The manufacturing process of maraging steel parts include forging, heat treatment and other technological links, and the strengthening mechanism at different stages is different, which has an important impact on the process design of forgings. To investigate the strengthening behavior of maraging steel, forging experiments with different deformation amounts and heat treatment conditions were carried out, and the microstructural and mechanical properties evolution of 18Ni(250) steel was analyzed. The experimental results show that the size of the martensite lath is affected by multiple factors such as the influence of grain size, recrystallization and martensite substructure fraction. The strengthening mechanism of maraging steel during forging and heat treatment is different. Forging combined with heat treatment can refine grains, and the internal defects of the original material can be better eliminated. The thermal deformation can better play the role of grain refinement compared with cyclic phase transformation, which can improve the plasticity of 18Ni(250) maraging steel.
Keywords: forging; heat treatment; maraging steel; microstructural and mechanical evolution; strengthening mechanism.