Improve fatigue and mechanical properties of high carbon bearing steel by a new double vacuum melting route

A new double vacuum melting route (conventional second refining + vacuum arc refining [CSR + VAR]) with 33% lower production cost than the traditional VIM + VAR route has been tried. Compared with the CSR route, the CSR + VAR route reduces the average inclusion size from 27.1 +/- 12.3 mu m to 13.7 +/- 2.4 mu m, and the CSR + VAR steel processes a 13.1% higher rotatory bending fatigue (RBF) fatigue strength ( sigma-1$$ {\sigma}_{-1} $$) and a 3-timeslonger RCF L-10 life. The crescent-shaped granular bright facet (GBF) zone, normally found in high-strength steels' very high cycle fatigue regimes beyond 10(7) cycles normally under a much lower stress amplitude, appears around inner inclusions on the CSR + VAR steel RBF fracture surfaces in high cycle fatigue regimes beyond 3 x 10(5) cycles. The development of GBF zones is estimated to account for 79%-90% of the RBF fatigue life. The average crack propagation rate (da/dN) for GBF zones varies from 1.3 x 10(-12) m/cycle to 24 x 10(-12) m/cycle and increases with the stress amplitude.

Automated summary

A new method of double vacuum melting (conventional second refining + vacuum arc refining [CSR + VAR]) has been tried, which has 33% lower production cost compared to the traditional VIM + VAR method. The new method reduces the size of inclusions and improves fatigue strength and life. The development of crescent-shaped granular bright facet (GBF) zones is estimated to be responsible for a large portion of fatigue life.