The durability of injection molds is closely related to the materials used, therefore, it is necessary to pay attention to the selection of mold materials. Generally speaking, mold materials should have the following properties:

1. High wear resistance

In order to increase the rigidity and mechanical properties of plastic products, fiberglass and inorganic fillers are widely used in plastic formulations for reinforcement. After adding these additives, they enter the mold cavity at high speed together with the melt, causing great friction on the mold cavity. If the mold material is not wear-resistant, it is easy to cause excessive wear on the mold cavity. Therefore, the material used to make such molds should have good wear resistance.

2. High corrosion resistance

Many plastic additives, such as flame retardants, and even the chemical reactions of the melt itself can corrode the mold cavity. When fillers and reinforcing materials containing abrasives are mixed in plastic raw materials, it is more likely to aggravate the damage of the mold. Therefore, it is best to use corrosion-resistant steel or perform electroplating treatment on the surface of the mold cavity, such as chrome plating or nickel plating.

3. Good thermal conductivity

Good mold temperature control has a significant impact on the quality of plastic parts during injection molding, especially when processing semi crystalline thermoplastic plastics. Generally, copper alloys have much better thermal conductivity than alloy steels, but their elastic modulus, hardness, and durability are lower. The insufficient thermal conductivity of steel can be compensated for by a cooling system.

4. Good dimensional stability

During the molding operation of injection molds, the temperature of the mold cavity can reach over 300 ℃. Such a large temperature difference can easily cause microscopic changes in the cavity structure, resulting in changes in the mold size and instability of the plastic part size. Therefore, appropriate tempered tool steel, namely heat-treated steel, can be selected. In order to improve hardness and wear resistance, it is generally necessary to perform appropriate heat treatment on the mold, but the impact of this heat treatment on the size of the mold should be minimized; Pre hardened steel that can be machined can also be used, which does not require heat treatment after mechanical processing.

5. Good polishing performance

The inner wall of the mold cavity has high requirements and very low roughness to meet the requirement of good glossiness on the surface of the plastic part. Therefore, the mold cavity generally needs to be polished, and the brighter the surface, the better. Therefore, it is required that the mold material is easy to polish, and the selected material should not have defects such as impurities and pores.