Generally, the mold is divided into five grades according to the length of its service life. The first grade is more than one million times, the second grade is 500,000---one million times, the third grade is 300,000----500,000 times, and the fourth grade is 100,000--300,000 times, and the fifth grade is below 100,000 times. Both the first-level and second-level molds are required to heat the steel with a hardness of about HRC50. Otherwise, it is easy to wear and the products are easy to wear. The steel has good heat treatment properties and good cutting performance under high hardness. Of course, there are other considerations. Usually used in Sweden 8407, S136, the United States 420, H13, Europe's 2316, 2344, 083, or Japan's SKD61, DC53 (formerly metal mold materials, used in special cases). In addition, the injection molding materials and the added fillers have a great influence on the selection, especially the wear of the glass fibers on the mold.
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          Some plastic materials are acid corrosive, and some are added with reinforcing agents or other modifying agents, such as glass fiber to damage the mold, and all materials should be considered. Strongly corrosive plastics are generally selected from S136, 2316, 420, and weakly corrosive except S136, 2316, 420, and SKD61, NAK80, PAK90, and 718M. Strong acid plastic materials are: PVC, POM, PBT weakly acidic plastic materials: PC, PP, PMMA, PA, the appearance of the product requires a great influence on the choice of mold materials, transparent parts and surfaces require mirroring For the products, the available materials are S136, 2316, 718S, NAK80, PAK90, 420. The mold with high transparency should be S136, followed by 420.

        The above is from satisfying the product requirements, but as a designer, if you only consider these, you can not only become a good designer, maybe your rice bowl has problems, the cost of the mold you are involved is heavy. The weight of the middle, you have to consider the price, take S136 and 2316 to compare, the difference of 55-60 yuan per kilogram, if you choose improperly, your boss is not unable to receive the order, is to go bankrupt.
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            There are many pre-hard materials for the three-stage mold. The grades are: S136H, 2316H, 718H, 083H, hardness HB270----340, and the four-five-level molds are P20, 718, 738, 618, 2311, 2711. Mold, it is also possible to use S50C, 45# steel, that is, directly on the mold embryo.

1. High Corrosion Resistance Many resins and additives have corrosive effects on the surface of the cavity. This corrosion causes the surface of the cavity to corrode and peel off, the surface condition deteriorates, and the quality of the molded part deteriorates. Therefore, it is best to use corrosion-resistant steel or chrome-plated, nickel-plated surfaces on the cavity surface.
   2. Good wear resistance The gloss and precision of the surface of the injection molded plastic part are directly related to the wear resistance of the cavity surface of the injection mold. Especially when some plastics are added with glass fiber, inorganic filler and some pigments, they are Together with the plastic melt, it flows at idle speed in the flow channel and the cavity. The friction on the surface of the cavity is very large. If the material is not wear-resistant, it will wear quickly and the quality of the plastic part will be damaged.
   3. Good dimensional stability During injection molding, the temperature of the injection mold cavity should reach above 300 °C. For this reason, it is preferable to use a suitably tempered tool steel (heat treated steel). Otherwise, it will cause a change in the microstructure of the material, resulting in a change in the size of the injection mold.
   4. Easy to process Mold parts are mostly made of metal materials, and some structural shapes are still very complicated. In order to shorten the production cycle and improve efficiency, the mold materials are required to be easily processed into the shape and precision required by the drawings. 5 L2 h1 j) @3 G
   5. Good polishing performance Plastic injection parts usually require good gloss and surface condition. Therefore, the surface roughness of the cavity is required to be very small. Therefore, the surface of the cavity must be surface-processed, such as polishing and grinding. Therefore, the selected steel should not contain rough impurities and pores. 8 x7 J* N7 m4 k( k& _
   6. Small effect by heat treatment In order to improve the hardness and wear resistance, the injection mold is generally subjected to heat treatment, but this treatment should have a small dimensional change. Therefore, it is preferable to use a pre-hardenable steel that can be machined.

Injection mold steel is divided into the following 6 categories: 0 g5 W4 U) d, Y& G
   1. Carbon mold steel: mainly adopts medium carbon structural steel, representing steel grades such as S45C, S48C, S50C and S55C. Commonly used in the manufacture of small dip molds or mold holders with low precision requirements
   2. Pre-hardened die steel: mainly adopts medium carbon alloy steel with high hardenability. The steel grades are P20, 718, 2311, 2738, 42CrMnMoV and WSM30B. The steel plate is pre-hardened and can be used directly without heat treatment. It is suitable for molds with large batch size, large mold size and complex shape and high precision.
   3, age hardening mold steel: in the low carbon alloy, adding a certain amount of trace elements, the hardness is low, easy to mold processing, and then through heat treatment, to achieve high hardness requirements, the common steel number is P80B, for complex shape, polishing performance requirements High mold.
   4. Corrosion-resistant mold steel: The representative steel number is WSM136B.
   5. Free cutting die steel: representative steel number: 2312B.
   6. Electroslag mold steel: It can achieve the effect of polishing to mirror surface, and has strong corrosion resistance. It represents 20R, 718R4 J! N0