Effect of quenching, lamellarizing, and tempering heat treatment on cryogenic toughness of ZG14Ni3Cr1MoV steel

• QLT heat treatment produces a dual-phase microstructure of soft ferrite and hard tempered bainite, significantly refining grain size compared to QT (38.87–46.51 μm vs. 64.93 μm). • QLT samples exhibit superior cryogenic impact toughness at -80 °C to -120 °C, with optimal values of 215.97 J, 207.80 J, and 183.17 J respectively, after 910 °C quenching + 780 °C lamellarizing + 670 °C tempering. • The enhanced cryogenic toughness is attributed to low dislocation density suppressing crack initiation and crack-tip passivation by soft ferrite, along with crack deflection at high-angle grain boundaries. • While QLT yields lower strength than QT, it provides better elongation and strength-elongation synergy, making it a viable method for improving cryogenic performance in HSLA steels.