Abstract: Effect of different holding time and heating temperatures on the depth of decarburization layer of S2 tool steel under air atmosphere was studied. Fick's first law was used to predict the depth of surface decarburization layer, and the theoretical value calculation model was fitted with the actual depth of decarburization layer of the S2 tool steel. The results show that a full decarburization layer is formed easily on the surface when heated at 770 ℃, and the maximum depth is 0.40 mm. The depth of decarburization layer deepens with the extension of heating time. When the heating time reaches 7 h, the depth of decarburization layer decreases due to the surface oxidation of the S2 steel surface. Ferrite + bainite semi-decarburization layer on the S2 steel surface is formed when heated at 1000 ℃. When heated at 950-1000 ℃, the minimum depth of decarburization layer is 0.06 mm.

Key words: S2 tool steel, surface decarburization, decarburization layer depth