A viewer in the live stream asked, “Is 2344 or S136 better for plastic molds?” Both 2344 and S136 can be used to make hard plastic molds with a heat-treated hardness of 50 HRC. Since their properties differ somewhat, the specific choice of mold steel depends on the trade-offs for your particular mold.
2344 is a 4Cr5MoSiV1 medium-carbon hot-work die steel with a carbon content of 0.38% and a hardness of 50 HRC. It offers good toughness, and since the smelting quality of hot-work die steels is generally high, it can be used to make hard molds for plastic injection molding and also achieves a certain degree of mirror-like polish. If the 2344 you purchase has been produced via electroslag remelting and has undergone six-side forging, it can achieve a mirror finish while maintaining a certain level of toughness. If your plastic mold has narrow flanges, is relatively large in size, has particularly high toughness requirements, and also needs to balance wear resistance, 2344 mold steel is highly suitable for hard mold plates, as well as sliders and inserts.
S136 is a 4Cr13-type stainless steel that offers a certain degree of rust resistance. If the S136 you purchase is of very high smelting quality—specifically, if it has undergone electroslag remelting and six-sided forging—it will not only possess corrosion resistance and rust prevention properties but can also be polished to a mirror finish.
If your mold is used in environments containing acidic substances or moisture—where rusting is likely—and you want a mold steel that resists rust and is easy to maintain in the future, then S136 mold steel is a good choice. It has a carbon content of 0.38% and can achieve a hardness of 50 HRC, making it convenient for use in hard mold applications.
There is also a pre-hardened variant of S136 called S136H. It undergoes quenching and tempering at the factory, achieving a hardness of 33–36 HRC. This eliminates the need for heat treatment, allowing it to be machined directly into a mold. This saves on heat treatment costs and mold production time, and the mold can be machined to final dimensions in a single operation, reducing machining costs. Materials requiring heat treatment are typically rough-machined, then quenched and tempered, followed by finish machining. This process effectively requires producing one and a half sets of mold components for a single mold, resulting in higher costs.
For plastic molds, S136 and S136H are the most commonly used steels, while 2344 is primarily used for hard molds. The specific choice of mold steel depends on the exact requirements of your mold. Generally, for large molds that require both toughness and a mirror-finish polish, 2344 is the standard choice; if rust resistance is required, S136H is typically used; and if rust resistance, high hardness, and a mirror-finish polish are all required, quenched and tempered S136 is generally used.
There is no standard, fixed answer when selecting mold steel. The choice must be based on a comprehensive evaluation of factors such as the properties of the injection molding compound, the mold operating conditions, the mold structure, the required surface finish of the product, mold cost, and the required mold service life. Only by considering all these factors can you select the ideal mold steel that matches your specific mold conditions and requirements.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.