What are the reasons for quenching cracks in high-strength graphite molds?

In the production of high-strength graphite molds, there will be various problems, so what are the reasons for quenching cracks in high-strength graphite molds?
1. When the graphite mold is repaired and quenched, it is heated and quenched without intermediate annealing;
2. The quenching heating temperature is too high to cause overheating or overburning;
3. There is mechanical processing or cold plastic deformation stress in the graphite mold;
4. The material has severe network carbide segregation;
5. After quenching, the tempering is not timely or the tempering holding time is insufficient;
6. Improper heat treatment operation of graphite mold, if heating or cooling is too fast, improper selection of quenching cooling medium, cooling temperature is too low, cooling time is too long, etc.;
7. When EDM is performed after graphite mold heat treatment, there are high tensile stress and microcracks in the hardened layer;
8. Improper grinding process for graphite mold heat treatment;
9. The graphite mold has complex shape, uneven thickness, sharp corners and threaded holes, etc., which cause excessive thermal stress and tissue stress.