In the selection of plastic mould steel, in addition to the constraints of production, the choice of plastics will be the decisive factor for mould steel selection. However, in order to compensate for the shortcomings of conventional plastics to some extent, a certain proportion of additives are added inside, and some of these additives have a great influence on the mould.
For example, common glass fiber, many PP, PE products, in order to increase the hardness and toughness of the product will add glass fiber to the product, the proportion is generally about 20%, then this addition will cause corrosion on the mould surface. So P20 and the like pre-hardened steel will be damaged in a short time of production. If contain the glass fiber in products then need choose one level higher steel. Like 718H, any way it is best to apply quenched steel S136. Of course, glass fiber can also be added to steel materials such as PPS. At least to choose S136 and 2316 imported steel also can be considered. If the output is big, we can use NAK80. This steel has good corrosion resistance and hardness and is very suitable for moulds of these materials.
Lime powder, also known as calcium carbonate, is added to increase the weight and hardness of the product. It does not have too much effect on the steel, but if it is added, the plastic will be very brittle. There is also a flame retardant addition, which is more corrosive than the glass fiber to the mould, so the first choice is stainless steel. As for antistatic agents, crystallization agents, antibacterial agents, color masterbatch, etc., the impact on the mould is not large, but it should be mentioned that the foaming agent should be distinguished by plastic. Normal PP, PE does not matter, but PVC, PS, PU and so on, the choice of steel materials must be cautious.