Heat treatment process of high strength and high toughness cast lock ring for dredger

Dredger is a common dredger, working in sand and silt. It is generally used to excavate various kinds of silt, soft clay, sand and hard clay underwater. With the improvement of dredging engineering efficiency, dredger is developing towards large and super large scale, and the size of lock ring is also increasing, and the force of lock ring is also increasing, which requires the material of lock ring to have higher strength and toughness.

As shown in the picture is a physical picture of the lock ring for dredging ships. The outer diameter of the lock ring is 1400mm, the inner diameter is 1200 mm and the height is 240 mm. Due to the large size and high performance requirements of cast lock ring, the use of traditional materials (ordinary carbon steel 45 steel and alloy steel 40Cr) can not meet the application requirements. Therefore, it is necessary to prepare new alloy materials and study the corresponding heat treatment process.

(1) After 890 ℃× 2 h water quenching and 620 ℃× 2 h water cooling tempering, the microstructure of the steel is tempered martensite, with high strength and toughness, and the best comprehensive mechanical properties. Its yield strength is 917 MPa, tensile strength is 978 MPa, elongation after fracture is 16%, and Rockwell hardness is 34 HRC.

(2) After tempering, the tensile strength and hardness of the steel gradually increase with the tempering temperature of 650 ℃. When the tempering temperature is 550 ℃, the hardness of the steel is higher and secondary hardening occurs. When tempering temperature is 500 ℃, the impact energy of the steel is low.