With the demand of plastic products and the expansion of application fields, higher and higher requirements are put forward for plastic mold, which promotes the continuous opening of plastic mold, and also drives the rapid opening of plastic mold steel. The main performance is the accelerated development of plastic mold steel and the rapid increase of species, but now plastic mold materials are still mainly steel. According to statistics, China's plastic die steel has accounted for more than half of all die steel. Reasonable selection of plastic mold steel and heat treatment process is of great importance to ensure the quality of plastic mold, travel the life of plastic mold and reduce the production cost.

Plastic mold can be divided into thermosetting plastic mold and thermoplastic plastic mold according to the different curing process. Thermosetting plastic mold, such as compression mold, the plastic is solid powder or preformed blank during operation, participates in the cavity and is hot pressed at a certain temperature. Thermoplastic molding plastic mold, such as injection mold, kneading mold. During the operation, the plastic enters the mold cavity through injection, kneading and other methods under the viscous flow state and is processed and formed.

(1) wear failure; (2) plastic deformation failure; (3) cracking failure

(1) functional requirements for the use of plastic mold materials (2) technological functional requirements for plastic mold materials

4. Function and classification of plastic mould steel

① Ensure moderate hardness and excellent durability.

③ During the heat treatment of the mould, special attention should be paid to the protection of the surface of the mould cavity to avoid all kinds of heat treatment defects.

(1) carburized plastic mold steel

Carburized plastic mould steel is mainly used in cold kneading plastic mould. Generally, the carbon content is low, which is 0.1% - 0.25%. Cr and Ni elements are added in the steel together, so that the hardenability of the steel can be trudged, and the effect of ferritic solid solution strengthening is also small, while the content of Si element should be as low as possible. This kind of steel needs carburizing, quenching and tempering treatment after cold kneading, which can make the surface of die cavity have high hardness and wear resistance, the surface hardness can reach 58-62hrc, and the center part has good resistance.

The common types of carburized plastic die steel in China are carbon carburizing steel and alloy carburizing steel, the former is 10 and 20 steel, the latter is 20Cr, 12CrNi3A, 20cr2ni4, 2crni3moals, etc.

① Function of pre hardening plastic mould steel ② types of pre hardening plastic mould steel

The former commonly used types are 10 and 20 steel, the latter are 3crmo, 3cr2mnnimo, 42CrMo, 4Cr5MoSiV, 5crnimnmosca, 8Cr2MnWMoVS (8cr2s), 40crmnvbsca, y55crnimnmov (SM1), Japan Datong die steel Px4, pac5000, Sweden yishengbai die steel 618hh, 718hh (IMPAX HH), Germany glitz die steel 1.2311, 1.2738, 1.2711, etc.

① Functions of age hardening plastic mould steel ② types of age hardening plastic mould steel (4) corrosion resistant plastic mould steel

In the production of PVC, polystyrene, ABS and other chemical corrosive plastic products, corrosive gases will be decomposed during the forming process, and the corrosion effect will occur on the mold. Therefore, it is necessary for the mold material to have better anti-corrosion function. In addition to excellent corrosion function, corrosion-resistant plastic mold steel, like other types of plastic mold steel, also needs certain hardness, strength, wear resistance and other functional requirements.

The commonly used corrosion-resistant plastic mold steel types are: high carbon and high chromium corrosion-resistant steel, such as 9Cr18, 9Cr18Mo, cr18mov, cr14mo4v, 4Cr13, Japan Datong mold steel s-star, G-STAR, D-star, Sweden yishengbai mold steel S136 (Stavax ESR), s136sup (STAVAX supreme), elmax (elmax LH / HH), s336 (corrax), 168 (ramax 2), polmax (420 var), Germany glitz mold steel 1.2083 victory ESR, 1.2316 victory ESR, etc.; martensitic stainless and acid resistant steel, such as 1Cr17Ni2; separate hardened stainless steel, such as 0cr16ni4cu3nb, etc.

Copper alloy

Aluminum alloy

The commonly used brand of cast aluminum alloy is ZL101, which is suitable for making plastic mould with high thermal conductivity, messy shape and short manufacturing cycle.

Zinc alloy

Most of the zinc alloys used to make plastic molds are zn-4al-3cu eutectic alloy, as well as beryllium zinc alloy and nickel titanium zinc alloy. Beryllium zinc alloy has high hardness (150hbs) and good heat resistance. The service life of the injection mould can reach tens of thousands to hundreds of thousands of pieces. Nickel titanium zinc alloy because of the participation of nickel and titanium can make the strength, hardness trek, and then make the mold life multiplied.