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Influences of Quenching Temperature on the Microstructure Evolution and Strength−Toughness of a Novel Medium‐Carbon Ti−Mo‐Bearing Martensite Steel

The simultaneous improvement of strength and toughness in high‐strength steels is a challenging task. Herein, a novel medium‐carbon Ti−Mo‐bearing martensite steel is developed. The influences of quenching temperature on microstructure evolution and strength−toughness are investigated. Microstructure and precipitation analyses are conducted to clarify possible reasons for the improvement of strength−toughness in the as‐developed steel. After the addition of Ti and Mo, the martensite steel yields a high tensile strength of ≈1700 MPa and an impact energy of 43 J at –40 °C. The improved strength and toughness is attributed to better grain refinement strengthening and precipitation strengthening by combination of thermo−mechanical control process (TMCP) and quenching and tempering (Q−T) processes. Although no significant variation is observed in the strengths of Ti−Mo‐bearing martensite steels quenched at a temperature range of 850−910 °C, the impact energy of Ti−Mo‐bearing martensite steel obviously decreases at a higher quenching temperature of 910 °C. The decreased low‐temperature impact energy is caused by the coarsening of (Ti, Mo)C precipitates.