Abstract: The lock ring is the key component at the pipeline interface of dredging ship, which bears a large load and requires high strength and toughness of the material. The heat treatment technology of a kind of steel for high strength and high toughness casting lock ring for dredged marine was studied.The results show that when the quenching temperature is 890 ℃, the strength of the test steel decreases and the elongation after break increases with the increase of tempering temperature.After water quenching at 890 ℃and tempering at 620 ℃, the microstructure is tempered martensite, and the hardness and impact work are 34 HRC and 29 J, respectively, the strength and toughness of the material are well matched.