What are the causes of outer race bearing breakage?

Causes of outer race bearing

1. If the outer race bearing and inner race bearing are too loosely matched, the inner or outer ring of the bearing will squirm during rotation. The squirming deformation will cause the bearing to fatigue along the cross-sectional direction (accompanied by noise). Fatigue will cause cracks for a certain period of time. Eventually leading to breakage.

2. The inner ring of the bearing is too tight, resulting in excessive tensile stress on the inner ring of the bearing along the circumferential direction. When the bearing is rotating, external impact forces (more or less inevitable) cause local stress concentration and superposition. Cracks will occur in the bearing (accompanied by noise), which will eventually expand and eventually break.

Dynamic balance is not good. Due to poor dynamic balance, the cyclic stress is maximum in a local area of the cross-sectional surface of the heavier end of the bearing, where fatigue is the fastest (accompanied by noise generation). Fatigue will cause cracks for a certain period of time, eventually leading to fracture.

1. Cracks and causes of outer ring of deep groove ball bearings
If the outer race bearing breaks, the section is basically perpendicular to the surface. The section starts from the lower surface of the outer and inner diameters on the right side of the raceway in the figure, and rapidly expands toward the outer surface and to the left until it breaks. The fracture surface of the outer race bearing has no obvious plastic deformation and shows brittle fracture characteristics.

After analysis, during the heat treatment process of the bearing ring, the protective atmosphere in the heat treatment furnace is a mixture of various gases, including oxidizing gas, neutral gas, reducing gas and carburizing gas. The chemical reaction is very complex when heated at high temperatures. Whether it is a decarburization reaction or a carburization reaction, in addition to the participation of free oxygen atoms, it can reach equilibrium under certain conditions and even undergo a reversible reaction.

Correctly select and design heating parameters such as heating medium, heating speed, heating temperature and holding time; strictly control the uniformity of furnace temperature and avoid excessive fluctuations. By controlling the carbon potential in the furnace, the carbon concentration and concentration gradient of the bearing rings are strictly controlled to ensure the heat treatment quality and service life of the rings.

2. Cracked bearing rings and their causes

If the bearing cracks during use, contact fatigue spalling of the bearing ring will cause it to become unstable. In addition, the material has high hardness and brittleness, and a one-time brittle fracture, that is, a relatively straight macro crack, will begin to occur in the local spalling area. , the microscopic fracture surface is relatively straight, exhibits cleavage characteristics and rapidly expands, and the rapid expansion area accounts for most of the fracture section.
Factors that cause contact fatigue include material structure, surface strengthening process, workpiece surface roughness, lubricant, stress, etc.

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