The influence of heat treatment process for plastic mould life

Mold heat treatment is an important process of ensure mold performance, strength of the manufacturing precision of mould, plastic mould, the working life of the mold, mold manufacturing costs and so on have a direct impact. Mold heat treatment is to play the potential of die material, improve the use performance of mould. The performance of the mold must satisfy: high strength, Including high temperature strength, resistance to cold and hot fatigue performance) High hardness ( Wear-resisting performance) And high toughness and good machinability, ( Including good polishing) The weldability and corrosion resistance, etc. Plastic mold heat treatment deformation is generally considered to be caused by the cooling, this is not correct. Mold especially complex mold, the processing technology of the right of the mould deformation tend to produce bigger effect, the comparison of some mould heating process can obviously see that heat faster, tend to produce bigger deformation. （ 1) Any the cause of the deformation of metal heating expansion, due to steel during heating, uneven within the same mold, the temperature of each part, The uneven heating) Will inevitably cause the mould parts of the expansion of the inconsistencies, thus forming internal stress due to the uneven heating. In steel below phase transition temperature, uneven heating main produce thermal stress, more than phase change temperature heating uneven, also can produce organization transformation range of sex, both organizational stress. So the faster the heating speed, temperature difference of mold surface and the core, the greater the stress is, the greater the mold heat treatment after deformation. （ 2) Preventive measures for complex mould under phase transition point when heating should slow heating, in general, mold vacuum heat treatment deformation is much smaller than salt bath furnace heating quenching. Adopting preheating, for low alloy steel mold to adopt a preheating ( 550 - 620° C) ； Double preheating (should be adopted for high alloy steel mould 550 - 620° And 800 - C 850° C) 。