If the outer ring of the fractured bearing is acid immersed, black burn marks and transverse cracks perpendicular to the grinding direction can be seen on its groove surface, and a fine porcelain shaped crescent shaped burn layer appears on the fracture surface.

The parallel cracks on the surface of the bearing outer ring groove are typical manifestations of grinding cracks, mainly caused by excessive grinding volume or poor process conditions; In addition, insufficient tempering of the bearing outer ring can increase its sensitivity to grinding cracking, which is also a common cause of bearing outer ring cracking.

Cracking and causes of bearing inner ring groove surface

Roughly grind the inner raceway surface, and through magnetic particle inspection, many small cracks were found on both sides of the raceway, especially near the oil groove. In severe cases, multiple deep cracks and warping phenomena perpendicular to the grinding direction may also occur. The inner ring of the bearing is subjected to hot acid washing, and the raceway surface has mostly mesh shaped cracks, as well as straight cracks perpendicular to the grinding direction.

What measures in production can prevent the occurrence of these phenomena?

(1) Selection of cutting fluid and sufficient and uniform cooling.

(2) Selection of grinding wheels. After determining the abrasive, choose a large porosity grinding wheel with lower hardness and larger organizational number; Its good self sharpening and heat dissipation can effectively avoid burns and grinding cracks.

(3) The selection of grinding feed rate, appropriately reducing the feed rate and increasing the circumferential speed of the workpiece can lower the grinding temperature, reduce the possibility of burns, and avoid the occurrence of grinding cracks.