感应热处理对50CrV弹簧钢力学性能与马氏体亚结构的影响

Taking 50CrV spring steel as the research object, the grain was refined by induction heat treatment, and the effects of grain refinement on its mechanical properties and martensitic transformation substructure were studied. The results show that the grain size of the experimental steel can be refined from 31.9 μm of the initial state to 11.8 μm by induction heat treatment for one time, and that can be refined to 9.8 μm by induction heat treatment for 5 times, which shows that the effect of refinement is reduced. The mechanical property test shows that the conventional heat-treated samples (quenched at 850 ℃ and tempered at 250 ℃ for 2 h) show brittle state, the strength reaches 1655 MPa, the elongation is only 0.9%, and the fracture is intergranular fracture. The induction hardened samples are also tempered at 250 ℃ for 2 h, after induction heat treatment for one time, the strength reaches 2180 MPa and the elongation recovers to 2.5%, after induction heat treatment for 5 times, the tensile strength does not further improve, but the elongation reaches 7.2%, and the fracture surface morphology changes from intergranular to dimple. The results of transmission electron microscope analysis show that the martensite substructure of conventional heat-treated samples is mainly twins, while the martensite substructure of induction heat-treated samples for 5 times is mainly dislocations, which shows that grain refinement has an effect on the high-carbon martensite substructure. The coarse grains (conventional grain size) are twin substructures and the fine grains are dislocation substructures.