Selection principle of mould steel for die cavity and parts
According to the types of plastic, the shape of the products, the size accuracy, the appearance quality of the products, the requirements of the use and the size of the production, the cutting, polishing, welding, etch, deformation and wear resistance of the materials are taken into consideration, and the economy and the manufacturing conditions and processing methods of the mould are taken into consideration in order to choose different types. Type of steel.
For the moulds forming transparent plastic products, the cavity and core of the mold must be used for high quality imported die steel, such as 718 (P20+Ni), NAK80 (P21), S136 (category 420), H13 type steel, of which 718 and NAK80 are prehardened, and no heat treatment is needed; both S136 and H13 steel are annealed. State, the hardness is generally HB160-200, after rough processing, the need for vacuum quenching and tempering treatment, the hardness of S136 is generally HRC40-50, the hardness of the H13 type steel is generally HRC45-55 (can be determined according to the specific brand).
For mould with high appearance quality, long life and mass production, the mould steel for mold cavity and parts is selected as follows:
A) type of high quality imported steel, such as 718 (P20+Ni), NAK80 (P21) and so on, should be selected for high mirror polishing properties. All of them are prehardened, and no heat treatment needs to be done.
B) can choose medium and low grade imported P20 or P20+Ni type steel, such as 618, 738, 2738, 638, 718, etc., all of which are prehardened, and the imported high quality carbon steel, such as domestic plastic mould steel or S50C and S55C, can be used for the mould with small batch production.
For the general mould for the appearance quality of the products, the mould steels for mold cavity and parts are selected as follows:
A) small, precision mold cavity and core are all imported with medium grade P20 or P20+Ni steel.
B) large and medium mold, the molded plastic has no special requirements for the steel. The cavity can be imported P20 or P20+Ni steel in the middle and low gear. The core can be imported from low grade P20 steel or imported high quality carbon steel S50C, S55C and so on, and the domestic plastic mould steel can also be selected.
C) for the pitting cavity, when the pear pattern is worn, we should try to avoid the 2738 (738) grade of P20+Ni.
The molding material has no special requirements for the mould steel, and the mold cavity and parts are chosen as follows:
A) for large and medium-sized molds, the cavity can be imported with low grade imported P20 or P20+Ni steel, and imported high-quality carbon steel S55C and S50C can also be imported.