Effects of quenching at 780,830,and 880 ℃ and high-temperature tempering at 500-580 ℃ on the microstructure and mechanical properties of a Cr-Ni-Mo-V ultra-high strength and toughness steel were studied by means of scanning electron microscope,metallographic microscope,impact testing machine,and Vickers hardness tester.The results show that with the increase of tempering temperature,the carbides with larger size undergo dissolution transformation,while the alloy carbides continuously precipitate out dispersively from the the matrix.Both the hardness and impact properties show a trend of first increasing and then decreasing with the increase of tempering temperature,which are related to the dispersion morphologies of the precipitated carbides and the decomposition of retained austenite.The tested steels quenched at three different temperatures all show secondary hardening peaks when tempering at 540 ℃,with the highest hardness values being 488,517,and 532 HV20,respectively.The maximum impact absorbed energy is obtained when tempering at 540-560 ℃,with values of 49.7,58.5,and 51.0 J,respectively.In order to fully ensure the strength and toughness of the steel,the optimal heat treatment process is subcritical quenching at 830 ℃ and then tempering at 560 ℃.
Cr-Ni-Mo-V ultra-high strength and toughness steelquenching and tempering treatmentsecondary hardeningimpact property
万方数据
