Experimental validation and thermodynamics analysis of (Nb, V)(C, N) coupling precipitation in high-strength spring steel FAS3550

Abstract Based on the thermodynamic coupling model of multiple microelements in steels, solid solution and precipitation behavior Nb-V-N-C system quaternary secondary phase was further verified microalloyed combining with engineering practice high-strength spring steel FAS3550 containing nanoparticles. According to calculations, dissolved V (or Nb) content increased increasing addition Nb), while decreased increase C, N or Nb V). The complete dissolution temperature 1314 °C, effective carbonitride 1060 °C 0.49%C-0.0060%N-0.03%Nb-0.12%V FAS3550, grains began coarsen above 1100 during heat treatment, (Nb, V)(C, N) nanoprecipitates were smaller than 100 nm. strength plasticity have been improved simultaneously, its fatigue life has by 13% after optimizing treatment process.