Based on the analysis of the usage, damage types, and causes of graphite molds, the editor of Qingdao Sanhe Yongchang Machinery Co., Ltd. believes that graphite mold materials should have the following technical properties:
1. Having suitable electrical resistivity
The resistivity of graphite materials should be matched with different heating methods and hot pressing winding process conditions. The resistivity can characterize the transformation process of the graphite structure of a material, that is, the degree of graphitization of the material. The resistivity of a material is proportional to its thermal conductivity, with low resistivity and high thermal conductivity. The degree of graphitization also affects a series of properties of the material, such as wettability, lubricity, strength, thermal expansion coefficient, elastic modulus, specific heat, etc., all of which affect the performance of the mold.
2. Has excellent oxidation resistance
The oxidation of graphite mold materials is the primary cause of mold damage. Therefore, the lower the impurity content of graphite mold materials, the better. The impurities in the material are mainly various metal elements, and most metal elements catalyze the oxidation of stone tool materials. The lower the porosity of the material, the better, and the smaller the pore size, the better, especially for the open porosity. This is because the oxidation process of graphite mold materials is related to the diffusion rate of the oxidizing gas, and the oxidation rate is controlled by the diffusion rate of the oxidizing gas.
3. Structure of graphite material
The structure of graphite mold material should be fine and dense to ensure high bulk density, low porosity, and high surface smoothness of the processed mold.
4. Mechanical strength
The mechanical strength is high, and the specially designed material requires high tensile and compressive strength.
5. Thermal shock resistance
If the coefficient of thermal expansion is small and the thermal conductivity and tensile strength are high, the ability of the material to withstand thermal shock can be greatly improved, and the thermal stability of the material will be better.