Structural strength of low-carbon rotor steel

Conclusions

• 1. The addition of niobium in amounts ranging from 0.01 to 0.08% to generator-rotor steels with a reduced carbon content (from 0.13 to 0.16%) and with a reduced nickel content (from 4.2 to 4.5%) tends to increase its structural strength and lower its semibrittleness temperature.

  The introduction of cobalt in amounts ranging from 2.8 to 3.0% to the steel is ineffective as a result of an increase in the semibrittleness temperature.

• 2. Melts 2 and 4 from which an impressive set of strength and plastic properties and high resistance to brittle failure were obtained in the range of cooling rates investigated (10³−10⁵\dgK/h) are recommended for the fabrication of large generator rotors: σ_{o · 2} = 550−590 N/mm², σ_u = 760–800 N/mm², δ = 21–23%, ψ = 66–74%,a _{o η25} = 168–200 J/cm², T₅₀=−80%C, K_C=7260–7800 N/nm^3/2, and α_C = 0.98–1.12.