Composition Design of low alloy Low-temperature Cast Steel and Its mechanical Properties

摘要

The composition of the low alloy low-temperature cast steel containing Cr and Ni was designed according to the performance requirements on the key components, such as hook, of oil drilling rig serving in cold area and arctic region. The effect of eat treatment on the microstructure, room-temperature mechanical properties and low-temperature impact toughness of the steel was also investigated by means of optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile tester and impact tester. The results show that, after annealing at 930℃, quenching at 920℃ and tempering at 680℃, the tempered sorbite consisted of equiaxed ferrite and spheroidal cementite in the low alloy low-temperature cast steel appeared. Room-temperature mechanical properties of the steel are very excellent (σ{sub}b 676 MPa, σ{sub}s 519 MPa, δ{sub}5 21 %, ψ 58 %). Its low-temperature impact energy values at -20℃ and at -45℃ exceeded 50 J and 32 J, respectively. Meanwhile, the steel has simple melting process, contains lower costly elements and so has low production cost.