The Deformation and Microstructure Analysis of Medium Carbon Steel During Die Forging Process and the Effect of Microalloying Elements

The deformation and microstructure of medium carbon steel during die forgingDie forging process was analyzed by using thermo-simulation test in this paper. The effect of microalloying elementsMicroalloying elements V, Ti, and Nb on the microstructures after deformation was also analyzed. The results showed that there are a critical deformation amount of 6% which increases the grain sizeGrain size of steel in die forging process. The deformation amount during die forgingDie forging process should reach 20% in order to refine the microstructures. The addition of Ti can largely reduce the grain size of the final product while the further addition of Nb doesn’t have significant effect on the grain sizeGrain size. The addition of Ti can significantly increase the ferrite and intra-granular ferriteIntra-granular ferrite in the steel by refining the microstructure and offering the precipitates (V, Ti)(C, N) as the nuclei of intra-granular ferrite. The further addition of Nb in the V-Ti-N steel can further increase the size of the precipitates (V, Ti, Nb)(C, N) but suppress the formation of ferrite by improving the hardenability of steel. Thus, there are few ferrite and intra-granular ferriteIntra-granular ferrite in the V-Ti-Nb-N steel than that in the V-Ti-N steel.