What is plastic mold steel?

The United States is the first country to list special steels for plastic molds in tool steels. It is mainly represented by duP and is divided into five categories.
Carburized plastic dao die steel: P1, P2, P3, P4, P5, P6. This kind of steel has very low carbon content, mainly in the early United States and the extrusion molding method, which requires good cold plasticity and high extrusion performance. After forming, surface carburizing and quenching improve surface hardness and long service life. The ultra-low carbon core can minimize the deformation during quenching.
Quenched and tempered plastic mold: P20, P21. At present, the amount of P20 in plastic molds is large and has become the main body, and most of them are used in the pre-hardened state.
 Medium-carbon alloy tool steel is used for thermosetting plastic molds. Steel grade has H13, while L2 and S7, O1 and A2 are also used. The characteristics of this category are:

(1) It is basically a secondary hardened steel, with good thermal strength at 500-600oC.
(2) High chromium content, good atmospheric corrosion.
(3) Excellent hardenability, suitable for large modules.
Stainless steel is used for plastic molds with high corrosion resistance. The main steel grades are 420, 414L, 440, 416.
 Aging steel obtains high performance after aging treatment. There are two types, one is P21 low carbon Ni-A1 aged steel; the other is 18Ni maraging steel. The latter is a carbon-free, high-purity, high-strength, and high-toughness material used in the aerospace industry. Used in plastic molds that require high mechanical properties, dimensional accuracy, smoothness and corrosion resistance.
Selection of plastic mold steel
For thin-walled plastic boxes, when the production batch is less than 100,000 pieces, use P20, P21 to pre-harden (HB250~300), and use 414L when it is more corrosive.
Ordinary plastic molds with long life, use P6 or P20, and the hardness is HRC54-58 after carburizing and quenching; when the plastic parts are not too large, O1, S7 can be used. Use 420 when corrosive.
Non-high temperature thermosetting molds use P6 and P20 after carburizing and quenching. Use 420 for strong corrosiveness.
High temperature thermosetting plastic molds use H13 and S7 or carburized steel P4. These higher chromium content has good tempering resistance and high temperature oxidation resistance.