When producing graphite molds, the carbon content of the mold is still very critical, and graphite molds have very high requirements for strength performance. The carbon content determines the hardness of the graphite mold. The following describes the carbon content of the high-purity graphite mold:
1. Hardness is the main technical index of the mold. If the graphite mold wants to keep its shape and size under the action of high stress, it must have a sufficiently high hardness. The general hardness of graphite mold is kept at about HRC60 at room temperature, and according to its working conditions, it is generally required to be kept in the range of HRC40~55. For the same graphite, within a certain hardness value range, the hardness is proportional to the deformation resistance, but the plastic deformation resistance may be significantly different between steel types with the same hardness value but different components and structures.
2. The red hardness of graphite mold The hot work mold working at high temperature requires to maintain the stability of its structure and performance, so as to maintain a sufficiently high hardness. This performance is called red hardness. Carbon tool steel and low alloy tool steel can usually maintain this performance in the temperature range of 180~250°C, and chromium-molybdenum hot work die steel can generally maintain this performance in the temperature range of 550~600°C. The red hardness of graphite mainly depends on the chemical composition and heat treatment process of steel.
3. Compressive yield strength and compressive bending strength of graphite mold Molds are often subjected to high-intensity pressure and bending during use, so the mold material is required to have a certain compressive strength and bending strength. In many cases, the conditions for the compression test and bending test are close to the actual working conditions of the graphite die (for example, the measured compressive yield strength of the die steel is more consistent with the deformation resistance exhibited by the punch when it is working. ). Another advantage of the bending test is that the absolute value of the strain is large, which can more sensitively reflect the difference in deformation resistance between different steel types and under different heat treatments and organizational states.