Different materials are generally treated by different heat treatment methods. The plastic molds of the low-carbon steel and low-carbon alloy steels are generally subjected to a carburizing treatment method, which has a fast percolation speed, a deep layer, and a layer. The composition gradient and hardness gradient can be easily controlled and low cost. After being carburized, the plastic molds of this type have a carbon content of 0.8% to 1.05% on the surface (0.5 to 2.0 mm). After the layer is quenched and tempered at low temperature, the hardness becomes high, and the wear resistance and fatigue strength are also increased, thereby prolonging the use time of the mold.
However, if the crystal grains are coarse at the time of carburization, embrittlement of the bleeding layer may occur, and the surface of the mold may be peeled off. At the same time, since the carburizing temperature is high and heat treatment is required after the infiltration, the deformation of the mold is large. Therefore, such plastic molds with high precision requirements are not suitable for carburizing. Carburizing methods for plastic molds are commonly found in solid carburizing, gas carburizing, vacuum carburizing and ion carburizing. Because of its high carburizing efficiency, mild carbon concentration gradient, small deformation of the workpiece, environmental protection, and the advantages of slits and small holes, ion carburizing is currently used in plastic molds and dies.