Mould heat treatment is to play the potential of mould materials and improve the performance of the mold. The performance of the mould must meet: high strength, including high temperature strength, resistance to cold and heat fatigue, high hardness (wear resistance) and high toughness, and also requires good machinability, including good polishability. ) weldability and corrosion resistance, etc.
Mold heat treatment is an important process to ensure the performance of the mold, which has a direct impact on the manufacturing precision of the mould, the strength of the plastic mould, the working life of the mold, and the manufacturing cost of the mold.
Complex moulds, the correctness of the processing technology often has a greater impact on the deformation of the mold, the comparison of some mold heating processes can clearly see that the heating speed is faster, often resulting in greater deformation.
(1) Reasons for deformation
Any metal should be expanded when heated. Because the steel is heated, the temperature of each part in the same mould is uneven (that is, the uneven heating) will inevitably cause the inconsistency of the expansion of the various parts in the mould, resulting in heating. Uneven internal stress. At temperatures below the phase transition point of the steel, uneven heating mainly produces thermal stress, which is unevenly heated beyond the phase transition temperature, and also causes unequality of the structural transformation, which causes both tissue stress. Therefore, the faster the heating rate, the greater the difference in temperature between the surface of the mold and the core, the greater the stress, and the greater the deformation caused by the heat treatment of the mould.
(2) Preventive measures
When the complex mould is heated below the phase change point, it should be heated slowly. Generally, the mold vacuum heat treatment deformation is much smaller than the salt bath furnace heat quenching. Preheating can be used for one-time preheating of low alloy steel molds and secondary preheating for high alloy steel molds.
