Bearing steel GCr15 is one of the most commonly used bearing materials. The comprehensive sign of internal quality is fatigue life. Some scholars put forward the view that reducing oxygen content has not significantly improved the fatigue life of bearing steel. In fact, only by reducing the oxide and sulfide content at the same time can we fully tap the material potential and greatly improve the fatigue life of bearing steel.
Why can’t reducing oxygen content improve fatigue life of bearing steel? Shanghai royal micro bearing Company technical department engineers analyzed that the reason: after the oxide inclusion reduced, the excess sulfide has become an adverse factor affecting the fatigue life of steel. Only by reducing the content of oxide and sulfide at the same time, can we fully tap the material potential and greatly improve the fatigue life of bearing steel.
What factors will affect the fatigue life of bearing steel? The above problems are analyzed as follows:
1. Influence of nitride on fatigue life
Some scholars point out that when nitrogen is increased in steel, the volume fraction of nitrides decreases. This is because the average size of inclusions in steel decreases. Due to technical limitations, a considerable number of inclusions smaller than 0.2 in are not included. It is precisely the existence of these tiny nitride particles that has a direct influence on the fatigue life of bearing steel. Ti is one of the strongest elements to form nitrides, with small specific gravity and easy to float, and some Ti will remain in the steel to form angular inclusions. The inclusion is easy to cause local stress concentration and fatigue crack, so the generation of such inclusion should be controlled.
The test results show that the oxygen content in steel is reduced to less than 20ppm, the nitrogen content is increased, the size, type and distribution of non-metallic inclusions are improved, and the stable inclusions are obviously reduced. Although the nitride particles in steel increase, they are very sma