In order to strengthen the hardness of the metal surface, many manufacturers will use the quenching process to promote the production of moulds, and the cracks generated after the quenching of the moulds are a defect in the heat treatment process *, which is likely to cause the processed moulds to be scrapped. What are the factors? There are nine major factors.
1. Severe network carbide segregation exists in the mould material.
2. There are mechanical processing or cold plastic deformation stress in the mould.
3. Improper heat treatment of the mould (heating or cooling too fast, improper selection of quenching cooling medium, too low cooling temperature, too long cooling time, etc.).
4, the mould shape is complex, uneven thickness, with sharp corners and threaded holes, etc., making the thermal stress and tissue stress too large.
5, the mould quenching heating temperature is too high to produce overheating or overheating.
6. After the mould is quenched, the tempering is not timely or the heat preservation time is insufficient.
7. When the mould is reworked and quenched and heated, it is reheated and quenched without intermediate annealing.
8, mould heat treatment, grinding process is improper.
9. When EDM is performed after heat treatment of the mould, there are high tensile stress and microcracks in the hardened layer.