on the carbide belt first melts and creates voids, forming holes. Based on the above analysis, the magnetic marks on the end of the ferrule are related to the microscopic pores of the raw material.
