The bearing ring is one of the important parts of the bearing. During the use of the bearing, the cracking and fracture of the bearing ring is a common form of damage. Some bearings cracked in the early use of the ring, and some bearings broke due to fatigue. The following China bearing network (hereinafter referred to as: China bearing network) shares the information according to the understanding of the bearing knowledge In daily life, we often see some macroscopic appearance of bearing ring cracking, and analyze the real cause of cracking.
1. Macroscopic appearance and causes of outer ring cracking of deep groove ball bearing
As shown in Figure 1 below, the macro morphology of bearing fracture shows that the outer ring of the bearing is fractured, and the section is basically perpendicular to the surface. As indicated by the arrow in Figure 1, the section starts from the lower surface of the outer inner diameter on the right side of the raceway in the figure, and rapidly expands to the fracture on the outer surface and to the left side. There is no obvious plastic deformation on the fracture surface of the bearing outer ring, showing brittle fracture characteristics,
After analysis, the protective atmosphere in the heat treatment furnace is a mixture of various gases, including oxidizing gas, neutral gas, reducing gas and carburizing gas. When heated at high temperature, the chemical reaction is very complex, whether it is decarburization or carburization, except for the participation of free oxygen atoms, it can reach equilibrium under certain conditions, even reversible reaction. The carbon potential in the furnace has great influence on the thickness of carburized layer, carbon content and carbon concentration gradient.
Generally speaking, the higher the carbon potential in the furnace, the steeper the carbon concentration gradient, and the greater the tendency of forming coarse and network carbides. In order to avoid the phenomenon of Carburization on the surface of bearing rings caused by high carbon potential, it is necessary to adopt appropriate heating temperature to prevent the grain growth of the steel. The heating parameters such as heating medium, heating speed, heating temperature and holding time should be selected and designed correctly, and the uniformity of furnace temperature should be strictly controlled without excessive fluctuation. By controlling the carbon potential in the furnace, the carbon concentration and concentration gradient of the bearing rings are strictly controlled, so as to ensure the heat treatment quality and service life of the rings.
